android 画布放大缩小,在Android画布上应用缩放效果后,缩放比例位置错误
首先这是一个跟随问题,原来在这里提出,Pan,Zoom and Scale a custom View for Canvas drawing in Android
应用缩放/缩放手势后,我发现画布绘图坐标仍然指向旧位置(在应用缩放之前),而不是绘制完全相同的触摸坐标.基本上,在缩放或拖动画布后,无法获得正确的画布坐标.
放大前,
缩小之后,触摸点正在绘制上一个位置.我想让它画在当前的触摸位置,
示例代码,
public class DrawingView extends View {
private void setupDrawing() {
mScaleDetector = new ScaleGestureDetector(getContext(),new ScaleListener());
mgd = new MoveGestureDetector(ctx,mgl);
sgd = new ScaleGestureDetector(ctx,sgl);
rgd = new RotateGestureDetector(ctx,rgl);
}
class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
@Override
public boolean onScale(ScaleGestureDetector detector) {
mScaleFactor *= detector.getScaleFactor();
// Don't let the object get too small or too large.
mScaleFactor = Math.max(0.1f,Math.min(mScaleFactor,5.0f));
invalidate();
return true;
}
}
MoveGestureDetector.SimpleOnMoveGestureListener mgl = new MoveGestureDetector.SimpleOnMoveGestureListener() {
@Override
public boolean onMove(MoveGestureDetector detector) {
PointF delta = detector.getFocusDelta();
matrix.postTranslate(delta.x,delta.y);
invalidate();
return true;
}
};
ScaleGestureDetector.SimpleOnScaleGestureListener sgl = new ScaleGestureDetector.SimpleOnScaleGestureListener() {
@Override
public boolean onScale(ScaleGestureDetector detector) {
float scale = detector.getScaleFactor();
matrix.postScale(scale,scale,detector.getFocusX(),detector.getFocusY());
invalidate();
return true;
}
};
RotateGestureDetector.SimpleOnRotateGestureListener rgl = new RotateGestureDetector.SimpleOnRotateGestureListener() {
@Override
public boolean onRotate(RotateGestureDetector detector) {
matrix.postRotate(-detector.getRotationDegreesDelta(),detector.getFocusY());
invalidate();
return true;
}
};
@Override
protected void onSizeChanged(int w,int h,int oldw,int oldh) {
//view given size
super.onSizeChanged(w,h,oldw,oldh);
canvasBitmap = Bitmap.createBitmap(w,Bitmap.Config.ARGB_8888);
drawCanvas = new Canvas(canvasBitmap);
}
private void touch_start(float x,float y) {
undonePaths.clear();
drawPath.reset();
drawPath.moveTo(x,y);
mX = x;
mY = y;
}
private void touch_move(float x,float y,float x2,float y2) {
float dx = Math.abs(x - mX);
float dy = Math.abs(y - mY);
if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
/* QUad to curves using a quadratic line (basically an ellipse of some sort).
LineTo is a straight line. QuadTo will smooth out jaggedies where they turn.
*/
drawPath.quadTo(mX,mY,(x + mX) / 2,(y + mY) / 2);
mX = x;
mY = y;
}
}
private void touch_up() {
drawPath.lineTo(mX,mY);
// commit the path to our offscreen
drawCanvas.drawPath(drawPath,drawPaint);
// kill this so we don't double draw
paths.add(drawPath);
drawPath = new Path();
drawPath.reset();
invalidate();
}
@Override
public boolean onTouchEvent(MotionEvent event) {
if (isZoomable) {
mgd.onTouchEvent(event);
sgd.onTouchEvent(event);
rgd.onTouchEvent(event);
}
if (!isTouchable) {
return super.onTouchEvent(event);
} else {
//detect user touch
float x = event.getX();
float y = event.getY();
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
if (!isZoomable) {
touch_start(x,y);
}
invalidate();
break;
case MotionEvent.ACTION_MOVE:
if (!isZoomable) {
//mPositions.add(new Vector2(x - mBitmapBrushDimensions.x / 2,y - mBitmapBrushDimensions.y / 2));
if (isCustomBrush && mBitmapBrushDimensions != null) {
mPositions = new Vector2(x - mBitmapBrushDimensions.x / 2,y - mBitmapBrushDimensions.y / 2);
touch_move(x,y,x - mBitmapBrushDimensions.x / 2,y - mBitmapBrushDimensions.y / 2);
} else {
touch_move(x,0);
}
}
invalidate();
break;
case MotionEvent.ACTION_UP:
if (!isZoomable) {
touch_up();
}
invalidate();
break;
}
mScaleDetector.onTouchEvent(event);
return true;
}
}
@Override
protected void onDraw(Canvas canvas) {
canvas.save();
canvas.setMatrix(matrix);
for (Path p : paths) {
canvas.drawPath(p,drawPaint);
drawPaint.setColor(selectedColor);
drawPaint.setStrokeWidth(brushSize);
canvas.drawPath(drawPath,drawPaint);
}
canvas.restore();
}
}
PS：MoveGestureDetector(),ScaleGestureDetector()& RotateGestureDetector()是从android-gesture-detectors继承的自定义类