java - 替换底部导航中的 fragment

Question

我已经创建了一个底部导航，但当我在底部导航中选择该选项时，该 fragment 并未将其自身替换为另一个 fragment 。这是我的代码。任何帮助将不胜感激。这是我在 android studio 项目中编写的代码，我不知道为什么它没有加载 fragment 。

主要 Activity

package com.divesh.ss;

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.design.widget.BottomNavigationView;
import android.support.design.widget.CoordinatorLayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.view.MenuItem;


public class MainActivity extends AppCompatActivity {


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    loadFragment(new dash());
    BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
    navigation.setSelectedItemId(R.id.dashboard);
}

private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
        = new BottomNavigationView.OnNavigationItemSelectedListener() {

    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        Fragment fragment;
        switch (item.getItemId()) {

            case R.id.settings:
                fragment = new settings();
                loadFragment(fragment);
                return true;
            case R.id.work:
                fragment = new work();
                loadFragment(fragment);
                return true;
            case R.id.donate:
                fragment = new donate();
                loadFragment(fragment);
                return true;
            case R.id.team:
                fragment = new team();
                loadFragment(fragment);
                return true;
        }

        return false;
    }
};

private void loadFragment(Fragment fragment) {
    // load fragment
    FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
    transaction.replace(R.id.frame_container, fragment);
        transaction.addToBackStack(null);
        transaction.commit();
    }

}

Activity_main.xml

<?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:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.divesh.ss.MainActivity">

    <FrameLayout
        android:id="@+id/frame_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />

    <android.support.design.widget.BottomNavigationView
        android:id="@+id/navigation"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom"
        android:background="?android:attr/windowBackground"
        app:itemBackground="@color/colorPrimary"
        android:foreground="?attr/selectableItemBackground"
        app:itemIconTint="@android:color/white"
        app:itemTextColor="@android:color/white"
        app:menu="@menu/navigation" />

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

Answer 1

您为 BottomView 导航创建了监听器，但没有设置它。

您需要为导航设置监听器:

navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);