及时在画布上移动点，在Android中加快速度（java）

Question

let's say I have a canvas with a point at coords [0,0] (in pixels probably) and I want to move the point to [0,200] in a specific timeframe (5s eg) at a constant/accelerating speed. Is there a function for that?

I can't just Point.set(X,Y). I know I probably have to use a loop but I have never worked with a loop that can run every let's say 0.05s and redraw it.

Is there some delay function for the loop? I can easily calculated the coords where the point will be at time T but I have no idea how to prevent it finishing in an instant.

I basically want to create an animation in canvas but pretty customizable considering not constant speed etc.

Thank you for your responses. If something is not clear, I'll gladly explain it.

Answer 1

One possible solution is to have many images and set them in time for build the animation. There is an example of one of my apps. You should use a Handler to set the image and one thread to control the animation. You can see the source code here: https://github.com/andresuarezz26/ocenglow/tree/master/AndroidApp/animationExample

/**
 * Exceution thread that control the animation
 * @author usuario
 *
 */
private class TickClass extends TimerTask {
    @Override
    public void run() {

        // TODO Auto-generated method stub
        handler.sendEmptyMessage(_index);
        if(isLeft){
            if (_index <= 30) {
                _index++;
                iteraciones++;

            } else {
                _index = 0;
                handler.sendEmptyMessage(_index);
                this.cancel();
                isMoving=false;

            }
        }else{
            if (_index <= 63) {
                _index++;
                iteraciones++;

            } else {
                _index = 32;
                handler.sendEmptyMessage(_index);
                this.cancel();
                isMoving=false;

            }

        }
    }
}

/**
 * This class handdle the animation´s images
 * @author usuario
 *
 */
private class MyHandler extends Handler {
    @Override
    public void handleMessage(Message msg) {
        // TODO Auto-generated method stub
        super.handleMessage(msg);

        try {
            Bitmap bmp = BitmapFactory.decodeStream(MainActivity.this
                    .getAssets().open("jelly"+ _index + ".png"));
            _imagView.setImageBitmap(bmp);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            Log.v("Exception in Handler ", e.getMessage());
        }
    }
}

Answer 2

You can do this with a Canvas but I would recommend using a SurfaceView .

With a Canvas you could use a Handler or a TimerTask to cause the view to Invalidate and redraw but that just seems messy.

With a SurfaceView you actually control the drawing thread. So if you want to draw every 1 second or every 1/8th of a second you can easily do so. The setup for a SurfaceView takes a few extra moments but for what you want to do i would suggest using it.

Some tutorials

Tutorial 1

Tutorial 2