Java 如果未播放mediaplayer，应用程序在应用程序退出时崩溃

我的应用程序在应用程序退出时崩溃。除非歌曲正在播放且您退出，否则它永远不会崩溃。但如果歌曲未播放/播放，我退出应用程序，它将退出并崩溃。我在ondestroy函数的活动中终止了您的任务。 请帮帮我

这是Tip1Activity.java

public class Tip1Activity extends AppCompatActivity {
    private ArrayList<Music> arrayList;
    private CustomMusicAdapter adapter;
    private RecyclerView recyclerView;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_tip1);



        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

        recyclerView =  findViewById(R.id.recyclerViewList);

        arrayList = new ArrayList<>();
        arrayList.add(new Music("001 Veni, veni, Emmanuel", "SONGS OF WORSHIP", R.raw.veni_emmanuel));
        arrayList.add(new Music("002 O come. O come Emmanuel", "SONGS OF WORSHIP", R.raw.o_come_emmanuel));
        arrayList.add(new Music("003 Savior of the nations, come", "SONGS OF WORSHIP", R.raw.savior_of_nations));
        arrayList.add(new Music("004 On Jordan's bank the Baptist's cry", "SONGS OF WORSHIP", R.raw.on_jordans_bank));
        arrayList.add(new Music("005 Lo, he comes", "SONGS OF WORSHIP", R.raw.lo_he_comes));
        arrayList.add(new Music("006 O Word that goest forth on high", "SONGS OF WORSHIP", R.raw.o_word_that_goes_forth));
        arrayList.add(new Music("007 Wake, awake", "SONGS OF WORSHIP", R.raw.wake_awake));
        arrayList.add(new Music("008 Rorate caeli", "SONGS OF WORSHIP", R.raw.rorate_caeli));
        arrayList.add(new Music("009 Conditor alme siderum", "SONGS OF WORSHIP", R.raw.conditor_alme_siderum));
        arrayList.add(new Music("010 Creator of the stars of night", "SONGS OF WORSHIP", R.raw.creator_of_the_stars));



        adapter = new CustomMusicAdapter(this, R.layout.custom_music_row, arrayList);
        recyclerView.setAdapter(adapter);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        recyclerView.setHasFixedSize(false);

    }



    public void onDestroy() {
        super.onDestroy();
        if( adapter !=null ){
            adapter.release();
        }
    }

    @Override
    public void onBackPressed() {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setMessage("Do you want to close App?")
                .setCancelable(false)
                .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int id) {
                        Tip1Activity.this.finish();
                    }
                })
                .setNegativeButton("No", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int id) {
                        dialog.cancel();
                    }
                });
        AlertDialog alert = builder.create();
        alert.show();

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu, menu);

        MenuItem menuItem = menu.findItem(R.id.search_view);

        SearchView searchView = (SearchView) menuItem.getActionView();

        searchView.setMaxWidth(Integer.MAX_VALUE);

        searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
            @Override
            public boolean onQueryTextSubmit(String query) {
                return false;
            }

            @Override
            public boolean onQueryTextChange(String newText) {

                adapter.getFilter().filter(newText);
                return true;
            }
        });



        return  true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()){

            case R.id.item1:
                Toast.makeText(this, "Settings Selected", Toast.LENGTH_SHORT).show();
                startActivity(new Intent(this, Main2Activity.class));
                return true;

            //DO YOUR FUNCTIONALITY HERE




            default:
                return super.onOptionsItemSelected(item);
        }

    }
}

这就是我所做的，仍然给我带来错误的事情

//停止播放器
holder.mImageStop.setOnClickListener（新视图.OnClickListener（）{
@凌驾
公共void onClick（视图）{
如果（mediaPlayer！=null）
{
if（mediaPlayer.isPlaying（））
{
mediaPlayer.stop（）；
mediaPlayer.release（）；
}
holder.mImageaplay.setImageResource（R.drawable.ic_播放）；
}}
});
}

原因：java.lang.NullPointerException:尝试调用虚拟机 空对象上的方法“void android.media.MediaPlayer.stop（）” 参考文献

试一试

    if(mediaPlayer!=null)
    {     
      if(mediaPlayer.isPlaying())
      {
             mediaPlayer.stop();         
             mediaPlayer.release(); 
      }

  }

---

除非有人单击播放按钮，否则您的

mediaPlayer

不会初始化，您必须在调用

mediaPlayer.stop（）之前检查它是否为null它发生在这里：
CustomMusicAdapter.release（CustomMusicAdapter.java:38）
检查
（mediaplayer！=null）
如果mediaplyser不是
null
它仍然是空的，您只能毫无例外地释放它crashing@Joseph您是否在
release（）
方法上添加了空检查？
2020-06-24 12:44:35.598 27137-27137/com.josephgritchen.songsofworship E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.josephgritchen.songsofworship, PID: 27137
    java.lang.RuntimeException: Unable to destroy activity {com.josephgritchen.songsofworship/com.josephgritchen.songsofworship.Tip1Activity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.media.MediaPlayer.stop()' on a null object reference
        at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:4425)
        at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:4443)
        at android.app.ActivityThread.-wrap5(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1684)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6549)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:888)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.media.MediaPlayer.stop()' on a null object reference
        at com.josephgritchen.songsofworship.CustomMusicAdapter.release(CustomMusicAdapter.java:38)
        at com.josephgritchen.songsofworship.Tip1Activity.onDestroy(Tip1Activity.java:67)
        at android.app.Activity.performDestroy(Activity.java:7239)
        at android.app.Instrumentation.callActivityOnDestroy(Instrumentation.java:1249)
        at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:4412)
        at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:4443) 
        at android.app.ActivityThread.-wrap5(Unknown Source:0) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1684) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:164) 
        at android.app.ActivityThread.main(ActivityThread.java:6549) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:888) 

    if(mediaPlayer!=null)
    {     
      if(mediaPlayer.isPlaying())
      {
             mediaPlayer.stop();         
             mediaPlayer.release(); 
      }

  }