<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() {     //要先設計模式后再添加圖標！     //設置按鈕模式 MODE_FIXED表示固定  MODE_SHIFTING表示轉移     bottomNavigationBar.setMode(BottomNavigationBar.MODE_FIXED);     //設置背景風格     // BACKGROUND_STYLE_STATIC表示靜態的     //BACKGROUND_STYLE_RIPPLE表示漣漪的，也就是可以變化的 ，跟隨setActiveColor里面的顏色變化     bottomNavigationBar.setBackgroundStyle(BottomNavigationBar.BACKGROUND_STYLE_RIPPLE);     //添加并設置圖標、圖標的顏色和文字     bottomNavigationBar         .addItem(new BottomNavigationItem(R.drawable.im_botton_message, "消息")).setActiveColor(R.color.blue)         .addItem(new BottomNavigationItem(R.drawable.im_botton_contacts, "聯系人")).setActiveColor(R.color.red)         .addItem(new BottomNavigationItem(R.drawable.im_botton_dongtai, "動態")).setActiveColor(R.color.orign)         .setFirstSelectedPosition(lastSelectedPosition )         .initialise();      bottomNavigationBar.setTabSelectedListener(this);     setDefaultFragment();   }    //設置初始界面   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("聯系人");         }         transaction.replace(R.id.layFrame, contactsFragment);         break;       case 2:         if (dongtaiFragment == null) {           dongtaiFragment = DongtaiFragment.newInstance("動態");         }         transaction.replace(R.id.layFrame, dongtaiFragment);         break;       default:         break;     }     // 事務提交     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 {   /**    * 標志位，標志已經初始化完成    */   private boolean isPrepared;   /**    * 是否已被加載過一次，第二次就不再去請求數據了    */   private boolean mHasLoadedOnce;   TextView textView;   @Nullable   @Override   public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {     if (mView == null) {       // 需要inflate一個布局文件 填充Fragment       mView = inflater.inflate(R.layout.fragment_msg, container, false);       initView();       isPrepared = true; //    實現懶加載       lazyLoad();     }     //緩存的mView需要判斷是否已經被加過parent， 如果有parent需要從parent刪除，要不然會發生這個mView已經有parent的錯誤。     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;     }     //填充各控件的數據     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;   } } 

<?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當前狀態是否可見    */   public boolean isVisible;    /**    * inflate布局文件 返回的view    */   public View mView;    /**    * 簡化 findViewById    *    * @param viewId    * @param <T>    * @return    */   protected <T extends View> T find(int viewId) {     return (T) mView.findViewById(viewId);   }    /**    * setUserVisibleHint是在onCreateView之前調用的    * 設置Fragment可見狀態    */   @Override   public void setUserVisibleHint(boolean isVisibleToUser) {     super.setUserVisibleHint(isVisibleToUser);     /**      * 判斷是否可見      */     if (getUserVisibleHint()) {       isVisible = true;       onVisible();     } else {       isVisible = false;       onInvisible();     }   }    /**    * 可見    */   private void onVisible() {     lazyLoad();   }    /**    * 不可見    */   private void onInvisible() {   }    /**    * 延遲加載    * 子類必須重寫此方法    */   public abstract void lazyLoad(); }