导航抽屉不显示片段 [英] Navigation Drawer doesn't show fragments

问题描述

我创建了一个新的Android Studio项目，而MainActivity是一个导航抽屉活动.

I've created a new Android Studio Project and my MainActivity is a Navigation Drawer Activity.

因此，我无法显示片段.我在互联网上和这里都读过很多文章.

So, I can't show up fragments. I've read many post on internet and here too.

说明:

我打开导航抽屉，选择菜单播客". 应该显示PodcastsFragment，但仍显示活动.

I open navigation drawer, select menu "Podcast". PodcastsFragment should be shown, but it still showing activity.

MainActivity代码:

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.util.Log;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;

import com.google.android.gms.analytics.HitBuilders;
import com.google.android.gms.analytics.Tracker;

public class MainActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {

    private Tracker mTracker;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        // [START shared_tracker]
        // Obtain the shared Tracker instance.
        AnalyticsApplication application = (AnalyticsApplication) getApplication();
        mTracker = application.getDefaultTracker();
        // [END shared_tracker]

        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);


    }

    @Override
    protected void onResume() {
        Log.i("TESTE", "Setting screen name: " + "teste");
        mTracker.setScreenName("Main " + "teste");
        mTracker.send(new HitBuilders.ScreenViewBuilder().build());
        super.onResume();
    }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.                                                                                                        
        int id = item.getItemId();

        Fragment fragment = null;
        FragmentTransaction ft = null;




        if (id == R.id.nav_podcasts) {
            Log.d("Clicked:", "nav_podcasts");
            fragment = new PodcastsFragment();
        } else if (id == R.id.nav_feed) {
            //fragment = new FeedFragment();
            Log.d("Clicked:", "nav_feed");
            //fragment = new FeedFragment();
            FragmentManager fragmentManager = getSupportFragmentManager();
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            FeedFragment ff = new FeedFragment();
            fragmentTransaction.add(R.id.container_body, ff);
            fragmentTransaction.commit();
        } else if (id == R.id.nav_downloads) {
            //fragment = new DownloadsFragment();
            Log.d("Clicked:", "nav_downloads");
        } else if (id == R.id.nav_add) {
            //fragment = new OPMLFragment();
            Log.d("Clicked:", "nav_add");
        } else if (id == R.id.nav_settings) {
            //fragment = new SettingsFragment();
            Log.d("Clicked:", "nav_settings");
        }

        if (fragment != null) {
            FragmentManager fragmentManager = getSupportFragmentManager();
            fragmentManager.beginTransaction()
                    .replace(R.id.container_body, fragment).commit();
        }

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }
}

播客片段代码:

import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class PodcastsFragment extends Fragment {

    public PodcastsFragment() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        //return inflater.inflate(R.layout.fragment_podcasts, container, false);

        View rootView = inflater.inflate(R.layout.fragment_podcasts, container, false);

        // Inflate the layout for this fragment
        return rootView;
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
    }

    @Override
    public void onDetach() {
        super.onDetach();
    }
}

app_bar_main代码:

    <?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context="com.test.test.MainActivity">

    <android.support.design.widget.AppBarLayout
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:popupTheme="@style/AppTheme.PopupOverlay" />

    </android.support.design.widget.AppBarLayout>

    <include layout="@layout/content_main"/>



    <!--<android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="@dimen/fab_margin"
        android:src="@android:drawable/ic_dialog_email" />-->

</android.support.design.widget.CoordinatorLayout>

activity_main代码:

    <?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:openDrawer="start">

    <include
        layout="@layout/app_bar_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <android.support.design.widget.NavigationView
        android:id="@+id/nav_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:fitsSystemWindows="true"
        app:headerLayout="@layout/nav_header_main"
        app:menu="@menu/activity_main_drawer" />

</android.support.v4.widget.DrawerLayout>

content_main代码:

    <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:showIn="@layout/app_bar_main"
    tools:context="com.test.test.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="teste"/>
    <FrameLayout
        android:id="@+id/container_body"
        android:layout_width="fill_parent"
        android:layout_height="0dp"
        android:layout_weight="1"/>

</RelativeLayout>

推荐答案

在活动中创建抽屉列表，并添加setOnItemClickListener().当用户在抽屉列表中选择一个项目时，系统会在OnItemClickListener上调用onItemClick()赋予setOnItemClickListener().

Make the drawer's list in Your activity and add setOnItemClickListener().When the user selects an item in the drawer's list, the system calls onItemClick() on the OnItemClickListener given to setOnItemClickListener().

在onItemClick()方法中执行的操作取决于实现应用程序结构的方式.在以下示例中，选择列表中的每个项目都会在主内容视图(由R.id.content_frame ID标识的FrameLayout元素)中插入一个不同的Fragment: 有关更多详细信息，请阅读以下文章 youtube 和

What you do in the onItemClick() method depends on how you've implemented your app structure. In the following example, selecting each item in the list inserts a different Fragment into the main content view (the FrameLayout element identified by the R.id.content_frame ID): for more delail please read these articles youtube and github example

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