Help Me To Show Android Track Selection Dialogue

E/AndroidRuntime: FATAL EXCEPTION: main

    Process: com.mi.corns, PID: 15911

    java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.android.exoplayer2.trackselection.MappingTrackSelector$MappedTrackInfo com.google.android.exoplayer2.trackselection.MappingTrackSelector.ﾠ()' on a null object reference

        at com.mi.corns.DetailsActivity$o.onClick(:619)

        at android.view.View.performClick(View.java:6256)

        at android.view.View$PerformClick.run(View.java:24701)

        at android.os.Handler.handleCallback(Handler.java:789)

        at android.os.Handler.dispatchMessage(Handler.java:98)

        at android.os.Looper.loop(Looper.java:164)

        at android.app.ActivityThread.main(ActivityThread.java:6541)

        at java.lang.reflect.Method.invoke(Native Method)

        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)

        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)

E/Surface: queueBuffer: error queuing buffer to SurfaceTexture, -19

E/EGL_emulation: tid 16020: swapBuffers(550): error 0x300d (EGL_BAD_SURFACE

imgQuality.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               MappingTrackSelector.MappedTrackInfo mappedTrackInfo = trackSelector.getCurrentMappedTrackInfo();
               if (mappedTrackInfo != null) {
                   //CharSequence title = ((Button) view).getText();
                   int rendererIndex = 1;
                   int rendererType = mappedTrackInfo.getRendererType(rendererIndex);
                   boolean allowAdaptiveSelections =
                           rendererType == C.TRACK_TYPE_VIDEO
                                   || (rendererType == C.TRACK_TYPE_AUDIO
                                   && mappedTrackInfo.getTypeSupport(C.TRACK_TYPE_VIDEO)
                                   == MappingTrackSelector.MappedTrackInfo.RENDERER_SUPPORT_NO_TRACKS);
                   TrackSelectionDialogBuilder build = new TrackSelectionDialogBuilder(DetailsActivity.this, title, trackSelector, rendererIndex);
                   build.setAllowAdaptiveSelections(allowAdaptiveSelections);
                   build.build().show();
                   build.setShowDisableOption(true);
                   build.setAllowAdaptiveSelections(allowAdaptiveSelections);
               }
           }
       });

MappingTrackSelector.MappedTrackInfo mappedTrackInfo = trackSelector.getCurrentMappedTrackInfo();