深陷困境添加撤消和刪除以FingerPaint.java

Question

我以前在fingerpaint類的工作，我是非常舒適，但這個時候，我發現自己執行這兩個撤消的功能和刪除

這是我的畫鑑於

public class MyView extends View {  
     private Bitmap mBitmap; 
     private Canvas mCanvas; 
     private Path mPath; 
     private Paint mBitmapPaint; 

     public MyView(Context c) { 
      super(c); 
      mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);    
      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) { 
      /*canvas.drawColor(Color.WHITE);   
      canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);*/ 

      for (int i=0;i<paths.size();i++){ 
       canvas.drawPath(paths.get(i).path, paths.get(i).paint); 
      } 

      canvas.drawPath(mPath, mPaint); 

     } 

     private float mX, mY; 
     private static final float TOUCH_TOLERANCE = 4; 

     private void touch_start(float x, float y) 
     { 
      if (erase == true) 
      { 
       mPath.reset(); 
      } 
      undonePaths.clear(); 
      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 (check == 1 || (selectedId == ERASE_MENU_ID)) 
      { 
       if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) 
       { 
        mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2); 
        mX = x; 
        mY = y; 
        mCanvas.drawPath(mPath, mPaint); 
       } 

      } 

      if(selectedId == ERASE_MENU_ID) 
      { 
       mCanvas.drawPath(mPath, mPaint); 
       mPath=new Path(); 
       mX = x; 
       mY = y; 
       mPath.moveTo(x, y); 
      } 

     } 

     public void onClickUndo() { 
      if (paths.size()>0) 
      { 
       paths.remove(paths.size()-1); 
       invalidate(); 
      } 
      else 
      { 

      } 
      //toast the user 
     } 
     private void touch_up() {  
      mCanvas.drawPath(mPath, mPaint);  

      MyDataHolder md=new MyDataHolder(); 
      md.paint=mPaint; 
      md.path=mPath; 

      paths.add(md); 

      mPath=new Path(); 
     } 


     @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; 
     } 
    } 

現在的問題是，當我改變mPaint的方式來清除

  erase=true; 
    mPaint.setXfermode(null); 
    mPaint.setStrokeWidth(25.0f); 
    //mPaint.setColor(Color.TRANSPARENT); 
    mPaint.setXfermode(new PorterDuffXfermode(Mode.CLEAR)); 

每繪製路徑變爲黑色與25寬有人sugges特德，我使用相同的油漆，所以我做了一個包裝類來存儲油漆和路徑對象，但它不工作。

Answer 1

我可以幫你刪除（清除屏幕）。這是非常簡單和基本的方法。 創建一個布爾變量（比如mclears）。當您按下「清除」按鈕時將其設置爲真。 中的OnDraw（），使用

if(clears){ 
myBitmap.eraseColor(bcolor); 
//Sets your canvas (bitmap) color to your background color. i.e. clears canvas 
    clears=false; 
      } 

您可能需要改變你的Touch_up方法的位。像

 private void touch_up() {  
     mCanvas.drawPath(mPath, mPaint);  
     MyDataHolder md=new MyDataHolder(); 
     mPath.reset(); 
     md.paint=mPaint; 
     md.path=mPath; 
     paths.add(md); 
     mPath=new Path(); 
    } 

我已經在我的應用程序中實現了這一點。希望對你有效。