How to implemement undo features in painting application in Android?

Question

i want to do undo features in in my application.. for this i searched i net found that take arraylist of x,y points which i have done below code i am unable for undo the drawing

Answer 1

here some code: create:

private Canvas mCanvas;
private Bitmap mBitmap;

private Canvas mRestoreCanvas;
private Bitmap mRestoreBitmap;

init:

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    mPictureWidth = w;
    mPictureHeight = h;

    Loge.i("mPictureWidth = " + mPictureWidth + " mPictureHeight = "
            + mPictureHeight);
    if (mCanvas == null && mBitmap == null && mPictureWidth > 0
            && mPictureHeight > 0) {
        mBitmap = Bitmap.createBitmap(mPictureWidth, mPictureHeight,
                Bitmap.Config.ARGB_8888);
        mCanvas = new Canvas(mBitmap);
        mCanvas.save();

        mRestoreBitmap = Bitmap.createBitmap(mPictureWidth, mPictureHeight,
                Bitmap.Config.ARGB_8888);
        mRestoreCanvas = new Canvas(mRestoreBitmap);
        mRestoreCanvas.save();
    }
    super.onSizeChanged(w, h, oldw, oldh);
}

onDraw:

@Override
protected void onDraw(Canvas canvas) {
    if (mPattern == DRAW_LINE) {
        mCanvas.restore();
        mCanvas.drawPath(path, paint);
        mCanvas.save();
    }
    mCanvas.save();
    if (mBitmap != null)
        canvas.drawBitmap(mBitmap, 0, 0, null);
}

onTouchEvent:

@Override
public boolean onTouchEvent(MotionEvent event) {

    if(event.getAction() == MotionEvent.ACTION_DOWN){
        mRestoreCanvas.drawBitmap(mBitmap, 0, 0, bitmapPaint);
    }

    if (mPattern == DRAW_LINE) {
        return drawLines(event);
    } else if (mPattern == DRAW_PATTERN) {
        return drawPattern(event);
    }
    return false;
}

Undo:

public void dust() {
    path.reset();
    mBitmap.recycle();
    mBitmap = Bitmap.createBitmap(mPictureWidth, mPictureHeight,
            Bitmap.Config.ARGB_8888);
    mCanvas.setBitmap(mBitmap);

    mCanvas.drawBitmap(mRestoreBitmap, 0, 0, bitmapPaint);

    invalidate();
}

Tested OK;