получение Cursor.getColumnIndexOrThrow (java.lang.String) 'для ссылки на пустой объект, когда курсор не является нулевым - PullRequest
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получение Cursor.getColumnIndexOrThrow (java.lang.String) 'для ссылки на пустой объект, когда курсор не является нулевым

0 голосов
/ 22 июня 2019

Я вставлял данные курсора в arrayList, и приложение зависало из-за этой ошибки.Когда я проверяю размер курсора с помощью cursor.getCount (), он показывает мне 188. Но когда я являюсь курсором .getColumnIndexOrThrow (MediaStore.Audio.Media.DATA), я получаю эту ошибку.Как нулевой объект дает мне счетчик и затем показывает мне пустую ссылку на объект. 

    public ArrayList<songInfo> getSongArray(){
        ArrayList<songInfo> songsList = new ArrayList<>();
        songInfo sInfo;

        Cursor c = getSongCursor();
        /*if(c==null) {
            Log.v("empty_cursor","yes");
            return songsList;
        }else{
            Log.v("cursor'sLength",""+c.getCount()); \\ giving me 188.
            return songsList;
        }*/



        int songPathIndex = c.getColumnIndexOrThrow(MediaStore.Audio.Media.DATA); \\ giving me ERROR here.
        /*int songTitleIndex = c.getColumnIndexOrThrow(MediaStore.Audio.Media.TITLE);
        //Toast.makeText(, "", Toast.LENGTH_SHORT).show();

        sInfo = new songInfo("Hello Mayank","no path to this");
        songsList.add(sInfo);
        songsList.add(sInfo);
        Log.v("Cursor_length",""+c.getCount());
        for(int i=0;i<c.getCount();i++){
            sInfo = new songInfo(c.getString(songTitleIndex),c.getString(songPathIndex));
            //songsList.add(sInfo);
        }*/
        return songsList;
    }

public Cursor getSongCursor(){
        try{
            Uri externalUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
            String[] projection = new String[]{
                    MediaStore.Audio.Media._ID,
                    MediaStore.Audio.Media.TITLE,
                    MediaStore.Audio.Media.ALBUM,
                    MediaStore.Audio.Media.DATA
                    //MediaStore.Audio.Media._ID,
            };
            String selection = null;
            String[] selectionArgs = null;
            String sortOrder = MediaStore.Audio.Media.TITLE+" ASC";
            Cursor songCursor = getContext().getContentResolver().query(externalUri,projection,selection,selectionArgs,sortOrder);
            Log.v("cursor_length","" + songCursor.getCount());
            Toast.makeText(getActivity(), "Okay till now", Toast.LENGTH_SHORT).show();
            return songCursor;
        }catch (Exception e){
            return null;
        }
    }

ОШИБКИ (пустая ссылка на объект): 

java.lang.NullPointerException: Attempt to invoke interface method 'int android.database.Cursor.getColumnIndexOrThrow(java.lang.String)' on a null object reference

Полные ошибки: 

2019-06-22 11:44:05.909 14962-14962/com.example.mymusicplayer E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.mymusicplayer, PID: 14962
    java.lang.NullPointerException: Attempt to invoke interface method 'int android.database.Cursor.getColumnIndexOrThrow(java.lang.String)' on a null object reference
        at com.example.mymusicplayer.RecyclerViewFragment.getSongArray(RecyclerViewFragment.java:78)
        at com.example.mymusicplayer.RecyclerViewFragment.onViewCreated(RecyclerViewFragment.java:60)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1471)
        at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1784)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1852)
        at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:802)
        at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2625)
        at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2411)
        at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2366)
        at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:2243)
        at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:654)
        at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:146)
        at android.support.v4.view.ViewPager.populate(ViewPager.java:1244)
        at android.support.v4.view.ViewPager.populate(ViewPager.java:1092)
        at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1622)
        at android.view.View.measure(View.java:22105)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6606)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1514)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:806)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:685)
        at android.view.View.measure(View.java:22105)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6606)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
        at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:143)
        at android.view.View.measure(View.java:22105)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6606)
        at android.support.v7.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:401)
        at android.view.View.measure(View.java:22105)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6606)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
        at android.view.View.measure(View.java:22105)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6606)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1514)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:806)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:685)
        at android.view.View.measure(View.java:22105)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6606)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
        at com.android.internal.policy.DecorView.onMeasure(DecorView.java:727)
        at android.view.View.measure(View.java:22105)
        at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2467)
        at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1549)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1806)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1437)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6886)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:1029)
        at android.view.Choreographer.doCallbacks(Choreographer.java:841)
        at android.view.Choreographer.doFrame(Choreographer.java:772)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:1015)
        at android.os.Handler.handleCallback(Handler.java:794)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:176)
2019-06-22 11:44:05.909 14962-14962/com.example.mymusicplayer E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:6651)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:824)
...