アンドロイドキャンバスでアンドゥ/リドゥが動作しません

Question

アンドゥとリドゥ機能は以下のコードでは動作しません。以下は私の描画コードの実装です。

以下のコードに問題はありますか？

 
public class DrawingArea extends View { 

    private Path drawPath; 
    private Paint drawPaint, canvasPaint; 
    private int paintColor = 0xFF660000; 
    private Canvas drawCanvas; 
    private Bitmap canvasBitmap; 
    private ArrayList paths = new ArrayList(); 
    private ArrayList undonePaths = new ArrayList(); 
    private float mX, mY; 
    private static final float TOUCH_TOLERANCE = 4; 

    // for Undo, Redo 
    private int historyPointer = 0; 

    private boolean erase = false; 

    public DrawingArea(Context context) { 
     super(context); 
     setupDrawing(); 
    } 

    public DrawingArea(Context context, AttributeSet attrs) { 
     super(context, attrs); 
     setupDrawing(); 
    } 

    public void setupDrawing() { 
     drawPath = new Path(); 
     drawPaint = new Paint(); 
     drawPaint.setAntiAlias(true); 
     drawPaint.setStrokeWidth(20); 
     drawPaint.setStyle(Paint.Style.STROKE); 
     drawPaint.setStrokeJoin(Paint.Join.ROUND); 
     drawPaint.setStrokeCap(Paint.Cap.ROUND); 
     canvasPaint = new Paint(Paint.DITHER_FLAG); 

     //paths.add(drawPath); 
    } 

    public void setColor(String newColor) { 
     invalidate(); 
     paintColor = Color.parseColor(newColor); 
     drawPaint.setColor(paintColor); 
    } 

    @Override 
    protected void onDraw(Canvas canvas) { 
     super.onDraw(canvas); 
     canvas.drawBitmap(canvasBitmap, 0, 0, canvasPaint); 
     canvas.drawPath(drawPath, drawPaint); 
    } 

    @Override 
    protected void onSizeChanged(int w, int h, int oldw, int oldh) { 
     super.onSizeChanged(w, h, oldw, oldh); 
     canvasBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888); 
     drawCanvas = new Canvas(canvasBitmap); 
    } 

    @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; 
    } 

    private void touch_start(float x, float y) { 
     drawPath.reset(); 
     drawPath.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) { 
      drawPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2); 
      mX = x; 
      mY = y; 
     } 
    } 

    private void touch_up() { 
     drawPath.lineTo(mX, mY); 
     // commit the path to our offscreen 
     drawCanvas.drawPath(drawPath, drawPaint); 
     // kill this so we don't double draw 
     drawPath = new Path(); 
     paths.add(drawPath); 
    } 

    public void setErase() { 
     canvasBitmap.eraseColor(Color.TRANSPARENT); 
     drawPath.reset(); 
     invalidate(); 
    } 

    public void startNew() { 
     drawCanvas.drawColor(0, PorterDuff.Mode.CLEAR); 
     invalidate(); 
    } 

    public void undo() { 
     if (paths.size() > 0) { 
      undonePaths.add(paths.remove(paths.size() - 1)); 
      invalidate(); 
     } 
    } 

    public void redo() { 
     if (undonePaths.size() > 0) { 
      paths.add(undonePaths.remove(undonePaths.size() - 1)); 
      invalidate(); 
     } 
    } 
} 

Answer 1

この

protected void onDraw(Canvas canvas) { 
    super.onDraw(canvas); 
    canvas.drawBitmap(mBitmap, 0, 0, canvasPaint); 
    canvas.drawPath(mPath,drawPaint); 

    for (Path p : paths) { 
     canvas.drawPath(p, drawPaint); 
    } 



} 

のようなあなたのOnDraw（）を変更

、データがパス ArrayListの

ArrayList<Path> paths = new ArrayList<Path>();