Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/--><?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="fill_parent" android:orientation="vertical"android:layout_height="fill_parent"><LinearLayout android:gravity="center_horizontal"android:background="@drawable/myinfor2" android:layout_width="fill_parent"android:layout_height="wrap_content"><TextView android:id="@+id/cust_title" android:textColor="@android:color/white"android:textSize="28sp" android:text="模块1" android:layout_width="wrap_content"android:layout_height="wrap_content"></TextView></LinearLayout><!-- 中间动态加载View --><ScrollView android:measureAllChildren="true" android:id="@+id/containerBody"android:layout_weight="1" android:layout_height="fill_parent"android:layout_width="fill_parent"></ScrollView><LinearLayout android:background="@android:color/black"android:layout_gravity="bottom" android:orientation="horizontal"android:layout_width="fill_parent" android:layout_height="wrap_content"><!-- 功能模块按钮1 --><ImageView android:id="@+id/btnModule1" android:src="@android:drawable/ic_dialog_dialer"android:layout_marginLeft="7dp" android:layout_marginTop="3dp"android:layout_marginBottom="3dp" android:layout_width="wrap_content"android:layout_height="wrap_content" /><!-- 功能模块按钮2 --><ImageView android:id="@+id/btnModule2" android:src="@android:drawable/ic_dialog_info"android:layout_marginLeft="7dp" android:layout_marginTop="3dp"android:layout_marginBottom="3dp" android:layout_width="wrap_content"android:layout_height="wrap_content" /><!-- 功能模块按钮3 --><ImageView android:id="@+id/btnModule3" android:src="@android:drawable/ic_dialog_alert"android:layout_marginLeft="7dp" android:layout_marginTop="3dp"android:layout_marginBottom="3dp" android:layout_width="wrap_content"android:layout_height="wrap_content" /></LinearLayout>
</LinearLayout>

Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->/*** 使用ActivityGroup来切换Activity和Layout* @author 农民伯伯* @version 2010-9-7* */
public class TestView extends ActivityGroup {private ScrollView container = null;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);// 隐藏标题栏requestWindowFeature(Window.FEATURE_NO_TITLE);// 设置视图setContentView(R.layout.layout);container = (ScrollView) findViewById(R.id.containerBody);// 模块1ImageView btnModule1 = (ImageView) findViewById(R.id.btnModule1);btnModule1.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {container.removeAllViews();container.addView(getLocalActivityManager().startActivity("Module1",new Intent(TestView.this, ModuleView1.class).addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)).getDecorView());}});// 模块2ImageView btnModule2 = (ImageView) findViewById(R.id.btnModule2);btnModule2.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {container.removeAllViews();container.addView(getLocalActivityManager().startActivity("Module2",new Intent(TestView.this, ModuleView2.class).addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)).getDecorView());}});// 模块3ImageView btnModule3 = (ImageView) findViewById(R.id.btnModule3);btnModule3.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {container.removeAllViews();container.addView(getLocalActivityManager().startActivity("Module3",new Intent(TestView.this, ModuleView3.class).addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)).getDecorView());}});}
}

此前，我们对Activity进行了一些学习，在Android中，还提供了一个ActivityGroup类，该类是Activity的容器，可以包含多个嵌套进来的Activitys，我们接下来依然采用源码分析的方式来了解该类的内部实现。

首先，从SDK中和源码中都可以获知，ActivityGroup类的父类是Activity，也就是说二者具有相同的接口和生命周期，同Activity一样，也有onCreate()、onPause()等函数可供我们重载。

在ActivityGroup的源码中有成员变量

protected LocalActivityManager mLocalActivityManager;

该变量在ActivityGroup的构造函数中创建并初始化，可见，ActivityGroup的功能实现肯定是要委托给这个对象来完成了。为了给用户开放对此对象的访问，ActivityGroup提供了

    public final LocalActivityManager getLocalActivityManager() {

        return mLocalActivityManager;

    }

通过浏览ActivityGroup的源码可以发现，几乎全部是以通过LocalActivityManager对象来完成的具体动作，比如：

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        Bundle states = savedInstanceState != null

                ? (Bundle) savedInstanceState.getBundle(STATES_KEY) : null;

        mLocalActivityManager.dispatchCreate(states);

}

下面，我们就来看一下LocalActivityManager的源码。

在该类中，提供了一个私有类

    private static class LocalActivityRecord extends Binder {

        LocalActivityRecord(String _id, Intent _intent) {

            id = _id;

            intent = _intent;

        }

        final String id;                // Unique name of this record.

        Intent intent;                  // Which activity to run here.

        ActivityInfo activityInfo;      // Package manager info about activity.

        Activity activity;              // Currently instantiated activity.

        Window window;                  // Activity's top-level window.

        Bundle instanceState;           // Last retrieved freeze state.

        int curState = RESTORED;        // Current state the activity is in.

    }

用于保存Activity的信息，并提供了

    private final Map<String, LocalActivityRecord> mActivities

            = new HashMap<String, LocalActivityRecord>();

    private final ArrayList<LocalActivityRecord> mActivityArray

            = new ArrayList<LocalActivityRecord>();

采用这样的数据结构用于对所有嵌入的子Activity信息进行保存处理。其中前者用于通过String快速查找，后者用于以数组的方式快速访问，是典型的以空间换时间的的方式。

    public void dispatchCreate(Bundle state) {

        if (state != null) {

            final Iterator<String> i = state.keySet().iterator();

            while (i.hasNext()) {

                try {

                    final String id = i.next();

                    final Bundle astate = state.getBundle(id);

                    LocalActivityRecord r = mActivities.get(id);

                    if (r != null) {

                        r.instanceState = astate;

                    } else {

                        r = new LocalActivityRecord(id, null);

                        r.instanceState = astate;

                        mActivities.put(id, r);

                        mActivityArray.add(r);

                    }

                } catch (Exception e) {

……

                }

            }

        }

        mCurState = CREATED;

    }

从这里我们可以看出，当有一个ActivityGroup被Create的时候，就会有对应的Activity信息被保存到数组中。

当我们调用LocalActivityManager的startActivity()以产生Window的时候，我们也可以看到

public Window startActivity(String id, Intent intent) {

                   ……

        LocalActivityRecord r = mActivities.get(id);

        if (r == null) {

            r = new LocalActivityRecord(id, intent);

            adding = true;

        }

                   ……

        if (adding) {

            mActivities.put(id, r);

            mActivityArray.add(r);

        }

        ……

    }

有了这个数组，就可以遍历到ActivityGroup中嵌入的Activitys了，从而可以实现ActivityGroup的功能。

以上的分析结果产生的类图如下：