我正在嘗試制作一個里面有一個片段的活動，上面有一個recyclerView和cards?，F在，它只顯示活動，片段是空的，我不知道這里發生了什么。這是的代碼activity中，fragment和adapter活動：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);        }