<com.ashokvarma.bottomnavigation.BottomNavigationBar     android:layout_gravITy="bottom"     android:id="@+id/bottom_navigation_bar"     android:layout_width="match_parent"     android:layout_height="wrap_content"/>

 BottomNavigationBar bottomNavigationBar = (BottomNavigationBar) findViewById(R.id.bottom_navigation_bar);   bottomNavigationBar         .addItem(new BottomNavigationItem(R.drawable.ic_home_white_24dp, "Home"))         .addItem(new BottomNavigationItem(R.drawable.ic_Book_white_24dp, "Books"))         .addItem(new BottomNavigationItem(R.drawable.ic_music_note_white_24dp, "Music"))         .addItem(new BottomNavigationItem(R.drawable.ic_tv_white_24dp, "Movies & TV"))         .addItem(new BottomNavigationItem(R.drawable.ic_videogame_asset_white_24dp, "Games"))         .initialise();

  bottomNavigationBar.setTabSelectedListener(new BottomNavigationBar.OnTabSelectedListener(){       @override       public void onTabSelected(int position) {       }       @Override       public void onTabUnselected(int position) {]       }       @Override       public void onTabreselected(int position) {       }     });

 package com.android.xiaobai;    import android.os.Bundle;  import android.support.annotation.Nullable;  import android.support.v4.app.Fragment;  import android.support.v4.app.FragmentManager;  import android.support.v4.app.FragmentTransaction;  import android.support.v7.app.AppCompatActivity;  import android.util.LOG;    import com.ashokvarma.bottomnavigation.BottomNavigationBar;  import com.ashokvarma.bottomnavigation.BottomNavigationItem;    import java.util.ArrayList;    import fragment.ContactsFragment;  import fragment.DongtaiFragment;  import fragment.MsgFragment;    /**   * Created by xiaobai on 2018/1/31/031.   */    public class MessageActivity extends AppCompatActivity implements BottomNavigationBar.OnTabSelectedListener {    PRivate ArrayList<Fragment> fragments;    private BottomNavigationBar bottomNavigationBar;    private MsgFragment msgFragment;    private ContactsFragment contactsFragment;    private DongtaiFragment dongtaiFragment;    private FragmentManager fragmentManager;    private FragmentTransaction transaction;    int lastSelectedPosition = 0;      @Override    protected void onCreate(@Nullable Bundle savedInstanceState) {      suPEr.onCreate(savedInstanceState);      setContentView(R.layout.activty_message);        bottomNavigationBar = findViewById(R.id.bottom_navigation_bar);      init();    }      private void init() {      //要先设计模式后再添加图标！      //设置按钮模式 MODE_FIXED表示固定  MODE_SHIFTING表示转移      bottomNavigationBar.setMode(BottomNavigationBar.MODE_FIXED);      //设置背景风格      // BACKGROUND_STYLE_STATIC表示静态的      //BACKGROUND_STYLE_RIPPLE表示涟漪的，也就是可以变化的 ，跟随setActiveColor里面的颜色变化      bottomNavigationBar.setBackgroundStyle(BottomNavigationBar.BACKGROUND_STYLE_RIPPLE);      //添加并设置图标、图标的颜色和文字      bottomNavigationBar          .addItem(new BottomNavigationItem(R.drawable.im_botton_message, "消息")).setActiveColor(R.color.blue)          .addItem(new BottomNavigationItem(R.drawable.im_botton_contacts, "联系人")).setActiveColor(R.color.red)          .addItem(new BottomNavigationItem(R.drawable.im_botton_dongtai, "动态")).setActiveColor(R.color.orign)          .setFirstSelectedPosition(lastSelectedPosition )          .initialise();        bottomNavigationBar.setTabSelectedListener(this);      setDefaultFragment();    }      //设置初始界面    private void setDefaultFragment() {      fragmentManager = getSupportFragmentManager();      transaction = fragmentManager.beginTransaction();      transaction.replace(R.id.layFrame, MsgFragment.newInstance("消息"));      transaction.COMmit();    }      @Override    public void onTabSelected(int position) {      fragmentManager = getSupportFragmentManager();      transaction = fragmentManager.beginTransaction();      switch (position) {        case 0:          if (msgFragment == null) {            msgFragment = MsgFragment.newInstance("消息");          }          transaction.replace(R.id.layFrame, msgFragment);          break;        case 1:          if (contactsFragment == null) {            contactsFragment = ContactsFragment.newInstance("联系人");          }          transaction.replace(R.id.layFrame, contactsFragment);          break;        case 2:          if (dongtaiFragment == null) {            dongtaiFragment = DongtaiFragment.newInstance("动态");          }          transaction.replace(R.id.layFrame, dongtaiFragment);          break;        default:          break;      }      // 事务提交      transaction.commit();    }      @Override    public void onTabUnselected(int position) {      Log.d("dongtaiFragment", "onTabUnselected() called with: " + "position = [" + position + "]");    }      @Override    public void onTabReselected(int position) {      }  } 

 package fragment;    import android.os.Bundle;  import android.support.annotation.Nullable;  import android.view.LayoutInflater;  import android.view.View;  import android.view.ViewGroup;  import android.widget.TextView;    import com.android.xiaobai.R;    /**   * Created by xiaobai on 2018/1/31/031.   */    public class MsgFragment extends BaseFragment {    /**     * 标志位，标志已经初始化完成     */    private boolean isPrepared;    /**     * 是否已被加载过一次，第二次就不再去请求数据了     */    private boolean mHasLoadedOnce;    TextView textView;    @Nullable    @Override    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {      if (mView == null) {        // 需要inflate一个布局文件 填充Fragment        mView = inflater.inflate(R.layout.fragment_msg, container, false);        initView();        isPrepared = true;  //    实现懒加载        lazyLoad();      }      //缓存的mView需要判断是否已经被加过parent， 如果有parent需要从parent删除，要不然会发生这个mView已经有parent的错误。      ViewGroup parent = (ViewGroup) mView.getParent();      if (parent != null) {        parent.removeView(mView);      }        return mView;    }    /**     * 初始化控件     */    private void initView() {      }      @Override    public void lazyLoad() {      if (!isPrepared || !isVisible || mHasLoadedOnce) {        return;      }      //填充各控件的数据      mHasLoadedOnce = true;    }    public static MsgFragment newInstance(String param1) {      MsgFragment fragment = new MsgFragment();      Bundle args = new Bundle();      args.putString("agrs1", param1);      fragment.setarguments(args);      return fragment;    }  }  

 <&#63;XMl version="1.0" encoding="utf-8"?>  <LinearLayout xMLns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    tools:context=".MessageActivity">      <FrameLayout      android:id="@+id/layFrame"      android:layout_width="match_parent"      android:layout_height="0dp"      android:layout_weight="1" />      <com.ashokvarma.bottomnavigation.BottomNavigationBar      android:id="@+id/bottom_navigation_bar"      android:layout_width="match_parent"      android:layout_height="wrap_content"      android:layout_gravity="bottom" />  </LinearLayout> 

 package fragment;    import android.support.v4.app.Fragment;  import android.view.View;      /**   * Created by xiaobai on 2018/1/31/031.   */    public abstract class BaseFragment extends Fragment {    /**     * Fragment当前状态是否可见     */    public boolean isVisible;      /**     * inflate布局文件 返回的view     */    public View mView;      /**     * 简化 findViewById     *     * @param viewId     * @param <T>     * @return     */    protected <T extends View> T find(int viewId) {      return (T) mView.findViewById(viewId);    }      /**     * setUserVisibleHint是在onCreateView之前调用的     * 设置Fragment可见状态     */    @Override    public void setUserVisibleHint(boolean isVisibleToUser) {      super.setUserVisibleHint(isVisibleToUser);      /**       * 判断是否可见       */      if (getUserVisibleHint()) {        isVisible = true;        onVisible();      } else {        isVisible = false;        onInvisible();      }    }      /**     * 可见     */    private void onVisible() {      lazyLoad();    }      /**     * 不可见     */    private void onInvisible() {    }      /**     * 延迟加载     * 子类必须重写此方法     */    public abstract void lazyLoad();  }