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

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。