無法更改Android Studio中的全局變量

Question

我是android新手。我正在嘗試獲取存儲權限。但不能在onRequestPermissionsResult方法中更改全局布爾變量。我無法使permissionIsGranted = true。那麼，有沒有人可以幫助我。我該怎麼辦？

package com.plutianclub.musicappv1; 

import android.content.pm.PackageManager; 
import android.os.Build; 
import android.os.Environment; 
import android.support.annotation.NonNull; 
import android.support.v4.app.ActivityCompat; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.widget.ListView; 
import android.widget.Toast; 

import java.io.File; 
import java.util.ArrayList; 
import java.util.jar.Manifest; 

public class MainActivity extends AppCompatActivity { 

    private static final int MY_PERMISSION_REQUEST_STORAGE_READ = 101; 
    private boolean permissionIsGranted = false; 

    ListView lv; 
    String items; 


    @Override 
    protected void onCreate(Bundle savedInstanceState) { 

     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 

     lv = (ListView) findViewById(R.id.lvPlaylist); 


     requestStoragePermission(); 
     Toast.makeText(getApplicationContext(), "Hello", Toast.LENGTH_SHORT).show(); 

      if (permissionIsGranted) { 
       Toast.makeText(getApplicationContext(), "wow", Toast.LENGTH_SHORT).show(); 
       ArrayList<File> mySongs = findSongs(Environment.getExternalStorageDirectory()); 

       for (int i = 0; i < mySongs.size(); i++) { 
        toast(mySongs.get(i).getName()); 

       } 
      } 


    } 




    private void requestStoragePermission() { 
     if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) { 
      if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) { 
       requestPermissions(new String[]{android.Manifest.permission.READ_EXTERNAL_STORAGE}, MY_PERMISSION_REQUEST_STORAGE_READ); 
      } 

     } 

    } 


    public ArrayList<File> findSongs (File root) { 
     ArrayList<File> al = new ArrayList<File>(); 

     File[] files = root.listFiles(); 
     for (File singleFile : files){ 
      if (singleFile.isDirectory() && !singleFile.isHidden()) { 
       al.addAll(findSongs(singleFile)); 
      }else { 
       if (singleFile.getName().endsWith(".mp3")){ 
        al.add(singleFile); 
       } 
      } 
     } 
     return al; 

    } 

    public void toast(String text){ 
     Toast.makeText(getApplicationContext(),text,Toast.LENGTH_SHORT).show(); 
    } 

    @Override 
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) { 
     super.onRequestPermissionsResult(requestCode, permissions, grantResults); 
     switch (requestCode){ 
      case MY_PERMISSION_REQUEST_STORAGE_READ: 
       if (grantResults[0] == PackageManager.PERMISSION_GRANTED) { 
        //permission granted 
        permissionIsGranted = true; 
        Toast.makeText(getApplicationContext(), "Permission Granted", Toast.LENGTH_SHORT).show(); 
       }else { 
        //permission denied 
        permissionIsGranted = false; 
        Toast.makeText(getApplicationContext(), "This application needs Storage permission", Toast.LENGTH_SHORT).show(); 
       } 

       break; 

     } 
    } 





} 

Answer 1

您需要將上下文傳遞給requestPermissions方法。那麼只有你的 onRequestPermissionsResult方法將被調用，你將能夠設置權限。

requestPermissions(this, 
               new String[]{android.Manifest.permission.READ_EXTERNAL_STORAGE}, MY_PERMISSION_REQUEST_STORAGE_READ);