Animation in andriod

n this Post i will tell you about the simple blinking animation using apha property of android.
First create a class as follows by extending the Animation class:

BlinkAnimation,java

public class BlinkAnimation extends Animation {
    private int totalBlinks;
    private boolean finishOff;
  
    public BlinkAnimation(int totalBlinks, boolean finishOff) {
        this.totalBlinks = totalBlinks;
        this.finishOff = finishOff;
    }

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {
        float period = interpolatedTime * totalBlinks * 3.14f + (finishOff ? 3.14f / 2 : 0);
        t.setAlpha(Math.abs(FloatMath.cos(period)));
    }

    @Override
    public boolean willChangeBounds() {
        return false;
    }

    @Override
    public boolean willChangeTransformationMatrix() {
        return false;
    }
}

Next step is to create a avtivity to instaniate the animation as follows:

TestActivity.java


public class TestActivity extends Activity implements OnClickListener, AnimationListener {
    private ImageView image;
  
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
      
        image = (ImageView) findViewById(R.id.image);
        ((Button) findViewById(R.id.button)).setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        if (view.getId() == R.id.button) {
            Animation animation;
            if (image.getVisibility() == View.VISIBLE) {
                animation = new BlinkAnimation(3, true);
                animation.setInterpolator(new DecelerateInterpolator());
            } else {
                animation = new BlinkAnimation(3, false);
                animation.setInterpolator(new AccelerateInterpolator());
            }
            animation.setDuration(1000L);
            animation.setAnimationListener(this);
          
            image.startAnimation(animation);
        }
    }

    @Override
    public void onAnimationEnd(Animation animation) {
        image.setVisibility(image.getVisibility() == View.VISIBLE ?
                View.INVISIBLE : View.VISIBLE);
    }

    @Override
    public void onAnimationRepeat(Animation animation) {}

    @Override
    public void onAnimationStart(Animation animation) {}
}


and your XML file would look like this a follows:

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent">
  <ImageView
    android:id="@+id/image"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:layout_marginTop="30dip"
    android:src="@drawable/icon" />
  <Button
    android:id="@+id/button"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:layout_marginTop="30dip"
    android:text="Please click me" />
</LinearLayout>