在做一个写入sd卡文件的app时无法获取读写权限 代码如下

Question

在做一个写入sd卡文件的app时无法获取读写权限
代码如下

package com.example.timemachine;

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

import android.Manifest;
import android.annotation.SuppressLint;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.text.SimpleDateFormat;
import java.util.Date;
public class MainActivity extends AppCompatActivity {
    private static final int REQUEST_EXTERNAL_STORAGE = 1;
    private static String[] PERMISSIONS_STORAGE = {
            Manifest.permission.READ_EXTERNAL_STORAGE,
            Manifest.permission.WRITE_EXTERNAL_STORAGE
    };
    private String fileName;
    // 记录目录路径
    private String fileDir;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {//android 6.0以上
            //进入程序，申请读写权限
            int permission = ActivityCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE);
            if (permission != PackageManager.PERMISSION_GRANTED) {
                ActivityCompat.requestPermissions(this, PERMISSIONS_STORAGE, REQUEST_EXTERNAL_STORAGE);
            }
        }
    }
    public void TimeC1(View view){
         @SuppressLint("SimpleDateFormat") SimpleDateFormat format = new SimpleDateFormat("yyyyMM");
         String y= format.format(new Date());
        TextView textView1=(TextView) findViewById(R.id.TimeY);
        textView1.setText(y);
    }
    public void TimeC2(View view){
        @SuppressLint("SimpleDateFormat") SimpleDateFormat format1=new SimpleDateFormat("ddHHmm");
        String d=format1.format(new Date());
        TextView textView2=(TextView) findViewById(R.id.TimeD);
        textView2.setText(d);
    }
    public void TimeC(View view){
        String y1;
        String d1;
        String date;
        TextView textView1=(TextView) findViewById(R.id.TimeY);
        TextView textView2=(TextView) findViewById(R.id.TimeD);
        y1=textView1.getText().toString();
        d1=textView2.getText().toString();
        String yd;
        yd=(y1+"\ndayTime "+d1);
        String head;
        {head=("default 0\nmres 24\nphoto_size 0\nsplit 222\nyearMonth");}
        date=(head+" "+yd);
        TextView textView3=(TextView) findViewById(R.id.textView);
        textView3.setText(date);

    }
    private void createFile(){
        String mStrPath = Environment.getExternalStorageDirectory().getPath() + "/default.ini";
        File mFile=new File(mStrPath);
        TextView textView=(TextView) findViewById(R.id.textView2);
        if (mFile.exists()){
            mFile.delete();
        }
        try {
            mFile.createNewFile();
            textView.setText("文件创建成功");
        }catch (IOException e){
            e.printStackTrace();
            textView.setText("文件创建失败");
        }
    }
    public void writText(String fileName, String date){
        String y1;
        String d1;
        TextView textView1=(TextView) findViewById(R.id.TimeY);
        TextView textView2=(TextView) findViewById(R.id.TimeD);
        y1=textView1.getText().toString();
        d1=textView2.getText().toString();
        String yd;
        yd=(y1+"\ndayTime "+d1);
        String head;
        {head=("default 0\nmres 24\nphoto_size 0\nsplit 222\nyearMonth");}
        date=(head+" "+yd);
        try {
            OutputStreamWriter osw=new OutputStreamWriter(new FileOutputStream(fileName,true),"gbk");
            osw.write(date);
            osw.close();
        }catch (IOException e){
            e.printStackTrace();
        }
    }
    public void YingY(View view){
        String y1;
        String d1;
        String date;
        TextView textView1=(TextView) findViewById(R.id.TimeY);
        TextView textView2=(TextView) findViewById(R.id.TimeD);
        y1=textView1.getText().toString();
        d1=textView2.getText().toString();
        String yd;
        yd=(y1+"\ndayTime "+d1);
        String head;
        {head=("default 0\nmres 24\nphoto_size 0\nsplit 222\nyearMonth");}
        date=(head+" "+yd);
        createFile();

    }



}

![img](https://img-mid.csdnimg.cn/release/static/image/mid/ask/206970695876142.png "#left")

Answer 1

在AndroidManifest.xml文件中添加以下代码申请读写权限：

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

另外，在Android 6.0及以上版本，需要动态申请权限，可以在onCreate()方法中添加以下代码：

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {//android 6.0以上
    //进入程序，申请读写权限
    int permission = ActivityCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE);
    if (permission != PackageManager.PERMISSION_GRANTED) {
        ActivityCompat.requestPermissions(this, PERMISSIONS_STORAGE, REQUEST_EXTERNAL_STORAGE);
    }
}

其中，PERMISSIONS_STORAGE和REQUEST_EXTERNAL_STORAGE是自定义的变量，可以在类中定义：

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