title: MediaStore.Images.Media.insertImage is returning null when trying to save the image
body: <p>I am using an custom view and in that i am using an canvas in which a user can draw anything and after that i want to save that image in sd card bt was not able to do that. Don't know what is going on. </p>
  
  <pre><code>else if(view.getId()==R.id.save_btn){
              //save drawing
              AlertDialog.Builder saveDialog = new AlertDialog.Builder(this);
              saveDialog.setTitle("Save drawing");
              saveDialog.setMessage("Save drawing to device Gallery?");
              saveDialog.setPositiveButton("Yes", new DialogInterface.OnClickListener(){
                  private FileOutputStream fOut;
  
                  public void onClick(DialogInterface dialog, int which){
                      //save drawing
                      drawView.setDrawingCacheEnabled(true);
  
                      //attempt to save
                      String imgSaved = MediaStore.Images.Media.insertImage(
                              getContentResolver(), drawView.getDrawingCache(),
                              UUID.randomUUID().toString()+".png", "drawing");
                      //feedback
                      if(imgSaved!=null){
                          Toast savedToast = Toast.makeText(getApplicationContext(), 
                                  "Drawing saved to Gallery!", Toast.LENGTH_SHORT);
                          savedToast.show();
                      }
                      else{
                          Toast unsavedToast = Toast.makeText(getApplicationContext(), 
                                  "Oops! Image could not be saved.", Toast.LENGTH_SHORT);
                          unsavedToast.show();
                      }
                      drawView.destroyDrawingCache();
                  }
              });
              saveDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener(){
                  public void onClick(DialogInterface dialog, int which){
                      dialog.cancel();
                  }
              });
              saveDialog.show();
          }
  </code></pre>
  
  <p>HERE IS THE ERROR DETAILS</p>
  
  <pre><code>04-14 11:24:28.700: E/MediaStore(6866): Failed to insert image
  04-14 11:24:28.700: E/MediaStore(6866): java.io.FileNotFoundException: No such file or directory
  04-14 11:24:28.700: E/MediaStore(6866):     at android.database.DatabaseUtils.readExceptionWithFileNotFoundExceptionFromParcel(DatabaseUtils.java:146)
  04-14 11:24:28.700: E/MediaStore(6866):     at android.content.ContentProviderProxy.openAssetFile(ContentProviderNative.java:577)
  04-14 11:24:28.700: E/MediaStore(6866):     at android.content.ContentResolver.openAssetFileDescriptor(ContentResolver.java:673)
  04-14 11:24:28.700: E/MediaStore(6866):     at android.content.ContentResolver.openOutputStream(ContentResolver.java:537)
  04-14 11:24:28.700: E/MediaStore(6866):     at android.content.ContentResolver.openOutputStream(ContentResolver.java:513)
  04-14 11:24:28.700: E/MediaStore(6866):     at android.provider.MediaStore$Images$Media.insertImage(MediaStore.java:891)
  04-14 11:24:28.700: E/MediaStore(6866):     at com.example.clent.MainActivity$9.onClick(MainActivity.java:238)
  04-14 11:24:28.700: E/MediaStore(6866):     at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:166)
  04-14 11:24:28.700: E/MediaStore(6866):     at android.os.Handler.dispatchMessage(Handler.java:99)
  04-14 11:24:28.700: E/MediaStore(6866):     at android.os.Looper.loop(Looper.java:137)
  04-14 11:24:28.700: E/MediaStore(6866):     at android.app.ActivityThread.main(ActivityThread.java:5103)
  04-14 11:24:28.700: E/MediaStore(6866):     at java.lang.reflect.Method.invokeNative(Native Method)
  04-14 11:24:28.700: E/MediaStore(6866):     at java.lang.reflect.Method.invoke(Method.java:525)
  04-14 11:24:28.700: E/MediaStore(6866):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
  04-14 11:24:28.700: E/MediaStore(6866):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
  04-14 11:24:28.700: E/MediaStore(6866):     at dalvik.system.NativeStart.main(Native Method)
  </code></pre>
  
  <p>I am always getting this message while trying to save image...."Oops! Image could not be saved.".....</p>