将逻辑从适配器移动到片段 - 错误：找不到视图 ID

Question

问题：我试图将我的mediaplayer方法(在我的适配器中(合并到我的片段(我想在那里拥有我的mediaplayer对象(
为什么-因为我希望我的适配器不包含任何方法/逻辑。它应该ONLY膨胀视图，而不是其他内容。

我试图将我的MediaPlayer方法(在我的适配器中(移动到我的片段中，但当我试图在片段中找到我的playB和stopB(应该播放并停止歌曲(时，它会给我一个nullexception。我查看了我的XML文件(我的playB+stopB ID在哪里(，一切都很好

我的适配器：

public class ListViewAdapter extends BaseAdapter {
//Create variables
MediaPlayer mediaPlayer;
Song currentSong;
int layout;
ArrayList<Song> arrayList;
Context context;
//Constructor
public ListViewAdapter(int layout, ArrayList<Song> arrayList, Context context) {
this.layout = layout;
this.arrayList = arrayList;
this.context = context;
}
//ViewHolder class holding my views
private class Viewholder {
TextView artistTxt, songNameTxt;
ImageView playB, stopB;
CircleImageView artistImg;
}
@Override
public int getCount() {
return arrayList.size();
}
@Override
public Object getItem(int position) {
return null;
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(int position, View view, ViewGroup parent) {
//Create viewholder variable
final Viewholder viewholder;
//Check if view is null
if (view == null) {
//Create new ViewHolder object
viewholder = new Viewholder();
//Inflate my view
LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
view = layoutInflater.inflate(R.layout.listview_customlayout, null);
//Find my view id's
viewholder.artistImg = view.findViewById(R.id.artistImgBackgroundDetail);
viewholder.artistTxt = view.findViewById(R.id.artistTxt);
viewholder.songNameTxt = view.findViewById(R.id.songNameTxt);
viewholder.playB = view.findViewById(R.id.playB);
viewholder.stopB = view.findViewById(R.id.stopB);
//Set my view to viewholder
view.setTag(viewholder);
} else {
viewholder = (Viewholder) view.getTag();
}
//Assign song to my arraylist
final Song song = arrayList.get(position);
//Set my views to their resources
viewholder.artistImg.setImageResource(song.getArtistImg());
viewholder.artistTxt.setText(song.getArtist());
viewholder.songNameTxt.setText(song.getSongName());
return view;

正如您所看到的-非常简单的适配器，我可以在其中调整我的自定义列表视图。

这是我的片段类，我**无法找到视图ID:**

MediaPlayer mediaPlayer;
Song currentSong;
int position;
ImageView playB, stopB;
@Nullable
@Override
public View onCreateView(@NonNull final LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_main, container, false);
//Actionbar
((AppCompatActivity) getActivity()).getSupportActionBar().setTitle("Song list");
//Find my listview
songListView = view.findViewById(R.id.songListView);
playB = getActivity().findViewById(R.id.playB);
stopB = getActivity().findViewById(R.id.stopB);
//create a new arraylist object
arrayList = new ArrayList<>();

adapter = new ListViewAdapter(R.layout.listview_customlayout, arrayList, getActivity());
//Set my listview to my custom adapter
songListView.setAdapter(adapter);
//Click on a specific song from my list
songListView.setOnItemClickListener(new ListViewClickListener());

final Song song = arrayList.get(position);

//get all songs
mediaPlayer = MediaPlayer.create(getActivity(), song.getSong());
//Play button click performed
playB.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {

//Checks if my current song is null and creates a new song
if (currentSong == null) {
mediaPlayer = MediaPlayer.create(getActivity(), song.getSong());
}
//if mediaplayer is not null and my current song is not equal to the new song i clicked on
if (mediaPlayer != null && currentSong != song) {
//resets the mediaplayer and creates a new song from the position in the list
mediaPlayer.reset();
mediaPlayer = MediaPlayer.create(getActivity(), song.getSong());
playB.setImageResource(R.drawable.play_orange);
mediaPlayer.start();
playB.setImageResource(R.drawable.pause_orange);
} else {
mediaPlayer.pause();
playB.setImageResource(R.drawable.play_orange);
}
//check if current song is null or the newly clicked song is equal to my current song
//if true then assign the newly clicked song as my CURRENT one
//--so it doesnt play the same song for every single one
if (currentSong == null || song != currentSong) {
currentSong = song;
}
}
});
//Stop song when click performed
stopB.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//stops my current song and make it null
if (currentSong != null) {
mediaPlayer.stop();
mediaPlayer.release();
currentSong = null;
playB.setImageResource(R.drawable.play_orange);
}
}
});

//return my view
return view;

我想把我的ListViewAdapter留给，只膨胀视图，这意味着我不能包含函数性。

任何建议都会受到赞赏，因为我正在努力做得更好：(

如果你需要更多的信息，请告诉我。我很乐意尽可能地把它说清楚。

谢谢。

Answer 1

试试这个制作一个接口

ClickUpdate.java

public interface ClickUpdate {
void getClicks();
}

内部

ListViewAdapter.java

public static ClickUpdate clickupadte;
public static void setonConnectionListener(ClickUpdate clicklisten) {
ListViewAdapter.clickupadte = clicklisten
}

同时点击listviewadapter 中的stopB

viewholder.stopB.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
clickupadte.getClicks();
}
});

最后进入

片段类内部oncreateview初始化

ListViewAdapter.setonConnectionListener(this);

还实现了ClickUpdate，然后在名为getClicks的片段类内部生成一个重写的方法，我认为该方法内部会给出

if (currentSong != null) {
mediaPlayer.stop();
mediaPlayer.release();
currentSong = null;
//playB.setImageResource(R.drawable.play_orange);//this will  cause null point error,if occured to avoid the error pass viewholder.playB inside clickupadte.getClicks(); function
}

Answer 2

在MVVM模式中，适配器应该与视图相关联，而不是与视图模型相关联。因此，您可能要做的是使适配器成为片段类的内部类。如果您为mediaPlayer提供了一个全局变量，那么您可以在适配器和片段中使用它的相同实例，如果这正是您想要的。

希望这能有所帮助！