Fragment其实就是一个小的Activity，他的生命周期和Activity差不多。Fragment概念的提出就是因为平板编程的需要，Fragment使得UI设计得以模块化，平板等大屏设备的UI设计得到了很好的技术支持。然而Fragment概念的提出是因为大屏UI设计的需求，但是使用并不局限于平板设计。下面这坨代码（的确是坨。。）实现的是一个类似微信的选项卡切换界面的功能，全局只有一个Activity，真正改变的只是Fragment。 Activity: ~~~ package com.example.myfragment; import android.os.Bundle; import android.app.Activity; import android.app.FragmentManager; import android.app.FragmentTransaction; import android.view.View; import android.view.View.OnClickListener; import android.widget.TextView; public class MainActivity extends Activity implements OnClickListener { private TextView tv1; private TextView tv2; private TextView tv3; private TextView tv4; private FragmentManager fm; private Fragment1 fragment1; private Fragment2 fragment2; private Fragment3 fragment3; private Fragment4 fragment4; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); tv1 = (TextView) findViewById(R.id.text1); tv2 = (TextView) findViewById(R.id.text2); tv3 = (TextView) findViewById(R.id.text3); tv4 = (TextView) findViewById(R.id.text4); tv1.setOnClickListener(this); tv2.setOnClickListener(this); tv3.setOnClickListener(this); tv4.setOnClickListener(this); fm = getFragmentManager(); FragmentTransaction ft = fm.beginTransaction(); fragment1 = new Fragment1(); fragment2 = new Fragment2(); fragment3 = new Fragment3(); fragment4 = new Fragment4(); ft.replace(R.id.content, fragment1); ft.commit(); } @Override public void onClick(View v) { // TODO Auto-generated method stub FragmentTransaction ft = fm.beginTransaction(); switch (v.getId()) { case R.id.text1: ft.replace(R.id.content, fragment1); break; case R.id.text2: ft.replace(R.id.content, fragment2); break; case R.id.text3: ft.replace(R.id.content, fragment3); break; case R.id.text4: ft.replace(R.id.content, fragment4); break; } ft.commit(); } } ~~~ activity xml: ~~~ <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" > <LinearLayout android:layout_width="fill_parent" android:layout_height="wrap_content" android:orientation="horizontal" > <TextView android:id="@+id/text1" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:gravity="center" android:text="Text1" /> <TextView android:id="@+id/text2" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:gravity="center" android:text="Text2" /> <TextView android:id="@+id/text3" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:gravity="center" android:text="Text3" /> <TextView android:id="@+id/text4" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:gravity="center" android:text="Text4" /> </LinearLayout> <RelativeLayout android:id="@+id/content" android:layout_width="fill_parent" android:layout_height="fill_parent" > </RelativeLayout> </LinearLayout> ~~~ fragment1: ~~~ package com.example.myfragment; import android.app.Fragment; import android.os.Bundle; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; public class Fragment1 extends Fragment { @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View view = inflater.inflate(R.layout.fragment1, null); return view; } } ~~~ f1 xml: ~~~ <?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="wrap_content" android:layout_height="wrap_content" android:text="Fragment1" android:textSize="20dp" > </TextView> </LinearLayout> ~~~ fragment2到fragment4的定义方式和fragment1类似，这里就不贴出来了。