Android 10-将documentUri转换为mediaStoreUri会引发错误

Question

谁能回答为什么尝试从documentUri获取mediaUri时得到此异常。我想用mediaUri查询contentResolver以从外部存储获取所有audioFiles

Uri mediaUri = MediaStore.getMediaUri(mContext,docUri); 

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    Log.d(TAG, "onActivityResult Result erreicht " + requestCode);

    if (requestCode != PICK_AUDIO_REQUEST || resultCode != RESULT_OK) {
        Log.d(TAG, "no selection");
        return;
    }

    mUri = data.getData();
    getContentResolver().takePersistableUriPermission(mUri, Intent.FLAG_GRANT_READ_URI_PERMISSION);
    childrenUri = DocumentsContract.buildChildDocumentsUriUsingTree(mUri,
            DocumentsContract.getTreeDocumentId(mUri));
    docUri = DocumentsContract.buildDocumentUriUsingTree(mUri,
            DocumentsContract.getTreeDocumentId(mUri));

    Uri mediaUri = MediaStore.getMediaUri(mContext, docUri);
}

mUri: content://com.android.providers.downloads.documents/tree/downloads

docUri: content://com.android.providers.downloads.documents/tree/downloads/document/downloads

Stacktrace：

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.cl.languagetranslation.testandroid10, PID: 29419
java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=3, result=-1, data=Intent { dat=content://com.android.providers.downloads.documents/tree/downloads flg=0xc3 }} to activity {com.cl.languagetranslation.testandroid10/com.cl.languagetranslation.testandroid10.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.net.Uri.getPath()' on a null object reference
    at android.app.ActivityThread.deliverResults(ActivityThread.java:4845)
    at android.app.ActivityThread.handleSendResult(ActivityThread.java:4886)
    at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:51)
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
    at android.os.Handler.dispatchMessage(Handler.java:107)
    at android.os.Looper.loop(Looper.java:214)
    at android.app.ActivityThread.main(ActivityThread.java:7356)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.net.Uri.getPath()' on a null object reference
    at android.os.Parcel.createException(Parcel.java:2077)
    at android.os.Parcel.readException(Parcel.java:2039)
    at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:188)
    at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:140)
    at android.content.ContentProviderProxy.call(ContentProviderNative.java:658)
    at android.content.ContentProviderClient.call(ContentProviderClient.java:558)
    at android.content.ContentProviderClient.call(ContentProviderClient.java:546)
    at android.provider.MediaStore.getMediaUri(MediaStore.java:3501)
    at com.cl.languagetranslation.testandroid10.MainActivity.onActivityResult(MainActivity.java:121)
    at android.app.Activity.dispatchActivityResult(Activity.java:8110)
    at android.app.ActivityThread.deliverResults(ActivityThread.java:4838)
    at android.app.ActivityThread.handleSendResult(ActivityThread.java:4886) 
    at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:51) 
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016) 
    at android.os.Handler.dispatchMessage(Handler.java:107) 
    at android.os.Looper.loop(Looper.java:214) 
    at android.app.ActivityThread.main(ActivityThread.java:7356) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930) 

感谢您的帮助！从存储中获取音频文件确实是一项艰巨的任务……还有其他人也在苦苦挣扎……所以，我并不孤单地试图做到这一点……

GGK

Answer 1

getMediaUri（）允许具有Storage Access Framework权限的应用程序在MediaStore和引用相同基础项的DocumentsProvider Uris之间进行转换。请注意，此方法不会授予任何新权限。调用者必须已经拥有通过Intent＃ACTION_OPEN_DOCUMENT或相关API获得的权限。