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() { @Override public 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; @Override protected 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; @Override protected 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; @Override protected 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。