import android.app.Fragment;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.example.cerian.marcon.R;
/**
 * Created by Cerian on 2017/7/9.
 */
public class homeFragment extends Fragment {
  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container,
               Bundle savedInstanceState) {
    View view=inflater.inflate(R.layout.fragment_home, null);
    //找到按钮前要加view.
    return view;
  }
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
  android:id="@+id/rl_layout"
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="match_parent"
  android:layout_height="match_parent">
  <LinearLayout
    android:id="@+id/ll_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
  </LinearLayout>
  <LinearLayout
    android:showDividers="beginning|end|middle"
    android:background="#ffffff"
    android:layout_width="match_parent"
    android:layout_height="40dp"
    android:orientation="horizontal"
    android:layout_alignParentBottom="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true">
    <ImageView
      android:id="@+id/ig_home"
      android:clickable="true"
      android:layout_weight="1"
      android:layout_width="0dp"
      android:layout_height="wrap_content"
      android:src="@mipmap/homepage1"/>
    <ImageView
      android:id="@+id/ig_lib"
      android:clickable="true"
      android:layout_weight="1"
      android:layout_width="0dp"
      android:layout_height="wrap_content"
      android:src="@mipmap/library1"/>
    <ImageView
      android:id="@+id/ig_my"
      android:clickable="true"
      android:layout_weight="1"
      android:layout_width="0dp"
      android:layout_height="wrap_content"
      android:src="@mipmap/my1"/>
  </LinearLayout>
</RelativeLayout>

import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.ImageView;
import com.example.cerian.marcon.fragment.homeFragment;
import com.example.cerian.marcon.fragment.libFragment;
import com.example.cerian.marcon.fragment.myFragment;
/**
 * Created by Cerian on 2017/7/9.
 */
public class home extends AppCompatActivity implements View.OnClickListener {
  private ImageView ig_home, ig_lib, ig_my;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.menufunction);
    ig_home = (ImageView) findViewById(R.id.ig_home);
    ig_lib = (ImageView) findViewById(R.id.ig_lib);
    ig_my = (ImageView) findViewById(R.id.ig_my);
    ig_home.setOnClickListener(this);
    ig_lib.setOnClickListener(this);
    ig_my.setOnClickListener(this);
/**
 * 第一步：拿到管理者
 * 第二步：开启事务
 * 第三步：替换
 * 第四步：提交
 */
    FragmentManager fragmentManager = getFragmentManager();
    FragmentTransaction beginTransaction = fragmentManager.beginTransaction();
    beginTransaction.replace(R.id.ll_layout, new homeFragment());
    ig_home.setImageResource(R.mipmap.homepage2);
    beginTransaction.commit();
  }
  @Override
  public void onClick(View view) {
    FragmentManager fragmentManager = getFragmentManager();
    FragmentTransaction beginTransaction = fragmentManager.beginTransaction();
    switch (view.getId()) {
      case R.id.ig_home: //点击的是主页
        beginTransaction.replace(R.id.ll_layout, new homeFragment());
        ig_home.setImageResource(R.mipmap.homepage2);
        ig_my.setImageResource(R.mipmap.my1);
        ig_lib.setImageResource(R.mipmap.library1);
        break;
      case R.id.ig_lib: //点击的是收藏
        beginTransaction.replace(R.id.ll_layout, new libFragment());
        ig_home.setImageResource(R.mipmap.homepage1);
        ig_my.setImageResource(R.mipmap.my1);
        ig_lib.setImageResource(R.mipmap.library2);
        break;
      case R.id.ig_my: //点击的是我的
        beginTransaction.replace(R.id.ll_layout, new myFragment());
        ig_home.setImageResource(R.mipmap.homepage1);
        ig_my.setImageResource(R.mipmap.my2);
        ig_lib.setImageResource(R.mipmap.library1);
        break;
    }
    beginTransaction.commit();
  }
}