Android代码截屏后生成的图片文件无法获取权限

[JerryLee_mh]

root机 通过代码
Runtime.getRuntime().exec("su -c screencap -p " + savedPath);
 实现截屏, 并将文件长传至服务器.
截屏可以成功生成图片文件 但是上传或者复制操作就会出现权限问题 
通过Runtime.getRuntime().exec("chmod 777 "+ fileName); 代码也获取不到权限.. 求助.. 
错误信息:
java.io.FileNotFoundException: /data/data/com.lmh.cut/files/screenshot.png: open failed: EACCES (Permission denied)


	public String screenshot() {
		String savedPath = context.getFilesDir() +
				File.separator+Tags.CutScreen.SAVE_NAME;
		try {
			Runtime.getRuntime().exec("su -c screencap -p " + savedPath);
		} catch (IOException e) {
			Log.e(Tags.SERVICE_CUT, "line:41 " + e.getMessage());
			return Tags.CutScreen.CUT_FAIL;
		}
		return savedPath;
	}

	public static void getPermission(String fileName){
		try {
			Runtime.getRuntime().exec("su");
			Runtime.getRuntime().exec("chmod 777 "+ fileName);
		} catch (IOException e) {
			Log.e(Tags.SERVICE_CUT, "line:23 " + e.getMessage());
		}
	}