private static final String TAG = "SetPolyToPoly";

private int testPoint = 0;

private int triggerRadius = 180; // 触发半径为180px

private Bitmap mBitmap; // 要绘制的图片

private Matrix mPolyMatrix; // 测试setPolyToPoly用的Matrix

private float[] src = new float[8];

private float[] dst = new float[8];

private Paint pointPaint;

public SetPolyToPoly(Context context) {

this(context, null);

}

public SetPolyToPoly(Context context, AttributeSet attrs) {

this(context, attrs, 0);

}

public SetPolyToPoly(Context context, AttributeSet attrs, int defStyleAttr) {

super(context, attrs, defStyleAttr);

initBitmapAndMatrix();

}

private void initBitmapAndMatrix() {

mBitmap = BitmapFactory.decodeResource(getResources(),

R.drawable.poly_test2);

float[] temp = {0, 0, // 左上

mBitmap.getWidth(), 0, // 右上

mBitmap.getWidth(), mBitmap.getHeight(), // 右下

0, mBitmap.getHeight()}; // 左下

src = temp.clone();

dst = temp.clone();

pointPaint = new Paint();

pointPaint.setAntiAlias(true);

pointPaint.setStrokeWidth(50);

pointPaint.setColor(0xffd19165);

pointPaint.setStrokeCap(Paint.Cap.ROUND);

mPolyMatrix = new Matrix();

mPolyMatrix.setPolyToPoly(src, 0, src, 0, 4);

}

@Override

public boolean onTouchEvent(MotionEvent event) {

switch (event.getAction()){

case MotionEvent.ACTION_MOVE:

float tempX = event.getX();

float tempY = event.getY();

// 根据触控位置改变dst

for (int i=0; i<testPoint*2; i+=2 ) {

if (Math.abs(tempX - dst[i]) <= triggerRadius && Math.abs(tempY - dst[i+1]) <= triggerRadius){

dst[i] = tempX-100;

dst[i+1] = tempY-100;

break; // 防止两个点的位置重合

}

}

resetPolyMatrix(testPoint);

invalidate();

break;

}

return true;

}

public void resetPolyMatrix(int pointCount){

mPolyMatrix.reset();

// 核心要点

mPolyMatrix.setPolyToPoly(src, 0, dst, 0, pointCount);

}

@Override

protected void onDraw(Canvas canvas) {

canvas.translate(100,100);

// 绘制坐标系

CanvasAidUtils.setCoordinateLen(900, 0, 1200, 0);

CanvasAidUtils.drawCoordinateSpace(canvas);

// 根据Matrix绘制一个变换后的图片

canvas.drawBitmap(mBitmap, mPolyMatrix, null);

float[] dst = new float[8];

mPolyMatrix.mapPoints(dst,src);

// 绘制触控点

for (int i=0; i<testPoint*2; i+=2 ) {

canvas.drawPoint(dst[i], dst[i+1],pointPaint);

}

}

public void setTestPoint(int testPoint) {

this.testPoint = testPoint > 4 || testPoint < 0 ? 4 : testPoint;

dst = src.clone();

resetPolyMatrix(this.testPoint);

invalidate();

}