我正在创建一个音乐播放器，我尝试从SD卡访问歌曲。但它显示了与许可相关的一些错误。如何确保授予权限。我是android的初学者。任何帮助将不胜感激。
这就是我访问歌曲的方式。
public void getSongList(){
ContentResolver musicResolver = getContentResolver();
Uri musicUri = android.provider.MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
Cursor musicCursor = musicResolver.query(musicUri, null, null, null, null);
if(musicCursor!=null && musicCursor.moveToFirst()){
int titleColumn = musicCursor.getColumnIndex
(android.provider.MediaStore.Audio.Media.TITLE);
int idColumn = musicCursor.getColumnIndex
(android.provider.MediaStore.Audio.Media._ID);
int artistColumn = musicCursor.getColumnIndex
(android.provider.MediaStore.Audio.Media.ARTIST);
do {
long thisId = musicCursor.getLong(idColumn);
String thisTitle = musicCursor.getString(titleColumn);
String thisArtist = musicCursor.getString(artistColumn);
songList.add(new Song(thisId, thisTitle, thisArtist));
}
while (musicCursor.moveToNext());
}
}
我正在onCreate中对列表进行排序。
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//retrieve list view
songView = (ListView)findViewById(R.id.song_list);
//instantiate list
songList = new ArrayList<Song>();
//get songs from device
getSongList();
//sort alphabetically by title
Collections.sort(songList, new Comparator<Song>(){
public int compare(Song a, Song b){
return a.getTitle().compareTo(b.getTitle());
}
});
即使在添加了@hasbi建议的功能后，我也遇到了同样的错误。这是我的logcat摘要。
FATAL EXCEPTION: main
Process: com.example.john.musicplayer, PID: 2716
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.john.musicplayer/com.example.john.musicplayer.MainActivity}: java.lang.SecurityException: Permission Denial: reading com.android.providers.media.MediaProvider uri content://media/external/audio/media from pid=2716, uid=10083 requires android.permission.READ_EXTERNAL_STORAGE, or grantUriPermission()
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2646)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
Caused by: java.lang.SecurityException: Permission Denial: reading com.android.providers.media.MediaProvider uri content://media/external/audio/media from pid=2716, uid=10083 requires android.permission.READ_EXTERNAL_STORAGE, or grantUriPermission()
at android.os.Parcel.readException(Parcel.java:1683)
at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:183)
at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:135)
at android.content.ContentProviderProxy.query(ContentProviderNative.java:421)
at android.content.ContentResolver.query(ContentResolver.java:530)
at android.content.ContentResolver.query(ContentResolver.java:472)
at com.example.john.musicplayer.MainActivity.getSongList(MainActivity.java:147)
at com.example.john.musicplayer.MainActivity.onCreate(MainActivity.java:63)
at android.app.Activity.performCreate(Activity.java:6662)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2599)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
答案 0 :(得分：0)
添加
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
到您的清单文件
将此代码添加到mainactivity的oncreate函数
ActivityCompat.requestPermissions(MainActivity.this,
new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},
1);
将此代码添加到主活动文件的全局区域
@Override
public void onRequestPermissionsResult(int requestCode,
String permissions[], int[] grantResults)
{
switch (requestCode) {
case 1: {
// If request is cancelled, the result arrays are empty.
if (grantResults.length > 0
&& grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// permission was granted, yay! Do the
// contacts-related task you need to do.
} else {
// permission denied, boo! Disable the
// functionality that depends on this permission.
Toast.makeText(MainActivity.this, "Permission denied to read your External storage", Toast.LENGTH_SHORT).show();
}
return;
}
// other 'case' lines to check for other
// permissions this app might request
}
}`
答案 1 :(得分：0)
在logcat中，它显示权限拒绝，请清楚应用数据并重新检查。另外，再次检查@hasbi提到的代码