(转)Android:Activity+Fragment及它们之间的数据交换

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原地址：http://blog.csdn.net/jdsjlzx/article/details/41750249

简介：

为什么要用Fragment？使用Fragment可以在一个Activity中实现不同的界面。Fragment与Fragment之间的动画切换，远比Activity与Activity之间的动画切换变化方式多。很多时候，我们通过使用一个Activity，切换多个Fragment。本次博客，主要列举一下Fragment与它的Activity之间进行数据交换的方式。

1.Fragment中通过getActivity()然后进行强制转化，调用Activity中的公有方法

((XXXXActivity)getActivity()).fun();

2.Activity在切换Fragment的时候，通过setArguments向Fragment传递参数，Fragment通过getArguments();获得从activity中传递过来的值

3.Activity实现一个接口，Fragment在onAttach方法中，将该Activity转化为该接口，在需要调用的时候回调。

注意：本Demo是通过FragmentManager来管理Fragment的，通过FragmentManager管理，我们创建Fragment和销毁Fragment的时候，可以通过栈的方式：

a.FragmentTransaction的add方法，添加一个Fragment

b.FragmentTransaction的popBackStack()弹出该Fragment

演示实例：

fragment1.xml

<RelativeLayout 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:background="#FFFFFFFF"      android:paddingBottom="@dimen/activity_vertical_margin"      android:paddingLeft="@dimen/activity_horizontal_margin"      android:paddingRight="@dimen/activity_horizontal_margin"      android:paddingTop="@dimen/activity_vertical_margin"      tools:context="com.example.testfragment.MainActivity$PlaceholderFragment" >      <TextView          android:id="@+id/tv"          android:layout_width="wrap_content"          android:layout_height="wrap_content"          android:layout_alignParentTop="true"          android:text="fragment1" />      <Button          android:id="@+id/btn"          android:layout_width="wrap_content"          android:layout_height="wrap_content"          android:layout_below="@id/tv"          android:text="跳转到Fragment2" />  </RelativeLayout>

MyFragment1.java

/*  * $filename: MyFragment.java,v $  * $Date: 2014-5-16  $  * Copyright (C) ZhengHaibo, Inc. All rights reserved.  * This software is Made by Zhenghaibo.  */  package com.example.testfragment;    import android.app.Activity;  import android.os.Bundle;  import android.support.v4.app.Fragment;  import android.view.LayoutInflater;  import android.view.View;  import android.view.View.OnClickListener;  import android.view.ViewGroup;  import android.widget.Button;    /*  *@author: ZhengHaibo    *web:     http://blog.csdn.net/nuptboyzhb  *mail:    zhb931706659@126.com  *2014-5-16  Nanjing,njupt,China  */  public class MyFragment1 extends Fragment {            FragmentCallBack fragmentCallBack = null;      Button btn;      @Override      public View onCreateView(LayoutInflater inflater, ViewGroup container,              Bundle savedInstanceState) {          View rootView = inflater.inflate(R.layout.fragment1, container,                  false);          btn = (Button)rootView.findViewById(R.id.btn);          btn.setOnClickListener(new OnClickListener() {                            @Override              public void onClick(View v) {                  // TODO Auto-generated method stub                  fragmentCallBack.callbackFun1(null);              }          });          return rootView;      }            @Override      public void onAttach(Activity activity) {          // TODO Auto-generated method stub          super.onAttach(activity);          fragmentCallBack = (MainActivity)activity;      }  }

fragment2.xml

<RelativeLayout 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:background="#FFFFFFFF"      android:paddingBottom="@dimen/activity_vertical_margin"      android:paddingLeft="@dimen/activity_horizontal_margin"      android:paddingRight="@dimen/activity_horizontal_margin"      android:paddingTop="@dimen/activity_vertical_margin"      tools:context="com.example.testfragment.MainActivity$PlaceholderFragment" >      <TextView          android:id="@+id/tv"          android:layout_width="wrap_content"          android:layout_height="wrap_content"          android:layout_alignParentTop="true"          android:text="fragment2" />      <Button          android:id="@+id/btn1"          android:layout_width="wrap_content"          android:layout_height="wrap_content"          android:layout_below="@id/tv"          android:text="直接调用Activity" />      <Button          android:id="@+id/btn2"          android:layout_width="wrap_content"          android:layout_height="wrap_content"          android:layout_below="@id/btn1"          android:text="回调Activity" />  </RelativeLayout>

MyFragment2.java

/*  * $filename: MyFragment.java,v $  * $Date: 2014-5-16  $  * Copyright (C) ZhengHaibo, Inc. All rights reserved.  * This software is Made by Zhenghaibo.  */  package com.example.testfragment;    import android.app.Activity;  import android.os.Bundle;  import android.support.v4.app.Fragment;  import android.view.LayoutInflater;  import android.view.View;  import android.view.View.OnClickListener;  import android.view.ViewGroup;  import android.widget.Button;  import android.widget.Toast;    /*  *@author: ZhengHaibo    *web:     http://blog.csdn.net/nuptboyzhb  *mail:    zhb931706659@126.com  *2014-5-16  Nanjing,njupt,China  */  public class MyFragment2 extends Fragment {            FragmentCallBack fragmentCallBack = null;      Button btn1;      Button btn2;      @Override      public View onCreateView(LayoutInflater inflater, ViewGroup container,              Bundle savedInstanceState) {          View rootView = inflater.inflate(R.layout.fragment2, container,                  false);          Bundle data = getArguments();//获得从activity中传递过来的值          Toast.makeText(getActivity(), data.getString("TEXT"), Toast.LENGTH_SHORT).show();          btn1 = (Button)rootView.findViewById(R.id.btn1);          btn1.setOnClickListener(new OnClickListener() {                            @Override              public void onClick(View v) {                  // 直接调用Activity中的方法                  ((MainActivity)getActivity()).changeButtonColor();              }          });          btn2 = (Button)rootView.findViewById(R.id.btn2);          btn2.setOnClickListener(new OnClickListener() {                            @Override              public void onClick(View v) {                  // 回调的方式                  fragmentCallBack.callbackFun2(null);              }          });          return rootView;      }            @Override      public void onAttach(Activity activity) {          // TODO Auto-generated method stub          super.onAttach(activity);          fragmentCallBack = (MainActivity)activity;      }  }

回调接口：

/*  * $filename: FragmentCallBack.java,v $  * $Date: 2014-5-16  $  * Copyright (C) ZhengHaibo, Inc. All rights reserved.  * This software is Made by Zhenghaibo.  */  package com.example.testfragment;    import android.os.Bundle;    /*  *@author: ZhengHaibo    *web:     http://blog.csdn.net/nuptboyzhb  *mail:    zhb931706659@126.com  *2014-5-16  Nanjing,njupt,China  */  public interface FragmentCallBack {      public void callbackFun1(Bundle arg);        public void callbackFun2(Bundle arg);  }

main.xml

<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"      android:paddingLeft="@dimen/activity_horizontal_margin"      android:paddingRight="@dimen/activity_horizontal_margin"      android:paddingTop="@dimen/activity_vertical_margin" >      <Button          android:id="@+id/btn"          android:layout_width="match_parent"          android:layout_height="wrap_content"          android:layout_alignParentBottom="true"          android:text="切换" />      <RelativeLayout          android:id="@+id/rl_container"          android:layout_width="match_parent"          android:layout_height="wrap_content"          android:layout_above="@id/btn" />  </RelativeLayout>

MainActivity.java

package com.example.testfragment;    import android.graphics.Color;  import android.os.Bundle;  import android.support.v4.app.Fragment;  import android.support.v4.app.FragmentManager;  import android.support.v4.app.FragmentTransaction;  import android.support.v7.app.ActionBarActivity;  import android.view.View;  import android.view.View.OnClickListener;  import android.widget.Button;    public class MainActivity extends ActionBarActivity implements FragmentCallBack{            private Button btn;            private MyFragment1 fragment1;      private MyFragment2 fragment2;      private FragmentManager fragmentManager;      private Fragment currentFragment;      @Override      protected void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.activity_main);          fragmentManager = getSupportFragmentManager();                    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();          fragmentTransaction.setCustomAnimations(android.R.anim.fade_in, android.R.anim.fade_out);          fragment1 = new MyFragment1();          Bundle data = new Bundle();          data.putString("TEXT", "这是Activiy通过Bundle传递过来的值");          fragment1.setArguments(data);//通过Bundle向Activity中传递值          fragmentTransaction.add(R.id.rl_container,fragment1);//将fragment1设置到布局上          fragmentTransaction.addToBackStack(null);          fragmentTransaction.commitAllowingStateLoss();          currentFragment = fragment1;          //初始化button控件          btn = (Button)findViewById(R.id.btn);          btn.setOnClickListener(new OnClickListener() {              @Override              public void onClick(View v) {                  if(currentFragment instanceof MyFragment1){                      switchFragment();                  }else{//当前是fragment2，因此，只需要将fragment2出栈即可变成fragment1                      fragmentManager.popBackStack();                      currentFragment = fragment1;                  }              }          });      }      /**      * 切换Fragment      */      private void switchFragment(){          if(null == fragment2){//可以避免切换的时候重复创建              fragment2 = new MyFragment2();          }          Bundle data = new Bundle();          data.putString("TEXT", "传递给fragment2");          fragment2.setArguments(data);          FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();          fragmentTransaction.setCustomAnimations(android.R.anim.fade_in, android.R.anim.fade_out);          fragmentTransaction.add(R.id.rl_container,fragment2);          fragmentTransaction.addToBackStack(null);          fragmentTransaction.commitAllowingStateLoss();          currentFragment = fragment2;      }            public void changeButtonColor(){          btn.setBackgroundColor(Color.RED);      }        @Override      public void callbackFun1(Bundle arg) {          // TODO Auto-generated method stub          switchFragment();//通过回调方式切换      }        @Override      public void callbackFun2(Bundle arg) {          // TODO Auto-generated method stub          changeButtonColor();//通过回调方式调用Activity中的方法      }    }

初始画面

切换到第二个Fragment之后，通过Fragment2回调，改变按钮背景后的截图。

注意：

1.直接在Fragment中通过getActivity然后强转Activity的方式调用Activity的方法，这个方式不推荐！因为这会使Fragment的适配性变差。

解决方法：在使用之前，使用instanceof 判断一下Activity的类型

2.FragmentTransaction通过使用setCustomAnimations方法，可以为Fragment的切换增添各种不同的动画。变化方式远比Activity与Activity之间的切换动画要多。

3.多个Fragment之间，可以通过Activity复用很多代码，提高效率。

4.我们还可以通过ViewPager来管理Fragment，通过Adapter添加多个Fragment，然后通过setcurrentitem进行切换。我们同样可以通过setArguments向Fragment传递数据。

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