ViewPager+Fragment+BottomNavigationView实现底部导航

昨天我学习了ViewPager+Fragment+BottomNavigationView实现底部导航并将其应用在我的地铁app中。

这种底部导航就是最常见的手机app 的导航形式，典型例子就是微信。

效果展示：

我们可以看到，我们可以左右滑动切换页面，同时也能点击底部导航栏实现切换，并且两者是同步的。

 

 具体实现就是要用到 ViewPager+Fragment+BottomNavigationView

1.我们首先要准备好我们的三个fragment，用来做三个主要功能的页面，我已经准备好了：

 

 2.然后创建ViewPager的适配器，这里我们要结合Fragment，因此我们要用到的就不是 PagerAdapter了，

这里我们需要继承  androidx.fragment.app.FragmentPagerAdapter。

package com.example.dataapplication.adapter;

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentStatePagerAdapter;

import java.util.List;

public class MyFragStateAdapter extends FragmentStatePagerAdapter {

    private List<Fragment> mFragmentList;

    public MyFragStateAdapter(@NonNull FragmentManager fm,List<Fragment> fragmentList) {
        super(fm);
        this.mFragmentList =fragmentList;

    }

    @NonNull
    @Override
    public Fragment getItem(int position) {
        return mFragmentList == null ? null : mFragmentList.get(position);
    }

    @Override
    public int getCount() {
        return mFragmentList == null ? 0 : mFragmentList.size();
    }
}

3.然后再在activity中重写两个方法。

我们首先要将我们需要的东西都声明一下：

　　 private ViewPager mViewPager;
    private BottomNavigationView mBottomNavigationView;
    private MyFragStateAdapter FragStateAdapter;
    private List<Fragment> mFragmentList;

然后重写下面的两个方法：

menu_1

menu_2

menu_3
分别是三个菜单的控件

mBottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {

                switch (item.getItemId()){
                    case R.id.menu_1:
                        mViewPager.setCurrentItem(0);
                        break;
                    case R.id.menu_2:
                        mViewPager.setCurrentItem(1);
                        break;
                    case R.id.menu_3:
                        mViewPager.setCurrentItem(2);
                        break;
                    default:
                        break;
                }
                return true;
            }
        });

还有：

mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
           @Override
           public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

           }

           @Override
           public void onPageSelected(int position) {
               switch (position){
                   case 0:
                       mBottomNavigationView.setSelectedItemId(R.id.menu_1);
                       break;
                   case 1:
                       mBottomNavigationView.setSelectedItemId(R.id.menu_2);
                       break;
                   case 2:
                       mBottomNavigationView.removeBadge(R.id.menu_3);
                       mBottomNavigationView.setSelectedItemId(R.id.menu_3);
                       break;
                   default:
                       break;
               }
           }

           @Override
           public void onPageScrollStateChanged(int state) {

           }
       });

最后把需要的三个fragment放入mFragmentList供ViewPager使用

private void initData() {
        mFragmentList = new ArrayList<>();

        SearchFragment fragment1 = SearchFragment.newInstance("","");
        LeftListFragment fragment2 = LeftListFragment.newInstance("","");
        MapFragment fragment3 = MapFragment.newInstance("","");

        mFragmentList.add(fragment1);
        mFragmentList.add(fragment2);
        mFragmentList.add(fragment3);
    }

完整代码：

package com.example.dataapplication;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
import androidx.viewpager.widget.PagerAdapter;
import androidx.viewpager.widget.ViewPager;

import android.os.Bundle;
import android.view.MenuItem;
import android.view.View;

import com.example.dataapplication.OtherActivity.DynamicFragmentActivity;
import com.example.dataapplication.adapter.MyFragStateAdapter;
import com.example.dataapplication.fragment.BlankFragment2;
import com.example.dataapplication.fragment.frag1.SearchFragment;
import com.example.dataapplication.fragment.frag2.LeftListFragment;
import com.example.dataapplication.fragment.frag3.MapFragment;
import com.google.android.material.badge.BadgeDrawable;
import com.google.android.material.bottomnavigation.BottomNavigationView;

import java.util.ArrayList;
import java.util.List;

public class PagerActivity extends AppCompatActivity {

    private ViewPager mViewPager;
    private BottomNavigationView mBottomNavigationView;
    private MyFragStateAdapter FragStateAdapter;
    private List<Fragment> mFragmentList;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_pager);

        mViewPager = findViewById(R.id.vp2);
        mBottomNavigationView = findViewById(R.id.bottom_menu);
        
        initData();
        FragStateAdapter = new MyFragStateAdapter(getSupportFragmentManager(),mFragmentList);
        mViewPager.setAdapter(FragStateAdapter);

       mBottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {

                switch (item.getItemId()){
                    case R.id.menu_1:
                        mViewPager.setCurrentItem(0);
                        break;
                    case R.id.menu_2:
                        mViewPager.setCurrentItem(1);
                        break;
                    case R.id.menu_3:
                        mViewPager.setCurrentItem(2);
                        break;
                    default:
                        break;
                }
                return true;
            }
        });

       mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
           @Override
           public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

           }

           @Override
           public void onPageSelected(int position) {
               switch (position){
                   case 0:
                       mBottomNavigationView.setSelectedItemId(R.id.menu_1);
                       break;
                   case 1:
                       mBottomNavigationView.setSelectedItemId(R.id.menu_2);
                       break;
                   case 2:
                       mBottomNavigationView.removeBadge(R.id.menu_3);
                       mBottomNavigationView.setSelectedItemId(R.id.menu_3);
                       break;
                   default:
                       break;
               }
           }

           @Override
           public void onPageScrollStateChanged(int state) {

           }
       });


    }

    private void initData() {
        mFragmentList = new ArrayList<>();

        SearchFragment fragment1 = SearchFragment.newInstance("","");
        LeftListFragment fragment2 = LeftListFragment.newInstance("","");
        MapFragment fragment3 = MapFragment.newInstance("","");

        mFragmentList.add(fragment1);
        mFragmentList.add(fragment2);
        mFragmentList.add(fragment3);
    }
}