Read_EXTERNAL_STORAGE权限目标SDK 29

问题描述

询问许可，我正在我的简单音乐应用中寻求许可以读取外部存储
它请求许可，但未在ListView中列出歌曲
minSdkVersion 27
targetSdkVersion 29

它在我终止应用程序并重新启动后显示歌曲列表。

这是我的代码：

public class MainActivity extends AppCompatActivity {

private  int STORAGE_PERMISSION_CODE = 1;
ListView lvMusic;
MediaPlayer mp;
String name[],path[];
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    lvMusic = (ListView) findViewById(R.id.lvMusic);
    mp = new MediaPlayer();

    ContentResolver contentResolver = getContentResolver();
    Cursor cursor = contentResolver.query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,null,null);

    name = new String[cursor.getCount()];
    path = new String[cursor.getCount()];

    int i = 0;
    while(cursor.movetoNext()){
        name[i] =cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.disPLAY_NAME));
        path[i] = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DATA));
        i++;
    }

    ArrayAdapter arrayAdapter =new ArrayAdapter(this,android.R.layout.simple_list_item_1,name);


    if(ContextCompat.checkSelfPermission(this,Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED){
        requestStoragePermission();

    }
   
    lvMusic.setAdapter(arrayAdapter);
}

private void requestStoragePermission(){
    if(ActivityCompat.shouldShowRequestPermissionRationale(this,Manifest.permission.READ_EXTERNAL_STORAGE)){
        new AlertDialog.Builder(this)
                .setTitle("Permission Needed")
                .setMessage("This Permission is needed to Read Files")
                .setPositiveButton("OK",new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog,int which) {
                        ActivityCompat.requestPermissions(MainActivity.this,new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},STORAGE_PERMISSION_CODE);
                    }
                })
                .setNegativeButton("Cancle",int which) {
                        dialog.dismiss();
                    }
                })
                 .create().show();
    }else{
        ActivityCompat.requestPermissions(this,STORAGE_PERMISSION_CODE);
    }
}

@Override
public void onRequestPermissionsResult(int requestCode,@NonNull String[] permissions,@NonNull int[] grantResults) {
    if(requestCode == STORAGE_PERMISSION_CODE ){
        if(grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
            Toast.makeText(this,"Permission Granted",Toast.LENGTH_SHORT).show();
        }else{
            Toast.makeText(this,"Permission not Granted",Toast.LENGTH_SHORT).show();
        }
    }
}

}

谢谢！

解决方法

创建一个函数loadSongs（）并在授予权限时调用它。

void loadSongs(){
    ContentResolver contentResolver = getContentResolver();
    Cursor cursor = contentResolver.query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,null,null);
    name = new String[cursor.getCount()];
    path = new String[cursor.getCount()];
    int i = 0;
    while(cursor.moveToNext()){
        name[i] =cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DISPLAY_NAME));
        path[i] = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DATA));
        i++;
    }
    ArrayAdapter arrayAdapter =new ArrayAdapter(this,android.R.layout.simple_list_item_1,name);
    lvMusic.setAdapter(arrayAdapter);
)

现在在创建时，检查是否已授予许可，如果已授予，请调用loadSongs（）

if(ContextCompat.checkSelfPermission(this,Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED)
    requestStoragePermission();
else
 loadSongs();

如果已授予许可，现在onRequestPermission结果中将调用loadSongs：

@Override
public void onRequestPermissionsResult(int requestCode,@NonNull String[] permissions,@NonNull int[] grantResults) {
    if(requestCode == STORAGE_PERMISSION_CODE ){
        if(grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
            loadSongs();
            Toast.makeText(this,"Permission Granted",Toast.LENGTH_SHORT).show();
        }else{
            Toast.makeText(this,"Permission not Granted",Toast.LENGTH_SHORT).show();
        }
    }
}