android应用仿QQ使用fragment来实现

最近反复研究日常经典必用的几个android app，从主界面带来的交互方式入手进行分析，我将其大致分为三类。今天记录第一种方式，即主界面下面有几个tab页，最上端是标题栏，tab页和tab页之间不是通过滑动切换的，而是通过点击切换tab页。早期这种架构一直是使用tabhost+activitygroup来使用，随着fragment的出现及google官方也大力推荐使用fragment，后者大有代替前者之势。本文也使用fragment进行搭建，标题中的“经典”指这种交互经典，非本文的代码框架结构，欢迎大家提出指出不足，帮助完善。文中的fragment部分参考了郭神的博文(链接1 链接2 链接3)，代码也是在郭神代码基础上加入了自己对框架的理解。

再次重申下这种主界面交互的特点:1,多个tab，不能滑动切换只能点击切换；2，上有标题栏。这种模式也是目前app中使用最多的。如qq、百度云盘、招商银行、微博、支付宝。几个月前支付宝还是能滑动切换的，后来取消了。视图如下:

                

             

下面本文从底部控制栏、顶部控制栏及中间的内容显示载体fragment三部分叙述。

一、底部控制栏

底部控制栏里每个控件都不是单一基础控件，上面是图片、下面是文字，右上角是红点，当有更新时红点显示，否则隐藏。另外像qq的右上角还能显示未读消息的个数，我的参考链接里是通过大量的layout一点一点搭出来的，这样的好处是方便控制比较直观，另外是可以利用Linearlayout里的layout_weight这个属性，让底部的这些item均匀分布，缺点是代码上有很多重复，维护起来不方便。既然是整理app的通用模板框架，因此我将每个item视为一个对象，然后将其放在底部就ok了。本代码里只封装了上面是图片下面是文字，右上角的红点么有封装进来。

ImageText.java就作了这样一件事:

 <span style="font-family:Comic Sans MS;font-size:18px;">package org.yanzi.ui;

 import org.yanzi.constant.Constant;

 import android.content.Context;
 import android.graphics.Color;
 import android.util.AttributeSet;
 import android.view.LayoutInflater;
 import android.view.MotionEvent;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.ImageView;
 import android.widget.LinearLayout;
 import android.widget.TextView;

 import com.example.fragmentproject.R;


 public class ImageText extends LinearLayout{
     private Context mContext = null;
     private ImageView mImageView = null;
     private TextView mTextView = null;
     private final static int DEFAULT_IMAGE_WIDTH = 64;
     private final static int DEFAULT_IMAGE_HEIGHT = 64;
     private int CHECKED_COLOR = Color.rgb(29, 118, 199); //选中蓝色
     private int UNCHECKED_COLOR = Color.GRAY;   //自然灰色
     public ImageText(Context context) {
         super(context);
         // TODO Auto-generated constructor stub
         mContext = context;
     }

     public ImageText(Context context, AttributeSet attrs) {
         super(context, attrs);
         // TODO Auto-generated constructor stub
         mContext = context;
         LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
         View parentView = inflater.inflate(R.layout.image_text_layout, this, true);
         mImageView = (ImageView)findViewById(R.id.image_iamge_text);
         mTextView = (TextView)findViewById(R.id.text_iamge_text);
     }
     public void setImage(int id){
         if(mImageView != null){
             mImageView.setImageResource(id);
             setImageSize(DEFAULT_IMAGE_WIDTH, DEFAULT_IMAGE_HEIGHT);
         }
     }

     public void setText(String s){
         if(mTextView != null){
             mTextView.setText(s);
             mTextView.setTextColor(UNCHECKED_COLOR);
         }
     }

     @Override
     public boolean onInterceptTouchEvent(MotionEvent ev) {
         // TODO Auto-generated method stub
         return true;
     }
     private void setImageSize(int w, int h){
         if(mImageView != null){
             ViewGroup.LayoutParams params = mImageView.getLayoutParams();
             params.width = w;
             params.height = h;
             mImageView.setLayoutParams(params);
         }
     }
     public void setChecked(int itemID){
         if(mTextView != null){
             mTextView.setTextColor(CHECKED_COLOR);
         }
         int checkDrawableId = -1;
         switch (itemID){
         case Constant.BTN_FLAG_MESSAGE:
             checkDrawableId = R.drawable.message_selected;
             break;
         case Constant.BTN_FLAG_CONTACTS:
             checkDrawableId = R.drawable.contacts_selected;
             break;
         case Constant.BTN_FLAG_NEWS:
             checkDrawableId = R.drawable.news_selected;
             break;
         case Constant.BTN_FLAG_SETTING:
             checkDrawableId = R.drawable.setting_selected;
             break;
         default:break;
         }
         if(mImageView != null){
             mImageView.setImageResource(checkDrawableId);
         }
     }





 }
 </span>

对应的布局:

 <span style="font-family:Comic Sans MS;font-size:18px;"><?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" >

     <ImageView
         android:id="@+id/image_iamge_text"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_gravity="center_horizontal" />

     <TextView
         android:id="@+id/text_iamge_text"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_gravity="center_horizontal" />

 </LinearLayout></span>

代码里用到了Constant.java，这里面放的都是常量：

 <span style="font-family:Comic Sans MS;font-size:18px;">package org.yanzi.constant;

 public class Constant {
     //Btn的标识
     public static final int BTN_FLAG_MESSAGE = 0x01;
     public static final int BTN_FLAG_CONTACTS = 0x01 << 1;
     public static final int BTN_FLAG_NEWS = 0x01 << 2;
     public static final int BTN_FLAG_SETTING = 0x01 << 3;

     //Fragment的标识
     public static final String FRAGMENT_FLAG_MESSAGE = "消息";
     public static final String FRAGMENT_FLAG_CONTACTS = "联系人";
     public static final String FRAGMENT_FLAG_NEWS = "新闻";
     public static final String FRAGMENT_FLAG_SETTING = "设置";
     public static final String FRAGMENT_FLAG_SIMPLE = "simple";


 }
 </span>

第一排是复合Button的标识，下面的string类型的是将来创建fragment的标识。

完成了ImageText之后，下面就是将4个这样的控件放到一个布局里。为了控制方便，我们将底部栏抽象为一个对象BottomControlPanel.java，这样在维护底部栏相关内容时直接找他就行了。BottomControlPanel继承自RelativeLayout，先来看它的布局:

bottom_panel_layout.xml

 <span style="font-family:Comic Sans MS;font-size:18px;"><?xml version="1.0" encoding="utf-8"?>
 <org.yanzi.ui.BottomControlPanel xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="60dp"
     android:layout_alignParentBottom="true"
     android:gravity="center_vertical"
     android:paddingLeft="20dp"
     android:paddingRight="20dp" >

     <org.yanzi.ui.ImageText
         android:id="@+id/btn_message"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentLeft="true" />

     <org.yanzi.ui.ImageText
         android:id="@+id/btn_contacts"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_toRightOf="@id/btn_message" />

     <org.yanzi.ui.ImageText
         android:id="@+id/btn_news"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_toRightOf="@id/btn_contacts" />

     <org.yanzi.ui.ImageText
         android:id="@+id/btn_setting"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentRight="true" />

 </org.yanzi.ui.BottomControlPanel></span>

对应的java文件:

BottomControlPanel.java

 <span style="font-family:Comic Sans MS;font-size:18px;">package org.yanzi.ui;

 import java.util.ArrayList;
 import java.util.List;

 import org.yanzi.constant.Constant;

 import android.content.Context;
 import android.graphics.Color;
 import android.util.AttributeSet;
 import android.util.Log;
 import android.view.View;
 import android.widget.RelativeLayout;

 import com.example.fragmentproject.R;

 public class BottomControlPanel extends RelativeLayout implements View.OnClickListener {
     private Context mContext;
     private ImageText mMsgBtn = null;
     private ImageText mContactsBtn = null;
     private ImageText mNewsBtn = null;
     private ImageText mSettingBtn = null;
     private int DEFALUT_BACKGROUND_COLOR = Color.rgb(243, 243, 243); //Color.rgb(192, 192, 192)
     private BottomPanelCallback mBottomCallback = null;
     private List<ImageText> viewList = new ArrayList<ImageText>();

     public interface BottomPanelCallback{
         public void onBottomPanelClick(int itemId);
     }
     public BottomControlPanel(Context context, AttributeSet attrs) {
         super(context, attrs);
         // TODO Auto-generated constructor stub
     }
     @Override
     protected void onFinishInflate() {
         // TODO Auto-generated method stub
         mMsgBtn = (ImageText)findViewById(R.id.btn_message);
         mContactsBtn = (ImageText)findViewById(R.id.btn_contacts);
         mNewsBtn = (ImageText)findViewById(R.id.btn_news);
         mSettingBtn = (ImageText)findViewById(R.id.btn_setting);
         setBackgroundColor(DEFALUT_BACKGROUND_COLOR);
         viewList.add(mMsgBtn);
         viewList.add(mContactsBtn);
         viewList.add(mNewsBtn);
         viewList.add(mSettingBtn);

     }
     public void initBottomPanel(){
         if(mMsgBtn != null){
             mMsgBtn.setImage(R.drawable.message_unselected);
             mMsgBtn.setText("消息");
         }
         if(mContactsBtn != null){
             mContactsBtn.setImage(R.drawable.contacts_unselected);
             mContactsBtn.setText("联系人");
         }
         if(mNewsBtn != null){
             mNewsBtn.setImage(R.drawable.news_unselected);
             mNewsBtn.setText("新闻");
         }
         if(mSettingBtn != null){
             mSettingBtn.setImage(R.drawable.setting_unselected);
             mSettingBtn.setText("设置");
         }
         setBtnListener();

     }
     private void setBtnListener(){
         int num = this.getChildCount();
         for(int i = 0; i < num; i++){
             View v = getChildAt(i);
             if(v != null){
                 v.setOnClickListener(this);
             }
         }
     }
     public void setBottomCallback(BottomPanelCallback bottomCallback){
         mBottomCallback = bottomCallback;
     }
     @Override
     public void onClick(View v) {
         // TODO Auto-generated method stub
         initBottomPanel();
         int index = -1;
         switch(v.getId()){
         case R.id.btn_message:
             index = Constant.BTN_FLAG_MESSAGE;
             mMsgBtn.setChecked(Constant.BTN_FLAG_MESSAGE);
             break;
         case R.id.btn_contacts:
             index = Constant.BTN_FLAG_CONTACTS;
             mContactsBtn.setChecked(Constant.BTN_FLAG_CONTACTS);
             break;
         case R.id.btn_news:
             index = Constant.BTN_FLAG_NEWS;
             mNewsBtn.setChecked(Constant.BTN_FLAG_NEWS);
             break;
         case R.id.btn_setting:
             index = Constant.BTN_FLAG_SETTING;
             mSettingBtn.setChecked(Constant.BTN_FLAG_SETTING);
             break;
         default:break;
         }
         if(mBottomCallback != null){
             mBottomCallback.onBottomPanelClick(index);
         }
     }
     public void defaultBtnChecked(){
         if(mMsgBtn != null){
             mMsgBtn.setChecked(Constant.BTN_FLAG_MESSAGE);
         }
     }
     @Override
     protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
         // TODO Auto-generated method stub
         super.onLayout(changed, left, top, right, bottom);
         layoutItems(left, top, right, bottom);
     }
     /**最左边和最右边的view由母布局的padding进行控制位置。这里需对第2、3个view的位置重新设置
      * @param left
      * @param top
      * @param right
      * @param bottom
      */
     private void layoutItems(int left, int top, int right, int bottom){
         int n = getChildCount();
         if(n == 0){
             return;
         }
         int paddingLeft = getPaddingLeft();
         int paddingRight = getPaddingRight();
         Log.i("yanguoqi", "paddingLeft = " + paddingLeft + " paddingRight = " + paddingRight);
         int width = right - left;
         int height = bottom - top;
         Log.i("yanguoqi", "width = " + width + " height = " + height);
         int allViewWidth = 0;
         for(int i = 0; i< n; i++){
             View v = getChildAt(i);
             Log.i("yanguoqi", "v.getWidth() = " + v.getWidth());
             allViewWidth += v.getWidth();
         }
         int blankWidth = (width - allViewWidth - paddingLeft - paddingRight) / (n - 1);
         Log.i("yanguoqi", "blankV = " + blankWidth );

         LayoutParams params1 = (LayoutParams) viewList.get(1).getLayoutParams();
         params1.leftMargin = blankWidth;
         viewList.get(1).setLayoutParams(params1);

         LayoutParams params2 = (LayoutParams) viewList.get(2).getLayoutParams();
         params2.leftMargin = blankWidth;
         viewList.get(2).setLayoutParams(params2);
     }



 }
 </span>

在onFinishInflate()函数里实例化里面的子元素，在initBottomPanel()里设置每个孩子的图片和文字、监听.onLayout()里对中间的2个孩子的位置进行调整，使其均匀分布，见我的前文。这个BottomControlPanel实现了View.OnClickListener接口，在onClick()里通过id来判断用户点击了哪一个孩子。判断出来后需要做两件事，一是对这个被点击的对象进行处理，如字体颜色、图片资源的变化，右上角小红点的隐藏等等。另一方面，BottomControlPanel要告诉将来它的主人，也就是Activity到底是点了哪个，通知Activity去切换fragment。可以看到，activity类似个总控中心，BottomControlPanel管理属于它的ImageText，同时上报Activity。Activity知道消息后再切换fragment，每个fragment都有自己的事务逻辑。

这里定义了

public interface BottomPanelCallback{
public void onBottomPanelClick(int itemId);
}这个接口，通过传递Id来通知Activity。defaultBtnChecked()函数是apk初次打开后，默认切换到第一个消息fragment上。

这里有个地方需要注意，就是虽然ImageText和BottomControlPanel都是自定义控件，但两者在方式上是有区别的。在ImageText的构造函数里通过inflater将布局加载进来，它对应的布局是个普通的布局。而BottomControlPanel对应的布局文件里，直接使用了定义的BottomControlPanel，在onFinishInflate函数里实例化孩子View。前者是inflate之后实例化的。在使用ImageText到一个新的母布局时是通过<org.yanzi.ui.ImageText />这种方式进行的，那么使用BottomControlPanel有何区别，请见下文介绍Activity的布局时。

二、顶部控制栏

有了底部控制栏，顶部控制栏就可以如法炮制了。这里先交代几句，虽然Android3.0 后Google推出的有ActionBar来做顶部导航栏，参见郭神的这篇博文。但我发现，本文最前面贴图的几款应用应该都没有使用ActionBar，因为它不够灵活。ActionBar使用起来什么样，大家看看微信就知道了，那个的顶部控制栏就是ActionBar做的，这个应该没跑。

通过观察，顶部控制栏除了标题居中外，在右上角通常会再放一个按钮。不是ImageView就是TextView，这里我为了方便放的是两个TextView，右侧的按钮效果可以再TextView上弄个背景来实现。

HeadControlPanel.java

 <span style="font-family:Comic Sans MS;font-size:18px;">package org.yanzi.ui;

 import org.yanzi.constant.Constant;

 import com.example.fragmentproject.R;

 import android.content.Context;
 import android.graphics.Color;
 import android.util.AttributeSet;
 import android.widget.RelativeLayout;
 import android.widget.TextView;

 public class HeadControlPanel extends RelativeLayout {

     private Context mContext;
     private TextView mMidleTitle;
     private TextView mRightTitle;
     private static final float middle_title_size = 20f;
     private static final float right_title_size = 17f;
     private static final int default_background_color = Color.rgb(23, 124, 202);

     public HeadControlPanel(Context context, AttributeSet attrs) {
         super(context, attrs);
         // TODO Auto-generated constructor stub
     }

     @Override
     protected void onFinishInflate() {
         // TODO Auto-generated method stub
         mMidleTitle = (TextView)findViewById(R.id.midle_title);
         mRightTitle = (TextView)findViewById(R.id.right_title);
         setBackgroundColor(default_background_color);
     }
     public void initHeadPanel(){

         if(mMidleTitle != null){
             setMiddleTitle(Constant.FRAGMENT_FLAG_MESSAGE);
         }
     }
     public void setMiddleTitle(String s){
         mMidleTitle.setText(s);
         mMidleTitle.setTextSize(middle_title_size);
     }


 }
 </span>

布局文件head_panel_layout.xml

 <span style="font-family:Comic Sans MS;font-size:18px;"><?xml version="1.0" encoding="utf-8"?>
 <org.yanzi.ui.HeadControlPanel xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="50dp"
     android:layout_alignParentTop="true">
     <TextView
         android:id="@+id/midle_title"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_centerInParent="true"
         android:textColor="@android:color/white"/>
     <TextView
          android:id="@+id/right_title"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentRight="true"
         android:textColor="@android:color/white"/>

 </org.yanzi.ui.HeadControlPanel>
 </span>

三、总控中心Activity和Fragment

先交代下Fragment的使用大致分两种，一种是将Fragment作为一个View写死在布局中，布局里使用android:name来告诉它对应的是哪个实体Fragment。这种添加fragment的方式不能delete和replace掉。另一种是通过获得activity的fragmentmanager和fragmentTransaction和进行动态的添加。这种方式更加灵活，一般使用此种方法。

先看Activity的布局activity_main.xml:

 <span style="font-family:Comic Sans MS;font-size:18px;"><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:id="@+id/root_layout"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     tools:context="org.yanzi.fragmentproject.MainActivity" >

     <include
         android:id="@+id/bottom_layout"
         layout="@layout/bottom_panel_layout" />

     <View
         android:layout_width="match_parent"
         android:layout_height="1dip"
         android:layout_above="@id/bottom_layout"
         android:background="#FFE7E7E7" />

     <include
         android:id="@+id/head_layout"
         layout="@layout/head_panel_layout" />

     <View
         android:layout_width="match_parent"
         android:layout_height="1dip"
         android:layout_below="@id/head_layout"
         android:background="#FFE7E7E7" />
     <FrameLayout
         android:id="@+id/fragment_content"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:layout_below="@id/head_layout"
         android:layout_above="@id/bottom_layout" >
     </FrameLayout>

 </RelativeLayout></span>

注意看这里是通过include的方式把刚才自定义的上下panel加过来，而不能直接用<org.yanzi.ui.BottomControlPanel />这种方式直接加载。当然如果也模仿ImageText的构造方式，也是可以这样用的。关于include方式的使用有几个注意事项，就是最好让它的母布局是RelativeLayout，否则的话很难控制include进来的布局的位置。另外，include布局的位置一定要写在include之前，如底部面板在最底部，android:layout_alignParentBottom="true"这句话是在bottom_panel_layout.xml里写的，如果写在activity_main.xml里就是无效的，这着实是个蛋疼的问题。再就是include后设置的id会覆盖掉以前的，所以这里只在include的时候设置id。其中的两个View是分割线。整体是按照底部栏、上部栏、中间Fragment的容器来放置的。

在放Fragment的时候需要注意，究竟是否要将顶部控制栏放到各自的fragment里合适还是放到Activity里合适要看具体情况，如果顶部栏里多是显示标题这种功能或少量的点击事件，应该放到Activity里，即顶部栏的事务逻辑和当前fragment的事务逻辑耦合的不是很紧。举个例子，比如微信的顶部栏，不管你处在哪个Tab页(聊天、发现、通讯录)，点击顶部栏里的按钮都呈现出同样的内容。但反过来讲，如果顶部栏里的事务逻辑和fragment耦合很紧，即在不同的fragment，顶部栏呈现的内容都不一样，且点击后处理的事务也和当前fragment紧密联系一起，那就应该一个fragment配套一个顶部栏，方便控制。本文是将两者分开的。所以让fragment的容器在顶部栏之下，底部栏之上，不这样写的话，就会遮挡。

    <FrameLayout
        android:id="@+id/fragment_content"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/head_layout"
        android:layout_above="@id/bottom_layout" >
    </FrameLayout>

MainActivity.java代码：

 <span style="font-family:Comic Sans MS;font-size:18px;">package org.yanzi.activity;

 import org.yanzi.constant.Constant;
 import org.yanzi.fragment.BaseFragment;
 import org.yanzi.fragment.ContactsFragment;
 import org.yanzi.fragment.MessageFragment;
 import org.yanzi.fragment.NewsFragment;
 import org.yanzi.fragment.SettingFragment;
 import org.yanzi.ui.BottomControlPanel;
 import org.yanzi.ui.BottomControlPanel.BottomPanelCallback;
 import org.yanzi.ui.HeadControlPanel;

 import android.app.Activity;
 import android.app.Fragment;
 import android.app.FragmentManager;
 import android.app.FragmentTransaction;
 import android.os.Bundle;
 import android.text.TextUtils;
 import android.util.Log;
 import android.view.Menu;
 import android.widget.Toast;

 import com.example.fragmentproject.R;

 public class MainActivity extends Activity implements BottomPanelCallback {
     BottomControlPanel bottomPanel = null;
     HeadControlPanel headPanel = null;

     private FragmentManager fragmentManager = null;
     private FragmentTransaction fragmentTransaction = null;

 /*  private MessageFragment messageFragment;
     private ContactsFragment contactsFragment;
     private NewsFragment newsFragment;
     private SettingFragment settingFragment;*/

     public static String currFragTag = "";
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         initUI();
         fragmentManager = getFragmentManager();
         setDefaultFirstFragment(Constant.FRAGMENT_FLAG_MESSAGE);
     }

     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         // Inflate the menu; this adds items to the action bar if it is present.
         getMenuInflater().inflate(R.menu.main, menu);
         return true;
     }
     private void initUI(){
         bottomPanel = (BottomControlPanel)findViewById(R.id.bottom_layout);
         if(bottomPanel != null){
             bottomPanel.initBottomPanel();
             bottomPanel.setBottomCallback(this);
         }
         headPanel = (HeadControlPanel)findViewById(R.id.head_layout);
         if(headPanel != null){
             headPanel.initHeadPanel();
         }
     }

     /* 处理BottomControlPanel的回调
      * @see org.yanzi.ui.BottomControlPanel.BottomPanelCallback#onBottomPanelClick(int)
      */
     @Override
     public void onBottomPanelClick(int itemId) {
         // TODO Auto-generated method stub
         String tag = "";
         if((itemId & Constant.BTN_FLAG_MESSAGE) != 0){
             tag = Constant.FRAGMENT_FLAG_MESSAGE;
         }else if((itemId & Constant.BTN_FLAG_CONTACTS) != 0){
             tag = Constant.FRAGMENT_FLAG_CONTACTS;
         }else if((itemId & Constant.BTN_FLAG_NEWS) != 0){
             tag = Constant.FRAGMENT_FLAG_NEWS;
         }else if((itemId & Constant.BTN_FLAG_SETTING) != 0){
             tag = Constant.FRAGMENT_FLAG_SETTING;
         }
         setTabSelection(tag); //切换Fragment
         headPanel.setMiddleTitle(tag);//切换标题
     }

     private void setDefaultFirstFragment(String tag){
         Log.i("yan", "setDefaultFirstFragment enter... currFragTag = " + currFragTag);
         setTabSelection(tag);
         bottomPanel.defaultBtnChecked();
         Log.i("yan", "setDefaultFirstFragment exit...");
     }

     private void commitTransactions(String tag){
         if (fragmentTransaction != null && !fragmentTransaction.isEmpty()) {
             fragmentTransaction.commit();
             currFragTag = tag;
             fragmentTransaction = null;
         }
     }

     private FragmentTransaction ensureTransaction( ){
         if(fragmentTransaction == null){
             fragmentTransaction = fragmentManager.beginTransaction();
             fragmentTransaction
             .setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);

         }
         return fragmentTransaction;

     }

     private void attachFragment(int layout, Fragment f, String tag){
         if(f != null){
             if(f.isDetached()){
                 ensureTransaction();
                 fragmentTransaction.attach(f);

             }else if(!f.isAdded()){
                 ensureTransaction();
                 fragmentTransaction.add(layout, f, tag);
             }
         }
     }

     private Fragment getFragment(String tag){

         Fragment f = fragmentManager.findFragmentByTag(tag);

         if(f == null){
             Toast.makeText(getApplicationContext(), "fragment = null tag = " + tag, Toast.LENGTH_SHORT).show();
             f = BaseFragment.newInstance(getApplicationContext(), tag);
         }
         return f;

     }
     private void detachFragment(Fragment f){

         if(f != null && !f.isDetached()){
             ensureTransaction();
             fragmentTransaction.detach(f);
         }
     }
     /**切换fragment
      * @param tag
      */
     private  void switchFragment(String tag){
         if(TextUtils.equals(tag, currFragTag)){
             return;
         }
         //把上一个fragment detach掉
         if(currFragTag != null && !currFragTag.equals("")){
             detachFragment(getFragment(currFragTag));
         }
         attachFragment(R.id.fragment_content, getFragment(tag), tag);
         commitTransactions( tag);
     }

     /**设置选中的Tag
      * @param tag
      */
     public  void setTabSelection(String tag) {
         // 开启一个Fragment事务
         fragmentTransaction = fragmentManager.beginTransaction();
 /*       if(TextUtils.equals(tag, Constant.FRAGMENT_FLAG_MESSAGE)){
            if (messageFragment == null) {
                 messageFragment = new MessageFragment();
             }

         }else if(TextUtils.equals(tag, Constant.FRAGMENT_FLAG_CONTACTS)){
             if (contactsFragment == null) {
                 contactsFragment = new ContactsFragment();
             }

         }else if(TextUtils.equals(tag, Constant.FRAGMENT_FLAG_NEWS)){
             if (newsFragment == null) {
                 newsFragment = new NewsFragment();
             }

         }else if(TextUtils.equals(tag,Constant.FRAGMENT_FLAG_SETTING)){
             if (settingFragment == null) {
                 settingFragment = new SettingFragment();
             }
         }else if(TextUtils.equals(tag, Constant.FRAGMENT_FLAG_SIMPLE)){
             if (simpleFragment == null) {
                 simpleFragment = new SimpleFragment();
             }

         }*/
          switchFragment(tag);

     }

     @Override
     protected void onStop() {
         // TODO Auto-generated method stub
         super.onStop();
         currFragTag = "";
     }

     @Override
     protected void onSaveInstanceState(Bundle outState) {
         // TODO Auto-generated method stub
     }

 }
 </span>

注意这块我作了改动，不需要申明

/* private MessageFragment messageFragment;
private ContactsFragment contactsFragment;
private NewsFragment newsFragment;
private SettingFragment settingFragment;*/
这些内容，因为Fragment的生成是通过BaseFragment.newInstance()来生成的，传进去Tag生成相应的Fragment。所有的Fragment，ContactsFragment、MessageFragment、NewsFragment、SettingFragment都继承自BaseFragment，通过BaseFragment里的newInstance()接口进行实例化对应的fragment。优点是方便管理，缺点么也有，因为java继承继承一个类，不能同时继承两个类。所以如ListFragment这些，就没法同时继承了。不过好在有listview这些，也妨碍不了我们做到同样的效果。

Activity里事件的入口是在onBottomPanelClick()监听点击了谁，然后：

setTabSelection(tag); //切换Fragment

headPanel.setMiddleTitle(tag);//切换标题 

先切换Fragment再切换顶部栏的标题。setTabSelection()里直接调switchFragment(),在switchFragment函数里先判断标签是否一样，一样则意外着无需切换，否则的话就先把当前Fragment找到然后detach掉，之后进到attachFragment()函数里。在这里，先判断这个fragment是不是被detach掉的，如果是的话意味着之前曾被add过，所以只需attach就ok了。否则的话，意味着这是第一次，进行add.这里记录下Fragment的声明周期:

MessageFragment正常打开：
Line 155: 01-04 11:50:46.688 E/MessageFragment( 2546): onAttach-----
Line 159: 01-04 11:50:46.688 E/MessageFragment( 2546): onCreate------
Line 161: 01-04 11:50:46.693 D/MessageFragment( 2546): onCreateView---->
Line 165: 01-04 11:50:46.694 E/MessageFragment( 2546): onActivityCreated-------
Line 169: 01-04 11:50:46.694 E/MessageFragment( 2546): onStart----->
Line 173: 01-04 11:50:46.694 E/MessageFragment( 2546): onresume---->
返回键退出：
Line 183: 01-04 11:52:26.506 E/MessageFragment( 2546): onpause
Line 259: 01-04 11:52:27.131 E/MessageFragment( 2546): onStop
Line 263: 01-04 11:52:27.132 E/MessageFragment( 2546): ondestoryView
Line 269: 01-04 11:52:27.134 E/MessageFragment( 2546): ondestory
Line 271: 01-04 11:52:27.135 D/MessageFragment( 2546): onDetach------

按home按键退出:
Line 97: 01-05 05:06:15.659 E/MessageFragment(18835): onpause
Line 215: 01-05 05:06:16.292 E/MessageFragment(18835): onStop
再次打开：
Line 81: 01-05 05:07:02.408 E/MessageFragment(18835): onStart----->
Line 85: 01-05 05:07:02.408 E/MessageFragment(18835): onresume---->

通过detach的方式切换至其他Fragment：
Line 69: 01-04 11:53:33.381 E/MessageFragment( 2546): onpause
Line 73: 01-04 11:53:33.382 E/MessageFragment( 2546): onStop
Line 77: 01-04 11:53:33.382 E/MessageFragment( 2546): ondestoryView
再次切换过来:
Line 55: 01-04 11:54:59.462 D/MessageFragment( 2546): onCreateView---->
Line 59: 01-04 11:54:59.463 E/MessageFragment( 2546): onActivityCreated-------
Line 63: 01-04 11:54:59.463 E/MessageFragment( 2546): onStart----->
Line 67: 01-04 11:54:59.464 E/MessageFragment( 2546): onresume---->

四、适配器和MessageBean

本来要连数据库的，时间原因用个简单的MessageBean代替了。一个消息分联系人头像、名字、消息正文和时间四部分组成，封装到一个MessageBean里。

MessageBean.java

 <span style="font-family:Comic Sans MS;font-size:18px;">package org.yanzi.bean;

 public class MessageBean {
     private int PhotoDrawableId;
     private String MessageName;
     private String MessageContent;
     private String MessageTime;

     public MessageBean(){

     }

     public MessageBean(int photoDrawableId, String messageName,
             String messageContent, String messageTime) {
         super();
         PhotoDrawableId = photoDrawableId;
         MessageName = messageName;
         MessageContent = messageContent;
         MessageTime = messageTime;
     }

     public int getPhotoDrawableId() {
         return PhotoDrawableId;
     }
     public void setPhotoDrawableId(int mPhotoDrawableId) {
         this.PhotoDrawableId = mPhotoDrawableId;
     }
     public String getMessageName() {
         return MessageName;
     }
     public void setMessageName(String messageName) {
         MessageName = messageName;
     }
     public String getMessageContent() {
         return MessageContent;
     }
     public void setMessageContent(String messageContent) {
         MessageContent = messageContent;
     }
     public String getMessageTime() {
         return MessageTime;
     }
     public void setMessageTime(String messageTime) {
         MessageTime = messageTime;
     }
     @Override
     public String toString() {
         return "MessageBean [mPhotoDrawableId=" + PhotoDrawableId
                 + ", MessageName=" + MessageName + ", MessageContent="
                 + MessageContent + ", MessageTime=" + MessageTime + "]";
     }



 }
 </span>

然后就是MessageFragment的ListView里的适配器，MessageAdapter.java

 <span style="font-family:Comic Sans MS;font-size:18px;">package org.yanzi.fragment.adapter;

 import java.util.List;

 import org.yanzi.bean.MessageBean;

 import com.example.fragmentproject.R;

 import android.content.Context;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.BaseAdapter;
 import android.widget.ImageView;
 import android.widget.TextView;

 public class MessageAdapter extends BaseAdapter {
     private List<MessageBean> mListMsgBean = null;
     private Context mContext;
     private LayoutInflater mInflater;
     public MessageAdapter(List<MessageBean> listMsgBean, Context context){
         mListMsgBean = listMsgBean;
         mContext = context;
         mInflater = LayoutInflater.from(mContext);
     }
     @Override
     public int getCount() {
         // TODO Auto-generated method stub
         return mListMsgBean.size();
     }

     @Override
     public Object getItem(int position) {
         // TODO Auto-generated method stub
         return mListMsgBean.get(position);
     }

     @Override
     public long getItemId(int position) {
         // TODO Auto-generated method stub
         return position;
     }

     @Override
     public View getView(int position, View convertView, ViewGroup parent) {
         // TODO Auto-generated method stub
         View v = mInflater.inflate(R.layout.message_item_layout, null);

         ImageView imageView = (ImageView) v.findViewById(R.id.img_msg_item);
         imageView.setImageResource(mListMsgBean.get(position).getPhotoDrawableId());

         TextView nameMsg = (TextView)v.findViewById(R.id.name_msg_item);
         nameMsg.setText(mListMsgBean.get(position).getMessageName());

         TextView contentMsg = (TextView)v.findViewById(R.id.content_msg_item);
         contentMsg.setText(mListMsgBean.get(position).getMessageContent());

         TextView timeMsg = (TextView)v.findViewById(R.id.time_msg_item);
         timeMsg.setText(mListMsgBean.get(position).getMessageTime());

         return v;
     }

 }
 </span>

因为是示例，getView里没用ViewHolder。
最后是MessageFragment里通过对listview设置适配器，将MessageBean作为信息的提供者也填充到适配器里。

MessageFragment.java代码：

 <span style="font-family:Comic Sans MS;font-size:18px;">package org.yanzi.fragment;

 import java.util.ArrayList;
 import java.util.List;

 import org.yanzi.activity.MainActivity;
 import org.yanzi.bean.MessageBean;
 import org.yanzi.constant.Constant;
 import org.yanzi.fragment.adapter.MessageAdapter;

 import android.app.Activity;
 import android.os.Bundle;
 import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.AdapterView;
 import android.widget.Toast;
 import android.widget.AdapterView.OnItemClickListener;
 import android.widget.ListView;

 import com.example.fragmentproject.R;

 public class MessageFragment extends BaseFragment {

     private static final String TAG = "MessageFragment";
     private MainActivity mMainActivity ;
     private ListView mListView;
     private MessageAdapter mMsgAdapter;
     private List<MessageBean> mMsgBean = new ArrayList<MessageBean>();
     public View onCreateView(LayoutInflater inflater, ViewGroup container,
             Bundle savedInstanceState) {
         View messageLayout = inflater.inflate(R.layout.message_layout,
                 container, false);
         Log.d(TAG, "onCreateView---->");
         mMainActivity = (MainActivity) getActivity();
         mFragmentManager = getActivity().getFragmentManager();
         mListView = (ListView)messageLayout.findViewById(R.id.listview_message);
         mMsgAdapter = new MessageAdapter(mMsgBean, mMainActivity);
         mListView.setAdapter(mMsgAdapter);
         mListView.setOnItemClickListener(new OnItemClickListener() {

             @Override
             public void onItemClick(AdapterView<?> parent, View view,
                     int position, long id) {
                 // TODO Auto-generated method stub
                 Toast.makeText(mMainActivity, mMsgBean.get(position).toString(),
                         Toast.LENGTH_SHORT).show();
             }

         });
         return messageLayout;
     }


     @Override
     public void onAttach(Activity activity) {
         // TODO Auto-generated method stub
         super.onAttach(activity);
         Log.e(TAG, "onAttach-----");

     }
     @Override
     public void onCreate(Bundle savedInstanceState) {
         // TODO Auto-generated method stub
         super.onCreate(savedInstanceState);
         Log.e(TAG, "onCreate------");
         mMsgBean.add(new MessageBean(R.drawable.ic_photo_1, "张三", "吃饭没?", "昨天"));
         mMsgBean.add(new MessageBean(R.drawable.ic_photo_2, "李四", "哈哈", "昨天"));
         mMsgBean.add(new MessageBean(R.drawable.ic_photo_3, "小明", "吃饭没?", "昨天"));
         mMsgBean.add(new MessageBean(R.drawable.ic_photo_4, "王五", "吃饭没?", "昨天"));
         mMsgBean.add(new MessageBean(R.drawable.ic_photo_5, "Jack", "吃饭没?", "昨天"));
         mMsgBean.add(new MessageBean(R.drawable.ic_photo_6, "Jone", "吃饭没?", "昨天"));
         mMsgBean.add(new MessageBean(R.drawable.ic_photo_7, "Jone", "吃饭没?", "昨天"));
         mMsgBean.add(new MessageBean(R.drawable.ic_photo_8, "Jone", "吃饭没?", "昨天"));
         mMsgBean.add(new MessageBean(R.drawable.ic_photo_9, "Jone", "吃饭没?", "昨天"));
     }

     @Override
     public void onActivityCreated(Bundle savedInstanceState) {
         // TODO Auto-generated method stub
         super.onActivityCreated(savedInstanceState);
         Log.e(TAG, "onActivityCreated-------");
     }

     @Override
     public void onStart() {
         // TODO Auto-generated method stub
         super.onStart();

         Log.e(TAG, "onStart----->");
     }

     @Override
     public void onResume() {
         // TODO Auto-generated method stub
         super.onResume();
         Log.e(TAG, "onresume---->");
         MainActivity.currFragTag = Constant.FRAGMENT_FLAG_MESSAGE;
     }

     @Override
     public void onPause() {
         // TODO Auto-generated method stub
         super.onPause();
         Log.e(TAG, "onpause");
     }

     @Override
     public void onStop() {
         // TODO Auto-generated method stub
         super.onStop();
         Log.e(TAG, "onStop");
     }

     @Override
     public void onDestroyView() {
         // TODO Auto-generated method stub
         super.onDestroyView();
         Log.e(TAG, "ondestoryView");
     }
     @Override
     public void onDestroy() {
         // TODO Auto-generated method stub
         super.onDestroy();
         Log.e(TAG, "ondestory");
     }

     @Override
     public void onDetach() {
         // TODO Auto-generated method stub
         super.onDetach();
         Log.d(TAG, "onDetach------");

     }



 }
 </span>

最后来看下效果吧，只有MessageFragment填充了数据：

      

横屏情况下:

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