关于QQ游戏大厅的架构我也想说几句

先抛砖引玉一下，接个例子说明，现在的例子是要实现：

一个安装的apk里面的一个activity A要去调用一个放在sd卡上的没安装的apk里面的activity B，点返回键又回到Activity A，而不是直接退出。

ok，我这里已经有现成的方法了，先上代码：

主动去加载的SD上类的activity

import java.lang.reflect.Constructor;
import java.lang.reflect.Method;

import android.app.Activity;
import android.content.Intent;
import android.content.pm.PackageInfo;
import android.os.Bundle;
import android.util.Log;
import android.view.KeyEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;
import dalvik.system.DexClassLoader;

public class MainActivity
extends Activity {
private static final String TAG = "MainActivity";
private boolean isJumped = false;
private Class localClass;
private Object instance;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

Button btn = (Button) findViewById(R.id.btn);
btn.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
isJumped = true;
Bundle paramBundle = new Bundle();
paramBundle.putBoolean("KEY_START_FROM_OTHER_ACTIVITY", true);
String dexpath = "/mnt/sdcard/ToolA.apk";
String dexoutputpath = "/mnt/sdcard/";
LoadAPK(paramBundle, dexpath, dexoutputpath);
}
});
}

@Override
protected void onDestroy() {
super.onDestroy();
}

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
if (isJumped) {
Bundle paramBundle = new Bundle();
paramBundle.putBoolean("KEY_START_FROM_OTHER_ACTIVITY", true);
closeAPK(paramBundle);
isJumped = false;
return true;
}
}
return super.onKeyDown(keyCode, event);
}

public void LoadAPK(Bundle paramBundle, String dexpath, String dexoutputpath) {
ClassLoader localClassLoader = ClassLoader.getSystemClassLoader();
DexClassLoader localDexClassLoader =
new DexClassLoader(dexpath, dexoutputpath, null, localClassLoader);
try {
PackageInfo plocalObject = getPackageManager().getPackageArchiveInfo(dexpath, 1);

if ((plocalObject.activities != null) && (plocalObject.activities.length > 0)) {
String activityname = plocalObject.activities[0].name;
Log.d(TAG, "activityname = " + activityname);

localClass = localDexClassLoader.loadClass(activityname);
Constructor localConstructor = localClass.getConstructor(new Class[] {});
instance = localConstructor.newInstance(new Object[] {});
Log.d(TAG, "instance = " + instance);

Method localMethodSetActivity =
localClass.getDeclaredMethod("setActivity", new Class[] {Activity.class});
localMethodSetActivity.setAccessible(true);
localMethodSetActivity.invoke(instance, new Object[] {this});

Method methodonCreate = localClass.getDeclaredMethod("onCreate", new Class[] {Bundle.class});
methodonCreate.setAccessible(true);
methodonCreate.invoke(instance, new Object[] {paramBundle});
}
return;
}
catch (Exception ex) {
ex.printStackTrace();
}
}

public void closeAPK(Bundle paramBundle) {
try {
Method methodonCreate = localClass.getDeclaredMethod("onGoBack");
methodonCreate.setAccessible(true);
methodonCreate.invoke(instance);
} catch (Exception ex) {
ex.printStackTrace();
}
}
}

另外一个是sd卡上待加载的activity：

package mobi.thinkchange.android.toola;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.KeyEvent;
import android.widget.Toast;

public class ToolAActivity
extends Activity {
private static final String TAG = "ToolAActivity";
private Activity otherActivity;

@Override
public void onCreate(Bundle savedInstanceState) {
boolean b = false;
if (savedInstanceState != null) {
b = savedInstanceState.getBoolean("KEY_START_FROM_OTHER_ACTIVITY", false);
if (b) {
this.otherActivity.setContentView(new TBSurfaceView(this.otherActivity));
}
}
if (!b) {
super.onCreate(savedInstanceState);
setContentView(new TBSurfaceView(this));
}
}

public void setActivity(Activity paramActivity) {
Log.d(TAG, "setActivity..." + paramActivity);
this.otherActivity = paramActivity;
}

public void onGoBack() {
otherActivity.setContentView(R.layout.main);
}
}

上面是实现我说的例子最核心的两个类，全部代码详见：http://download.csdn.net/detail/androidzhaoxiaogang/4903804

（代码只是片段，如果要实际应用还需要完善，比如在返回的时候终端执行的runnable可参考我的另外一篇文章如何终端执行的java线程）

也许网上有很多关于QQ游戏大厅的分析或者类似上面的例子，但是我想做进一步的分析。

1.我们知道一个activity具有严格意义上的生命周期必须要在ActivityThread里面去创建，所以通过DexClassLoader加载的ActivityB是没有生命周期的，它也就是一个普通的类；

2.有人会问，为什么还要让ActivityA 来加载ActivityB，而不是直接ActivityA去load 另外一个类比如classC呢？ 这个问题很简单，因为我们在打包成APK的时候，有activity会更方便和直观（自己去体会）。简单的游戏，往往一个activity就够了。那么ActivityA 也仅仅只需要加载一个类实例。