我在Android上制作了一个绘图应用程序，它能够将图像加载到画布上并在其上绘制，但我不知道如何仅删除绘制路径，如果我是擦除drawpath它也会删除我放在画布上的图像，有没有办法只删除drawpath？
这是我的代码：
public class DrawingView extends View {
private Path drawPath;
private Paint drawPaint, canvasPaint;
private Canvas drawCanvas;
private Bitmap canvasBitmap,image=null;
private Rect clipBounds;
private Rect destImageRect;
private int paintColor = 0xFF660000;
private float mScaleFactor = 1.f,pivotPointX = 0.f,pivotPointY=0.f,offSetX=1.00f,offSetY=1.00f;
private float brushSize, lastBrushSize;
private boolean isGesture = false;
private boolean brushScalling = true,erase = false;
private ScaleGestureDetector SGD;
private GestureDetector GD;
public DrawingView(Context context, AttributeSet attrs){
super(context, attrs);
SGD = new ScaleGestureDetector(context,new ScaleGestureListener());
GD = new GestureDetector(context, new GestureListener());
setupDrawing();
}
protected void setupDrawing(){
drawPath = new Path();
drawPaint = new Paint();
brushSize = getResources().getInteger(R.integer.medium_size);
lastBrushSize = brushSize;
drawPaint.setColor(paintColor);
drawPaint.setAntiAlias(true);
drawPaint.setStrokeWidth(brushSize);
drawPaint.setStyle(Paint.Style.STROKE);
drawPaint.setStrokeJoin(Paint.Join.ROUND);
drawPaint.setStrokeCap(Paint.Cap.ROUND);
canvasPaint = new Paint(Paint.DITHER_FLAG);
destImageRect = new Rect(0,0,getWidth(),getHeight());
}
public void setBrushSize(float newSize){
float pixelAmount = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, newSize, getResources().getDisplayMetrics());
brushSize = pixelAmount;
drawPaint.setStrokeWidth(brushSize);
}
public void setLastBrushSize(float lastSize){
lastBrushSize = lastSize;
}
public float getLastBrushSize(){
return lastBrushSize;
}
public void setErase(boolean isErase){
erase = isErase;
if(erase) {
drawPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
}else{
drawPaint.setXfermode(null);
}
}
public void changeBackground(Bitmap bitmap){
//store image to local var
image = bitmap;
//get offset of resolution between image and canvas
offSetY = (float)image.getHeight()/getHeight();
offSetX = (float)image.getWidth()/getWidth();
//creating new canvas
canvasBitmap = image.copy(Bitmap.Config.ARGB_8888, true);
drawCanvas = new Canvas(canvasBitmap);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
//when size changed, store the new size
destImageRect = new Rect(0,0,w,h);
//check whether to use image as background or not
if(image == null) {
canvasBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
drawCanvas = new Canvas(canvasBitmap);
}else{
canvasBitmap = image.copy(Bitmap.Config.ARGB_8888, true);
drawCanvas = new Canvas(canvasBitmap);
}
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.save();
canvas.scale(mScaleFactor, mScaleFactor, pivotPointX, pivotPointY);
clipBounds = canvas.getClipBounds();
canvas.drawPath(drawPath, drawPaint);
canvas.drawBitmap(canvasBitmap,null, destImageRect,canvasPaint);
canvas.restore();
}
public class GestureListener extends GestureDetector.SimpleOnGestureListener{
@Override
public boolean onDoubleTap(MotionEvent e) {
//zoom out with zoom point of (0,0) top,left
mScaleFactor=1.f;
pivotPointX=pivotPointY=0;
return super.onDoubleTap(e);
}
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
//need two finger to be on the screen to be register as scrolling
if(e1.getPointerCount()==2 || e2.getPointerCount()==2){
pivotPointX += distanceX / mScaleFactor;
pivotPointY += distanceY / mScaleFactor;
}
return super.onScroll(e1, e2, distanceX, distanceY);
}
}
public class ScaleGestureListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
@Override
public boolean onScaleBegin(ScaleGestureDetector detector) {
//get the zoom point or center point of the zoom
pivotPointX = (detector.getFocusX()/mScaleFactor)+clipBounds.left;
pivotPointY = (detector.getFocusY()/mScaleFactor)+clipBounds.top;
return super.onScaleBegin(detector);
}
@Override
public boolean onScale(ScaleGestureDetector detector) {
//get scale factor
mScaleFactor*=detector.getScaleFactor();
//set the limit of zoom
mScaleFactor = Math.max(1f, Math.min(mScaleFactor, 20.0f));
return true;
}
@Override
public void onScaleEnd(ScaleGestureDetector detector) {
super.onScaleEnd(detector);
drawPaint.setStrokeWidth(brushSize/mScaleFactor);
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
float touchX = (event.getX()*offSetX/mScaleFactor) + clipBounds.left;
float touchY = (event.getY()*offSetY/mScaleFactor) + clipBounds.top ;
//pass the motion event to the gesture detector first
SGD.onTouchEvent(event);
GD.onTouchEvent(event);
//preventing the used of two finger to trigger drawing event
if(event.getPointerCount() == 1) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
if (!isGesture) {
drawPath.moveTo(touchX, touchY);
drawCanvas.drawPath(drawPath, drawPaint);
}
break;
case MotionEvent.ACTION_MOVE:
if (!isGesture) {
drawPath.lineTo(touchX, touchY);
drawCanvas.drawPath(drawPath, drawPaint);
}
break;
case MotionEvent.ACTION_UP:
isGesture = false;
drawPath.reset();
break;
default:
return true;
}
}else if(event.getPointerCount() > 1){
//if two finger are registered at the screen then it is flag as gesture
//until no finger are on the screen
isGesture = true;
}
//trigger the onDraw() function
invalidate();
return true;
}
public void setColor(String newColor){
invalidate();
paintColor = Color.parseColor(newColor);
drawPaint.setColor(paintColor);
}
}
答案 0 :(得分：0)
只需更改您的onDraw代码即可分两个阶段进行绘制。
首先，绘制图像。由于它是单独绘制的，因此不会将图像放在画布位图中。
然后用绘制的路径绘制画布位图。 ARGB8888位图应该是透明的，所以这样做不应该有任何不同。
public void changeBackground(Bitmap bitmap){
//store image to local var
image = bitmap;
//get offset of resolution between image and canvas
offSetY = (float)image.getHeight()/getHeight();
offSetX = (float)image.getWidth()/getWidth();
//creating new canvas
// DON'T COPY IMAGE canvasBitmap = image.copy(Bitmap.Config.ARGB_8888, true);
// just make a blank bitmap
canvasBitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
drawCanvas = new Canvas(canvasBitmap);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
//when size changed, store the new size
destImageRect = new Rect(0,0,w,h);
// DON'T COPY IMAGE - just make a blank bitmap
canvasBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
drawCanvas = new Canvas(canvasBitmap);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.save();
canvas.scale(mScaleFactor, mScaleFactor, pivotPointX, pivotPointY);
clipBounds = canvas.getClipBounds();
if (image != null) {
canvas.drawBitmap(image, 0, 0, canvasPaint);
}
// first update the canvas bitmap
drawCanvas.drawPath(drawPath, drawPaint);
// then draw it on top of the image
canvas.drawBitmap(canvasBitmap,null, destImageRect,canvasPaint);
canvas.restore();
}