我目前正在对网页视图中的一张图片(下面是大象)实现绘图功能。我在绘制方面没有问题,但缩放功能却会对绘图产生一些奇怪的影响(如下面的第二张图所示)。当我放大时,绘图不会跟着缩放而是会移动位置。同时,在缩放后进行绘图也不起作用。我的代码如下:
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.save();
canvas.drawBitmap(canvasBitmap, 0, 0, canvasPaint);
canvas.drawPath(drawPath, drawPaint);
canvas.scale(mScaleFactor, mScaleFactor);
canvas.restore();
clipBounds = canvas.getClipBounds();
}
@Override
public boolean onTouchEvent(MotionEvent event) {
mScaleDetector.onTouchEvent(event);
float touchX = event.getX() / mScaleFactor + clipBounds.left;
float touchY = event.getY() / mScaleFactor + clipBounds.top;
if (Deal.on)
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
drawPath.moveTo(touchX, touchY);
break;
case MotionEvent.ACTION_MOVE:
drawPath.lineTo(touchX, touchY);
break;
case MotionEvent.ACTION_UP:
drawCanvas.drawPath(drawPath, drawPaint);
drawPath.reset();
break;
default:
return false;
}
else {
super.onTouchEvent(event);
}
invalidate();
return true;
}
public class ScaleGestureListener extends 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;
}
}
编辑: 我使用GestureDetector的比例因子使画布重新绘制,实现了缩放效果。此外,我有一个开关,可以从绘图切换到缩放/WebView控件。遇到的问题是WebView上的双击不会触发onScale手势,这意味着画布不会重新绘制,在缩放时会产生偏移。
我需要实现一个功能,检测双击缩放对比例因子的影响程度。如果有人能提出解决方案,请告诉我。以下是更新代码:
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
clipBounds = canvas.getClipBounds();
canvas.save();
drawPaint.setStrokeWidth(8/mScaleFactor);
canvas.scale(mScaleFactor, mScaleFactor, 0, 0);
canvas.drawPath(drawPath, drawPaint);
canvas.drawBitmap(canvasBitmap, 0, 0, canvasPaint);
canvas.restore();
}
@Override
public boolean onTouchEvent(MotionEvent event) {
pointerCount = event.getPointerCount();
mScaleDetector.onTouchEvent(event);
float touchX = (event.getX() + clipBounds.left) / mScaleFactor;
float touchY = (event.getY() + clipBounds.top) / mScaleFactor;
if (Deal.on){
if (event.getPointerCount() > 1){
return false;
}
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
drawPath.moveTo(touchX, touchY);
break;
case MotionEvent.ACTION_MOVE:
drawPath.lineTo(touchX, touchY);
break;
case MotionEvent.ACTION_UP:
drawCanvas.drawPath(drawPath, drawPaint);
drawPath.reset();
break;
default:
return false;
}
}
else {
super.onTouchEvent(event);
}
invalidate();
return true;
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
// Try for a width based on our minimum
int minw = getPaddingLeft() + getPaddingRight() + getSuggestedMinimumWidth();
int w = resolveSizeAndState(minw, widthMeasureSpec, 1);
//int minh = MeasureSpec.getSize(w) - (int)mTextWidth + getPaddingBottom() + getPaddingTop();
int h = resolveSizeAndState(MeasureSpec.getSize(w), heightMeasureSpec, 0);
setMeasuredDimension(w, h);
}
public class ScaleGestureListener extends SimpleOnScaleGestureListener {
@Override
public boolean onScale(ScaleGestureDetector detector) {
// Don't let the object get too small or too large.
if(Deal.on == false) {
mScaleFactor *= detector.getScaleFactor();
mScaleFactor = Math.max(1f, Math.min(mScaleFactor, 20.0f));
}
invalidate();
return true;
}
}