Android image fade animation

Question

When I'd ran this code, it did nothing, I'm sure that this event is called when I touch the button. but It doesn't change the opacity of imageView.

View.OnTouchListener mDelayHideTouchListener = new View.OnTouchListener() {
    @Override
    public boolean onTouch(View view, MotionEvent motionEvent) {
        ObjectAnimator fadeAltAnim = ObjectAnimator.ofFloat(R.id.imgTest, "alpha", 0.2f);
        fadeAltAnim.start();
    }
};


findViewById(R.id.dummy_button).setOnTouchListener(mDelayHideTouchListener);

Is there anything wrong with my code?

Answer 1

Try this code, its using ViewPropertyAnimator :

View.OnTouchListener mDelayHideTouchListener = new View.OnTouchListener()   {
    @Override
    public boolean onTouch(View view, MotionEvent motionEvent) {

    view.animate().alpha(0.2f).setDuration(1000);
    }
};

Its always good to set a duration, so the Animation knows how long its supposed to run.

EDIT : You might want to attach it to a MotionEvent if you are using onTouchListener , something like :

View.OnTouchListener mDelayHideTouchListener = new View.OnTouchListener()   {
@Override
public boolean onTouch(View view, MotionEvent motionEvent) {
    if(motionEvent == MotionEvent.ACTION_DOWN)
        view.animate().alpha(0.2f).setDuration(1000);
    }
}; 

EDIT 2 :

If you want to use a Button its best to use an OnClickListener instead of onTouchListener, if you want to attach an Image you have to initiate it(for example in an ImageView) :

Button button = (Button) findViewById(R.id.your_button);
ImageView imageView = (ImageView) findViewById(R.id.imgTest);

button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            imageView.animate().alpha(0.2f).setDuration(1000);

    }
};