我的绘画应用程序中实现了撤消功能,并且它运行良好。 但是,如果我更改了画笔颜色或画笔笔划,则所有以前绘制的路径都会更改为新的绘画颜色。 代码如下:
public class CustomView extends View implements OnTouchListener {
public Canvas mCanvas;
private Path mPath;
public Paint mPaint, mBitmapPaint;
Bitmap mBitmap;
Canvas canvas;
public ArrayList<Path> paths = new ArrayList<Path>();
public ArrayList<Path> undonePaths = new ArrayList<Path>();
private Bitmap im;
public CustomView(Context context) {
super(context);
setFocusable(true);
setFocusableInTouchMode(true);
setOnTouchListener(this);
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setDither(true);
mPaint.setColor(0xFFFFFFFF);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(6);
mCanvas = new Canvas();
mPath = new Path();
im = BitmapFactory.decodeResource(context.getResources(), R.drawable.ic_launcher);
DisplayMetrics metrics = getContext().getResources().getDisplayMetrics();
int w = metrics.widthPixels;
int h = metrics.heightPixels;
mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
mBitmapPaint = new Paint(Paint.DITHER_FLAG);
// mBitmapPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC));
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
}
@Override
protected void onDraw(Canvas canvas) {
// mPath = new Path();
// canvas.drawPath(mPath, mPaint);
canvas.drawColor(Color.TRANSPARENT);
canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
for (Path p : paths) {
canvas.drawPath(p, mPaint);
}
canvas.drawPath(mPath, mPaint);
}
private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;
private void touch_start(float x, float y) {
undonePaths.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
mCanvas.drawPath(mPath, mPaint);
// kill this so we don't double draw
paths.add(mPath);
mPath = new Path();
}
public void onClickUndo() {
if (paths.size() > 0) {
undonePaths.add(paths.remove(paths.size() - 1));
invalidate();
} else {
}
// toast the user
}
public void onClickRedo() {
if (undonePaths.size() > 0) {
paths.add(undonePaths.remove(undonePaths.size() - 1));
invalidate();
} else {
}
// toast the user
}
@Override
public boolean onTouch(View arg0, MotionEvent event) {
float x = event.getX();
float y = event.getY();
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;
}
}