通过反射获取当前Activity实例_android 反射获取activity实例-优快云博客

本文介绍了一种通过反射机制获取Android应用中当前处于活跃状态的Activity实例的方法。此方法首先获取ActivityThread中的所有ActivityRecord，然后筛选出未暂停的Activity，最终返回该Activity实例。

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转自：https://blog.youkuaiyun.com/baidu_31093133/article/details/52785580

步骤：

1、获取ActivityThread中保存的所有的ActivityRecord
2 、从ActivityRecord中获取状态不是pause的Activity并返回，这个Activity就是当前处于活动状态的Activity

public static Activity getActivity() {
    Class activityThreadClass = null;
    try {
        activityThreadClass = Class.forName("android.app.ActivityThread");
        Object activityThread = activityThreadClass.getMethod("currentActivityThread").invoke(null);
        Field activitiesField = activityThreadClass.getDeclaredField("mActivities");
        activitiesField.setAccessible(true);
        Map activities = (Map) activitiesField.get(activityThread);
        for (Object activityRecord : activities.values()) {
            Class activityRecordClass = activityRecord.getClass();
            Field pausedField = activityRecordClass.getDeclaredField("paused");
            pausedField.setAccessible(true);
            if (!pausedField.getBoolean(activityRecord)) {
                Field activityField = activityRecordClass.getDeclaredField("activity");
                activityField.setAccessible(true);
                Activity activity = (Activity) activityField.get(activityRecord);
                return activity;
            }
        }
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } catch (NoSuchMethodException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    } catch (InvocationTargetException e) {
        e.printStackTrace();
    } catch (NoSuchFieldException e) {
        e.printStackTrace();
    }
    return null;
}