Question

我要实现的是在垂直horizontal内的recyclerview recyclerview（例如Google Play商店）。我认为位置参数取决于getItemCount方法。但是我的getItemcount返回4，而onBindView()仅循环2次（下面的代码）。

MainActivity和VericalRecyclerview

  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    String title[] = this.getResources().getStringArray(R.array.titleArray);
    String subTitle[] = this.getResources().getStringArray(R.array.subTitleArray);
    String recy1[] = this.getResources().getStringArray(R.array.recy1);
    String recy2[] = this.getResources().getStringArray(R.array.recy2);
    String recy3[] = this.getResources().getStringArray(R.array.recy3);

    String recy1Titles[] = this.getResources().getStringArray(R.array.recy1Title);
    String recy2Titles[] = this.getResources().getStringArray(R.array.recy2Title);
    String recy3Titles[] = this.getResources().getStringArray(R.array.recy3Title);


    Play2G_S play2G_s = new Play2G_S(); //getter setter class
    play2G_s.setImages(recy1);
    play2G_s.setImageTitles(recy1Titles);
    list1.add(play2G_s);
    Log.i("sand2", list1+ "");

    Play2G_S play2G_s2 = new Play2G_S();//getter setter class
    play2G_s2.setImages(recy2);
    play2G_s2.setImageTitles(recy2Titles);
    list1.add(play2G_s2);
    Log.i("sand2", list1+ "");

    Play2G_S play2G_s3 = new Play2G_S();//getter setter class
    play2G_s3.setImages(recy3);
    play2G_s3.setImageTitles(recy3Titles);
    list1.add( play2G_s3);

    Log.i("sand2", Arrays.toString(list1.get(1).getImageTitles()) + "");

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });
    for (int i = 0; i < title.length; i++) {
        PlayStore1G_S g_s = new PlayStore1G_S();
        g_s.setSubTitle(subTitle[i]);
        g_s.setTitle(title[i]);
        g_s.setgSList(list1.get(i));
        list.add(g_s);
    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.addDrawerListener(toggle);
    toggle.syncState();

    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);

    RecyclerView recyclerView = findViewById(R.id.recyView);
    RecyclerView.LayoutManager manager = new LinearLayoutManager(MainActivity.this);
    recyclerView.setLayoutManager(manager);
    PlayStore1Adapter adapter = new PlayStore1Adapter(list);
    recyclerView.setAdapter(adapter);
}

适配器

class PlayStore1Adapter extends RecyclerView.Adapter<PlayStore1Adapter.MyViewHolder> {
Context context;
List<PlayStore1G_S> list;
public PlayStore1Adapter(List<PlayStore1G_S> list) {
    this.list = list;
}

@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    this.context= parent.getContext();
    View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.single_row1,parent,false);
    return new MyViewHolder(v);
}

@Override
public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {

    holder.title.setText(list.get(position).getTitle());
    holder.subTitle.setText(list.get(position).getSubTitle());/*
    Log.i("sand", Arrays.toString(list.get(position).getList().getImages()));
    Log.i("sand", Arrays.toString(list1.get(0).getImageTitles()));*/

    RecyclerView.LayoutManager manager = new LinearLayoutManager(this.context,LinearLayoutManager.HORIZONTAL,false);
    holder.recyclerView.setLayoutManager(manager);
    PlayStore2Adapter adapter = new PlayStore2Adapter(list.get(position).getgSList(),context );
    holder.recyclerView.setAdapter(adapter);

    Log.i("sand3", Arrays.toString(list.get(position).getgSList().getImageTitles()) +"");

}

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

public class MyViewHolder extends RecyclerView.ViewHolder {
       TextView title,subTitle;
       RecyclerView recyclerView;
       public MyViewHolder(View v) {
           super(v);

            title = v.findViewById(R.id.title1);
            subTitle = v.findViewById(R.id.subTitle1);
             recyclerView = v.findViewById(R.id.newRecyView);
         }
       }
    }

和水平适配器

public class PlayStore2Adapter extends RecyclerView.Adapter<PlayStore2Adapter.MyViewHolder> {
Play2G_S list;
Context context;
public PlayStore2Adapter(Play2G_S list, Context context) {
    this.list = list;

}

@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.single_row2,parent,false);
    return new MyViewHolder(v);
}

@Override
public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {

//     holder.textView.setText(list.getImageTitles()[position]+"");  /// shows error set null

    Log.i("sand34", Arrays.toString(list.getImageTitles()) +"");
}


@Override
public int getItemCount() {

    return list.getImageTitles().length;  //returns 4
}

public class MyViewHolder extends RecyclerView.ViewHolder {
    TextView textView;
    public MyViewHolder(View v) {
        super(v);

        textView = v.findViewById(R.id.textView);
    }
 }
 }

Answer 1

方法getItemCount()将返回附加到相应适配器的项目数。

每次视图持有人需要在屏幕上显示时，都会调用方法onBindViewHolder。

getItemCount仅被调用2次而onBindViewHolder返回4的原因是因为尚未创建另外两个视图持有者。

recyclerview将推迟绑定视图持有人，直到它需要出现在屏幕上为止。

如果您进一步滚动，将调用onBindViewHolder。

希望它有所帮助！

绑定视图上的位置参数取决于哪些因素？（回收者视图）

1 个答案: