BottomBar

　　BottomBar是Github上的一个开源框架，因为从1.3.3开始不支持fragments了，要自己配置，弄了很久，不管是app的fragment还是V4 的程序总是总是闪退。于是就用这种方式实现了，效果还不错。github有详细说明，多余的就不说了。

　　这个roughike是这个项目的所有者（大神致敬）。

　　我用的是Android studio开发，fragment全部导的V4的包（以为最开始就支持的是v4的，后面也支持了app.fragment）.

首先是dependencies

compile 'com.jakewharton:butterknife:7.0.0'
compile 'com.roughike:bottom-bar:1.3.3'

添加第二个就行了，我这用到了butterknife（不知道的可以百度，出自jakewharton大神的一款View注入框架）。

从menu添加items

res/menu/bottombar_menu.xml

<?xml version="1.0" encoding="utf-8"?><menu xmlns:android="http://schemas.android.com/apk/res/android"><itemandroid:id="@+id/bb_menu_recents"android:icon="@drawable/ic_recents"android:title="Recents" /><itemandroid:id="@+id/bb_menu_favorites"android:icon="@drawable/ic_favorites"android:title="Favorites" /><itemandroid:id="@+id/bb_menu_nearby"android:icon="@drawable/ic_nearby"android:title="Nearby" /><itemandroid:id="@+id/bb_menu_friends"android:icon="@drawable/ic_friends"android:title="Friends" /><itemandroid:id="@+id/bb_menu_food"android:icon="@drawable/ic_restaurants"android:title="Food" /></menu>

在activity中初始化BottomBar和ViewPager

public class MainActivity extends FragmentActivity {@Bind(R.id.viewPager)ViewPager viewPager;@Bind(R.id.myCoordinator)CoordinatorLayout myCoordinator;private BottomBar mBottomBar;private List<Fragment> fragmentList;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);ButterKnife.bind(this);initViewPager();createBottomBar(savedInstanceState);}private void createBottomBar(Bundle savedInstanceState) {mBottomBar = BottomBar.attachShy(myCoordinator,viewPager, savedInstanceState);mBottomBar.setItemsFromMenu(R.menu.bottombar_menu, new OnMenuTabClickListener() {@Overridepublic void onMenuTabSelected(@IdRes int menuItemId) {switch (menuItemId) {case R.id.bb_menu_recents:viewPager.setCurrentItem(0);break;case R.id.bb_menu_favorites:viewPager.setCurrentItem(1);break;case R.id.bb_menu_nearby:break;case R.id.bb_menu_friends:break;case R.id.bb_menu_food:break;}}@Overridepublic void onMenuTabReSelected(@IdRes int menuItemId) {}});// Setting colors for different tabs when there's more than three of them.// You can set colors for tabs in three different ways as shown below.mBottomBar.mapColorForTab(0, ContextCompat.getColor(this, R.color.colorAccent));mBottomBar.mapColorForTab(1, 0xFF5D4037);mBottomBar.mapColorForTab(2, "#7B1FA2");mBottomBar.mapColorForTab(3, "#FF5252");mBottomBar.mapColorForTab(4, "#FF9800");}@Overridepublic void onSaveInstanceState(Bundle outState) {super.onSaveInstanceState(outState);// Necessary to restore the BottomBar's state, otherwise we would// lose the current tab on orientation change.mBottomBar.onSaveInstanceState(outState);}private void initViewPager() {fragmentList = new ArrayList<>();fragmentList.add(new FragmentOne());fragmentList.add(new FragmentTwo());viewPager.setAdapter(new FragmentStatePagerAdapter(getSupportFragmentManager()) {@Overridepublic Fragment getItem(int position) {return fragmentList.get(position);}@Overridepublic int getCount() {return fragmentList.size();}});viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {@Overridepublic void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {}@Overridepublic void onPageSelected(int position) {mBottomBar.selectTabAtPosition(position, true);}@Overridepublic void onPageScrollStateChanged(int state) {}});}}

　　BottomBar的github上提供了两种初始化方式，这里是第二种实现下滑隐藏，因为是fragment滚动所以fragment的布局要被NestedScrollView包裹（下面贴代码，很简单的），同时注意viewPager.setOnPageChangeListener已经过时了。

layout/activity_main.xml

<?xml version="1.0" encoding="utf-8"?><android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"android:id="@+id/myCoordinator"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:fitsSystemWindows="true"tools:context="com.example.bottombar.bottombar.MainActivity"><android.support.v4.view.ViewPagerandroid:id="@+id/viewPager"android:layout_width="match_parent"android:layout_height="match_parent"/></android.support.design.widget.CoordinatorLayout>

FragmentOne.Java

public class FragmentOne extends Fragment {View v;Context context;@Nullable@Overridepublic View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {v = inflater.inflate(R.layout.fragment_one, container,false);context = getActivity();return v;}}

layout/fragment_one.xml

<?xml version="1.0" encoding="utf-8"?><android.support.v4.widget.NestedScrollViewandroid:id="@+id/myScrollView"xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"><RelativeLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:padding="20dp"><TextViewandroid:layout_centerInParent="true"android:layout_width="match_parent"android:layout_height="wrap_content"android:text="@string/baiduInfo"/></RelativeLayout></android.support.v4.widget.NestedScrollView>

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