Basic Programs for Android

The following article provides some Basic Programs for Android.

Hello World Program. The following program creates an activity that displays “Hello World” on the screen.

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        TextView textView = findViewById(R.id.text_view);
        textView.setText("Hello, World!");
    }
}

Button Click Program. The following program displays a Button. When a user clicks on it, it displays a short message using the makeText() method of the Toast class.

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button = findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(MainActivity.this, "Button clicked", Toast.LENGTH_SHORT).show();
            }
        });
    }
}

ListView Program. The following program displays a ListView. Also, it displays the array elements in that ListView.

public class MainActivity extends AppCompatActivity {
    private ListView listView;
    private String[] items = {"Apple", "Banana", "Orange", "Grape"};

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listView = findViewById(R.id.list_view);
        ArrayAdapter<String> adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, items);
        listView.setAdapter(adapter);
    }
}

WebView Program. The following program demonstrates a WebView control. Also, it opens the given URL in the WebView.

public class MainActivity extends AppCompatActivity {
    private WebView webView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        webView = findViewById(R.id.web_view);
        webView.loadUrl("https://www.google.com");
    }
}

Camera Program. The following program allows the Camera to take pictures and displays the pictures in an ImageView control.

public class MainActivity extends AppCompatActivity {
    private static final int REQUEST_IMAGE_CAPTURE = 1;
    private ImageView imageView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        imageView = findViewById(R.id.image_view);
        Button button = findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                dispatchTakePictureIntent();
            }
        });
    }

    private void dispatchTakePictureIntent() {
        Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
        if (takePictureIntent.resolveActivity(getPackageManager()) != null) {
            startActivityForResult(takePictureIntent, REQUEST_IMAGE_CAPTURE);
        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == REQUEST_IMAGE_CAPTURE && resultCode == RESULT_OK) {
            Bundle extras = data.getExtras();
            Bitmap imageBitmap = (Bitmap) extras.get("data");
            imageView.setImageBitmap(imageBitmap);
        }
    }
}

Further Reading

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Further Reading

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