實現底部導航欄切換

將java文件return的xml文件賦值給頁面FrameLayout控件

java文件BottomNavigationView，監聽器setOnNavigationItemSelectedListener

MainActivity.java代碼

package com.example.myapplication;import android.os.Bundle;import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;import com.google.android.material.bottomnavigation.BottomNavigationView;public class MainActivity extends AppCompatActivity {private BottomNavigationView bottomNavigationView;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main4);bottomNavigationView = findViewById(R.id.bottom_navigation);// 默認顯示首頁getSupportFragmentManager().beginTransaction().replace(R.id.frame_layout, new HomeFragment()).commit();// 設置切換監聽bottomNavigationView.setOnNavigationItemSelectedListener(item -> {Fragment selectedFragment;switch (item.getItemId()) {case R.id.nav_search:selectedFragment = new SearchFragment();break;case R.id.nav_profile:selectedFragment = new ProfileFragment();break;case R.id.nav_home:default:selectedFragment = new HomeFragment();break;}getSupportFragmentManager().beginTransaction().replace(R.id.frame_layout, selectedFragment).commit();return true;});}
}

HomeFragment.java代碼：

package com.example.myapplication;import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;import java.util.zip.Inflater;public class HomeFragment extends Fragment {private TextView homeText;private Button updateButton;public View onCreateView(@NonNull LayoutInflater inflater,@Nullable ViewGroup container,@Nullable Bundle savedInstanceState) {// 加載布局文件View view = inflater.inflate(R.layout.fragment_home, container, false);// 獲取控件homeText = view.findViewById(R.id.home_text);updateButton = view.findViewById(R.id.update_button);// 設置按鈕點擊事件updateButton.setOnClickListener(v -> {homeText.setText("文字已更新！");});return view;}
}

ProfileFragment.java代碼：

package com.example.myapplication;import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;public class ProfileFragment extends Fragment {public View onCreateView(@NonNull LayoutInflater inflater,@Nullable ViewGroup container,@Nullable Bundle savedInstanceState) {return inflater.inflate(R.layout.fragment_home, container, false);}
}

SearchFragment.java代碼：

package com.example.myapplication;import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;public class SearchFragment extends Fragment {public View onCreateView(@NonNull LayoutInflater inflater,@Nullable ViewGroup container,@Nullable Bundle savedInstanceState) {return inflater.inflate(R.layout.fragment_search, container, false);}
}

activity_main4.xml代碼：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:app="http://schemas.android.com/apk/res-auto"android:layout_width="match_parent"android:layout_height="match_parent"><!-- 用于切換內容的 Fragment 容器 --><FrameLayoutandroid:id="@+id/frame_layout"android:layout_width="match_parent"android:layout_height="match_parent"android:layout_above="@id/bottom_navigation"/><!-- 底部導航欄 --><com.google.android.material.bottomnavigation.BottomNavigationViewandroid:id="@+id/bottom_navigation"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_alignParentBottom="true"app:menu="@menu/bottom_nav_menu"/>
</RelativeLayout>

fragment_home.xml代碼：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:orientation="vertical"
android:padding="16dp"><TextViewandroid:id="@+id/home_text"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="這是首頁"android:textSize="24sp"android:padding="16dp" /><Buttonandroid:id="@+id/update_button"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="點我更新文字" />
</LinearLayout>

fragment_search.xml代碼：

<TextView xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:gravity="center"android:text="HOME 1"android:textSize="30sp" />

在resources/menu/bottom_nav_menu.xml代碼如下：

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"><itemandroid:id="@+id/nav_home"android:title="首頁"android:icon="@android:drawable/ic_menu_view" /><itemandroid:id="@+id/nav_search"android:title="搜索"android:icon="@android:drawable/ic_menu_search" /><itemandroid:id="@+id/nav_profile"android:title="我的"android:icon="@android:drawable/ic_menu_myplaces" />
</menu>

運行結果：