java - 当 Activity onStop 被触发时，RecyclerView 释放 MediaPlayer

Question

我正在创建一个简单的应用程序，其中包含一个 TextView 和 ImageButton View ，我使用 RecyclerView 来显示这些 View 对的列表，以便我编写了自定义适配器和 View 支架。但我有一个问题，如何在用户进入主屏幕时释放 MediaPlayer 。因为我在适配器内初始化 MediaPlayer ，并且我不知道如果 Activity 停止如何触发释放。这是我的代码:

Activity 类别:

public class NumbersActivity extends AppCompatActivity {

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

        List<Word> words = new ArrayList<>();
        words.add(new Word("one", R.raw.number_one));
        words.add(new Word("two", R.raw.number_two));
        words.add(new Word("three", R.raw.number_three));
        words.add(new Word("four", R.raw.number_four));
        words.add(new Word("five", R.raw.number_five));

        LinearLayoutManager numbersListLayoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
        RecyclerView listView = findViewById(R.id.word_list);
        listView.setLayoutManager(numbersListLayoutManager);
        listView.setAdapter(new WordAdapter(this, words));
    }
}

适配器类:

public class WordAdapter extends RecyclerView.Adapter<WordAdapter.ViewHolder> {

        private Context context;
        private List<Word> words;
        private MediaPlayer mediaPlayer;

        public WordAdapter(Context context, List<Word> words) {
            this.context = context;
            this.words = words;
        }

        @NonNull
        @Override
        public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View viewItem = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_item, parent, false);
            return new ViewHolder(viewItem);
        }

        @Override
        public void onViewDetachedFromWindow(@NonNull ViewHolder holder) {
            super.onViewDetachedFromWindow(holder);
            stopPlaying();
        }

        @Override
        public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
            holder.englishTranslation.setText(this.words.get(position).getDefaultTranslation());

            holder.itemView.setOnClickListener((view) -> {
                stopPlaying();
                mediaPlayer = MediaPlayer.create(this.context, this.words.get(position).getAudioResourceId());
                mediaPlayer.setOnCompletionListener((mp) -> {
                    stopPlaying();
                });
                mediaPlayer.start();
            });
        }

        @Override
        public int getItemCount() {
            return words.size();
        }

        public class ViewHolder extends RecyclerView.ViewHolder {
            TextView englishTranslation;
            ImageButton playButton;

            public ViewHolder(View wordView) {
                super(wordView);
                this.englishTranslation = wordView.findViewById(R.id.english_text_view);
                this.playButton = wordView.findViewById(R.id.play_button);
            }
        }

        private void stopPlaying() {
            if (mediaPlayer != null && mediaPlayer.isPlaying()) {
                mediaPlayer.stop();
                mediaPlayer.reset();
                mediaPlayer.release();
                mediaPlayer = null;
            }
        }
    }

我应该将 MediaPlayer 对象传递给适配器并从 Activity 类控制它的状态吗？或者是否可以从适配器内部执行此操作？

Answer 1

@Override
    public void onViewDetachedFromWindow(@NonNull ViewHolder holder) {
        super.onViewDetachedFromWindow(holder);
        stopPlaying();
    }

此处您要设置停止播放器。

当ViewHolder在屏幕上不可见时触发

您应该将播放器实例放在 Activity 中，并通过适配器的接口(interface)回调(监听器模式)来控制它。

此外，使用单个媒体播放器而不是多个内部 VH 的性能会更好

回调应如下所示:

interface PlayableItemCallback {
 void onItemVisible(int position);

 void onPlay(int position);

 void onStop(int position);
}

在您的 Activity 中实现它，并使用它来控制您的 MediaPlayer，并将其传递给适配器。 Activity 代码:

public class NumbersActivity extends AppCompatActivity implements PlayableItemCallback {
    MediaPlayer mediaPlayer;
    Adapter adapter = Adapter(this)

    //    .............
    @Override
    public void onItemVisible(int position) {

        // do stuff with player
    }

    @Override
    public void onPlay(int position) {
        // do stuff with player
    }

    @Override
    public void onStop(int position) {
        // do stuff with player
    }
}