我创建了一个底部导航栏，有3个图标和3个不同的链接片段。
点击图标
1。图标变了2. 图标颜色改变3.相关的片段出现在屏幕上
在刷卡
只有那个片段在改变。(图标没有变化).
3个图标菜单
<item
android:id="@+id/ic_birthdays"
android:title="@string/birthdays"
android:icon="@drawable/change_ic_cake"
/>
<item
android:id="@+id/ic_add"
android:title="@string/add"
android:icon="@drawable/change_ic_add"
/>
<item
android:id="@+id/ic_profile"
android:title="@string/profile"
android:icon="@drawable/change_ic_profile"
/>
菜单中链接的三个图标是:
1。
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_checked="true" android:drawable="@drawable/ic_cake_clicked" />
<item android:state_checked="false" android:drawable="@drawable/ic_cake_not_clicked"/>
</selector>
2。添加图标
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="@drawable/ic_add_not_clicked" android:state_checked="false"/>
<item android:drawable="@drawable/ic_add_clicked" android:state_checked="true"/>
</selector>
3。概要文件图标
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="@drawable/ic_profile_not_clicked" android:state_checked="false"/>
<item android:drawable="@drawable/ic_profile_clicked" android:state_checked="true"/>
</selector>
MainActivity.java
package com.example.bottom_nav;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import com.example.bottom_nav.databinding.ActivityMainBinding;
import com.google.android.material.navigation.NavigationBarView;
import android.os.Bundle;
import android.view.MenuItem;
import android.view.ViewGroup;
public class MainActivity extends AppCompatActivity {
ActivityMainBinding ui;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ui = ActivityMainBinding.inflate(getLayoutInflater());
ViewGroup root = ui.getRoot();
setContentView(root);
//Instantiating 3 fragments
ViewPageAdapter viewPageAdapter = new ViewPageAdapter(this);
ui.viewPager.setAdapter(viewPageAdapter);
//Linking those three fragments to their respective icons of bottom nav bar
ui.bottomNav.setOnItemSelectedListener(
new NavigationBarView.OnItemSelectedListener(){
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
switch (item.getItemId()){
case R.id.ic_birthdays:
ui.viewPager.setCurrentItem(0);
break;
case R.id.ic_add:
ui.viewPager.setCurrentItem(1);
break;
case R.id.ic_profile:
ui.viewPager.setCurrentItem(2);
break;
}
return true;
}
}
);
}
}
layout_main.xml
<?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"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<androidx.viewpager2.widget.ViewPager2
android:id="@+id/viewPager"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_above="@id/bottom_nav" />
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="@+id/bottom_nav"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
app:menu="@menu/bottom_navigation_menu" />
</RelativeLayout>
ViewPageAdapter.java
package com.example.bottom_nav;
import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentActivity;
import androidx.viewpager2.adapter.FragmentStateAdapter;
import com.example.bottom_nav.fragments.add;
import com.example.bottom_nav.fragments.birthdays;
import com.example.bottom_nav.fragments.profile;
public class ViewPageAdapter extends FragmentStateAdapter {
public ViewPageAdapter(@NonNull FragmentActivity fragmentActivity) {
super(fragmentActivity);
}
@NonNull
@Override
public Fragment createFragment(int position) {
switch (position){
case 1: return new add();
case 2: return new profile();
default: return new birthdays();
}
}
@Override
public int getItemCount() {
return 3;
}
}
3段代码
1. birthdays.java
package com.example.bottom_nav.fragments;
import android.os.Bundle;
import androidx.fragment.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.example.bottom_nav.R;
public class birthdays extends Fragment {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_birthdays, container, false);
}
}
2. add.java
package com.example.bottom_nav.fragments;
import android.os.Bundle;
import androidx.fragment.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.example.bottom_nav.R;
public class add extends Fragment {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_add, container, false);
}
}
3. profile.java
package com.example.bottom_nav.fragments;
import android.os.Bundle;
import androidx.fragment.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.example.bottom_nav.R;
public class profile extends Fragment {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_add, container, false);
}
}
你需要在viewpager上有一个监听器，并跟踪以前选中的项目，因此创建一个全局变量
全局变量:
MenuItem previousMenuItem;
然后是viewpager监听器:
viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
if (previousMenuItem != null) {
previousMenuItem.setChecked(false);
}
else {
mBottomNavigationView.getMenu().getItem(0).setChecked(false);
}
mBottomNavigationView.getMenu().getItem(position).setChecked(true);
previousMenuItem = mBottomNavigationView.getMenu().getItem(position);
}
@Override
public void onPageScrollStateChanged(int state) {
}
});
不要忘记在活动开始时设置一个默认的选项(首先)来选择底部导航