使用BottomNavigationView+ViewPager+Fragment的底部導航欄

使用BottomNavigationView作底部工具欄，使用ViewPager作頁面切換，使用Fragment完成每一個頁面的邏輯。
效果圖以下：

• 首先是activity_main.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"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.zhangda.meituan.activity.MainActivity">

    <android.support.design.widget.BottomNavigationView
        android:id="@+id/navigation"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:layout_alignParentBottom="true"
        android:background="?android:attr/windowBackground"
        app:menu="@menu/navigation" />

    <android.support.v4.view.ViewPager
        android:id="@+id/viewPager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@+id/navigation"/>


</RelativeLayout>

navigation.xml代碼

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

    <item
        android:id="@+id/navigation_home"
        android:icon="@drawable/ic_home_24dp"
        android:title="@string/title_home"/>

    <item
        android:id="@+id/navigation_near"
        android:icon="@drawable/ic_near_24dp"
        android:title="@string/title_near"/>

    <item
        android:id="@+id/navigation_go"
        android:icon="@drawable/ic_go_24dp"
        android:title="@string/title_go"/>

    <item
        android:id="@+id/navigation_order"
        android:icon="@drawable/ic_order_24dp"
        android:title="@string/title_order"/>

    <item
        android:id="@+id/navigation_mine"
        android:icon="@drawable/ic_mine_24dp"
        android:title="@string/title_mine"/>

</menu>

• MainActivity代碼

private ViewPager viewPager;
    private MenuItem menuItem;
    private BottomNavigationView bottomNavigationView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        viewPager = (ViewPager) findViewById(R.id.viewPager);

        bottomNavigationView = (BottomNavigationView) findViewById(R.id.navigation);
        BottomNavigationViewHelper.disableShiftMode(bottomNavigationView);
        bottomNavigationView.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);

        viewPager.addOnPageChangeListener(mViewPagerOnPageChangeListener);
        //禁止ViewPager滑動
        viewPager.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                return true;
            }
        });
        setupViewPager(viewPager);
    }
    private ViewPager.OnPageChangeListener mViewPagerOnPageChangeListener
            = new ViewPager.OnPageChangeListener(){
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

        }

        @Override
        public void onPageSelected(int position) {
            if (menuItem != null) {
                menuItem.setChecked(false);
            } else {
                bottomNavigationView.getMenu().getItem(0).setChecked(false);
            }
            menuItem = bottomNavigationView.getMenu().getItem(position);
            menuItem.setChecked(true);
        }

        @Override
        public void onPageScrollStateChanged(int state) {

        }
    };
    private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
            = new BottomNavigationView.OnNavigationItemSelectedListener() {

        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            switch (item.getItemId()) {
                case R.id.navigation_home:
                    viewPager.setCurrentItem(0);
                    break;
                case R.id.navigation_near:
                    viewPager.setCurrentItem(1);
                    break;
                case R.id.navigation_go:
                    viewPager.setCurrentItem(2);
                    break;
                case R.id.navigation_order:
                    viewPager.setCurrentItem(3);
                    break;
                case R.id.navigation_mine:
                    viewPager.setCurrentItem(4);
                    break;
            }
            return false;
        }
    };

    private void setupViewPager(ViewPager viewPager) {
        ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());

        adapter.addFragment(FragmentHome.newInstance());
        adapter.addFragment(FragmentNear.newInstance());
        adapter.addFragment(FragmentGo.newInstance());
        adapter.addFragment(FragmentOrder.newInstance());
        adapter.addFragment(FragmentMine.newInstance());
        viewPager.setAdapter(adapter);
    }

• ViewPagerAdapter代碼

public class ViewPagerAdapter extends FragmentPagerAdapter {

    private final List<Fragment> mFragmentList = new ArrayList<>();

    public ViewPagerAdapter(FragmentManager manager) {
        super(manager);
    }

    @Override
    public Fragment getItem(int position) {
        return mFragmentList.get(position);
    }

    @Override
    public int getCount() {
        return mFragmentList.size();
    }

    public void addFragment(Fragment fragment) {
        mFragmentList.add(fragment);
    }

}

fragment代碼就再也不贅述了，幾個tab頁面，對應幾個fragment，對應幾個佈局，各自寫邏輯便可。

• 須要特殊說明的是，BottomNavigationView組件當超過三個tab元素時，顯示不太美好，這塊須要特殊處理一下，其中在MainActivity中須要加入這句代碼：

BottomNavigationViewHelper.disableShiftMode(bottomNavigationView);

BottomNavigationViewHelper代碼以下：

public class BottomNavigationViewHelper {

    @SuppressLint("RestrictedApi")
    public static void disableShiftMode(BottomNavigationView navigationView)  {

        BottomNavigationMenuView menuView = (BottomNavigationMenuView) navigationView.getChildAt(0);
        Field shiftingMode = null;
        try {
            shiftingMode = menuView.getClass().getDeclaredField("mShiftingMode");
            shiftingMode.setAccessible(true);
            shiftingMode.setBoolean(menuView, false);
            shiftingMode.setAccessible(false);
            for (int i = 0; i < menuView.getChildCount(); i++) {
                BottomNavigationItemView itemView = (BottomNavigationItemView) menuView.getChildAt(i);
                itemView.setShiftingMode(false);
                itemView.setChecked(itemView.getItemData().isChecked());
            }
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
    }
}

若是想要改變底部工具欄的選中顏色，改變color.xml中colorPrimary的值便可。

• 另外，本次我使用vector圖標，也就是矢量圖標，底部工具欄的圖表會隨着手機分辨率自動調整，增長了分辨率的適應性。圖片能夠使用android studio自帶的，也能夠帶入svg圖片，下面舉例一個：

<vector xmlns:android="http://schemas.android.com/apk/res/android"
        android:width="24dp"
        android:height="24dp"
        android:viewportWidth="24.0"
        android:viewportHeight="24.0">
    <path
        android:fillColor="#FFF"
        android:strokeColor="#E8E8E8"
        android:strokeWidth="0.2"
        android:pathData="M10,20v-6h4v6h5v-8h3L12,3 2,12h3v8z"/>
</vector>