反射操作Activity栈的工具类

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本文介绍如何使用Java反射机制获取Android应用程序中的当前Activity、整个Activity栈以及特定的MainActivity实例。通过这些方法可以实现对Activity栈的有效管理和操作。

记录一下今天用到的几个反射操作activity栈的方法。

获取当前栈顶activity

        /**
     * 获取当前activity
     * @return
     */
    public static Activity getCurrentActivity() {
        try {
            Class 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 (InvocationTargetException e) {
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return null;
    }

获取整个Activity栈

        /**
     * 获取栈
     * @param application
     * @return
     */
    public static List<Activity> getActivitiesByApplication(Application application) {
        List<Activity> list = new ArrayList<>();
        try {
            Class<Application> applicationClass = Application.class;
            Field mLoadedApkField = applicationClass.getDeclaredField("mLoadedApk");
            mLoadedApkField.setAccessible(true);
            Object mLoadedApk = mLoadedApkField.get(application);
            Class<?> mLoadedApkClass = mLoadedApk.getClass();
            Field mActivityThreadField = mLoadedApkClass.getDeclaredField("mActivityThread");
            mActivityThreadField.setAccessible(true);
            Object mActivityThread = mActivityThreadField.get(mLoadedApk);
            Class<?> mActivityThreadClass = mActivityThread.getClass();
            Field mActivitiesField = mActivityThreadClass.getDeclaredField("mActivities");
            mActivitiesField.setAccessible(true);
            Object mActivities = mActivitiesField.get(mActivityThread);
            if (mActivities instanceof Map) {
                @SuppressWarnings("unchecked") Map<Object, Object> arrayMap = (Map<Object, Object>) mActivities;
                for (Map.Entry<Object, Object> entry : arrayMap.entrySet()) {
                    Object value = entry.getValue();
                    Class<?> activityClientRecordClass = value.getClass();
                    Field activityField = activityClientRecordClass.getDeclaredField("activity");
                    activityField.setAccessible(true);
                    Object o = activityField.get(value);
                    list.add((Activity) o);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
            list = null;
        }
        if(null != list ){
            for (Activity act:list) {
                L.i("act.getLocalClassName() =="+act.getLocalClassName());
                L.i("act.getComponentName() =="+act.getComponentName());
                L.i("act.getPackageName() =="+act.getPackageName());
            }
        }else {
            L.i("栈为空");
        }
        return list;
    }

获取栈中MainActivity的实例

这个方法其实就是调用上面那个获取全栈的方法，然后遍历调用Activity.getLocalName()，筛选出你项目内的MainActivity

        /**
     * 获取栈中MainActivity的实例
     * @param outActivity
     * @return
     */
    public static MainActivity getTheMainActivity(Activity outActivity) {
        Activity mainActivityObj = null;
        List<Activity> activitiesByApplication = AppUtils.getActivitiesByApplication(outActivity.getApplication());
        if (null != activitiesByApplication && activitiesByApplication.size() > 0) {
            for (Activity activity : activitiesByApplication) {
                if (activity.getLocalClassName().equals("com.xxx.yyy.main.MainActivity")) {
                    mainActivityObj = activity;
                    break;
                }
            }
        }
        return (MainActivity) mainActivityObj;
    }