通过反射获取当前Activity实例

Posted 2022-06-15 月色下的独轮车

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

具体代码：

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;