记一次在android的学习中遇到的SD卡权限问题。最开始题主本来是想做一个小的demo来操作SD卡。如图所示：

没想到在开发的过程中遇到了权限问题。
首先贴一下activity的代码。其实就是三个按钮，绑定三个事件。

package com.example.demo;

import android.Manifest;
import android.app.Activity;
import android.content.Context;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;

import java.io.IOException;

/**
 * @Author godv
 * Date on 2020/4/14  22:02
 */
public class FileActivity extends AppCompatActivity {
   
    private EditText editname;
    private EditText editdetail;
    private Button btnsave;
    private Button btnclean;
    private Button btnread;
    private Context mContext;

    private static final int REQUEST_EXTERNAL_STORAGE = 1;
    private static String[] PERMISSIONS_STORAGE = {
   
            "android.permission.READ_EXTERNAL_STORAGE",
            "android.permission.WRITE_EXTERNAL_STORAGE" };
    /*
     * android 动态权限申请
     * */
    public static void verifyStoragePermissions(Activity activity) {
   
        try {
   
            //检测是否有写的权限
            int permission = ActivityCompat.checkSelfPermission(activity,
                    "android.permission.WRITE_EXTERNAL_STORAGE");
            if (permission != PackageManager.PERMISSION_GRANTED) {
   
                // 没有写的权限，去申请写的权限，会弹出对话框
                ActivityCompat.requestPermissions(activity, PERMISSIONS_STORAGE,REQUEST_EXTERNAL_STORAGE);
            }
        } cat