android Fragment实现Tab功能（fragment相互切换时，可保存之前状态）

原文转自 http://blog.csdn.net/jjsyjiao/article/details/40980909

由于TabHost已经逐渐过时，现在开发已经不建议使用，将由Fragment代替，本文主要讲述Fragment替换TabHost的方法，代码简单易懂，适合初学者使用。

上个效果图先：

      

首先：

1、建个资源文件activity_main.xml;

 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="fill_parent"
     android:layout_height="fill_parent" >


     <LinearLayout
         android:id="@+id/bottom"
         android:layout_width="match_parent"
         android:layout_height="60dip"
         android:layout_alignParentBottom="true"
         android:orientation="horizontal" >


         <RelativeLayout
             android:id="@+id/fotune"
             android:layout_width="0dip"
             android:layout_height="fill_parent"
             android:layout_weight="1"
             android:background="@color/bottom_background_onclick_color" >


             <ImageView
                 android:id="@+id/fotune_img"
                 android:layout_width="35dip"
                 android:layout_height="35dip"
                 android:layout_centerInParent="true"
                 android:background="@drawable/fotune_a" />
         RelativeLayout>


         <RelativeLayout
             android:id="@+id/message"
             android:layout_width="0dip"
             android:layout_height="fill_parent"
             android:layout_weight="1"
             android:background="@color/bottom_background_unclick_color" >


             <ImageView
                 android:id="@+id/message_img"
                 android:layout_width="35dip"
                 android:layout_height="35dip"
                 android:layout_centerInParent="true"
                 android:background="@drawable/message_ia" />
         RelativeLayout>


         <RelativeLayout
             android:id="@+id/account"
             android:layout_width="0dip"
             android:layout_height="fill_parent"
             android:layout_weight="1"
             android:background="@color/bottom_background_unclick_color" >


             <ImageView
                 android:id="@+id/account_img"
                 android:layout_width="35dip"
                 android:layout_height="35dip"
                 android:layout_centerInParent="true"
                 android:background="@drawable/account_ia" />
         RelativeLayout>


         <RelativeLayout
             android:id="@+id/more"
             android:layout_width="0dip"
             android:layout_height="fill_parent"
             android:layout_weight="1"
             android:background="@color/bottom_background_unclick_color" >


             <ImageView
                 android:id="@+id/more_img"
                 android:layout_width="35dip"
                 android:layout_height="35dip"
                 android:layout_centerInParent="true"
                 android:background="@drawable/more_ia" />
         RelativeLayout>
     LinearLayout>


     <FrameLayout
         android:id="@+id/container"
         android:layout_width="fill_parent"
         android:layout_height="match_parent"
         android:layout_above="@id/bottom" />


 RelativeLayout>

    其中FrameLayout就是承载着Fragment的容器；

2、接下来编写我们的Activity，注意：Activity需要继承FragmentActivity，不然调用getSupportFragmentManager()方法会提示“The method getSupportFragmentManager() is undefined for the type MainActivity”；

 package com.example.tab;


 import android.content.Context;
 import android.os.Bundle;
 import android.support.v4.app.Fragment;
 import android.support.v4.app.FragmentActivity;
 import android.support.v4.app.FragmentTransaction;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.widget.ImageView;
 import android.widget.RelativeLayout;


 public class MainActivity extends FragmentActivity implements OnClickListener {


     public static Context context;


     private RelativeLayout fotune, message, account, more;


     private ImageView fotune_img, message_img, account_img, more_img;


     private Fragment1 fragment1 = new Fragment1();


     private Fragment2 fragment2 = new Fragment2();


     private Fragment3 fragment3 = new Fragment3();


     private Fragment4 fragment4 = new Fragment4();


     private Bundle bundle = new Bundle();


     /**
      * 记录当前Activity显示的fragment
      */
     private Fragment mContent;


     private String[] textStrings = new String[] { "第一个页面——Fragment1", "第一个页面——Fragment2",
             "第一个页面——Fragment3", "第一个页面——Fragment4" };


     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         context = MainActivity.this;
         initLayout();
         if (savedInstanceState == null) {


             bundle.putString("text", textStrings[0]);
             fragment1.setArguments(bundle);
             mContent = fragment1;
             getSupportFragmentManager().beginTransaction()
                     .add(R.id.container, fragment1).commit();
         }
     }


     /**
      * 初始化控件
      */
     private void initLayout() {
         fotune = (RelativeLayout) findViewById(R.id.fotune);
         fotune.setOnClickListener(this);
         message = (RelativeLayout) findViewById(R.id.message);
         message.setOnClickListener(this);
         account = (RelativeLayout) findViewById(R.id.account);
         account.setOnClickListener(this);
         more = (RelativeLayout) findViewById(R.id.more);
         more.setOnClickListener(this);
         fotune_img = (ImageView) findViewById(R.id.fotune_img);
         message_img = (ImageView) findViewById(R.id.message_img);
         account_img = (ImageView) findViewById(R.id.account_img);
         more_img = (ImageView) findViewById(R.id.more_img);
     }


     @Override
     public void onClick(View arg0) {
         // TODO Auto-generated method stub


         switch (arg0.getId()) {
         case R.id.fotune:


             fotune.setBackgroundColor(getResources().getColor(
                     R.color.bottom_background_onclick_color));
             message.setBackgroundColor(getResources().getColor(
                     R.color.bottom_background_unclick_color));
             account.setBackgroundColor(getResources().getColor(
                     R.color.bottom_background_unclick_color));
             more.setBackgroundColor(getResources().getColor(
                     R.color.bottom_background_unclick_color));


             fotune_img.setBackgroundDrawable(getResources().getDrawable(
                     R.drawable.fotune_a));
             message_img.setBackgroundDrawable(getResources().getDrawable(
                     R.drawable.message_ia));
             account_img.setBackgroundDrawable(getResources().getDrawable(
                     R.drawable.account_ia));
             more_img.setBackgroundDrawable(getResources().getDrawable(
                     R.drawable.more_ia));


             // switchContent(fragment1,
             // 0);若不想保留之前fragment的状态，每次都重新创建fragment，则选择该条命令；
             switchContent_keep(mContent, fragment1, 0);// 若想保留之前fragment的状态，则选择该条命令；
             break;
         case R.id.message:


             fotune.setBackgroundColor(getResources().getColor(
                     R.color.bottom_background_unclick_color));
             message.setBackgroundColor(getResources().getColor(
                     R.color.bottom_background_onclick_color));
             account.setBackgroundColor(getResources().getColor(
                     R.color.bottom_background_unclick_color));
             more.setBackgroundColor(getResources().getColor(
                     R.color.bottom_background_unclick_color));


             fotune_img.setBackgroundDrawable(getResources().getDrawable(
                     R.drawable.fotune_ia));
             message_img.setBackgroundDrawable(getResources().getDrawable(
                     R.drawable.message_a));
             account_img.setBackgroundDrawable(getResources().getDrawable(
                     R.drawable.account_ia));
             more_img.setBackgroundDrawable(getResources().getDrawable(
                     R.drawable.more_ia));


             // switchContent(fragment2,
             // 1);若不想保留之前fragment的状态，每次都重新创建fragment，则选择该条命令；
             switchContent_keep(mContent, fragment2, 1);// 若想保留之前fragment的状态，则选择该条命令；
             break;
         case R.id.account:


             fotune.setBackgroundColor(getResources().getColor(
                     R.color.bottom_background_unclick_color));
             message.setBackgroundColor(getResources().getColor(
                     R.color.bottom_background_unclick_color));
             account.setBackgroundColor(getResources().getColor(
                     R.color.bottom_background_onclick_color));
             more.setBackgroundColor(getResources().getColor(
                     R.color.bottom_background_unclick_color));


             fotune_img.setBackgroundDrawable(getResources().getDrawable(
                     R.drawable.fotune_ia));
             message_img.setBackgroundDrawable(getResources().getDrawable(
                     R.drawable.message_ia));
             account_img.setBackgroundDrawable(getResources().getDrawable(
                     R.drawable.account_a));
             more_img.setBackgroundDrawable(getResources().getDrawable(
                     R.drawable.more_ia));


             // switchContent(fragment3,
             // 2);若不想保留之前fragment的状态，每次都重新创建fragment，则选择该条命令；
             switchContent_keep(mContent, fragment3, 2);// 若想保留之前fragment的状态，则选择该条命令；
             break;
         case R.id.more:


             fotune.setBackgroundColor(getResources().getColor(
                     R.color.bottom_background_unclick_color));
             message.setBackgroundColor(getResources().getColor(
                     R.color.bottom_background_unclick_color));
             account.setBackgroundColor(getResources().getColor(
                     R.color.bottom_background_unclick_color));
             more.setBackgroundColor(getResources().getColor(
                     R.color.bottom_background_onclick_color));


             fotune_img.setBackgroundDrawable(getResources().getDrawable(
                     R.drawable.fotune_ia));
             message_img.setBackgroundDrawable(getResources().getDrawable(
                     R.drawable.message_ia));
             account_img.setBackgroundDrawable(getResources().getDrawable(
                     R.drawable.account_ia));
             more_img.setBackgroundDrawable(getResources().getDrawable(
                     R.drawable.more_a));


             // switchContent(fragment4,
             // 3);若不想保留之前fragment的状态，每次都重新创建fragment，则选择该条命令；
             switchContent_keep(mContent, fragment4, 3);// 若想保留之前fragment的状态，则选择该条命令；
             break;
         default:
             break;
         }
     }


     /**
      * fragment替换（不保留之前的状态）
      *
      * @param to
      * @param i
      */
     public void switchContent(Fragment to, int i) {
         bundle.putString("text", textStrings[i]);
         to.setArguments(bundle);
         getSupportFragmentManager().beginTransaction()
                 .replace(R.id.container, to).commit();
     }


     /**
      * fragment替换（保留之前的状态）
      *
      * @param from
      * @param to
      * @param i
      */
     public void switchContent_keep(Fragment from, Fragment to, int i) {
         if (from != to) {
             mContent = to;
             FragmentTransaction transaction = getSupportFragmentManager()
                     .beginTransaction();
             // 先判断是否被add过
             if (!to.isAdded()) {
                 bundle.putString("text", textStrings[i]);
                 to.setArguments(bundle);
                 // 隐藏当前的fragment，add下一个fragment到Activity中
                 transaction.hide(from).add(R.id.container, to).commit();
             } else {
                 // 隐藏当前的fragment，显示下一个fragment
                 transaction.hide(from).show(to).commit();
                 // to.onResume();该命令可注释，若希望fragment切换的过程中，被显示的fragment执行onResume方法，则解注；


             }
         }


     }
 }

如果在Fragment切换的过程中，不需要保留之前Fragment的状态，直接调用getSupportFragmentManager().beginTransaction().replace(R.id.Container, to).commit();即可。每次替换实质都是先remove再add，Fragment的onCreate方法都会被调用；

如果在Fragment切换的过程中，需要保留之前Fragment的状态，则需要定义一个变量Fragment mContent来保存当前activity显示fragment对象。如果你要显示的fragment对象之前未被添加过，则需要先隐藏当前显示的fragment对象，再添加你要显示的fragment对象；例如：transaction.hide(from).add(R.id.container, to).commit();若你要显示的fragment对象之前已经被添加过了，则先隐藏当前的fragment对象，再显示你要显示的fragment对象即可；例如：transaction.hide(from).show(to).commit();（注：如果此时希望调用显示的fragment对象的onResume方法，则执行to.onResume();即可。但注意的是：从fragmentActivity跳转到下一个Activity，再按返回键时，FrameLayout容器中所有的fragment都将会调用onResume方法；打印log如下所示：）

 11-10 15:54:48.546: E/onCreate(19070): Fragment1
 11-10 15:54:48.546: E/onCreateView(19070): Fragment1
 11-10 15:54:48.546: E/onResume(19070): Fragment1
 11-10 15:54:49.936: E/onCreate(19070): Fragment2
 11-10 15:54:49.936: E/onCreateView(19070): Fragment2
 11-10 15:54:49.936: E/onResume(19070): Fragment2
 11-10 15:54:51.656: E/onCreate(19070): Fragment3
 11-10 15:54:51.656: E/onCreateView(19070): Fragment3
 11-10 15:54:51.656: E/onResume(19070): Fragment3
 11-10 15:54:52.806: E/onCreate(19070): Fragment4
 11-10 15:54:52.806: E/onCreateView(19070): Fragment4
 11-10 15:54:52.806: E/onResume(19070): Fragment4
 <span style="color:#ff0000;">11-10 15:54:54.636: E/onResume(19070): Fragment1
 11-10 15:54:54.636: E/onResume(19070): Fragment2
 11-10 15:54:54.636: E/onResume(19070): Fragment3
 11-10 15:54:54.636: E/onResume(19070): Fragment4span>

FragmentActivity向Fragment传递数据：创建个Bundle数据包，Fragment对象调用setArguments(Bundle bundle)方法即可；

Fragment接收从FragmentActivity传来的数据：调用getArguments()接收数据包，返回Bundle对象；

3、Fragment的具体实现

 package com.example.tab;


 import android.content.Intent;
 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.view.View.OnClickListener;
 import android.widget.Button;
 import android.widget.TextView;


 public class Fragment1 extends Fragment {


     public Fragment1() {
     }


     @Override
     public void onCreate(Bundle savedInstanceState) {
         // TODO Auto-generated method stub
         super.onCreate(savedInstanceState);
         Log.e("onCreate", "Fragment1");
     }


     @Override
     public View onCreateView(LayoutInflater inflater, ViewGroup container,
             Bundle savedInstanceState) {
         Log.e("onCreateView", "Fragment1");
         View rootView = inflater.inflate(R.layout.fragment_main, container,
                 false);
         TextView text = (TextView) rootView.findViewById(R.id.text);
         text.setText(getArguments().getString("text"));
         Button button = (Button) rootView.findViewById(R.id.button);
         button.setOnClickListener(new OnClickListener() {


             @Override
             public void onClick(View arg0) {
                 // TODO Auto-generated method stub
                 Intent intent = new Intent();
                 intent.setClass(MainActivity.context, SecondActivity.class);
                 startActivity(intent);
             }


         });
         return rootView;
     }


     @Override
     public void onResume() {
         // TODO Auto-generated method stub
         super.onResume();
         Log.e("onResume", "Fragment1");
     }


 }