将位图保存到Android中的文件中

Question

我有一个DrawingView类，它实现了绘画方法。当我画一些东西的时候，它完美地工作，但之后，当我试图保存我在jpg文件中绘制的东西时，我会得到一个黑色的图像。我在stackoverflow中找到了许多答案，博客解释了如何做到这一点，并且不明白为什么我仍然拥有黑色图像。这里是我的代码：

DrawingView：

public class DrawingView extends View { 
    private Path drawPath; 
    private Paint drawPaint; 
    private Paint canvasPaint; 
    private Canvas drawCanvas; 
    private Bitmap canvasBitmap; 

    public DrawingView(Context context, AttributeSet attrs) { 
     super(context, attrs); 

     drawPath = new Path(); 
     drawPaint = new Paint(); 
     canvasPaint = new Paint(Paint.DITHER_FLAG); 

     drawPaint.setColor(Color.BLACK); 
     drawPaint.setAntiAlias(true); 
     drawPaint.setStrokeWidth(5f); 
     drawPaint.setStyle(Paint.Style.STROKE); 
     drawPaint.setStrokeJoin(Paint.Join.ROUND); 
     drawPaint.setStrokeCap(Paint.Cap.ROUND); 
    } 

    public DrawingView(Context context) { 
     super(context); 

     drawPath = new Path(); 
     drawPaint = new Paint(); 
     drawPaint.setColor(Color.BLACK); 
     drawPaint.setAntiAlias(true); 
     drawPaint.setStrokeWidth(5f); 
     drawPaint.setStyle(Paint.Style.STROKE); 
     drawPaint.setStrokeJoin(Paint.Join.ROUND); 
     drawPaint.setStrokeCap(Paint.Cap.ROUND); 
    } 

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

    @Override 
    public boolean onTouchEvent(MotionEvent event) { 
     float touchX = event.getX(); 
     float touchY = event.getY(); 

     switch (event.getAction()) { 
     case MotionEvent.ACTION_DOWN: 
      drawPath.moveTo(touchX, touchY); 
      break; 
     case MotionEvent.ACTION_MOVE: 
      drawPath.lineTo(touchX, touchY); 
      break; 
     case MotionEvent.ACTION_UP: 
      drawCanvas.drawPath(drawPath, drawPaint); 
      drawPath.reset(); 
      break; 

     default: 
      return false; 
     } 

     invalidate(); 

     return true; 
    } 
} 

而且我在这里使用：

public void btFirma_FRAGMENT_CIERRE(View v) { 
    final DrawingView dv = new DrawingView(this); 

    LayoutParams params = CierreFragment.getdvFirma().getLayoutParams(); 

    dv.setLayoutParams(params); 
    dv.setDrawingCacheEnabled(true); 
    dv.measure(MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED), 
      MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED)); 
    dv.layout(0, 0, v.getWidth(), v.getHeight()); 
    dv.buildDrawingCache(true); 

    AlertDialog.Builder builder = new AlertDialog.Builder(this); 
    builder.setView(dv); 
    builder.setPositiveButton("Aceptar", new OnClickListener() { 

     @Override 
     public void onClick(DialogInterface dialog, int which) { 
      Log.d("DialogFirma", "Se pulsa el botón aceptar del dialog"); 

      // TODO Establecer el nombre que se quiere asignar a la firma. 
      imageName = "prueba.jpg"; 

      // TODO Guardar imagen de la firma en la carpeta /FIRMAS/ 
      saveImageSign(dv.getDrawingCache()); 

      Drawable background = getImageSign(imageName); 

      if (background != null) 
       CierreFragment.setdvBackGround(background); 
     } 
    }); 
    builder.setNegativeButton("Cancelar", new OnClickListener() { 

     @Override 
     public void onClick(DialogInterface dialog, int which) { 
      // TODO Auto-generated method stub 
      Log.d("DialogFirma", "Se pulsa el botón cancelar del dialog"); 
     } 
    }); 

    builder.show(); 

} 
private void saveImageSign(Bitmap finalBitmap) { 
    File file = new File(
      ((AISApplication) getApplicationContext()) 
        .getLocalFolderFIRMAS() + imageName); 
    if (file.exists()) 
     file.delete(); 
    try { 
     FileOutputStream out = new FileOutputStream(file); 
     finalBitmap.compress(Bitmap.CompressFormat.JPEG, 90, out); 
     out.flush(); 
     out.close(); 

    } catch (Exception e) { 
     e.printStackTrace(); 
    } 
} 

private Drawable getImageSign(String imageName) { 
    FileInputStream in; 
    try { 
     in = new FileInputStream(new File(
       ((AISApplication) getApplication()).getLocalFolderFIRMAS() 
         + imageName)); 

     Bitmap bmp = BitmapFactory.decodeStream(in); 

     return new BitmapDrawable(getResources(), bmp); 
    } catch (FileNotFoundException e) { 
     e.printStackTrace(); 
    } 
    return null; 
} 

谁能告诉我哪里是我的失败？

Answer 1

我还没有看太深入到你的代码，但在这里就是我如何得到我刚刚绘制的图像：

private Bitmap getImage() { 
tile = Bitmap.createBitmap(faces[0]);  // create the bitmap (from existing or blank)   
Canvas c = new Canvas(tile);    // create a new canvas using that bitmap 
c.drawBitmap(tile, 0, 0, null);   // draw the bitmap onto the canvas 
              // do more drawing - here I add another image 
c.drawBitmap(scoresBm[initScores[0]], vertex.get(0).x, vertex.get(0).y, null); 

return tile;        // just return the bitmap 
} 

保存图像

// write the image back out (using compression in this one) 

try { 
    FileOutputStream out = new FileOutputStream(imgFile); 
    _bitmapScaled.compress(Bitmap.CompressFormat.JPEG, 50, out); 
    out.flush(); 
    out.close(); 
    } catch (Exception e) {