使用属性动画实现一个简单的加载动画

安卓的动画各种各样，新加的属性动画可以很好的实现动画效果。
如何实现一个简单的加载动画呢？
Frist of all, Because of you are custom view, you need extends the View,and implement there important method,such as onMeasure()、onDraw()、onLayout()..
Then, you need some paints to draw,so that…

public FourCirlceRotate(Context context, AttributeSet attrs) {        super(context, attrs);        paint1 = new Paint();        paint2 = new Paint();        paint3 = new Paint();        paint4 = new Paint();        paint5 = new Paint();        paint1.setColor(Color.parseColor("#ff0099cc"));        paint2.setColor(Color.parseColor("#ff669900"));        paint3.setColor(Color.parseColor("#ffcc0000"));        paint4.setColor(Color.parseColor("#ffaa66cc"));        paint5.setColor(Color.parseColor("#ffffbb33"));    }

and you should get the value animator, just like this!

private ValueAnimator getValueAnimator() {        ValueAnimator valueAnimator = ValueAnimator.ofFloat(0f, 8f);        valueAnimator.setDuration(4000);        valueAnimator.setInterpolator(new LinearInterpolator());        valueAnimator.start();        return valueAnimator;    }

and you should fresh your screen when your application had runing.

    public void startAnimation() {        if (valueAnimator == null) {            valueAnimator = getValueAnimator();        } else {            valueAnimator.start();        }        R = getHeight() / 6;        postDelayed(new Runnable() {            @Override            public void run() {                if (!stop) {                    startAnimation();                    invalidate();                }            }        }, valueAnimator.getDuration());        init = true;    }

then,The best part of it is you need set some coding on onDraw() method to make it happen.

 @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);//        Log.i(TAG, "onDraw " + where);        if (!init) {            startAnimation();        }        Log.e(">>>>>>>>>>>>>>>>>","show:"+show+"where:"+where);        //显示固定的圆，逐个出现        if (show <= 4) {            canvas.drawCircle(R, R, R, paint2);        }        if (show <= 3) {            canvas.drawCircle(getWidth() - R, R, R, paint3);        }        if (show <= 2) {            canvas.drawCircle(getWidth() - R, getHeight() - R, R, paint4);        }        if (show <= 1) {            canvas.drawCircle(R, getHeight() - R, R, paint5);        }        //逐个消失        if (show > 4) {            if (show <= 4) {                canvas.drawCircle(R, R, R, paint2);            }            if (show <= 5) {                canvas.drawCircle(getWidth() - R, R, R, paint3);            }            if (show <= 6) {                canvas.drawCircle(getWidth() - R, getHeight() - R, R, paint4);            }            if (show <= 7) {                canvas.drawCircle(R, getHeight() - R, R, paint5);            }        }        //移动        if (where < 1 && where > 0) {            canvas.drawCircle(R + (getWidth() - 2 * R) * where, R, R, paint1);            show = 4;        }        if (where < 2 && where > 1) {            canvas.drawCircle(getHeight() - R, R + (getHeight() - 2 * R) * (where - 1), R, paint1);            show = 3;        }        if (where < 3 && where > 2) {            canvas.drawCircle(getWidth() - R - (getWidth() - 2 * R) * (where - 2), getHeight() - R, R, paint1);            show = 2;        }        if (where < 4 && where > 3) {            canvas.drawCircle(R, getHeight() - R - (getHeight() - 2 * R) * (where - 3), R, paint1);            show = 1;        }        if (where > 4 && where < 5) {            canvas.drawCircle(R + (getWidth() - 2 * R) * (where - 4), R, R, paint1);            show = 5;        }        if (where > 5 && where < 6) {            canvas.drawCircle(getHeight() - R, R + (getHeight() - 2 * R) * (where - 5), R, paint1);            show = 6;        }        if (where > 6 && where < 7) {            canvas.drawCircle(getWidth() - R - (getWidth() - 2 * R) * (where - 6), getHeight() - R, R, paint1);            show = 7;        }        if (where > 7 && where < 8) {            canvas.drawCircle(R, getHeight() - R - (getHeight() - 2 * R) * (where - 7), R, paint1);            show = 8;        }        if (isStart) {            where = (float) valueAnimator.getAnimatedValue();        }        if (valueAnimator.isRunning()) {            isStart = true;          invalidate();        }    }