片段中带有卡片的 Recyclerview 不显示任何内容

Question

我正在尝试制作一个里面有一个片段的活动，上面有一个recyclerView和cards。现在，它只显示活动，片段是空的，我不知道这里发生了什么。这是的代码activity中，fragment和adapter活动：package com.laorden.goodreasons.habits;import android.content.Intent;import android.os.Bundle;import android.support.annotation.VisibleForTesting;import android.support.design.widget.NavigationView;import android.support.test.espresso.IdlingResource;import android.support.v4.view.GravityCompat;import android.support.v4.widget.DrawerLayout;import android.support.v7.app.ActionBar;import android.support.v7.app.AppCompatActivity;import android.support.v7.widget.Toolbar;import android.view.MenuItem;import android.view.Window;import android.view.WindowManager;import com.laorden.goodreasons.Injection;import com.laorden.goodreasons.R;import com.laorden.goodreasons.statistics.StatisticsActivity;import com.laorden.goodreasons.util.ActivityUtils;import com.laorden.goodreasons.util.EspressoIdlingResource;public class HabitsActivity extends AppCompatActivity {    private DrawerLayout mDrawerLayout;    private HabitsPresenter mHabitsPresenter;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.habits_act);        Window w = getWindow();        w.setFlags(WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS,WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS);        // Set up the toolbar.        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);        setSupportActionBar(toolbar);        ActionBar ab = getSupportActionBar();        ab.setHomeAsUpIndicator(R.drawable.ic_menu);        ab.setDisplayHomeAsUpEnabled(true);        // Set up the navigation drawer.        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);        mDrawerLayout.setStatusBarBackground(R.color.colorPrimaryDark);        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);        if (navigationView != null) {            setupDrawerContent(navigationView);        }

Answer 1

那是因为您在getItemCount方法中返回 0

改变这一点：

@Override

 public int getItemCount() {

    return 0;

 }

对此：

@Override

 public int getItemCount() {

    return (mData != null ?  mData.size():0);

}

Answer 2

你应该先设置布局管理器

@Override

public View onCreateView(LayoutInflater inflater, ViewGroup container,

                         Bundle savedInstanceState) {

    View root = inflater.inflate(R.layout.habits_frag, container, false);

    recyclerView = root.findViewById(R.id.rv_list);

    recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));

    recyclerView.setAdapter(mListAdapter);

    return root;

}

您还需要将 getItemCount 更改为

@Override

    public int getItemCount() {

         if(mData!=null){return mData.size();}else return 0;

    }