Android Activity中嵌套多个Fragment的使用

Fragment英文翻译为碎片，可以在一个Activity中可以嵌套多个Fragment，相当于多个页面。但是它们都在同一 个Activity中，fragment的生命周期和Activity类似，如果当前Activity没有注销（onDestory）其中的众多的fragment也不会被销毁，这点不利于资源的回收。所以有时候你要考虑是使用多个fragment还是使用多个Activity。

[java] view plaincopy在CODE上查看代码片派生到我的代码片

1.可以在XML中编写，也可以在代码中编写，写一个类继承android.support.v4.app.Fragment，记住：是V4包中的Fragment.（考虑到版本的兼容性问题:fragment是Android3.0才引入的）

2.重写父类Fragment的onCreate()，和onCreateView（）方法，onCreateView方法会返回一个VIew,这个View将被填充到Activity的界面中。所以一般我们重点就是把onCreateView()覆写好。

3.在Acticvty中产生一个fragment的实例，调用fragmentManager 和 fragmentTransaction;实现fragment的添加，移除，替换（add，remove,replace),记住，当这些事务写完以后要Commit(),保证事务被提交，这样才会生效。

[java] view plaincopy在CODE上查看代码片派生到我的代码片

[java] view plaincopy在CODE上查看代码片派生到我的代码片
下面是一个DEMO：
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.support.v4.app.FragmentManager;

/**
Fragment的生命周期:
* 第一次启动该fragment:   onCreate --> onCreateView -->onStart --> onResume
*  变得不处于前台的时候：onPause  -->onDestroyView
*  重新回到前台时候：OnCreateView -->onStart --> onResume
* @author yesong
*
*/
public class ContentFragment extends Fragment {

private Button mStartButton;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.i("yesongyesong", "ContentFragment : onCreate ");
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {

View view = inflater.inflate(R.layout.content_fragment_layout, null);
mStartButton = (Button) view.findViewById(R.id.start_button);
mStartButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
MainActivity activity = (MainActivity) getActivity();
activity.enterContentFrament01(mStartButton.getText().toString());

}
});

return view;
}

}
第二个fragment

[java] view plaincopy在CODE上查看代码片派生到我的代码片
package cn.mmb.fragment.product;

import android.annotation.SuppressLint;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import cn.mmb.fragment.MainActivity;
import cn.mmb.fragment.R;
import cn.mmb.fragment.inter.ViewClickListener;

@SuppressLint("ValidFragment")
public class Content01_Fragment extends Fragment {

private Button mStartButton;

/*
* private ViewClickListener viewClickListener; public
* Content01_Fragment(ViewClickListener clickListener){
* this.viewClickListener = clickListener; }
*/

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {

View view = inflater.inflate(R.layout.content_01_fragment_layout, null);
mStartButton = (Button) view.findViewById(R.id.content01_button);
mStartButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
MainActivity activity = (MainActivity) getActivity();
activity.enterContentFrament02(mStartButton.getText().toString());
}
});
[java] view plaincopy在CODE上查看代码片派生到我的代码片
<span style="font-family: Arial, Helvetica, sans-serif;">     return view;</span>

[java] view plaincopy在CODE上查看代码片派生到我的代码片
}
第三个fragment

[java] view plaincopy在CODE上查看代码片派生到我的代码片
package cn.mmb.fragment.product;

import android.annotation.SuppressLint;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import cn.mmb.fragment.MainActivity;
import cn.mmb.fragment.R;
import cn.mmb.fragment.inter.ViewClickListener;

@SuppressLint("ValidFragment")
public class Content02_Fragment extends Fragment {

private Button mStartButton;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {

View view = inflater.inflate(R.layout.content_02_fragment_layout, null);
mStartButton = (Button) view.findViewById(R.id.no_more_button);
mStartButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {

}
});

return view;
}

}
Activity使用我们已经写好的fragment

[java] view plaincopy在CODE上查看代码片派生到我的代码片
package cn.mmb.fragment;

import cn.mmb.fragment.product.ButtomFragment;
import cn.mmb.fragment.product.Content01_Fragment;
import cn.mmb.fragment.product.Content02_Fragment;
import cn.mmb.fragment.product.ContentFragment;
import cn.mmb.fragment.product.TitleBarFragment;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.view.KeyEvent;
import android.view.View;
import android.widget.FrameLayout;
import android.widget.LinearLayout;

public class MainActivity extends FragmentActivity/* implements ViewClickListener */{

private TitleBarFragment mTitleBarFragment;
private ContentFragment mContentFragment;
private Content01_Fragment mContent01Fragment;
private Content02_Fragment mContent02Fragment;
private ButtomFragment mButtomFragment;
//private FrameLayout mContentLayout;
private LinearLayout mTitleBarLayout;
private LinearLayout mButtomLayout;
private FragmentTransaction fragmentTransaction;
private FragmentManager fragmentManager;
/**
*  to remember  current fragment,
*  if mfragmentIndex == 0 that there is currently a  contentFragmemt
*/
private int mFragmentIndex = 0;
/**
*  to remember  last time title bar message
*/
private String mLastTitleMessage;

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

mTitleBarLayout = (LinearLayout) findViewById(R.id.titlebar_layout);
//mContentLayout = (FrameLayout) findViewById(R.id.content_layout);
mButtomLayout = (LinearLayout) findViewById(R.id.buttom_layout);
mTitleBarLayout.setVisibility(View.GONE);

fragmentManager = getSupportFragmentManager();
fragmentTransaction = fragmentManager.beginTransaction();

mContentFragment = new ContentFragment();
mButtomFragment = new ButtomFragment();

fragmentTransaction.add(R.id.content_layout, mContentFragment,null);
fragmentTransaction.add(R.id.buttom_layout, mButtomFragment,null);

/*fragmentTransaction.replace(R.id.content_layout, mContentFragment);
fragmentTransaction.replace(R.id.buttom_layout, mButtomFragment);*/
fragmentTransaction.commit();

}

/**
* Before using a callback to control other fragment and some view,
* but now find  a better method : Fragment.this.getActivity();
*/
/* @Override
public void buttonClick(View v, String msg) {
switch (v.getId()) {
case R.id.start_button: enterContentFrament01(msg);
break;
case R.id.content01_button: enterContentFrament02(msg); break;
default: break;
}
}*/

/**
* enter the  Third content fragment
* @param msg : the  titleBarMessage
*/
public void enterContentFrament02(String msg) {

if (mTitleBarFragment != null) {
mLastTitleMessage = mTitleBarFragment.getTitleMessage();
mTitleBarFragment.setTitleMessage(msg);
}
if (mContent02Fragment == null) {
mContent02Fragment = new Content02_Fragment();
}
fragmentTransaction = fragmentManager.beginTransaction();

fragmentTransaction.replace(R.id.content_layout, mContent02Fragment);

//fragmentTransaction.add(R.id.content_layout, mContent02Fragment);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
mFragmentIndex++;

}

/**
* enter the  second content fragment
* @param msg : the  titleBarMessage
*/
public void enterContentFrament01(String msg) {

if (mTitleBarFragment == null) {
mTitleBarFragment = new TitleBarFragment(msg);
}
mLastTitleMessage = mTitleBarFragment.getTitleMessage();
mTitleBarFragment.setTitleMessage(msg);  //set TitleBar message

if (mContent01Fragment == null) {
mContent01Fragment = new Content01_Fragment();
}
mTitleBarLayout.setVisibility(View.VISIBLE);
mButtomLayout.setVisibility(View.GONE);
fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.titlebar_layout, mTitleBarFragment);
fragmentTransaction.replace(R.id.content_layout, mContent01Fragment);

/*fragmentTransaction.add(R.id.titlebar_layout, mTitleBarFragment);
fragmentTransaction.add(R.id.content_layout, mContent01Fragment);*/

fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
mFragmentIndex++;

}

@Override
public boolean onKeyUp(int keyCode, KeyEvent event) {

if (keyCode == KeyEvent.KEYCODE_BACK) {
mFragmentIndex--;
if (mFragmentIndex == 0) {
mButtomLayout.setVisibility(View.VISIBLE);
mTitleBarLayout.setVisibility(View.GONE);
}
}
if (mTitleBarFragment != null) {
mTitleBarFragment.setTitleMessage(mLastTitleMessage);
}
return super.onKeyUp(keyCode, event);
}

}

运行效果图：

第一个fragment  （白色）                   第2个fragment  （黄色）              第3个fragment（红色）

点击button进入第2个fragment           点击button进入第3个fragment

下面的的menu也是fragment              上面的titleBar也是一个fragment

以上是多个fragment都在同一个Activity中跳转。