图像变化，多点触控

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图像绘制

//绘制图像(位图对象,位图左上角x坐标,位图左上角y坐标)canvas.drawBitmap(mBitmap, 50, 10, null);//第二个参数表示图像上的区域，可以null，null表示全图//第三个参数表示画布上显示图像的区域canvas.drawBitmap(gameBitmap, bitmapRect, showRect, null);

图像变换

需要有Matrix对象来处理

Matrix mMatrix = new Matrix(); //角度0 缩放倍数1 偏移0

set:

设置一个新状态mMatrix.setTranslate(100,200);

post：

基于上一个状态累加新状态mMatrix.postRotate(90);

pre:

前置状态，如需要对图片进行平移（100，200）放大2倍mMatrix.postTranslate(100,200);mMatrix.postScare(2,2);mMatrix.postScare(2,2);mMatrix.preTranslate(100,200);

//基于矩阵绘制图像

canvas.drawBitmap(mBitmap,mMatrix,null);

多点触控

 int action = event.getAction(); switch (action & MotionEvent.ACTION_MASK) {    case MotionEvent.ACTION_DOWN:            //单个触控按下            break;     case MotionEvent.ACTION_POINTER_DOWN:           //多个触控点按下            break;     case MotionEvent.ACTION_MOVE:            按下之后离开之前都会触发             break;     case MotionEvent.ACTION_UP:            单个触控离开            break;     case MotionEvent.ACTION_POINTER_UP:            多个触控离开            break;    }

获取精确的触控点个数

int count = event.getPointerCount(); //获取总个数for(int i = 0 ; i < count ; i++){    int x = event.getX(i);    int y = event.getY(i);}

自定义ViewGroup

onMeasure先measure孩子再measure自身

measureChildren(widthMeasureSpec,heightMeasureSpec);或者int count = getChildCount();    int totalHeight = MeasureSpec.getSize(heightMeasureSpec);    for (int i = 0; i < count; i++) {        View child = getChildAt(i);        measureChild(child, widthMeasureSpec,heightMeasureSpec);       }

measure自身

setMeasuredDimension(widthMeasureSpec, resolveSize(totalHeight, heightMeasureSpec));

onLayout布置孩子的显示

//对孩子进行布局的方法@Overrideprotected void onLayout(boolean changed, int l, int t, int r, int b) {    int width = getMeasuredWidth() / 2;    int count = getChildCount();    int currentHeight = 0;    for (int i = 0; i < count; i++) {        View child = getChildAt(i);        int left = 0;        if (i % 2 != 0) {            left = width;        }        child.layout(left, currentHeight,         left + width, currentHeight + child.getMeasuredHeight());        //累计高度        currentHeight += child.getMeasuredHeight();    }}

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