在android开发中,都需要一个类对activity实例进行管理

以前的写法是直接建一个Application然后直接在里面对activity进行管理,如:

public class MyApplication extends Application {
//存放所有开启的activity
    private List<Activity> activitys;
    public void onCreate() {
        activitys = new ArrayList<>();
    }
    public void addActivity(Activity activity) {
        activities.add(activity);
    }
    public void finishAllActivity() {
        for (Activity activity : activitys) {
            if (!activity.isFinishing()) {
                activity.finish();
            }
        }
    }
}

最近看到比较好的写法

public class MyApplication extends Application {
    private ActivityManager activityManager = null; // activity管理类
    public void onCreate() {
        activityManager = ActivityManager.getInstance(); // 获得实例
        super.onCreate();
    }
    public ActivityManager getActivityManager() {
        return activityManager;
    }

}


/**
 * activity管理类
 * 
 */
public class ActivityManager {
    /**
     * 接收activity的Stack
     */
    private static Stack<Activity> activityStack = null;
    private static ActivityManager activityManager = new ActivityManager();
    
    private ActivityManager(){}
    
    /**
     * 单实例
     * 
     * @return
     */
    public static ActivityManager getInstance() {
        return activityManager;
    }
    
    
    /**
     * 将activity移出栈
     * 
     * @param activity
     */
    public void popActivity(Activity activity) {
        if (activity != null) {
            activityStack.remove(activity);
        }
    }

    /**
     * 结束指定activity
     * 
     * @param activity
     */
    public void endActivity(Activity activity) {
        if (activity != null) {
            activity.finish();
            activityStack.remove(activity);
            activity = null;
        }
    }

    /**
     * 获得当前的activity(即最上层)
     * 
     * @return
     */
    public Activity currentActivity() {
        Activity activity = null;
        if (!activityStack.empty())
            activity = activityStack.lastElement();
        return activity;
    }

    /**
     * 将activity推入栈内
     * 
     * @param activity
     */
    public void pushActivity(Activity activity) {
        if (activityStack == null) {
            activityStack = new Stack<Activity>();
        }
        activityStack.add(activity);
    }

    /**
     * 弹出除cls外的所有activity
     * 
     * @param cls
     */
    public void popAllActivityExceptOne(Class<? extends Activity> cls) {
        while (true) {
            Activity activity = currentActivity();
            if (activity == null) {
                break;
            }
            if (activity.getClass().equals(cls)) {
                break;
            }
            popActivity(activity);
        }
    }
    
    /**
     * 结束除cls之外的所有activity,执行结果都会清空Stack
     * 
     * @param cls
     */
    public void finishAllActivityExceptOne(Class<? extends Activity> cls) {
        while (!activityStack.empty()) {
            Activity activity = currentActivity();
            if (activity.getClass().equals(cls)) {
                popActivity(activity);
            } else {
                endActivity(activity);
            }
        }
    }
    
    /**
     * 结束所有activity
     */
    public void finishAllActivity() {
        while (!activityStack.empty()) {
            Activity activity = currentActivity();
                endActivity(activity);
        }
    }
}