Activity 全平台生命周期监听

最近在搞公司的用户行为跟踪系统的时候碰到要统计用户在Activity的停留时间，然后就想到了在生命周期里面添加时间记录。在每个Activity里面重写生命周期函数添加时间记录？太麻烦了吧。写个BaseActivity，在BaseActivity里面做时间记录？嗯，还行。还有么有更简便的方式。有啊，在Application里面调用registerActivityLifecycleCallbacks方法就可以监听所有Activity的生命周期，问题妥妥的搞定了。当时我在公司接触的项目都是4.0以上的了，所以也没考虑那么多。问题搞定了，是骡子是马来出来溜溜就知道了。然后领导就接入到公司一个比较旧的项目里面，然后过几天我就懵逼了，全都是registerActivityLifecycleCallbacks报的错误。当时表情是这样的

后来发现旧项目最低支持2.3以上，所以只能用别的办法了，因此写下此文，记录一下解决办法。

解决之道

关键类 Instrumentation

Instrumentation这个类平时开发的时候可能接触的比较少，但如果弄过Android组件单元测试的话应该会接触过。这个类很强大，比如通过这个类我们可以在Activity创建之前做一些我们自己的事情，比如拦截掉启动的Activity，换成另外一个Activity，再比如获取Activity的生命周期。怎么获取的Activity生命周期？在Instrumentation类中有callActivityOnCreate、callActivityOnResume等一些生命周期的方法。既然有生命周期的这些方法，那我们只要Hook Instrumentation这个类，就可以实现Activity生命周期的监听。那怎么Hook呢，用反射啊。

实现方法

0、首先先定义一个MyInstrumentation继承自Instrumentation，重写callActivityOnCreate、callActivityOnResume等Activity生命周期的方法

代码如下：

public class MyInstrumentation extends Instrumentation {
	@Override
	public void callActivityOnCreate(Activity activity, Bundle icicle) {
		super.callActivityOnCreate(activity, icicle);
		ActivityLifeManager.getInstance().onActivityCreated(activity, icicle);
	}
	@Override
	public void callActivityOnPause(Activity activity) {
		super.callActivityOnPause(activity);
		ActivityLifeManager.getInstance().onActivityPaused(activity);
	}
	@Override
	public void callActivityOnDestroy(Activity activity) {
		super.callActivityOnDestroy(activity);
		ActivityLifeManager.getInstance().onActivityDestroyed(activity);
	}
	@Override
	public void callActivityOnResume(Activity activity) {
		super.callActivityOnResume(activity);
		ActivityLifeManager.getInstance().onActivityResumed(activity);
	}
	@Override
	public void callActivityOnStart(Activity activity) {
		super.callActivityOnStart(activity);
		ActivityLifeManager.getInstance().onActivityStarted(activity);
	}
	@Override
	public void callActivityOnStop(Activity activity) {
		super.callActivityOnStop(activity);
		ActivityLifeManager.getInstance().onActivityStoped(activity);
	}
}

注：ActivityLifeManager是自己定义的一个Activity生命周期管理类，方便管理4.0以上和4.0以下两种Activity生命周期监听方式

1、然后将我们自己定义的MyInstrumentation利用反射将系统原本的Instrumentation替换掉

代码如下：

/**
 * 替换系统默认的Instrumentation
 */
public static void replaceInstrumentation() {
	Class activityThreadClass;
	try {
		// 加载activity thread的class
		activityThreadClass = Class.forName("android.app.ActivityThread");
		// 找到方法currentActivityThread
		Method method = activityThreadClass
				.getDeclaredMethod("currentActivityThread");
		// 由于这个方法是静态的，所以传入Null就行了
		Object currentActivityThread = method.invoke(null);
		// 把之前ActivityThread中的mInstrumentation替换成我们自己的
		Field field = activityThreadClass
				.getDeclaredField("mInstrumentation");
		field.setAccessible(true);
		MyInstrumentation mInstrumentation = new MyInstrumentation();
		field.set(currentActivityThread, mInstrumentation);
	} catch (Exception e) {
		e.printStackTrace();
	}
}

至此，4.0以下Activity生命周期监听难点已经解决，接下来就是整合4.0以上和4.0以下Activity生命周期监听。

2、整合

ActivityLifeManager管理类，代码如下：

public class ActivityLifeManager implements IActivityLifecycleCallbacks {
	private static ActivityLifeManager manager;
	private List lifeChanges = new ArrayList();
	public static synchronized ActivityLifeManager getInstance() {
		if (manager == null) {
			manager = new ActivityLifeManager();
		}
		return manager;
	}
	private ActivityLifeManager() {
	}
	public void addIActivityLifeChange(IActivityLifecycleCallbacks lis) {
		lifeChanges.add(lis);
	}
	@Override
	public void onActivityStarted(Activity activity) {
		for (IActivityLifecycleCallbacks lis : lifeChanges) {
			lis.onActivityStarted(activity);
		}
	}
	@Override
	public void onActivityResumed(Activity activity) {
		for (IActivityLifecycleCallbacks lis : lifeChanges) {
			lis.onActivityResumed(activity);
		}
	}
	@Override
	public void onActivityPaused(Activity activity) {
		for (IActivityLifecycleCallbacks lis : lifeChanges) {
			lis.onActivityPaused(activity);
		}
	}
	@Override
	public void onActivityDestroyed(Activity activity) {
		for (IActivityLifecycleCallbacks lis : lifeChanges) {
			lis.onActivityDestroyed(activity);
		}
	}
	@Override
	public void onActivityCreated(Activity activity,
			Bundle savedInstanceState) {
		for (IActivityLifecycleCallbacks lis : lifeChanges) {
			lis.onActivityCreated(activity, savedInstanceState);
		}
	}
	@Override
	public void onActivityStoped(Activity activity) {
		for (IActivityLifecycleCallbacks lis : lifeChanges) {
			lis.onActivityStoped(activity);
		}
	}
}

IActivityLifecycleCallbacks生命周期回调接口，代码如下：

public interface IActivityLifecycleCallbacks {
	public void onActivityCreated(Activity activity, Bundle savedInstanceState);
	public void onActivityStarted(Activity activity);
	public void onActivityResumed(Activity activity);
	public void onActivityPaused(Activity activity);
	public void onActivityStoped(Activity activity);
	public void onActivityDestroyed(Activity activity);
}

MyActivityLifecycleCallbacks 4.0以上Activity生命周期回调实现类

public class MyActivityLifecycleCallbacks
		implements Application.ActivityLifecycleCallbacks {
	@Override
	public void onActivityCreated(Activity activity,
			Bundle savedInstanceState) {
		ActivityLifeManager.getInstance().onActivityCreated(activity,
				savedInstanceState);
	}
	@Override
	public void onActivityStarted(Activity activity) {
	}
	@Override
	public void onActivityResumed(Activity activity) {
		ActivityLifeManager.getInstance().onActivityResumed(activity);
	}
	@Override
	public void onActivityPaused(Activity activity) {
		ActivityLifeManager.getInstance().onActivityPaused(activity);
	}
	@Override
	public void onActivityStopped(Activity activity) {
		ActivityLifeManager.getInstance().onActivityStoped(activity);
	}
	@Override
	public void onActivitySaveInstanceState(Activity activity,
			Bundle outState) {
	}
	@Override
	public void onActivityDestroyed(Activity activity) {
		ActivityLifeManager.getInstance().onActivityDestroyed(activity);
	}
}

整合使用，代码如下：

public static void init(Application app) {
	if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
    //4.0以上使用系统自带的Activity生命周期监听方式
		app.registerActivityLifecycleCallbacks(
				new MyActivityLifecycleCallbacks());
	} else {
    //4.0以下，替换Instrumentation，实现Activity生命周期监听
		replaceInstrumentation();
	}
  //最终两种方式生命周期统一回调
	ActivityLifeManager.getInstance()
			.addIActivityLifeChange(new IActivityLifecycleCallbacks() {
				@Override
				public void onActivityStarted(Activity activity) {
				}
				@Override
				public void onActivityResumed(Activity activity) {
				}
				@Override
				public void onActivityPaused(Activity activity) {
				}
				@Override
				public void onActivityDestroyed(Activity activity) {
				}
				@Override
				public void onActivityCreated(Activity activity,
						Bundle savedInstanceState) {
				}
				@Override
				public void onActivityStoped(Activity activity) {
				}
			});
}

源码地址 ActivityLifecycle

总结