androidUI异步消息

 private Handler handler = new Handler(){
        public void handleMessage(android.os.Message msg) {
            switch (msg.what) {
                case 0:
                    if (isStart) {

//                        if(i>2)
//                        {
//                            isStart = false;
//                            return;
//                        }
                        i += 1;
                        double y = (Math.PI * i) / 180;
                        if (i <= 360) {
                            if( i<= 90){

                                px =  (float)radio + radio * (float) Math.sin(y);
                                py =  (float)radio - radio * (float) Math.cos(y);

                                px2 = (float)radio - radio * (float) Math.sin(y);
                                py2 = (float)radio + radio * (float) Math.cos(y);
                            }
                            else {

                                px =  radio + radio * (float) Math.sin(y);
                                py =  radio - radio * (float) Math.cos(y);

                                px2 = radio - radio * (float) Math.sin(y);
                                py2 = radio + radio * (float) Math.cos(y);
                            }
//                            px =  radio + radio * (float) Math.sin(y);
//                            py =  radio - radio * (float) Math.cos(y);
//
//
//
//                            px2 = radio - radio * (float) Math.sin(y);
//                            py2 = radio + radio * (float) Math.cos(y);

                            if (i == 360) {
                                i = 0;
                            }

                        }

                        invalidate();
                       // handler.sendEmptyMessageDelayed(0,10);
                    }
                    break;
                default:
                    break;
            }
        };
    };

 /**
     * 比onDraw先执行
     * <p>
     * 一个MeasureSpec封装了父布局传递给子布局的布局要求，每个MeasureSpec代表了一组宽度和高度的要求。
     * 一个MeasureSpec由大小和模式组成
     * 它有三种模式：UNSPECIFIED(未指定),父元素部队自元素施加任何束缚，子元素可以得到任意想要的大小;
     * EXACTLY(完全)，父元素决定自元素的确切大小，子元素将被限定在给定的边界里而忽略它本身大小；
     * AT_MOST(至多)，子元素至多达到指定大小的值。
     * <p>
     * 它常用的三个函数：
     * 1.static int getMode(int measureSpec):根据提供的测量值(格式)提取模式(上述三个模式之一)
     * 2.static int getSize(int measureSpec):根据提供的测量值(格式)提取大小值(这个大小也就是我们通常所说的大小)
     * 3.static int makeMeasureSpec(int size,int mode):根据提供的大小值和模式创建一个测量值(格式)
     */
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        final int minimumWidth = getSuggestedMinimumWidth();
        final int minimumHeight = getSuggestedMinimumHeight();

        int width = measureWidth(minimumWidth, widthMeasureSpec);
        int height = measureHeight(minimumHeight, heightMeasureSpec);

        radio = getMeasuredWidth()/ 2;

        px = Math.min(width,height) / 2;
        py = 0;
        px2 =  Math.min(width,height) / 2;
        py2 = Math.min(width,height) / 2;
        setMeasuredDimension(width, height);
    }

    private int measureWidth(int defaultWidth, int measureSpec) {

        int specMode = MeasureSpec.getMode(measureSpec);
        int specSize = MeasureSpec.getSize(measureSpec);

        switch (specMode) {
            case MeasureSpec.AT_MOST:
                defaultWidth =  getPaddingLeft() + getPaddingRight();
                break;
            case MeasureSpec.EXACTLY:

                defaultWidth = specSize;
                break;
            case MeasureSpec.UNSPECIFIED:

                defaultWidth = Math.max(defaultWidth, specSize);
        }
        return defaultWidth;
    }

    private int measureHeight(int defaultHeight, int measureSpec) {

        int specMode = MeasureSpec.getMode(measureSpec);
        int specSize = MeasureSpec.getSize(measureSpec);

        switch (specMode) {
            case MeasureSpec.AT_MOST:
                defaultHeight = getPaddingTop() + getPaddingBottom();

                break;
            case MeasureSpec.EXACTLY:
                defaultHeight = specSize;

                break;
            case MeasureSpec.UNSPECIFIED:
                defaultHeight = Math.max(defaultHeight, specSize);

//        1.基准点是baseline
//        2.ascent：是baseline之上至字符最高处的距离
//        3.descent：是baseline之下至字符最低处的距离
//        4.leading：是上一行字符的descent到下一行的ascent之间的距离,也就是相邻行间的空白距离
//        5.top：是指的是最高字符到baseline的值,即ascent的最大值
//        6.bottom：是指最低字符到baseline的值,即descent的最大值

                break;
        }
        return defaultHeight;

    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        //mPaint.setColor(Color.WHITE);
        // 绘制一个填充色为蓝色的矩形
        //canvas.drawRect(0, 0, getWidth(), getHeight(), mPaint);
       // canvas.drawCircle( getWidth()/2, getHeight()/2,radio, mPaint);
//        mPaint.setColor(Color.YELLOW);
//        mPaint.setTextSize(50);
//        String text = String.valueOf(mCount);
//        // 获取文字的宽和高
//        mPaint.getTextBounds(text, 0, text.length(), mBounds);
//        float textWidth = mBounds.width();
//        float textHeight = mBounds.height();
//
//        // 绘制字符串
//        canvas.drawText(text, getWidth() / 2 - textWidth / 2, getHeight() / 2
//                + textHeight / 2, mPaint);

//        System.out.println("px1  = "+ px1 + "  py1 =" +py1);
//
//        Paint paint = new Paint();
//        paint.setStyle(Paint.Style.STROKE);
//        paint.setColor(Color.BLACK);
//        canvas.drawCircle(px1, py1, radio, paint);

        Paint paint2 = new Paint();
        paint2.setStyle(Paint.Style.FILL);
        paint2.setColor(Color.GREEN);
        //px+150 py+150
        canvas.drawCircle(px , py ,4, paint2);
//
        Paint paint3 = new Paint();
        paint3.setStyle(Paint.Style.FILL);
        paint3.setColor(Color.RED);
        if(isInit){
            //px+150 py+150
            canvas.drawCircle(px2 , py2   ,4, paint3);
            isInit = false;
            System.out.println(" py2 =   "+py2);
            return;
        }
        //px+150 py+150
        //canvas.drawCircle( px2+200 , py2 + 300 ,10, paint3);
        // canvas.drawCircle( px2+200 , py2 + 300 ,10, paint3);
        canvas.drawCircle(px2 ,py2   ,4, paint3);

        handler.sendEmptyMessageDelayed(0, 100);

        isStart = true;
    }