具体代码在最下方给出

点击 CHECK 后 就是图二的效果
但是不太明白他这个绘制过程 所以用Log.e调试 还是没看懂
点击包含这个View的activity时 log打印为

不明白为什么是两次onDraw的打印

然后点击CHECK Log.e打印为(只发了一部分截图)

不明白为什么 又打印了两次onDraw
然后进行sendEmptyMessageDelayed的递归操作(不知道有没有说错)
在invalidate前后分别设置log
然后每次在handleMessage中判断的时候 为什么 又要打印onDraw(还是两次)

E/AAA: onDraw E/AAA: onDraw E/AAA: invalidate 1 + 0 E/AAA: invalidate 1 + 1 E/AAA: Count=1

public class CheckView extends View {      private static final int ANIM_NULL = 0;         //动画状态-没有     private static final int ANIM_CHECK = 1;        //动画状态-开启     private static final int ANIM_UNCHECK = 2;      //动画状态-结束      private Context mContext;           // 上下文     private int mWidth, mHeight;        // 宽高     private Handler mHandler;           // handler      private Paint mPaint;     private Bitmap okBitmap;      private int animCurrentPage = -1;       // 当前页码     private int animMaxPage = 13;           // 总页数     private int animDuration = 500;         // 动画时长     private int animState = ANIM_NULL;      // 动画状态      private boolean isCheck = false;        // 是否只选中状态      public CheckView(Context context, AttributeSet attrs) {         super(context, attrs);         Log.e("AAA","构造方法CheckView + 0");         init(context);         Log.e("AAA","构造方法CheckView + 1");     }      /**      * 初始化      * @param context      */     private void init(Context context) {         mContext = context;          mPaint = new Paint();         mPaint.setColor(0xffFF5317);//设置画笔颜色         mPaint.setStyle(Paint.Style.FILL);//设置画笔风格         mPaint.setAntiAlias(true);//抗锯齿          okBitmap = BitmapFactory.decodeResource(mContext.getResources(), R.drawable.checkes);//从资源文件获取Bitmap          mHandler = new Handler() {             @Override             public void handleMessage(Message msg) {                 super.handleMessage(msg);                 if (animCurrentPage < animMaxPage && animCurrentPage >= 0) {// 点击之前-1 <13 && -1>=0 点击后 0 < 13 && 0 >=0                     Log.e("AAA","invalidate 1 + 0");                     invalidate();//重绘 ==> 调用onDraw方法，重绘View中变化的部分                     Log.e("AAA","invalidate 1 + 1");                      if (animState == ANIM_NULL)// 动画状态==没有                         return;                     if (animState == ANIM_CHECK) {//动画状态==开启                          animCurrentPage++;//当前页数++                     } else if (animState == ANIM_UNCHECK) {//动画状态==关闭                         animCurrentPage--;//当前页数--                     }                     this.sendEmptyMessageDelayed(0, animDuration / animMaxPage);                     Log.e("AAA", "Count=" + animCurrentPage);                 } else {                     if (isCheck) { //isCheck==false                         animCurrentPage = animMaxPage - 1;// -1 = 13-1                     } else {                         animCurrentPage = -1;                     }                     Log.e("AAA","invalidate 2 + 0");                     invalidate();//重绘    ondraw中 使用invalidate   非UI线程中 使用 postInvalidate                     Log.e("AAA","invalidate 2 + 1");                     animState = ANIM_NULL;// 动画状态==没有                 }             }         };     }       /**      * View大小确定      * @param w      * @param h      * @param oldw      * @param oldh      */     @Override     protected void onSizeChanged(int w, int h, int oldw, int oldh) {         super.onSizeChanged(w, h, oldw, oldh);         mWidth = w;         mHeight = h;         Log.e("AAA","onSizeChanged");     }      /**      * 绘制内容      * @param canvas      */     @Override     protected void onDraw(Canvas canvas) {         super.onDraw(canvas);         Log.e("AAA","onDraw");         // 移动坐标系到画布中央         canvas.translate(mWidth / 2, mHeight / 2);          // 绘制背景圆形         canvas.drawCircle(0, 0, 240, mPaint);          // 得出图像边长         int sideLength = okBitmap.getHeight();          // 得到图像选区 和 实际绘制位置         Rect src = new Rect(sideLength * animCurrentPage, 0, sideLength * (animCurrentPage + 1), sideLength);         Rect dst = new Rect(-200, -200, 200, 200);          // 绘制         canvas.drawBitmap(okBitmap, src, dst, null);     }       /**      * 选择      */     public void check() {         if (animState != ANIM_NULL || isCheck)             return;         animState = ANIM_CHECK;         animCurrentPage = 0;         Log.e("AAA","check + 1");         mHandler.sendEmptyMessageDelayed(0, animDuration / animMaxPage);  // (0,500/13)         isCheck = true;         Log.e("AAA","check + 2");     }      /**      * 取消选择      */     public void unCheck() {         if (animState != ANIM_NULL || (!isCheck))             return;         animState = ANIM_UNCHECK;         animCurrentPage = animMaxPage - 1;         mHandler.sendEmptyMessageDelayed(0, animDuration / animMaxPage);         isCheck = false;     }      /**      * 设置动画时长      * @param animDuration      */     public void setAnimDuration(int animDuration) {         if (animDuration <= 0)             return;         this.animDuration = animDuration;     }      /**      * 设置背景圆形颜色      * @param color      */     public void setBackgroundColor(int color){         mPaint.setColor(color);     } }