bitmap转化为file

 public void saveBitmapFile(Bitmap bitmap){
        File file=new File("/mnt/sdcard/01.jpg");
        try {
                BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(file));
                bitmap.compress(Bitmap.CompressFormat.JPEG, 100, bos);
                bos.flush();
                bos.close();
        } catch (IOException e) {
                e.printStackTrace();
                System.out.println("broken");
        }

    }

加权限

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> 

<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" /> 

测试

File sd = Environment.getExternalStorageDirectory();  

boolean can_write = sd.canWrite();