[英]IllegalStateException: No activity when onStop() method called
[英]RecyclerView release MediaPlayer when activity onStop is triggered
我正在使用一個TextView和ImageButton視圖創建一個簡單的應用程序,我正在使用RecyclerView顯示這些對的列表,所以我編寫了我的自定義適配器和視圖支架。 但是當用戶進入主屏幕時,我有一個問題如何釋放MediaPlayer 。 因為我在適配器內部初始化MediaPlayer ,如果活動停止,我不知道如何觸發釋放。 這是我的代碼:
活動 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));
}
}
適配器 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;
}
}
}
我是否應該將 MediaPlayer object 傳遞給適配器並從活動 class 控制它的 state? 或者是否可以從適配器內部進行?
@Override
public void onViewDetachedFromWindow(@NonNull ViewHolder holder) {
super.onViewDetachedFromWindow(holder);
stopPlaying();
}
在這里你設置停止你的播放器。
當ViewHolder
在屏幕上不可見時觸發
您應該在 Activity 中擁有您的播放器實例,並通過來自適配器的接口回調(偵聽器模式)來控制它。
此外,在VH
中使用單個媒體播放器而不是多個播放器的性能會更好
回調應如下所示:
interface PlayableItemCallback {
void onItemVisible(int position);
void onPlay(int position);
void onStop(int position);
}
在您的活動中實現它並使用它來控制您的 MediaPlayer,並將其傳遞給適配器。 活動代碼:
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
方法停止媒體播放器。 為了讓它工作,你必須創建適配器的實例,當onStop()
調用時,只需從適配器調用方法,你就完成了!!!
創建適配器的實例
private WordAdapter mWordAdapter;
mWordAdapter = new WordAdapter(this, words)
listView.setAdapter(mWordAdapter)
覆蓋活動中的 onStop 方法
@Override
protected void onStop() {
super.onStop();
if(mWordAdapter!=null){
mWordAdapter.stopPlaying()
}
}
公開stopPlaying
方法,以便您可以通過 object 訪問它。
public void stopPlaying() {
if (mediaPlayer != null && mediaPlayer.isPlaying()) {
mediaPlayer.stop();
mediaPlayer.reset();
mediaPlayer.release();
mediaPlayer = null;
}
}
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