在AndroidManifest.xml文件中添加读写权限：

并在运行时请求权限：

if (ContextCompat.checkSelfPermission(getContext(), Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {

ActivityCompat.requestPermissions(getActivity(),
        new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},
        MY_PERMISSIONS_REQUEST_READ_EXTERNAL_STORAGE);

} else { // Permission has already been granted }

另外，可以使用try-catch语句来处理FileNotFoundException异常：

try { File file = new File("/abc.csv"); FileInputStream fis = new FileInputStream(file); // do something with fis } catch (FileNotFoundException e) { e.printStackTrace(); }