import android.os.Bundle;
import android.app.Activity;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity implements OnClickListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // [1]找到我们关心的控件
        Button btn_contact = (Button) findViewById(R.id.btn_contact);
        Button btn_discover = (Button) findViewById(R.id.btn_discover);
        Button btn_me = (Button) findViewById(R.id.btn_me);
        Button btn_wx = (Button) findViewById(R.id.btn_wx);

        // [2]给按钮设置点击事件
        btn_contact.setOnClickListener(this);
        btn_discover.setOnClickListener(this);
        btn_me.setOnClickListener(this);
        btn_wx.setOnClickListener(this);

    }

    @Override
    public void onClick(View v) {
        
        // [3]具体判断一下我点击的是哪个按钮
        
        //[4]获取fragment的管理者 
        FragmentManager fragmentManager = getFragmentManager();
        //[5]开启事物 
        FragmentTransaction transaction = fragmentManager.beginTransaction();
        
        switch (v.getId()) {
        case R.id.btn_wx: // 说明点击了微信按钮
            transaction.replace(R.id.ll, new WxFragment());
            break;

        case R.id.btn_contact: // 说明点击了微信按钮
            transaction.replace(R.id.ll, new ContactFragment());
            break;

        case R.id.btn_discover: // 说明点击了微信按钮
            transaction.replace(R.id.ll, new DiscoverFragment());
            break;

        case R.id.btn_me: // 说明点击了微信按钮
            transaction.replace(R.id.ll, new MeFragment());
            break;
        }
        //[6]最后一布 记得 提交事物 
        transaction.commit();

    }

import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;

public class WxFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_wx, null);
        view.findViewById(R.id.btn_test).setOnClickListener(new OnClickListener() {
            
            @Override
            public void onClick(View v) {
                System.out.println("哈哈哈 我被点击了");
            }
        });
        
        return view; 
    }
    
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="这是微信模块" />

    <Button
        android:id="@+id/btn_test"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" 
        android:text="test"
        />

</LinearLayout>