安卓 BottomNavigationView底部导航的使用

简介：上一篇讲解了BottomNavigationBar底部导航栏的使用，这一篇还是底部导航栏，它属于Material Design下面的，用法更加简单，扩展稍微少些，属于弱化版~

1、

这里写图片描述

2、项目build.gradle添加依赖：（注意studio3.0以下将implementation 换成 compile）

    implementation 'com.android.support:design:27.1.1'

3、MainActivity

import android.annotation.SuppressLint;
import android.support.annotation.NonNull;
import android.support.design.internal.BottomNavigationItemView;
import android.support.design.internal.BottomNavigationMenuView;
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.util.Log;
import android.view.LayoutInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;

import java.lang.reflect.Field;

public class MainActivity extends AppCompatActivity implements BottomNavigationView.OnNavigationItemSelectedListener {

    private BottomNavigationView navigation;
    //默认选择第一个fragment
    private int lastSelectedPosition = 0;

    private FirstFragment firstFragment;
    private SecondFragment secondFragment;
    private ThirdFragment thirdFragment;
    private FourthFragment fourthFragment;

    private Fragment[] fragments;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        navigation = this.findViewById(R.id.navigation);
        initFragments();
    }

    private void initFragments() {
        //监听切换事件
        navigation.setOnNavigationItemSelectedListener(this);
        //平均布局
        setItemType(navigation);
        //添加角标消息数
        setAddNumber();
        firstFragment = new FirstFragment();
        secondFragment = new SecondFragment();
        thirdFragment = new ThirdFragment();
         fourthFragment = new FourthFragment();
        fragments = new Fragment[]{firstFragment, secondFragment, thirdFragment,fourthFragment};
        lastSelectedPosition = 0;
        //默认提交第一个
        getSupportFragmentManager()
                .beginTransaction()
                .add(R.id.tb, firstFragment)//添加
                .show(firstFragment)//展示
                .commit();//提交
    }

    private void setAddNumber() {
        //获取整个的NavigationView
        BottomNavigationMenuView menuView = (BottomNavigationMenuView) navigation.getChildAt(0);
        //获取所添加的每一个Tab，并给第三个Tab添加消息角标
        View tabView = menuView.getChildAt(2 );
        BottomNavigationItemView itemView = (BottomNavigationItemView) tabView;
        //加载我们的角标布局View，新创建的一个布局
        View badgeView = LayoutInflater.from(this).inflate(R.layout.number_badge, menuView, false);
        TextView number=badgeView.findViewById(R.id.msg_number);
        //设置显示的内容
        number.setText("99");
        //添加到Tab上
        itemView.addView(badgeView);
    }

    /**
     * 切换Fragment
     * @param lastIndex 上个显示Fragment的索引
     * @param index     需要显示的Fragment的索引
     */
    private void setDefaultFragment(int lastIndex, int index) {
        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
        transaction.hide(fragments[lastIndex]);
        if (!fragments[index].isAdded()) {
            transaction.add(R.id.tb, fragments[index]);
        }
        //需要展示fragment下标的位置
        //commit：安排该事务的提交。这一承诺不会立即发生;它将被安排在主线程上，以便在线程准备好的时候完成。
        //commitAllowingStateLoss：与 commit类似，但允许在活动状态保存后执行提交。这是危险的，因为如果Activity需要从其状态恢复，
        // 那么提交就会丢失，因此，只有在用户可以意外地更改UI状态的情况下，才可以使用该提交
        transaction.show(fragments[index]).commit();
    }

    /**
     * 切换事件
     */
    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId()) {
            case R.id.navigation_homefirst:
                if (0 != lastSelectedPosition) {
                    setDefaultFragment(lastSelectedPosition, 0);
                    lastSelectedPosition = 0;
                }
                return true;
            case R.id.navigation_homesecond:
                if (1 != lastSelectedPosition) {
                    setDefaultFragment(lastSelectedPosition, 1);
                    lastSelectedPosition = 1;
                }
                return true;
            case R.id.navigation_homethird:
                if (2 != lastSelectedPosition) {
                    setDefaultFragment(lastSelectedPosition, 2);
                    lastSelectedPosition = 2;
                }
                return true;
            case R.id.navigation_homefourth:
                if (3 != lastSelectedPosition) {
                    setDefaultFragment(lastSelectedPosition, 3);
                    lastSelectedPosition = 3;
                }
                return true;
        }
        return false;
    }

    /**
     * 防止超过3个fragment布局不平分
     */
    @SuppressLint("RestrictedApi")
    private  void setItemType(BottomNavigationView view) {
        BottomNavigationMenuView menuView = (BottomNavigationMenuView) view.getChildAt(0);
        try {
            Field shiftingMode = menuView.getClass().getDeclaredField("mShiftingMode");
            shiftingMode.setAccessible(true);
            shiftingMode.setBoolean(menuView, false);
            shiftingMode.setAccessible(false);
            for (int i = 0; i < menuView.getChildCount(); i++) {
                BottomNavigationItemView item = (BottomNavigationItemView) menuView.getChildAt(i);
                //noinspection RestrictedApi
                item.setShiftingMode(false);
                // set once again checked value, so view will be updated
                //noinspection RestrictedApi
                item.setChecked(item.getItemData().isChecked());
            }
        } catch (NoSuchFieldException e) {
            Log.e("BNVHelper", "Unable to get shift mode field", e);
        } catch (IllegalAccessException e) {
            Log.e("BNVHelper", "Unable to change value of shift mode", e);
        }
    }
}

布局文件activity_main.xml

<?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"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical">

    <FrameLayout
        android:id="@+id/tb"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />

    <android.support.design.widget.BottomNavigationView
        android:id="@+id/navigation"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#fff"
        app:itemTextColor="@drawable/home_color_shape"
        app:itemIconTint="@drawable/home_color_shape"
        app:menu="@menu/navigation" />

</LinearLayout>

4、资源文件在res目录下新建一个menu文件，在里面新建navigation.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">

    <item
        android:id="@+id/navigation_homefirst"
        android:icon="@drawable/home1_shape"
        android:title="首页"
        android:tooltipText="drr" />

    <item
        android:id="@+id/navigation_homesecond"
        android:icon="@drawable/home2_shape"
        android:title="订单" />

    <item
        android:id="@+id/navigation_homethird"
        android:icon="@drawable/home3_shape"
        android:title="动态" />

    <item
        android:id="@+id/navigation_homefourth"
        android:icon="@drawable/home4_shape"
        android:title="我的" />

</menu>

home1_shape.xml、（1-4大同小异）

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:drawable="@drawable/ic_launcher_background" android:state_checked="true" />
    <item android:drawable="@drawable/home" android:state_checked="false" />

</selector>

home_color_shape.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:state_checked="true" android:color="@color/colorAccent" />
    <item android:state_checked="false"  android:color="@color/un_Accent"/>
</selector>

false 未选中的状态的文字或图片 true 选中的状态的文字或图片

5、replace方式（setDefaultFragment方法处改为如下即可）

private void setDefaultFragment( int index) {
        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
        transaction.replace(R.id.tb, fragments[index]);
        transaction.commit();
    }

安卓 BottomNavigationView底部导航的使用

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