我没有在此代码中执行撤消/重做操作画布。当我使用数组列表删除位置时，它不起作用，并且在从颜色选择器更改油漆颜色期间，先前的绘图颜色也已更改。我不明白如何为此执行 UNDO/REDO。所以请帮忙
//这是主类
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView (mView = new MyView(this));
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setDither(true);
mPaint.setColor(0xFFFF0000);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(4);
mEmboss = new EmbossMaskFilter(new float[] { 1, 1, 1 },
0.4f, 6, 3.5f);
mBlur = new BlurMaskFilter(8, BlurMaskFilter.Blur.NORMAL);
}
//而MyView类是
public class MyView extends View {
private static final float MINP = 0.25f;
private static final float MAXP = 0.75f;
private Bitmap mBitmap;
private Canvas mCanvas;
private Path mPath;
private Paint mBitmapPaint;
ArrayList<Path> paths = new ArrayList<Path>();
ArrayList<Path> undonePaths = new ArrayList<Path>();
public MyView(Context c)
{
super(c);
mBitmap = Bitmap.createBitmap(320, 480, Bitmap.Config.ARGB_8888);
mCanvas = new Canvas(mBitmap);
mPath = new Path();
mBitmapPaint = new Paint(Paint.DITHER_FLAG);
// mCanvas.setBackgroundResource(0xFFFFFFFF);
mCanvas.drawColor (0xFFFFFFFF);
paths.add(mPath);
}
public MyView (Context c, int color)
{
super(c);
mBitmap = Bitmap.createBitmap(320, 480, Bitmap.Config.ARGB_8888);
mCanvas = new Canvas(mBitmap);
mPath = new Path();
mBitmapPaint = new Paint(Paint.DITHER_FLAG);
mCanvas.drawColor (color);
paths.add(mPath);
}
@Override protected void onSizeChanged(int w, int h, int oldw, int oldh)
{
super.onSizeChanged(w, h, oldw, oldh);
}
@Override protected void onDraw(Canvas canvas)
{
canvas.drawColor(0xFF000000);
canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
for(Path p: paths)
{
canvas.drawPath(p, mPaint);
}
}
private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;
private void touch_start(float x, float y) {
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);
mCanvas.drawPath(mPath, mPaint);
paths.add(mPath);
mPath.reset();
}
@Override public boolean onTouchEvent(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;
}
public void clear ()
{
Paint p = new Paint();
p.setAntiAlias(true);
p.setDither(true);
p.setColor(0xFFFFFFFF);
mCanvas.drawPaint (p);
}
public void drawImage (int resourceId)
{
Bitmap _scratch = BitmapFactory.decodeResource(getResources(), resourceId);
mCanvas.drawBitmap(_scratch, 0, 0, null);
}
public void undo() {
// TODO Auto-generated method stub
mCanvas.drawCircle(posX, posY, 100, mPaint);
Toast.makeText(getApplicationContext(), "Hello", 1000).show();
if (paths.size()>0)
{
undonePaths.add(paths.remove(paths.size()-1));
mView.invalidate();
Toast.makeText(getApplicationContext(), "Undo", 1000).show();
}
else
{
Toast.makeText(getApplicationContext(), "Not", 1000).show();
}
}
public void redo() {
// TODO Auto-generated method stub
if (undonePaths.size()>0)
{
paths.add(undonePaths.remove(undonePaths.size()-1));
invalidate();
}
else
{
}
}
public void saveAsJpg (File f)
{
String fname = f.getAbsolutePath ();
FileOutputStream fos = null;
try {
fos = new FileOutputStream (f);
mBitmap.compress (CompressFormat.JPEG, 95, fos);
} catch (Throwable ex) {
ex.printStackTrace ();
}
} // end saveAsJpg
} // end MyView
} // end class FingerPaint