Android动画实现（一）

• 自定义View实现动画

• 原理：使用View的postDelayed方法实现延迟重绘操作。在重绘操作中每次绘制不同的图形就能实现动画。

• 代码如下：

public class CircleAnim extends View {    private Paint mPaint;    private static final int sColor = 0x33668843;    private int mRadius;    private int mMaxRadius;    private int mY;    public CircleAnim(Context context) {        super(context);        initView();    }    public CircleAnim(Context context, @Nullable AttributeSet attrs) {        super(context, attrs);        initView();    }    public CircleAnim(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        initView();    }    public void initView(){        Log.e("zxx", "initView");        mPaint = new Paint();        mPaint.setColor(sColor);        WindowManager wm = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);        mMaxRadius = wm.getDefaultDisplay().getWidth();        mY = wm.getDefaultDisplay().getHeight();    }    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        Log.e("zxx","onDraw");        //绘制不同大小圆形        canvas.drawCircle(mMaxRadius, mY / 2, mRadius, mPaint);        if (mRadius < mMaxRadius * 1.3){            mRadius = mRadius + 100;            postDelayed(new Runnable() {                @Override                public void run() {                     //重绘                    invalidate();                }            }, 100);        }else{            mRadius = 0;            postDelayed(new Runnable() {                @Override                public void run() {                    invalidate();            },100);        }    }}

• 动画效果如下