Android ImageView更改Alpha动画

Question

I have four images that need loaded. I want one animation to play, wait 500ms, another one play, wait 500ms, etc.. All the animation does is change the alpha from 255 to 0 and then back to 255. All four imageViews need that animation.

I am having two problems currently.

1.) All of the images play at the same time.
2.) The next time the method is called, the animations don't work.

public void computerLights()
{

    ImageView green = (ImageView)findViewById(R.id.imgViewGreen);
    ImageView red = (ImageView)findViewById(R.id.imgViewRed);
    ImageView blue = (ImageView)findViewById(R.id.imgViewBlue);
    ImageView yellow = (ImageView)findViewById(R.id.imgViewYellow);

    AlphaAnimation transparency = new AlphaAnimation(1, 0);

    transparency.setDuration(500);
    transparency.start();
    green.startAnimation(transparency);
    red.startAnimation(transparency);
    blue.startAnimation(transparency);
    yellow.startAnimation(transparency);
}

Answer 1

I'm not sure if this is the most elegant solution, but you could achieve this pretty easily with a handler that you can send messages to at 500ms intervals.

private int mLights = new ArrayList<ImageView>();
private int mCurrentLightIdx = 0;
private Handler mAnimationHandler = new Handler(){

    @Override
    public void handleMessage(Message msg) {
        super.handleMessage(msg);

        ImageView currentLightIdx = mLights.get(currentLight);

        AlphaAnimation transparency = new AlphaAnimation(1, 0);

        transparency.setDuration(500);
        transparency.start();
        currentLight.startAnimation(transparency);

        currentLightIdx++;
        if(currentLightIdx < mLights.size()){
            this.sendMessageDelayed(new Message(), 500);
    }
};

public void computerLights()
{

    ImageView green = (ImageView)findViewById(R.id.imgViewGreen);
    ImageView red = (ImageView)findViewById(R.id.imgViewRed);
    ImageView blue = (ImageView)findViewById(R.id.imgViewBlue);
    ImageView yellow = (ImageView)findViewById(R.id.imgViewYellow);

    mLights.add(green);
    mLights.add(red);
    mLights.add(blue);
    mLights.add(yellow);

    mAnimationHandler.sendMessage(new Message());
}

After the first message is sent the handler will continue to send messages every 500ms until all of the animations have been started.