有一个我似乎无法解决的问题：在我OnCreate的 中CameraActivity，如果有图片，我会先删除它。如果存在这样做的情况，则创建图片文件但图片为空白。（所以只有在文件不存在的情况下才能成功创建图片）。如何删除文件并成功创建？
我CameraActivity的定义如下：
public class CameraActivity extends Activity
{
final int PICTURE_ACTIVITY = 1;
@Override
public void onCreate(Bundle savedInstanceState)
{
Intent h = getIntent();
String filename = h.getStringExtra("string") + ".jpg";
String dir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES) + "/" + getString(R.string.app_name)+ "/";
File newdir = new File(dir);
try{
newdir.mkdirs();
}
catch(Exception e){}
String file = dir + filename;
File newfile = new File(file);
boolean deleted = newfile.delete();
try {
System.out.println("creating:");
newfile.createNewFile();
} catch (IOException e) {}
Uri outputFileUri = Uri.fromFile(newfile);
Intent cameraIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
cameraIntent.putExtra(MediaStore.EXTRA_OUTPUT, outputFileUri);
super.onCreate(savedInstanceState);
startActivityForResult(cameraIntent, PICTURE_ACTIVITY);
}
}