我想做的事情撤消我的应用程序的功能。对于这个我搜索我网发现，拍X的ArrayList中，我做了codeI上午下面无法为撤销图纸，θY点。

 公共drawView函数（上下文的背景下，浮法X，浮动Y，INT读）{
            超（上下文）;


            mBitmap = Bitmap.createBitmap（800，1200，Bitmap.Config.ARGB_8888）;
           // mainbitmap.add（mBitmap）;
            //System.out.println("**mBitmapPaint***"+mBitmapPaint）;
            mCanvas =新的Canvas（mBitmap）;
            的mpath =新路径（）;
            mBitmapPaint =新的油漆（Paint.DITHER_FLAG）;



        }

       @覆盖
       保护无效onSizeChanged（INT W，INT小时，INT oldw，诠释oldh）{
           super.onSizeChanged（W，H，oldw，oldh）;
       }

        @覆盖
        保护无效的OnDraw（帆布油画）{

            的System.out.println（*** Drawinglines ****+ Drawinglines）;

                canvas.drawBitmap（mBitmap，0，0，mBitmapPaint）;
                canvas.drawPath（的mpath，mPaint）;



        }


        私人浮动MX，我的;
        私有静态最终浮动TOUCH_TOLERANCE = 4;

        私人无效touch_start（浮X，浮动Y）{
            mPath.reset（）;
            mPath.moveTo（X，Y）;
            MX = X;
            我= Y;
        }

        私人无效TOUCH_MOVE（浮X，浮动Y）{
            浮DX = Math.abs（X  -  MX）;
            浮DY = Math.abs（Y  - 我的）;
            如果（DX＆GT; = TOUCH_TOLERANCE || DY＆GT; = TOUCH_TOLERANCE）{
                mPath.quadTo（MX，MY，（X + MX）/ 2，（Y +我）/ 2）;
                MX = X;
                我= Y;
            }
        }

        私人无效touch_up（）{


            mPath.lineTo（MX，MY）;
            mCanvas.drawPath（的mpath，mPaint）;
        ///    路径。
            //graphics.add(mPath）;
            mPath.reset（）;
        }

        //事件触摸屏幕时，
        公共布尔的onTouchEvent（MotionEvent事件）{

             event.getAction（）;
            INT eventaction = event.getAction（）;

            INT X =（int）的event.getX（）;
            INT Y =（INT）event.getY（）;

            开关（eventaction）{

            案例MotionEvent.ACTION_DOWN：

            {
                touch_start（X，Y​​）;
                }
                 无效（）;
                 打破;


            案例MotionEvent.ACTION_MOVE：

                的System.out.println（*** ACTION_MOVE **************+ X +************+ Y）;
                如果（（Drawinglines.equals（笔））||（Drawinglines.equals（擦除）））
                {
                  TOUCH_MOVE（X，Y）;
                  temp_point.add（新点（X，Y））;

                }
                无效（）;
                打破;

            案例MotionEvent.ACTION_UP：

                main_Points.add（temp_point）;
                temp_point = NULL;

                 润色（）;

                 无效（）;
                 打破;
            }

            返回true;

        }




        公共无效undopath（）
        {
              main_Points.remove（main_Points.size（） -  1）;
             无效（）;
        }

    }
    @覆盖
    公共无效的onClick（视图v）{


        如果（V ==撤消）
        {
            drawView函数ABC =新drawView函数（）;
             abc.undopath（）;
        }
 

但撤消撤消功能无法正常工作。

 私人板岩mSlate;
私人TiledBitmapCanvas mTiledCanvas;

 公共无效clickUndo（查看未使用的）{

        mSlate.undo（）;
    }


公共无效撤消（）{
        如果（mTiledCanvas == NULL）{
            Log.v（TAG，撤销之前mTiledCanvas inited）;
        }
        mTiledCanvas.step（-1）;

        无效（）;
    }
 

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 drawings ??

public Drawview(Context context, float x, float y, int r) {
            super(context);


            mBitmap = Bitmap.createBitmap(800, 1200, Bitmap.Config.ARGB_8888);
           // mainbitmap.add(mBitmap);
            //System.out.println("**mBitmapPaint***"+mBitmapPaint);
            mCanvas = new Canvas(mBitmap);
            mPath = new Path();
            mBitmapPaint = new Paint(Paint.DITHER_FLAG);



        }

       @Override
       protected void onSizeChanged(int w, int h, int oldw, int oldh) {
           super.onSizeChanged(w, h, oldw, oldh);
       }

        @Override 
        protected void onDraw(Canvas canvas) {

            System.out.println("***Drawinglines****"+Drawinglines);

                canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
                canvas.drawPath(mPath, 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);
        ///    path.
            //graphics.add(mPath);
            mPath.reset();
        }

        // events when touching the screen
        public boolean onTouchEvent(MotionEvent event) {

             event.getAction();
            int eventaction = event.getAction(); 

            int X = (int)event.getX(); 
            int Y = (int)event.getY(); 

            switch (eventaction ) { 

            case MotionEvent.ACTION_DOWN: 

            {
                touch_start(X, Y);
                }
                 invalidate(); 
                 break; 


            case MotionEvent.ACTION_MOVE:  

                System.out.println("***ACTION_MOVE**************"+X+"************"+Y);
                if((Drawinglines.equals("Pen"))||(Drawinglines.equals("Erase")))
                {
                  touch_move(X, Y);
                  temp_point.add(new Point(X,Y));

                }
                invalidate(); 
                break; 

            case MotionEvent.ACTION_UP: 

                main_Points.add(temp_point);
                temp_point = null;

                 touch_up();  

                 invalidate(); 
                 break; 
            } 

            return true; 

        }




        public void undopath()
        {   
              main_Points.remove(main_Points.size()-1);
             invalidate();
        }

    }
    @Override
    public void onClick(View v) {


        if(v ==  Undo)
        {    
            Drawview abc=new Drawview();
             abc.undopath();
        }

But undo undo functionality is not working.

private Slate mSlate;
private TiledBitmapCanvas mTiledCanvas;

 public void clickUndo(View unused) {

        mSlate.undo();
    }


public void undo() {
        if (mTiledCanvas == null) {
            Log.v(TAG, "undo before mTiledCanvas inited");
        }
        mTiledCanvas.step(-1);

        invalidate();
    }