Fragment为大量型号，尺寸，分辨率的设备提供了一种统一的UI优化方案。将Activity分解为多个Fragment，将极大地提高UI的灵活性，也更容易为一些新的设备配置带来更好的用户体验。

onCreate:

创建Fragment时系统调用它。

onCreateView:

首次绘制用户界面时系统调用这个方法。

onPause:

当用户离开Fragment时系统调用此方法。

onAttach:

当Fragment与Acitivity绑定时调用。

onActivityCreated:

当Fragment绑定的Activity调用onCreate方法时调用。

onDestroyView:

当与Fragment相关联的视图层次被删除时调用。

onDetach:

当Fragment与Acitivity解绑定时调用。

FragmentManager是每个Activity用来管理它所包含的Fragment。在Activity中切换Fragment时必须用到FragmentManager，Activity可以通过使用getFragmentManager方法来访问FragmentManager。

代码展示：

MainActivity.java

package com.example.demo15;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.content.Intent;
import android.os.Bundle;
import android.widget.RadioGroup;
import android.widget.RadioGroup.OnCheckedChangeListener;

public class MainActivity extends Activity implements OnCheckedChangeListener{

private RadioGroup group;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
group=(RadioGroup) findViewById(R.id.radiogroup);
group.setOnCheckedChangeListener(this);
}
@SuppressLint("NewApi") @Override
public void onCheckedChanged(RadioGroup group, int checkedId) {
switch(checkedId){
case R.id.first:{
Intent intent=new Intent(this,MainActivity2.class);
startActivity(intent);
break;
}
case R.id.second:{
MyFragment2 fragment2=new MyFragment2();
FragmentManager fragmentManager=getFragmentManager();
FragmentTransaction beginTransaction=fragmentManager.beginTransaction();
beginTransaction.add(R.id.frame ,fragment2);
beginTransaction.addToBackStack(null);
beginTransaction.commit();
break;
}
case R.id.thrid:{
Intent intent=new Intent(MainActivity.this,MainActivity3.class);
startActivity(intent);
break;
}
case R.id.fourth:{
Intent intent=new Intent(MainActivity.this,MainActivity4.class);
startActivity(intent);
break;
}
}
}
}

MainActivity2.java

package com.example.demo15;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity2 extends Activity{
private TextView tv;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main2);

Button button=(Button) findViewById(R.id.button);
tv=(TextView) findViewById(R.id.text);
button.setText("刀冲");
button.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
tv.setText("TextView from 刀冲");
}
});
}
}

MainActivity3.java

package com.example.demo15;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity3 extends Activity{
private Button button;
private Fragment frag;
private boolean flag=true;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main3);
init();
button=(Button) findViewById(R.id.button);
button.setOnClickListener(new OnClickListener() {

@SuppressLint("NewApi") public void onClick(View v) {
FragmentManager fragmentManager=getFragmentManager();
FragmentTransaction beginTransaction=fragmentManager.beginTransaction();

if(flag){
MyFragment4 frag4=new MyFragment4();
beginTransaction.replace(R.id.layout,frag4);
}else{
MyFragment3 frag3=new MyFragment3();
beginTransaction.replace(R.id.layout,frag3);
}

beginTransaction.commit();
}
});
}

@SuppressLint("NewApi") private void init() {
FragmentManager fragmentManager=getFragmentManager();
FragmentTransaction beginTransaction=fragmentManager.beginTransaction();
MyFragment3 frag3=new MyFragment3();
beginTransaction.add(R.id.layout,frag3);
beginTransaction.commit();
}
}

MainActivity4.java

package com.example.demo15;

import com.example.demo15.MyFragment5.MyListener;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity4 extends Activity implements MyListener{

private EditText editext;
private Button send;
@SuppressLint("NewApi") @Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main4);
editext=(EditText) findViewById(R.id.editText);
send=(Button) findViewById(R.id.send);

send.setOnClickListener(new OnClickListener() {

@SuppressLint("NewApi") @Override
public void onClick(View v) {
String text=editext.getText().toString();
MyFragment5 fragment5=new MyFragment5();
Bundle bundle=new Bundle();
bundle.putString("name",text);
fragment5.setArguments(bundle);
FragmentManager fragmentManager=getFragmentManager();
FragmentTransaction beginTransaction=fragmentManager.beginTransaction();

beginTransaction.add(R.id.layout,fragment5,"fragment5");
beginTransaction.commit();
Toast.makeText(MainActivity4.this,"fragment4"+text,Toast.LENGTH_SHORT).show();
}
});

FragmentManager fragmentManager=getFragmentManager();
Fragment findFragmentById=fragmentManager.findFragmentById(R.id.frag);
MyFragment frag=(MyFragment)findFragmentById;
frag.setAaa("frag-aaa-");
}

@Override
public void thank(String code) {
Toast.makeText(MainActivity4.this,"收到"+code+"，客气了",Toast.LENGTH_SHORT).show();
}

}

MyFragment.java

package com.example.demo15;

import android.annotation.SuppressLint;
import android.app.Fragment;
import android.os.Bundle;
import android.support.annotation.Nullable;

import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

@SuppressLint("NewApi") public class MyFragment extends Fragment{

private String aaa;

public String getAaa() {
return aaa;
}

public void setAaa(String aaa) {
this.aaa = aaa;
}

@Override
public View onCreateView(LayoutInflater inflater,
@Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
//layout布局文件转换为View对象
//1.Fragment加载的布局文件 2.加载layout的父ViewGroup 3.false 不返回父ViewGroup
View view=inflater.inflate(R.layout.fragment,container,false);
TextView text=(TextView) view.findViewById(R.id.text);
Button button=(Button) view.findViewById(R.id.button);
text.setText("静态加载Fragment");
button.setText("done");
button.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
String value=getAaa();
Toast.makeText(getActivity(),"value="+value,Toast.LENGTH_SHORT).show();
}
});
return view;
}
}

MyFragment2.java

package com.example.demo15;

import android.annotation.SuppressLint;
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 android.widget.TextView;

@SuppressLint("NewApi") public class MyFragment2 extends Fragment{
@Override
public View onCreateView(LayoutInflater inflater,
@Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view=inflater.inflate(R.layout.fragment,container,false);
TextView text=(TextView) view.findViewById(R.id.text);
text.setText("动态传值");
return view;
}
}

MyFragment3.java

package com.example.demo15;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

@SuppressLint("NewApi") public class MyFragment3 extends Fragment{
private TextView tv;

@Override
public View onCreateView(LayoutInflater inflater,
@Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view=inflater.inflate(R.layout.fragment2,container,false);
TextView tv=(TextView) view.findViewById(R.id.text);
tv.setText("第一个Fragment");
Log.i("Main","Fragment1--onCreateView()");
return view;
}

@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
Log.i("Main","Fragment1--onAttach()");
}

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.i("Main","Fragment1--onCreate()");
}

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Log.i("Main","Fragment1--onActivityCreated()");
}

@Override
public void onStart() {
super.onStart();
Log.i("Main","Fragment1--onStart()");
}

@Override
public void onResume() {
super.onResume();
Log.i("Main","Fragment1--onResume()");
}

@Override
public void onPause() {
super.onPause();
Log.i("Main","Fragment1--onPause()");
}

@Override
public void onStop() {
super.onStop();
Log.i("Main","Fragment1--onStop()");
}

@Override
public void onDestroyView() {
super.onDestroyView();
Log.i("Main","Fragment1--onDestroyView()");
}

@Override
public void onDestroy() {
super.onDestroy();
Log.i("Main","Fragment1--onDestroy()");
}

@Override
public void onDetach() {
super.onDetach();
Log.i("Main","Fragment1--onDetach()");
}
}

MyFragment4.java

package com.example.demo15;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.support.annotation.Nullable;

import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

@SuppressLint("NewApi") public class MyFragment4 extends Fragment{
private TextView tv;

@Override
public View onCreateView(LayoutInflater inflater,
@Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view=inflater.inflate(R.layout.fragment2,container,false);
TextView tv=(TextView) view.findViewById(R.id.text);
tv.setText("第二个Fragment");
Log.i("Main","Fragment2--onCreateView()");
return view;
}

@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
Log.i("Main","Fragment2--onAttach()");
}

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.i("Main","Fragment2--onCreate()");
}

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Log.i("Main","Fragment2--onActivityCreated()");
}

@Override
public void onStart() {
super.onStart();
Log.i("Main","Fragment2--onStart()");
}

@Override
public void onResume() {
super.onResume();
Log.i("Main","Fragment2--onResume()");
}

@Override
public void onPause() {
super.onPause();
Log.i("Main","Fragment2--onPause()");
}

@Override
public void onStop() {
super.onStop();
Log.i("Main","Fragment2--onStop()");
}

@Override
public void onDestroyView() {
super.onDestroyView();
Log.i("Main","Fragment2--onDestroyView()");
}

@Override
public void onDestroy() {
super.onDestroy();
Log.i("Main","Fragment2--onDestroy()");
}

@Override
public void onDetach() {
super.onDetach();
Log.i("Main","Fragment2--onDetach()");
}
}

MyFragment5.java

package com.example.demo15;

import android.annotation.SuppressLint;
import android.app.Activity;
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 android.widget.TextView;
import android.widget.Toast;

@SuppressLint("NewApi") public class MyFragment5 extends Fragment{
private String code="Thank you,Activity";
public MyListener listener;
public interface MyListener{
public void thank(String code);
}

@Override
public void onAttach(Activity activity) {
listener=(MyListener) activity;
super.onAttach(activity);
}

@Override
public View onCreateView(LayoutInflater inflater,
@Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view=inflater.inflate(R.layout.fragment2,container,false);
TextView tv=(TextView) view.findViewById(R.id.text);
String text=getArguments().get("name")+"";
tv.setText(text);
Toast.makeText(getActivity(),"你好"+text,Toast.LENGTH_SHORT).show();
Toast.makeText(getActivity(),code,Toast.LENGTH_SHORT).show();
listener.thank(code);
return view;
}
}

布局文件：

activity_main.xml

<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
tools:context="com.example.demo15.MainActivity"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/container"
/>

fragment_main.xml

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

<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_world"
/>

</RelativeLayout>

fragment.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:id="@+id/text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>

<Button
android:text="改变"
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"

/>
</LinearLayout>

fragment2.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:id="@+id/text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>

</LinearLayout>

main.xml

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

<LinearLayout
android:id="@+id/frame"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
></LinearLayout>

<RadioGroup
android:id="@+id/radiogroup"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:gravity="center_horizontal"
android:orientation="horizontal"
>

<RadioButton
android:id="@+id/first"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:background="@drawable/radio_pressed"
android:button="@null"
android:drawableTop="@drawable/ic_launcher"
android:gravity="center_horizontal"
android:text="静态加载"
/>
<RadioButton
android:id="@+id/second"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:background="@drawable/radio_pressed"
android:button="@null"
android:drawableTop="@drawable/ic_launcher"
android:gravity="center_horizontal"
android:text="动态加载"
/>
<RadioButton
android:id="@+id/thrid"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:background="@drawable/radio_pressed"
android:button="@null"
android:drawableTop="@drawable/ic_launcher"
android:gravity="center_horizontal"
android:text="生命周期"
/>
<RadioButton
android:id="@+id/fourth"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:background="@drawable/radio_pressed"
android:button="@null"
android:drawableTop="@drawable/ic_launcher"
android:gravity="center_horizontal"
android:text="传值通信"
/>

</RadioGroup>

</RelativeLayout>

main2.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" >

<fragment
android:id="@+id/fragment"
android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:name="com.example.demo15.MyFragment"
/>
</LinearLayout>

main3.xml

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

<Button
android:text="切换Fragment"
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>

</LinearLayout>

main4.xml

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

<EditText
android:id="@+id/editText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
/>

<Button
android:id="@+id/send"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="发送"
/>

<fragment
android:id="@+id/frag"
android:name="com.example.demo15.MyFragment"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
</LinearLayout>

配置文件：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.demo15"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="21" />

<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name="com.example.demo15.MainActivity2"></activity>
<activity android:name="com.example.demo15.MainActivity3"></activity>
<activity android:name="com.example.demo15.MainActivity4"></activity>
</application>

</manifest>