在自定义视图中执行路径动画

Question

So I have a custom view where I am trying to perform a drawing animation using the Path methods of moveto() and lineto(). I have an array of Points that I iterate through and call invalidate() at every iteration. In onDraw the path is drawn with drawPath(). Of course onDraw is not called until the loop is done. I believe I need to perform the iterations in a background thread. But at the same time I have read that it is bad practice perform UI changes in background thread. How can I can I redraw in every iteration?

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    canvas.drawPaint(mBackgroundPaint);
    canvas.drawPath(mPath, mStrokePaint);
}

public void drawPoints(){

    mPath = new Path();
    for (Stroke stroke : mStrokes){

        mDuration = stroke.getStrokeDuration();
        mInitialX = stroke.getInitialX();
        mInitialY = stroke.getInitialY();
        mPath.moveTo(mInitialX, mInitialY);
        invalidate();

        mPoints = new ArrayList<Point>();
        mPoints = stroke.getStrokePoints();
        int s = mPoints.size();

        long delayTime = mDuration / (long) s;


        for(Point point : mPoints){
            mX = point.getX();
            mY = point.getY();

            handler.postDelayed(new Runnable() {
                @Override
                public void run() {
                    mPath.lineTo(mX, mY);
                    // want to call invalidate to redraw canvas
                    invalidate(); 
                }
            }, delayTime);


        }

    }








}

Answer 1

I had the same prob, put this into your onDraw:

((Main) context).runOnUiThread(new Runnable() {
    @Override
    public void run() {
        CustomView.this.invalidate();

    }
});