Mobile Application Development Winter 2022 GTU Paper Solution | 3161612

The Android SDK (Software Development Kit) is a collection of software tools that developers use to create Android applications. The SDK includes several components that provide different functionalities, and they are:

1. Android Studio: Android Studio is the primary tool for Android application development. It is an integrated development environment (IDE) that provides developers with a graphical user interface for building, debugging, and testing Android apps.
2. Android SDK Tools: The Android SDK Tools are a set of command-line tools used for building and debugging Android applications. These tools include Android Debug Bridge (ADB), Android Asset Packaging Tool (AAPT), and Android Emulator.
3. Android SDK Platform-Tools: The Android SDK Platform-Tools are a set of command-line tools used for interacting with an Android device or emulator. These tools include ADB, Fastboot, and Systrace.
4. Android SDK Build-Tools: The Android SDK Build-Tools are a set of tools used for building Android applications. These tools include the Android Asset Packaging Tool (AAPT), the Android Debugging Bridge (ADB), and the Dalvik Debug Monitor Server (DDMS).
5. Android SDK Platforms: The Android SDK Platforms are collections of tools and libraries that developers use to create Android apps. They include the Android API, which provides access to the Android framework, and various other components like the Android Support Library, Google Play Services, and Android System Images.
6. Android Virtual Device (AVD) Manager: The AVD Manager is a tool that allows developers to create and manage Android Virtual Devices (AVDs). An AVD is an emulator instance that enables developers to test their applications on different Android versions, device configurations, and screen sizes.

The Android architecture is a layered architecture that is designed to provide a robust and flexible operating system for mobile devices. It is based on the Linux kernel and includes several layers of software components. The following is a detailed explanation of the Android architecture:

1. Linux Kernel Layer: This layer is the foundation of the Android architecture. It provides essential features such as memory management, process management, and security. The Linux kernel layer also provides support for hardware drivers and network protocols.
2. Hardware Abstraction Layer (HAL): This layer provides a standardized interface between the hardware and the upper layers of the Android architecture. It abstracts the hardware-specific details and provides a consistent API for device drivers.
3. Native Libraries: These libraries are written in C/C++ and provide access to the hardware features of the device. Examples of native libraries include the Media Framework, OpenGL ES, and SQLite.
4. Android Runtime: The Android Runtime (ART) is a virtual machine that executes the Dalvik bytecode used by Android applications. It compiles the bytecode into machine code when an application is installed, which results in improved performance compared to the previous Dalvik virtual machine.
5. Java API Framework: The Java API framework provides a rich set of APIs for developers to build Android applications. The APIs include classes for user interface (UI), data storage, networking, and multimedia.
6. System Applications: These are the pre-installed applications that come with Android devices. Examples include the phone app, messaging app, and browser.
7. Application Framework: The Application Framework provides a set of high-level services for building Android applications. These services include the Activity Manager, Content Provider, and Notification Manager.
8. Applications: Finally, the top layer of the Android architecture is the applications layer. This layer includes the applications that users download from the Google Play Store or other sources. Applications can be developed in Java or Kotlin and can use the Android API to access the device’s hardware features and system services.

The DatePicker allows the user to select a specific date from a calendar view, while the TimePicker allows the user to select a specific time with an hour and minute picker. Both widgets can be used together to select a specific date and time.

To use the Date and Time Picker in an Android application, developers can use the DatePicker and TimePicker widgets provided by the Android framework. These widgets can be added to a layout file using XML or programmatically added to a view hierarchy.

Here are some methods that can be used with the DatePicker and TimePicker widgets:

1. DatePicker

• init(int year, int monthOfYear, int dayOfMonth, DatePicker.OnDateChangedListener onDateChangedListener) – Initializes the DatePicker with the given year, month, and day, and sets an OnDateChangedListener to be notified of changes to the date.
• getYear() – Returns the currently selected year in the DatePicker.
• getMonth() – Returns the currently selected month in the DatePicker (0-11).
• getDayOfMonth() – Returns the currently selected day in the DatePicker (1-31).

2. TimePicker

• setCurrentHour(Integer currentHour) – Sets the current hour for the TimePicker.
• getCurrentHour() – Returns the current hour selected in the TimePicker.
• setCurrentMinute(Integer currentMinute) – Sets the current minute for the TimePicker.
• getCurrentMinute() – Returns the current minute selected in the TimePicker.

Here’s how you can display a circular progress bar in both XML and Android program:

1. XML code:

To display a circular progress bar in XML code, you can use the <ProgressBar> element and set its style attribute to @style/Widget.AppCompat.ProgressBar. You can also customize the appearance of the progress bar by setting its android:indeterminateTint attribute to a color value.

<ProgressBar
    android:id="@+id/progressBar"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    style="@style/Widget.AppCompat.ProgressBar"
    android:indeterminateTint="@color/colorAccent"
    />

2. Android program:

To display a circular progress bar in Android program, you can create an instance of the ProgressBar class and set its style and color attributes programmatically. You can then add the progress bar to your layout using a FrameLayout.

ProgressBar progressBar = new ProgressBar(context, null, android.R.attr.progressBarStyleLarge);
progressBar.setIndeterminate(true);
progressBar.getIndeterminateDrawable().setColorFilter(ContextCompat.getColor(context, R.color.colorAccent), PorterDuff.Mode.SRC_IN);

FrameLayout.LayoutParams layoutParams = new FrameLayout.LayoutParams(FrameLayout.LayoutParams.WRAP_CONTENT, FrameLayout.LayoutParams.WRAP_CONTENT);
layoutParams.gravity = Gravity.CENTER;

frameLayout.addView(progressBar, layoutParams);

To create a registration form in Android, you can follow the below steps:

1. Open Android Studio and create a new project.
2. Create a new layout file in the res/layout folder and name it as registration_form.xml.
3. In the registration_form.xml file, add the following code:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Registration Form"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <EditText
        android:id="@+id/editTextName"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Enter Name" />

    <EditText
        android:id="@+id/editTextUsername"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Enter Username" />

    <EditText
        android:id="@+id/editTextPassword"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Enter Password"
        android:inputType="textPassword" />

    <EditText
        android:id="@+id/editTextRepeatPassword"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Repeat Password"
        android:inputType="textPassword" />

    <Button
        android:id="@+id/buttonRegister"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Register" />

</LinearLayout>

4. In the MainActivity.java file, add the following code:

public class MainActivity extends AppCompatActivity {

    EditText editTextName, editTextUsername, editTextPassword, editTextRepeatPassword;
    Button buttonRegister;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.registration_form);

        editTextName = findViewById(R.id.editTextName);
        editTextUsername = findViewById(R.id.editTextUsername);
        editTextPassword = findViewById(R.id.editTextPassword);
        editTextRepeatPassword = findViewById(R.id.editTextRepeatPassword);
        buttonRegister = findViewById(R.id.buttonRegister);

        buttonRegister.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String name = editTextName.getText().toString();
                String username = editTextUsername.getText().toString();
                String password = editTextPassword.getText().toString();
                String repeatPassword = editTextRepeatPassword.getText().toString();

                // TODO: Check if all fields are filled and passwords match

                // TODO: Save user information to database or server
            }
        });
    }
}

5. Run the app to see the registration form in action.

LinearLayout is one of the most commonly used layout managers in Android, which allows you to organize views in a linear direction, either horizontally or vertically. In a LinearLayout, each view is arranged one after another in a single line.

Here are some of the key attributes of LinearLayout:

1. android:orientation: This attribute sets the orientation of the layout. You can set it to either horizontal or vertical.

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">

2. android:layout_weight: This attribute specifies the weight of the view in the layout. It determines how much space the view takes up in the layout relative to other views.

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Button"
    android:layout_weight="1"/>

3. android:gravity: This attribute specifies the gravity of the layout. You can use it to align the views inside the layout either horizontally or vertically.

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:gravity="center_vertical">

4. android:layout_margin: This attribute specifies the margin of the view from its parent layout. You can use it to set the margin of the view on all sides.

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Button"
    android:layout_margin="16dp"/>

5. android:layout_gravity: This attribute specifies the gravity of the view inside its parent layout. You can use it to align the view either horizontally or vertically inside the layout.

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Button"
    android:layout_gravity="center_horizontal"/>

Designing the Calculator layout

Open the activity_main.xml layout file, we will create our layout using Button and TextView controls. The layout code snippet is shown below.

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.jackrutorial.calculatorexample.MainActivity">

    <TableLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <TableRow
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            >

            <TextView
                android:id="@+id/txtResult"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_span="4"
                android:layout_gravity="right"
                />

        </TableRow>

        <TableRow
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            >

            <EditText
                android:id="@+id/edtInput"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_span="4"
                android:layout_gravity="right"
                android:inputType="number"
                />

        </TableRow>

        <TableRow
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            >

            <Button
                android:id="@+id/btnCE"
                android:text="CE"
                />

            <Button
                android:id="@+id/btnC"
                android:text="C"
                />

            <Button
                android:id="@+id/btnDelete"
                android:text="Delete"
                android:layout_span="2"

                />

        </TableRow>

        <TableRow
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            >

            <Button
                android:id="@+id/btnNumber7"
                android:text="7"
                />

            <Button
                android:id="@+id/btnNumber8"
                android:text="8"
                />

            <Button
                android:id="@+id/btnNumber9"
                android:text="9"
                />

            <Button
                android:id="@+id/btnNumberAdd"
                android:text="+"
                />

        </TableRow>

        <TableRow
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            >

            <Button
                android:id="@+id/btnNumber4"
                android:text="4"
                />

            <Button
                android:id="@+id/btnNumber5"
                android:text="5"
                />

            <Button
                android:id="@+id/btnNumber6"
                android:text="6"
                />

            <Button
                android:id="@+id/btnNumberSub"
                android:text="-"
                />

        </TableRow>

        <TableRow
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            >

            <Button
                android:id="@+id/btnNumber1"
                android:text="1"
                />

            <Button
                android:id="@+id/btnNumber2"
                android:text="2"
                />

            <Button
                android:id="@+id/btnNumber3"
                android:text="3"
                />

            <Button
                android:id="@+id/btnNumberMul"
                android:text="*"
                />

        </TableRow>

        <TableRow
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            >

            <Button
                android:id="@+id/btnNumber0"
                android:text="0"
                />

            <Button
                android:id="@+id/btnDot"
                android:text="."
                />

            <Button
                android:id="@+id/btnResult"
                android:text="="
                />

            <Button
                android:id="@+id/btnNumberDiv"
                android:text="/"
                />

        </TableRow>

    </TableLayout>

</android.support.constraint.ConstraintLayout> 

Main Activity

Change MainActivity activity code to the following.

package com.jackrutorial.calculatorexample;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    Button btnNumber0;
    Button btnNumber1;
    Button btnNumber2;
    Button btnNumber3;
    Button btnNumber4;
    Button btnNumber5;
    Button btnNumber6;
    Button btnNumber7;
    Button btnNumber8;
    Button btnNumber9;

    TextView txtResult;

    EditText edtInput;

    Button btnCE;
    Button btnC;
    Button btnDelete;

    Button btnAdd;
    Button btnSub;
    Button btnMul;
    Button btnDiv;

    Button btnDot;
    Button btnResult;

    double val1=Double.NaN;
    double val2;
    String ACTION;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        btnNumber0 = (Button) findViewById(R.id.btnNumber0);
        btnNumber1 = (Button) findViewById(R.id.btnNumber1);
        btnNumber2 = (Button) findViewById(R.id.btnNumber2);
        btnNumber3 = (Button) findViewById(R.id.btnNumber3);
        btnNumber4 = (Button) findViewById(R.id.btnNumber4);
        btnNumber5 = (Button) findViewById(R.id.btnNumber5);
        btnNumber6 = (Button) findViewById(R.id.btnNumber6);
        btnNumber7 = (Button) findViewById(R.id.btnNumber7);
        btnNumber8 = (Button) findViewById(R.id.btnNumber8);
        btnNumber9 = (Button) findViewById(R.id.btnNumber9);

        txtResult = (TextView) findViewById(R.id.txtResult);

        edtInput = (EditText) findViewById(R.id.edtInput);

        btnCE = (Button) findViewById(R.id.btnCE);
        btnC = (Button) findViewById(R.id.btnC);
        btnDelete = (Button) findViewById(R.id.btnDelete);

        btnAdd = (Button) findViewById(R.id.btnNumberAdd);
        btnSub = (Button) findViewById(R.id.btnNumberSub);
        btnMul = (Button) findViewById(R.id.btnNumberMul);
        btnDiv = (Button) findViewById(R.id.btnNumberDiv);

        btnDot = (Button) findViewById(R.id.btnDot);
        btnResult = (Button) findViewById(R.id.btnResult);

        btnCE.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                edtInput.setText(null);
            }
        });

        btnC.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                val1 = Double.NaN;
                txtResult.setText(null);
                edtInput.setText(null);
            }
        });

        btnDelete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String number = edtInput.getText().toString();
                if(number != null && number.length() > 0){
                    number = number.substring(0, number.length() - 1);
                }
                edtInput.setText(number);
                edtInput.setSelection(edtInput.getText().length());
            }
        });

        btnAdd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ACTION = "+";
                if(!Double.isNaN(val1)){
                    val2 = Double.parseDouble(edtInput.getText().toString());
                    val1 = val1 + val2;
                } else {
                    val1 = Double.parseDouble(edtInput.getText().toString());
                }

                txtResult.setText(val1 + " + ");
                edtInput.setText(null);
            }
        });

        btnSub.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ACTION = "-";
                if(!Double.isNaN(val1)){
                    val2 = Double.parseDouble(edtInput.getText().toString());
                    val1 = val1 - val2;
                } else {
                    val1 = Double.parseDouble(edtInput.getText().toString());
                }

                txtResult.setText(val1 + " - ");
                edtInput.setText(null);
            }
        });

        btnMul.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ACTION = "*";
                if(!Double.isNaN(val1)){
                    val2 = Double.parseDouble(edtInput.getText().toString());
                    val1 = val1 * val2;
                } else {
                    val1 = Double.parseDouble(edtInput.getText().toString());
                }

                txtResult.setText(val1 + " * ");
                edtInput.setText(null);
            }
        });

        btnDiv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ACTION = "/";
                if(!Double.isNaN(val1)){
                    val2 = Double.parseDouble(edtInput.getText().toString());
                    val1 = val1/val2;
                } else {
                    val1 = Double.parseDouble(edtInput.getText().toString());
                }

                txtResult.setText(val1 + " / ");
                edtInput.setText(null);
            }
        });

        btnResult.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(ACTION != null && ACTION.equals("+")){
                    double result = val1 + Double.parseDouble(edtInput.getText().toString());
                    txtResult.setText(null);
                    edtInput.setText(String.valueOf(result));
                } else if(ACTION != null && ACTION.equals("-")){
                    double result = val1 - Double.parseDouble(edtInput.getText().toString());
                    txtResult.setText(null);
                    edtInput.setText(String.valueOf(result));
                } else if(ACTION != null && ACTION.equals("*")){
                    double result = val1 * Double.parseDouble(edtInput.getText().toString());
                    txtResult.setText(null);
                    edtInput.setText(String.valueOf(result));
                } else if(ACTION != null && ACTION.equals("/")){
                    double result = val1 / Double.parseDouble(edtInput.getText().toString());
                    txtResult.setText(null);
                    edtInput.setText(String.valueOf(result));
                }

                ACTION = null;
                val1 = Double.NaN;
                edtInput.setSelection(edtInput.getText().length());
            }
        });

        btnNumber0.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                edtInput.setText(edtInput.getText() + "0");
                edtInput.setSelection(edtInput.getText().length());
            }
        });

        btnNumber1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                edtInput.setText(edtInput.getText() + "1");
                edtInput.setSelection(edtInput.getText().length());
            }
        });

        btnNumber2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                edtInput.setText(edtInput.getText() + "2");
                edtInput.setSelection(edtInput.getText().length());
            }
        });

        btnNumber3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                edtInput.setText(edtInput.getText() + "3");
                edtInput.setSelection(edtInput.getText().length());
            }
        });

        btnNumber4.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                edtInput.setText(edtInput.getText() + "4");
                edtInput.setSelection(edtInput.getText().length());
            }
        });

        btnNumber5.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                edtInput.setText(edtInput.getText() + "5");
                edtInput.setSelection(edtInput.getText().length());
            }
        });

        btnNumber6.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                edtInput.setText(edtInput.getText() + "6");
                edtInput.setSelection(edtInput.getText().length());
            }
        });

        btnNumber7.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                edtInput.setText(edtInput.getText() + "7");
                edtInput.setSelection(edtInput.getText().length());
            }
        });

        btnNumber8.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                edtInput.setText(edtInput.getText() + "8");
                edtInput.setSelection(edtInput.getText().length());
            }
        });

        btnNumber9.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                edtInput.setText(edtInput.getText() + "9");
                edtInput.setSelection(edtInput.getText().length());
            }
        });

        btnDot.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                edtInput.setText(edtInput.getText() + ".");
                edtInput.setSelection(edtInput.getText().length());
            }
        });

    }
}

In Android, GridLayout is a layout manager that allows you to create a grid of rows and columns to position child views. With GridLayout, you can create complex layouts by placing views in a grid pattern.

Here are some of the attributes that you can use with GridLayout:

1. rowCount and columnCount: These attributes specify the number of rows and columns in the grid.
2. layout_row and layout_column: These attributes specify the row and column index of a child view within the grid.
3. layout_rowSpan and layout_columnSpan: These attributes specify the number of rows and columns that a child view occupies within the grid.
4. layout_gravity: This attribute specifies how a child view is positioned within its cell. You can use values like top, bottom, left, right, center, and fill to control the alignment of the view.

Here’s an example of a simple GridLayout that contains three child views:

<GridLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:rowCount="2"
    android:columnCount="2">

    <TextView
        android:text="View 1"
        android:layout_row="0"
        android:layout_column="0"/>

    <TextView
        android:text="View 2"
        android:layout_row="0"
        android:layout_column="1"/>

    <TextView
        android:text="View 3"
        android:layout_row="1"
        android:layout_column="0"
        android:layout_columnSpan="2"/>

</GridLayout>

ListView is an Android widget that displays a vertical list of scrollable items. It is commonly used to display large amounts of data, such as a list of contacts, messages, or products in an e-commerce app.

Here is an example Java class that demonstrates how to add 10 items to a ListView:

import android.app.Activity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;

public class MainActivity extends Activity {

    private String[] items = {"Item 1", "Item 2", "Item 3", "Item 4", "Item 5", "Item 6", "Item 7", "Item 8", "Item 9", "Item 10"};

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Get a reference to the ListView
        ListView listView = findViewById(R.id.list_view);

        // Create an ArrayAdapter to populate the ListView
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
                android.R.layout.simple_list_item_1, android.R.id.text1, items);

        // Set the adapter for the ListView
        listView.setAdapter(adapter);
    }
}

In this example, we create a String array called items that contains 10 items. We then create an ArrayAdapter that takes the items array as its data source and uses the built-in simple_list_item_1 layout provided by Android. Finally, we set the ArrayAdapter as the adapter for the ListView using the setAdapter() method.

Note that you will also need to create a layout XML file that includes a ListView with the ID list_view in order for this code to work.

Implicit intents are a powerful feature of the Android operating system that allow different components of an app to communicate with each other, as well as with other apps on the device. Here are four key points to know about implicit intents:

1. Definition: An implicit intent is an intent that does not specify the component that should handle the intent. Instead, it defines an action to be performed, such as opening a web page, playing a video, or sending an email, and allows the system to find the appropriate component to handle the action.
2. Intent Filters: To receive an implicit intent, a component must define an intent filter in its manifest file. An intent filter specifies the types of intents that the component can handle, based on the action, data, and category of the intent.
3. Multiple Options: Since implicit intents can be handled by multiple components, the system presents the user with a list of options to choose from when the intent is launched. For example, if an app wants to play a video, it may launch an implicit intent with the action ACTION_VIEW and the data URI of the video. The system will then present a list of video player apps that can handle the intent, and the user can choose which one to use.
4. Flexibility: Implicit intents provide flexibility and extensibility to Android apps. They allow different components of an app to communicate with each other without knowing their specific implementation details. They also allow apps to interact with other apps on the device, opening up a wide range of possibilities for sharing data and functionality between apps.

Here’s an example Android program that captures an image using the device’s camera and displays it in an ImageView:

1. Add Camera and Storage Permissions to the AndroidManifest.xml file:

<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

2. Add a Button and ImageView to the layout file activity_main.xml:

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <Button
        android:id="@+id/button_capture"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Capture Image"/>

    <ImageView
        android:id="@+id/image_preview"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:scaleType="centerCrop"/>

</LinearLayout>

3. In the MainActivity class, define variables for the Button, ImageView, and the image file path:

public class MainActivity extends AppCompatActivity {

    private Button captureButton;
    private ImageView previewImage;
    private String imagePath;

    // other code here...

}

4. In the onCreate() method, initialize the variables and set an OnClickListener for the capture button:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // initialize the variables
    captureButton = findViewById(R.id.button_capture);
    previewImage = findViewById(R.id.image_preview);

    // set an OnClickListener for the capture button
    captureButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            captureImage();
        }
    });
}

5. Define the captureImage() method, which will launch the device’s camera app to take a picture:

private void captureImage() {
    // create a new file to store the image
    File imageFile = new File(getExternalFilesDir(null), "image.jpg");
    imagePath = imageFile.getAbsolutePath();

    // create a new intent to launch the camera app
    Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(imageFile));

    // start the camera app and wait for the result
    startActivityForResult(intent, 1);
}

6. Override the onActivityResult() method to handle the result of the camera app:

@Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    if (requestCode == 1 && resultCode == RESULT_OK) {
        // display the captured image in the ImageView
        Bitmap imageBitmap = BitmapFactory.decodeFile(imagePath);
        previewImage.setImageBitmap(imageBitmap);
    }
}

In Android, a dialog is a small window that prompts the user to make a decision or enter information. Dialogs can be used for various purposes, such as displaying error messages, asking for user input, or showing progress.

An AlertDialog is a specific type of dialog that is used to display an alert message to the user. It typically consists of a title, a message, and one or more buttons that the user can tap to perform an action.

Here is an example of how to create and show an AlertDialog in Android:

1. Define the AlertDialog.Builder object in your activity:

AlertDialog.Builder builder = new AlertDialog.Builder(this);

2. Set the title, message, and buttons for the AlertDialog:

builder.setTitle("Alert!")
       .setMessage("This is an alert dialog.")
       .setPositiveButton("OK", new DialogInterface.OnClickListener() {
           public void onClick(DialogInterface dialog, int id) {
               // Do something when OK button is clicked
           }
       })
       .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
           public void onClick(DialogInterface dialog, int id) {
               // Do something when Cancel button is clicked
           }
       });

3. Create and show the AlertDialog:

AlertDialog dialog = builder.create();
dialog.show();

This will display an AlertDialog with a title “Alert!”, a message “This is an alert dialog.”, and two buttons labeled “OK” and “Cancel”. When the user taps the “OK” button, the onClick() method defined in the setPositiveButton() method will be called. Similarly, when the user taps the “Cancel” button, the onClick() method defined in the setNegativeButton() method will be called.

To send an email from an Android app, you can use the JavaMail API, which provides classes for sending email messages. Here is an example program that demonstrates how to send an email using JavaMail API:

1. Add the JavaMail API library to your Android project by adding the following dependency in your build.gradle file:

implementation 'com.sun.mail:android-mail:1.6.2'

2. Request permission to access the user’s email account in your AndroidManifest.xml file:

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

3. Create a new activity in your Android project that contains an email form. The email form should include fields for the recipient’s email address, the subject, and the message body, as well as a button to send the email.
4. Add the following code to the button’s OnClickListener to send the email:

// Get the values from the email form
String recipient = recipientEditText.getText().toString();
String subject = subjectEditText.getText().toString();
String message = messageEditText.getText().toString();

// Create a new email message
Message email = new MimeMessage(session);
email.setFrom(new InternetAddress("your_email@example.com"));
email.setRecipient(Message.RecipientType.TO, new InternetAddress(recipient));
email.setSubject(subject);
email.setText(message);

// Send the email
Transport.send(email);

Note that you will need to set up an email session before you can send the email. You can do this by creating a new Properties object and setting the SMTP server and port number for your email provider, as well as your email account credentials. Here is an example of how to set up the email session:

Properties props = new Properties();
props.put("mail.smtp.host", "smtp.example.com");
props.put("mail.smtp.port", "587");
props.put("mail.smtp.auth", "true");
props.put("mail.smtp.starttls.enable", "true");

Session session = Session.getInstance(props, new Authenticator() {
    @Override
    protected PasswordAuthentication getPasswordAuthentication() {
        return new PasswordAuthentication("your_email@example.com", "your_password");
    }
});

This code sets up a new email session using the SMTP server at “smtp.example.com” on port 587. It also enables authentication and TLS encryption. You will need to replace “your_email@example.com” and “your_password” with your actual email account credentials.

A Broadcast Receiver is a component in the Android system that allows applications to receive and respond to system-wide broadcast messages. These broadcast messages are system events that are sent by the Android operating system or by other applications. A Broadcast Receiver allows an application to listen for these broadcast messages and take appropriate actions in response to them.

Broadcast Receivers can be used for a wide range of purposes, such as detecting when the device boots up or shuts down, monitoring battery level changes, receiving incoming SMS messages, or responding to custom broadcast messages sent by other applications.

To use a Broadcast Receiver in your application, you need to define a Java class that extends the BroadcastReceiver class and override its onReceive() method. The onReceive() method is called by the system when a broadcast message is received, and it allows you to perform any necessary actions in response to the message.

Here’s an example of how to define a simple Broadcast Receiver that responds to the ACTION_POWER_CONNECTED and ACTION_POWER_DISCONNECTED system broadcast messages:

public class PowerConnectionReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        if (action.equals(Intent.ACTION_POWER_CONNECTED)) {
            Toast.makeText(context, "Power connected", Toast.LENGTH_SHORT).show();
        } else if (action.equals(Intent.ACTION_POWER_DISCONNECTED)) {
            Toast.makeText(context, "Power disconnected", Toast.LENGTH_SHORT).show();
        }
    }
}

In this example, we define a PowerConnectionReceiver class that extends the BroadcastReceiver class. We override the onReceive() method, which takes two parameters: a Context object and an Intent object. The Context object provides access to system services and resources, while the Intent object contains information about the broadcast message.

Inside the onReceive() method, we extract the action string from the Intent object using the getAction() method. We then check if the action is ACTION_POWER_CONNECTED or ACTION_POWER_DISCONNECTED, and display a toast message to the user indicating whether the device has been connected or disconnected from a power source.

Once you have defined your Broadcast Receiver class, you need to register it with the system in order to receive broadcast messages. This can be done either in the manifest file or dynamically at runtime using the registerReceiver() method.

In the manifest file, you can register a Broadcast Receiver by adding a <receiver> element to the manifest file and specifying the receiver class and the broadcast messages it should listen for. Here’s an example of how to register the PowerConnectionReceiver in the manifest file:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.myapp">

    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />

    <application
        ...
        <receiver android:name=".PowerConnectionReceiver">
            <intent-filter>
                <action android:name="android.intent.action.ACTION_POWER_CONNECTED" />
                <action android:name="android.intent.action.ACTION_POWER_DISCONNECTED" />
            </intent-filter>
        </receiver>
    </application>

</manifest>

Here is an example Android application that allows users to store and retrieve student information using SQLite databases:

First, create a layout for the student details form (activity_main.xml):

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Roll No:" />
    <EditText
        android:id="@+id/editTextRollNo"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Name:" />
    <EditText
        android:id="@+id/editTextName"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Branch:" />
    <EditText
        android:id="@+id/editTextBranch"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Marks:" />
    <EditText
        android:id="@+id/editTextMarks"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

    <Button
        android:id="@+id/buttonSave"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Save"/>

    <Button
        android:id="@+id/buttonRetrieve"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Retrieve"/>

    <TextView
        android:id="@+id/textViewResult"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Result:" />
</LinearLayout>

Next, create a database helper class to manage the SQLite database (DatabaseHelper.java):

SQLiteOpenHelper is a class in Android that helps in creating, upgrading and managing an SQLite database. It provides the methods to create and manage the database, as well as to handle database versioning. The class helps in opening and closing the database connection and managing the creation and upgrade of database schemas.

The SQLiteOpenHelper class is an abstract class and provides the following methods:

1. onCreate(): This method is called when the database is created for the first time. It is used to create the database schema.
2. onUpgrade(): This method is called when the database needs to be upgraded to a new version. It is used to update the database schema to the new version.
3. getWritableDatabase(): This method is used to get a writable database connection.
4. getReadableDatabase(): This method is used to get a readable database connection.

When creating an SQLite database in Android, we extend the SQLiteOpenHelper class and override its methods to define our own schema and to handle database versioning. This makes the process of managing an SQLite database much easier and more efficient.

Here is a sample program in Java to get the user’s current location using the Android Location API:

MainActivity.java:

import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;

public class MainActivity extends AppCompatActivity implements LocationListener {

    private static final int PERMISSION_REQUEST_CODE = 1;

    private LocationManager locationManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

        if (ContextCompat.checkSelfPermission(MainActivity.this,
                Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(MainActivity.this,
                    new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, PERMISSION_REQUEST_CODE);
        } else {
            locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,
                    0, 0, this);
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        if (requestCode == PERMISSION_REQUEST_CODE) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,
                        0, 0, this);
            } else {
                Toast.makeText(MainActivity.this, "Permission denied", Toast.LENGTH_SHORT).show();
            }
        }
    }

    @Override
    public void onLocationChanged(Location location) {
        double latitude = location.getLatitude();
        double longitude = location.getLongitude();

        Toast.makeText(MainActivity.this, "Latitude: " + latitude + "\nLongitude: " + longitude,
                Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {

    }

    @Override
    public void onProviderEnabled(String provider) {

    }

    @Override
    public void onProviderDisabled(String provider) {

    }
}

AndroidManifest.xml:

xmlCopy code<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.locationdemo">

    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

    <application
        ...
    </application>

</manifest>

This program first checks if the app has permission to access the device’s location. If permission is not granted, it requests permission from the user. Once permission is granted, the app registers for location updates and listens for changes in the user’s location. When the user’s location changes, the onLocationChanged() method is called, which displays a toast message showing the latitude and longitude of the user’s current location.