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[英]IllegalStateException: No activity when onStop() method called
[英]RecyclerView release MediaPlayer when activity onStop is triggered
我正在使用一个TextView和ImageButton视图创建一个简单的应用程序,我正在使用RecyclerView显示这些对的列表,所以我编写了我的自定义适配器和视图支架。 但是当用户进入主屏幕时,我有一个问题如何释放MediaPlayer 。 因为我在适配器内部初始化MediaPlayer ,如果活动停止,我不知道如何触发释放。 这是我的代码:
活动 class:
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 class:
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;
}
}
}
我是否应该将 MediaPlayer object 传递给适配器并从活动 class 控制它的 state? 或者是否可以从适配器内部进行?
@Override
public void onViewDetachedFromWindow(@NonNull ViewHolder holder) {
super.onViewDetachedFromWindow(holder);
stopPlaying();
}
在这里你设置停止你的播放器。
当ViewHolder
在屏幕上不可见时触发
您应该在 Activity 中拥有您的播放器实例,并通过来自适配器的接口回调(侦听器模式)来控制它。
此外,在VH
中使用单个媒体播放器而不是多个播放器的性能会更好
回调应如下所示:
interface PlayableItemCallback {
void onItemVisible(int position);
void onPlay(int position);
void onStop(int position);
}
在您的活动中实现它并使用它来控制您的 MediaPlayer,并将其传递给适配器。 活动代码:
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
}
}
您可以使用stopPlaying
方法停止媒体播放器。 为了让它工作,你必须创建适配器的实例,当onStop()
调用时,只需从适配器调用方法,你就完成了!!!
创建适配器的实例
private WordAdapter mWordAdapter;
mWordAdapter = new WordAdapter(this, words)
listView.setAdapter(mWordAdapter)
覆盖活动中的 onStop 方法
@Override
protected void onStop() {
super.onStop();
if(mWordAdapter!=null){
mWordAdapter.stopPlaying()
}
}
公开stopPlaying
方法,以便您可以通过 object 访问它。
public void stopPlaying() {
if (mediaPlayer != null && mediaPlayer.isPlaying()) {
mediaPlayer.stop();
mediaPlayer.reset();
mediaPlayer.release();
mediaPlayer = null;
}
}
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