Android报错：open failed: EACCES (Permission denied)

使用Android读取SD卡数据的时候报错，原因是Android系统6.0之后除了在AndroidManifest.xml里面添加读写权限之外还需要在使用的时候手动请求一下权限。

1、在AndroidManifest.xml中添加读写权限：

2、在进行读写操作之前手动请求权限：

import android.support.v4.app.ActivityCompat;

private static final int REQUEST_EXTERNAL_STORAGE = 1;
private static String[] PERMISSIONS_STORAGE = {
    Manifest.permission.READ_EXTERNAL_STORAGE,
    Manifest.permission.WRITE_EXTERNAL_STORAGE
};

/**
 * 在对sd卡进行读写操作之前调用这个方法
 * Checks if the app has permission to write to device storage
 * If the app does not has permission then the user will be prompted to grant permissions
 */
public static void verifyStoragePermissions(Activity activity) {
    // Check if we have write permission
    int permission = ActivityCompat.checkSelfPermission(activity, Manifest.permission.WRITE_EXTERNAL_STORAGE);
    if (permission != PackageManager.PERMISSION_GRANTED) {
        // We don't have permission so prompt the user
        ActivityCompat.requestPermissions(activity, PERMISSIONS_STORAGE, REQUEST_EXTERNAL_STORAGE);
    }
}

说明：ActivityCompat是android-support-v4.jar里面的方法。