Android Studio 导航栏开发 BottomNavigationView+Fragment 简单实例 超详细
先看效果图：
然后在看项目和代码：
一、
新建空白的项目：Empety Activity
二、
先添加依赖：在build.gradle 的dependencies里面添加
compile 'com.android.support:design:26.1.0'
三、
先看MainActivity布局文件：
这里的ButtomNavigationView 对应的就是我们的导航栏 上面的LinearLayout用来填充fragment实现切换页面。
ButtomNavigationView 里面的app：menu 对应的是导航栏里面的内容，所以还有新建一个menu的布局文件。
Menu布局文件：
先新建menu 文件夹 （ 如果有就不用） 新建 android resources directory 里面的resource type选择menu.
直接在项目上右键 new--adnroid resource file 然后里面的resource type 选择menu.
四、
接下来写准备切换的三个界面Fragment。
三个fragment就要对应3个布局文件，所以再新建3个布局文件 layout。
非常的简单 只放了一个button和一个textview，其余两个布局相似。
五、
然后再新建3个Fragment。
package com.example.it_cty.myapplication;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
/**
* Created by IT-CTY on 2018/4/25.
*/
public class Fragment1 extends Fragment {
private TextView textView;
private Button button;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view=inflater.inflate(R.layout.fragment1,container,false);
return view;
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
textView=(TextView)getActivity().findViewById(R.id.textView1);
button=(Button)getActivity().findViewById(R.id.button1);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Toast.makeText(getActivity(),"Fragment1",Toast.LENGTH_SHORT).show();
}
});
}
}内容也是很简单 只实现了按钮点击显示一个内容，其他两个fragment 也是一样，fragment和布局文件要一一对应。
六、
接下来看最关键的 MainActivity
1、先看初始化函数
private void initFragment()
{
fragment1 = new Fragment1();
fragment2 = new Fragment2();
fragment3 = new Fragment3();
fragments = new Fragment[]{fragment1,fragment2,fragment3};
lastfragment=0;
getSupportFragmentManager().beginTransaction().replace(R.id.mainview,fragment1).show(fragment1).commit();
bottomNavigationView=(BottomNavigationView)findViewById(R.id.bnv);
bottomNavigationView.setOnNavigationItemSelectedListener(changeFragment);
}
在看初始化函数里面bottomNaviationView 绑定的一个点击监听的函数changeFragment：
private BottomNavigationView.OnNavigationItemSelectedListener changeFragment= new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
switch (item.getItemId())
{
case R.id.id1:
{
if(lastfragment!=0)
{
switchFragment(lastfragment,0);
lastfragment=0;
}
return true;
}
case R.id.id2:
{
if(lastfragment!=1)
{
switchFragment(lastfragment,1);
lastfragment=1;
}
return true;
}
case R.id.id3:
{
if(lastfragment!=2)
{
switchFragment(lastfragment,2);
lastfragment=2;
}
return true;
}
}
return false;
}
};
最后再来看看switchFragment 函数
private void switchFragment(int lastfragment,int index)
{
FragmentTransaction transaction =getSupportFragmentManager().beginTransaction();
transaction.hide(fragments[lastfragment]);//隐藏上个Fragment
if(fragments[index].isAdded()==false)
{
transaction.add(R.id.mainview,fragments[index]);
}
transaction.show(fragments[index]).commitAllowingStateLoss();
}隐藏上个fragment 显示选中的fragment。
最后贴个完整的MainActivity
package com.example.it_cty.myapplication;
import android.support.annotation.NonNull;
import android.support.design.widget.BottomNavigationView;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.MenuItem;
public class MainActivity extends AppCompatActivity {
private BottomNavigationView bottomNavigationView;
private Fragment1 fragment1;
private Fragment2 fragment2;
private Fragment3 fragment3;
private Fragment[] fragments;
private int lastfragment;//用于记录上个选择的Fragment
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initFragment();
}
//初始化fragment和fragment数组
private void initFragment()
{
fragment1 = new Fragment1();
fragment2 = new Fragment2();
fragment3 = new Fragment3();
fragments = new Fragment[]{fragment1,fragment2,fragment3};
lastfragment=0;
getSupportFragmentManager().beginTransaction().replace(R.id.mainview,fragment1).show(fragment1).commit();
bottomNavigationView=(BottomNavigationView)findViewById(R.id.bnv);
bottomNavigationView.setOnNavigationItemSelectedListener(changeFragment);
}
//判断选择的菜单
private BottomNavigationView.OnNavigationItemSelectedListener changeFragment= new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
switch (item.getItemId())
{
case R.id.id1:
{
if(lastfragment!=0)
{
switchFragment(lastfragment,0);
lastfragment=0;
}
return true;
}
case R.id.id2:
{
if(lastfragment!=1)
{
switchFragment(lastfragment,1);
lastfragment=1;
}
return true;
}
case R.id.id3:
{
if(lastfragment!=2)
{
switchFragment(lastfragment,2);
lastfragment=2;
}
return true;
}
}
return false;
}
};
//切换Fragment
private void switchFragment(int lastfragment,int index)
{
FragmentTransaction transaction =getSupportFragmentManager().beginTransaction();
transaction.hide(fragments[lastfragment]);//隐藏上个Fragment
if(fragments[index].isAdded()==false)
{
transaction.add(R.id.mainview,fragments[index]);
}
transaction.show(fragments[index]).commitAllowingStateLoss();
}
}
源码地址：点击打开链接