我正在创建一个利用以下DrawingSurfaceView类的绘图应用程序。在该类中，我有一个名为“erasePaint”的Paint，用户可以打开和关闭它。但相反，它只是画一条黑线。
当我将 Canvas 另存为透明png时，橡皮擦是正确的，但在屏幕上显示为黑色。
来自EraserPaint电话的屏幕截图，用于在Blob上写“Erik”
从 Canvas 上保存了PNG
橡皮擦油漆看起来像这样:
eraserPaint = new Paint();
eraserPaint.setAlpha(0);
eraserPaint.setColor(Color.TRANSPARENT);
eraserPaint.setStrokeWidth(60);
eraserPaint.setStyle(Style.STROKE);
eraserPaint.setMaskFilter(null);
eraserPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
eraserPaint.setAntiAlias(true);
整个类(class)
public KNDrawingSurfaceView(Context c, float width, float height, KNSketchBookActivity parent) {
super(c);
myWidth = width;
myHeight = height;
mBitmap = Bitmap.createBitmap((int) myWidth, (int) myHeight, Bitmap.Config.ARGB_8888);
mCanvas = new Canvas(mBitmap);
_parent = parent;
mEmboss = new EmbossMaskFilter(new float[] { 1, 1, 1 }, 0.4f, 6, 3.5f);
tile = new Paint();
tileImage = BitmapFactory.decodeResource(getResources(), R.drawable.checkerpattern);
shader = new BitmapShader(tileImage, Shader.TileMode.REPEAT, Shader.TileMode.REPEAT);
tile.setShader(shader);
mPath = new Path();
eraserPaint = new Paint();
eraserPaint.setAlpha(0x00);
eraserPaint.setColor(Color.TRANSPARENT);
eraserPaint.setStrokeWidth(60);
eraserPaint.setStyle(Style.STROKE);
//eraserPaint.setMaskFilter(null);
eraserPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
eraserPaint.setAntiAlias(true);
mBitmapPaint = new Paint(Paint.DITHER_FLAG);
mCanvas.drawRect(0, 0, myWidth, myHeight, tile);
mCanvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
mCanvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
}
@Override
protected void onDraw(Canvas canvas) {
if (!_parent.isDrawerOpen()&&mPaint!=null) {
Log.v("onDraw:", "curent paths size:" + paths.size());
//mCanvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);
//canvas.drawPath(mPath, mPaint);
for (int i=0;i< paths.size();i++) {
tempPaint = paints.get(i);
eraserPaint.setStrokeWidth(tempPaint.getStrokeWidth());
if(fills.get(i)){
tempPaint.setStyle(Style.FILL_AND_STROKE);
eraserPaint.setStyle(Style.FILL_AND_STROKE);
}else{
tempPaint.setStyle(Style.STROKE);
eraserPaint.setStyle(Style.STROKE);
}
if(erasers.get(i)){
//tempPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
canvas.drawPath(paths.get(i), eraserPaint);
}else{
//tempPaint.setXfermode(null);
canvas.drawPath(paths.get(i), tempPaint);
}
//canvas.drawPath(paths.get(i), tempPaint);
}
if(_parent.toggleFill.isChecked()){
mPaint.setStyle(Style.FILL_AND_STROKE);
eraserPaint.setStyle(Style.FILL_AND_STROKE);
}else{
mPaint.setStyle(Style.STROKE);
eraserPaint.setStyle(Style.STROKE);
}
if(_parent.toggleErase.isChecked()){
//mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
canvas.drawPath(mPath, eraserPaint);
}else{
//mPaint.setXfermode(null);
canvas.drawPath(mPath, mPaint);
}
//canvas.drawPath(mPath, mPaint);
}
}
public void onClickUndo() {
if (paths.size() > 0) {
undonePaths.add(paths.remove(paths.size() - 1));
undonePaints.add(paints.remove(paints.size() - 1));
undoneFills.add(fills.remove(fills.size() - 1));
undoneErasers.add(erasers.remove(erasers.size() - 1));
clearCanvasCache();
invalidate();
} else {
}
_parent.checkButtonStates();
}
public void onClickRedo() {
if (undonePaths.size() > 0) {
paths.add(undonePaths.remove(undonePaths.size() - 1));
paints.add(undonePaints.remove(undonePaints.size() - 1));
fills.add(undoneFills.remove(undoneFills.size() - 1));
erasers.add(undoneErasers.remove(undoneErasers.size() - 1));
clearCanvasCache();
invalidate();
} else {
}
_parent.checkButtonStates();
}
public void onClickClear() {
paths.clear();
paints.clear();
fills.clear();
erasers.clear();
undoneFills.clear();
undonePaths.clear();
undonePaints.clear();
undoneErasers.clear();
clearCanvasCache();
invalidate();
_parent.checkButtonStates();
}
public void saveDrawing() {
FileOutputStream outStream = null;
String fileName = "tempTag";
try {
outStream = new FileOutputStream("/sdcard/" + fileName + ".png");
mBitmap.compress(Bitmap.CompressFormat.PNG, 100, outStream);
outStream.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
}
}
private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;
private void touch_start(float x, float y) {
undonePaths.clear();
undonePaints.clear();
undoneFills.clear();
mPath.reset();
mPath.moveTo(x, y);
mX = x;
mY = y;
}
private void touch_move(float x, float y) {
float dx = Math.abs(x - mX);
float dy = Math.abs(y - mY);
if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
mPath.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2);
mX = x;
mY = y;
}
}
private void touch_up() {
mPath.lineTo(mX, mY);
// commit the path to our offscreen
if(_parent.toggleErase.isChecked()){
mCanvas.drawPath(mPath, eraserPaint);
erasers.add(true);
paints.add(eraserPaint);
}else{
mCanvas.drawPath(mPath, mPaint);
erasers.add(false);
paints.add(mPaint);
}
// kill this so we don't double draw
paths.add(mPath);
if(_parent.toggleFill.isChecked()){
fills.add(true);
}else{
fills.add(false);
}
if(_parent.toggleErase.isChecked()){
erasers.add(true);
}else{
erasers.add(false);
}
_parent.checkButtonStates();
mPath = new Path();
}
@Override
public boolean onTouchEvent(MotionEvent event) {
if(mPaint==null &&!_parent._showingAlert){
_parent.showNoPaintAlert();
}
if (!_parent.isDrawerOpen()&&mPaint!=null) {
float x = event.getX();
float y = event.getY();
if (x > myWidth) {
x = myWidth;
}
if (y > myHeight) {
y = myHeight;
}
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
touch_start(x, y);
invalidate();
break;
case MotionEvent.ACTION_MOVE:
touch_move(x, y);
invalidate();
break;
case MotionEvent.ACTION_UP:
touch_up();
invalidate();
break;
}
return true;
} else {
return true;
}
}
public void clearCanvasCache() {
mBitmap = Bitmap.createBitmap((int) myWidth, (int) myHeight, Bitmap.Config.ARGB_8888);
mCanvas = new Canvas(mBitmap);
}
}
我应该补充一点，就是将这个“自定义 View ”添加到具有该方格图案作为背景图像的相对布局中。
请帮助。.我需要使用橡皮擦涂料后预览图像不显示黑色。.我需要它在后面显示方格图案。.我知道橡皮擦正在工作，因为那些黑色橡皮擦标记保存为透明的。
新注释
我在玩耍，发现了其他有趣的东西。实验中，我尝试从绘图切换到
canvas，传递给onDraw方法，然后直接切换到我在名为mCanvas的构造器中设置的 Canvas ，并注意到它没有绘制到我能看到的程度。 onDraw像这样: protected void onDraw(Canvas canvas) {
Log.v("DRAWING SURFACE", "canvas:"+canvas+" mCanvas:"+mCanvas);
吐出来
06-21 11:10:43.994: V/DRAWING SURFACE(4532): canvas:android.view.Surface$CompatibleCanvas@42a8c030 mCanvas:android.graphics.Canvas@431df180
最佳答案
我的应用程序也遇到了同样的问题。我什至尝试了“手指画”示例代码，但仍然遇到相同的问题。我从来没有能够将橡皮擦用作路径，但是我能够找到一种解决方法。当用户放下手指或发生“移动”事件时，我会画一个圆(可以是任何形状)，而不是在擦除时画一条路径:
case MotionEvent.ACTION_DOWN:
mPaint.setStrokeWidth(25);
mPaint.setXfermode(new PorterDuffXfermode(
PorterDuff.Mode.CLEAR));
mCanvas.drawCircle(x, y, 10, mPaint);
isErase = true;
invalidate();
}
touch_start(x, y);
invalidate();
break;
case MotionEvent.ACTION_MOVE:
if(isErase)
{
mCanvas.drawCircle(x, y, 20, mPaint);
}
else{
touch_move(x, y);
}invalidate();
break;
将其合并到您的代码中将花费一些时间，但是我保证，与解决该问题所花费的时间相比，它所花费的时间更少。如果您认为有帮助的话，可以向我发送更多我的PaintView。
关于android - 尝试为 Canvas 创建橡皮擦颜料，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/17197435/