通过ActivityGroup与全局Handler管理Activity切换

关于ActivityGroup，对它最常见的应用就是自定义格式的标签页，用来取代灵活性不高的TabActivity。下面两个链接是很完整的ActivityGroup标签页的教程：

http://www.cnblogs.com/over140/archive/2010/09/07/1820876.html

http://blog.csdn.net/hellogv/article/details/6057174

 

ActivityGroup实质上就是在一个界面中管理多个Activity，用Android官方API文档的原话来说是：“A screen that contains and runs multiple embedded activities.”。其核心是包含这些Activity的LocalActivityManager对象，在ActivityGroup中通过getLocalActivityManager()方法获得。关于ActivityGroup源码的分析参见如下链接：

http://blog.csdn.net/caowenbin/article/details/5876019

 

简单地说，LocalActivityManager对象维护了一个Activity的哈希表，通过String标识来增删改查对应的Activity实例，并提供了对相应Activity实例操作的方法，如startActivity、destroyActivity以及其它dispatchXXXXX方法。

 

不过，在前面的ActivityGroup标签页教程示例中，标签页中的Activity都仅仅只是简单的文字Activity，并不包含能够跳转到其它Activity的按钮。也就是说，切换这些Activity的标签都是写到ActivityGroup的布局中，而没有在内嵌的Activity之中。（如农民伯伯那篇博文中的第一条回复所提的问题。）

 

关于Handler，其实就是一个消息处理队列，但是通常只是用到单独的Android组件之中。将其作为全局共享变量，就可以将不同组件间的消息统一处理了。Android全局共享变量参见如下的链接：

http://blog.csdn.net/androidbluetooth/article/details/6611138

 

下面这个示例就是将切换（或者说跳转）Activity的按钮放到了内嵌的Activity的布局中，在ActivityGroup中通过全局的Handler处理具体的Activity切换，以达到在内嵌Activity中添加跳转按钮的目的。

 

主类MainActivity，继承自ActivityGroup

package com.android.test.activitygroup;import android.app.ActivityGroup;import android.content.Intent;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.view.ViewGroup;public class MainActivity extends ActivityGroup {private ViewGroup container;    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);                container = (ViewGroup) findViewById(R.id.container);//        fillContainer(0);        Message msg = new Message();        msg.what = 0;        mHandler.sendMessage(msg);                ((SharedHandlerApp)getApplication()).setHandler(mHandler);    }        private Handler mHandler = new Handler() {@Overridepublic void handleMessage(Message msg) {fillContainer(msg.what);}        };        private void fillContainer(int index) {    if (index >= 0 && index < LABELS.length) {    String className = "com.android.test.activitygroup." + LABELS[index] + "Activity";    try {    Intent intent = new Intent(MainActivity.this, Class.forName(className));    container.removeAllViews();    container.addView(getLocalActivityManager().startActivity(LABELS[index], intent).getDecorView());        } catch (ClassNotFoundException e) {    e.printStackTrace();    }    }    }        private static final String[] LABELS = {"First", "Second", "Third"};    public static final int FIRST = 0;    public static final int SECOND = 1;    public static final int THIRD = 2;}

3个内嵌Activity类

FirstActivity

package com.android.test.activitygroup;import android.app.Activity;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.view.View;import android.view.View.OnClickListener;import android.widget.TextView;public class FirstActivity extends Activity implements OnClickListener {private Handler handler;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.child);findViewById(R.id.ahead).setOnClickListener(this);findViewById(R.id.back).setOnClickListener(this);((TextView)findViewById(R.id.title)).setText("This is FirstActivity!");handler = ((SharedHandlerApp)getApplication()).getHandler();}public void onClick(View v) {Message msg = new Message();if (v.getId() == R.id.ahead) {msg.what = MainActivity.SECOND;} else if (v.getId() == R.id.back) {msg.what = MainActivity.THIRD;}handler.sendMessage(msg);}} 

SecondActivity

package com.android.test.activitygroup;import android.app.Activity;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.view.View;import android.view.View.OnClickListener;import android.widget.TextView;public class SecondActivity extends Activity implements OnClickListener {private Handler handler;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.child);findViewById(R.id.ahead).setOnClickListener(this);findViewById(R.id.back).setOnClickListener(this);((TextView)findViewById(R.id.title)).setText("This is SecondActivity!");handler = ((SharedHandlerApp)getApplication()).getHandler();}public void onClick(View v) {Message msg = new Message();if (v.getId() == R.id.ahead) {msg.what = MainActivity.THIRD;} else if (v.getId() == R.id.back) {msg.what = MainActivity.FIRST;}handler.sendMessage(msg);}}

ThirdActivity

package com.android.test.activitygroup;import android.app.Activity;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.view.View;import android.view.View.OnClickListener;import android.widget.TextView;public class ThirdActivity extends Activity implements OnClickListener {private Handler handler;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.child);findViewById(R.id.ahead).setOnClickListener(this);findViewById(R.id.back).setOnClickListener(this);((TextView)findViewById(R.id.title)).setText("This is ThirdActivity!");handler = ((SharedHandlerApp)getApplication()).getHandler();}public void onClick(View v) {Message msg = new Message();if (v.getId() == R.id.ahead) {msg.what = MainActivity.FIRST;} else if (v.getId() == R.id.back) {msg.what = MainActivity.SECOND;}handler.sendMessage(msg);}}

全局变量设置类SharedHandlerApp，继承自Application

package com.android.test.activitygroup;import android.app.Application;import android.os.Handler;public class SharedHandlerApp extends Application {private Handler handler;public Handler getHandler() {return handler;}public void setHandler(Handler handler) {this.handler = handler;}}

xml布局文件

main.xml

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:orientation="vertical"    android:layout_width="fill_parent"    android:layout_height="fill_parent"    ><TextView      android:layout_width="fill_parent"     android:layout_height="wrap_content"     android:text="@string/hello"    android:textColor="@android:color/white"    android:textSize="23sp"    /><FrameLayout android:layout_width="fill_parent"android:layout_height="fill_parent"android:layout_weight="1"android:background="@android:color/background_light"android:id="@+id/container"/><ImageView android:layout_width="fill_parent"android:layout_height="wrap_content"android:background="@android:drawable/toast_frame"/></LinearLayout>

child.xml

<?xml version="1.0" encoding="utf-8"?><LinearLayout  xmlns:android="http://schemas.android.com/apk/res/android"  android:orientation="vertical"  android:layout_width="match_parent"  android:layout_height="match_parent">    <TextView     android:layout_width="fill_parent"    android:layout_height="wrap_content"    android:textColor="@android:color/black"    android:textSize="23sp"    android:id="@+id/title"    android:text="Hello World!"    />    <Button     android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:text="ahead"    android:id="@+id/ahead"    />    <Button     android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:text="back"    android:id="@+id/back"    /></LinearLayout>

配置文件AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"      package="com.android.test.activitygroup"      android:versionCode="1"      android:versionName="1.0">    <uses-sdk android:minSdkVersion="8" />    <application android:icon="@drawable/icon" android:label="@string/app_name" android:name=".SharedHandlerApp">        <activity android:name=".MainActivity"                  android:label="@string/app_name">            <intent-filter>                <action android:name="android.intent.action.MAIN" />                <category android:name="android.intent.category.LAUNCHER" />            </intent-filter>        </activity>        <activity android:name="FirstActivity"></activity>        <activity android:name="SecondActivity"></activity>        <activity android:name="ThirdActivity"></activity>    </application></manifest>

AndroidManifest.xml中一定不要忘了将<application>标签的android:name属性设置为前面的扩展自Application类的全局变量设置类。

最后需要补充的是，作为container容器的Layout只要是继承自ViewGroup的Layout类即可，即LinearLayout、FrameLayout、GridLayout、ScrollLayout、AbsoluteLayout等均可，而并不局限于只能是其中的某一种。