Android:Activity+Fragment及它们之间的数据交换（一）

简单介绍：

为什么要用Fragment？使用Fragment能够在一个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。非常多时候，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传递參数，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。在须要调用的时候回调。

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，能够通过栈的方式：

a.FragmentTransaction的add方法，加入一个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，仅仅须要将fragment2出栈就可以变成fragment1
					fragmentManager.popBackStack();
					currentFragment = fragment1;
				}
			}
		});
	}
	/**
	 * 切换Fragment
	 */
	private void switchFragment(){
		if(null == fragment2){//能够避免切换的时候反复创建
			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
	}

}

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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！由于这会使Fragment的适配性变差。

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

2.FragmentTransaction通过使用setCustomAnimations方法，能够为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，能够通过Activity复用非常多代码。提高效率。

4.我们还能够通过ViewPager来管理Fragment，通过Adapter加入多个Fragment，然后通过setcurrentitem进行切换。我们相同能够通过setArguments向Fragment传递数据。