How to rotate an imageView on seekbar in android

Question

I have made a demo project for image rotation in seekbar progresschange. I have successfully done it on button change but its not working on seekbar change. Here is what I tried:

xml

<ImageView
        android:id="@+id/iv_image"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@drawable/enr" />

    <SeekBar
        android:id="@+id/seekbar"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_marginBottom="20dp"
        android:max="360"
        android:padding="1dp"
        android:progress="0" />

    <Button
        android:id="@+id/bt"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/seekbar"
        android:layout_centerHorizontal="true"
        android:text="Rotate" />

code

public class MainActivity extends Activity implements OnSeekBarChangeListener {

    ImageView iv_image;
    SeekBar seekbar;
    Bitmap source;
    float angle = 0;
    Button buttonClick;
    Bitmap rotatedImage;
    static Matrix matrix;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        init();
        buttonClick = (Button) findViewById(R.id.bt);
        buttonClick.setOnClickListener(new OnClickListener() {
            public void onClick(View view) {
                angle += 90;
                iv_image.buildDrawingCache();
                source = iv_image.getDrawingCache();
                rotatedImage = rotateImage(source, angle);
                iv_image.setImageBitmap(rotatedImage);
            }
        });
    }

    void init() {
        iv_image = (ImageView) findViewById(R.id.iv_image);
        seekbar = (SeekBar) findViewById(R.id.seekbar);
        seekbar.setOnSeekBarChangeListener(this);

    }

    @Override
    public void onProgressChanged(SeekBar seekBar, int progress,
            boolean fromUser) {
        // TODO Auto-generated method stub

        angle = progress;
        iv_image.buildDrawingCache();
        source = iv_image.getDrawingCache();
        rotatedImage = rotateImage(source, angle);
        iv_image.setImageBitmap(null);
        iv_image.setImageBitmap(rotatedImage);
    }

    @Override
    public void onStartTrackingTouch(SeekBar seekBar) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onStopTrackingTouch(SeekBar seekBar) {
        // TODO Auto-generated method stub

    }

    public static Bitmap rotateImage(Bitmap sourceImage, float angle) {
        matrix = new Matrix();
        matrix.postRotate(angle);
        return Bitmap.createBitmap(sourceImage, 0, 0, sourceImage.getWidth(),
                sourceImage.getHeight(), matrix, true);

    }
}

Answer 1

You forgot to attach OnSeekBarChangeListener to your SeekBar:

void init() {
    iv_image = (ImageView) findViewById(R.id.iv_image);
    seekbar = (SeekBar) findViewById(R.id.seekbar);
    seekbar.setOnSeekBarChangeListener(this); // <-----
}