0x0.必现步骤:打开app,退出app.内存泄漏检测工具LeakCanary必报.

0x1.LeakCanary就一定准吗?不见得.秉着尽信它不如不用它原则.启用adb校验.如图所示,Activities数量一直恒定,那内存泄漏真心没跑了.

输入 adb shell dumpsys meminfo -a 包名

图片证据

0x2.分析内存hprof文件com.blankj.utilcode.util.UtilsActivityLifecycleImpl.mActivityList持有activity无法释放

内存泄漏

0x3.debug断点UtilsActivityLifecycleImpl.mActivityList 发现有两处.1是在生命周期onActivityCreated会被赋值2是getTopActivity时有机会会被赋值.为什么叫有机会呢?当app关闭时,生命周期正常分发mActivityList会被清空,此时调用getTopActivity就会被赋值,从而引起mActivityList持有activity无法被释放

image.png

0x4.结论.Activity activity = ActivityUtils.getTopActivity();//请注意该函数调用时机!

image.png

0x5.如上图所示.我只想获取栈顶activity.不影响mActivityList变动!把源码copy出来即可

package com.sinochem.helper;

import android.app.Activity;
import android.util.Log;

import com.blankj.utilcode.util.ActivityUtils;

import java.lang.reflect.Field;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

/**
 * @className: LeakHelper
 * @description:LeakHelper.getTopActivity();
 * @author:
 * @date: 2023/1/16 9:05 上午 星期一
 **/
public class LeakHelper {
    public static void fixInputMethodManagerLeakCompat() {
        ActivityUtils.startActivity(DumpActivity.class);
    }

    public static Activity getTopActivity() {
        List<Activity> activityList = getActivityList();
        for (Activity activity : activityList) {
            if (!ActivityUtils.isActivityAlive(activity)) {
                continue;
            }
            return activity;
        }
        return null;
    }

    private static List<Activity> getActivityList() {
        List<Activity> reflectActivities = getActivitiesByReflect();
        return reflectActivities;
    }

    private static Object getActivityThread() {
        Object activityThread = getActivityThreadInActivityThreadStaticField();
        if (activityThread != null) {
            return activityThread;
        }
        return getActivityThreadInActivityThreadStaticMethod();
    }

    private static Object getActivityThreadInActivityThreadStaticMethod() {
        try {
            Class activityThreadClass = Class.forName("android.app.ActivityThread");
            return activityThreadClass.getMethod("currentActivityThread").invoke(null);
        } catch (Exception e) {
            Log.e("UtilsActivityLifecycle", "getActivityThreadInActivityThreadStaticMethod: " + e.getMessage());
            return null;
        }
    }

    private static Object getActivityThreadInActivityThreadStaticField() {
        try {
            Class activityThreadClass = Class.forName("android.app.ActivityThread");
            Field sCurrentActivityThreadField = activityThreadClass.getDeclaredField("sCurrentActivityThread");
            sCurrentActivityThreadField.setAccessible(true);
            return sCurrentActivityThreadField.get(null);
        } catch (Exception e) {
            Log.e("UtilsActivityLifecycle", "getActivityThreadInActivityThreadStaticField: " + e.getMessage());
            return null;
        }
    }

    public static List<Activity> getActivitiesByReflect() {
        LinkedList<Activity> list = new LinkedList<>();
        Activity topActivity = null;
        try {
            Object activityThread = getActivityThread();
            Field mActivitiesField = activityThread.getClass().getDeclaredField("mActivities");
            mActivitiesField.setAccessible(true);
            Object mActivities = mActivitiesField.get(activityThread);
            if (!(mActivities instanceof Map)) {
                return list;
            }
            Map<Object, Object> binder_activityClientRecord_map = (Map<Object, Object>) mActivities;
            for (Object activityRecord : binder_activityClientRecord_map.values()) {
                Class activityClientRecordClass = activityRecord.getClass();
                Field activityField = activityClientRecordClass.getDeclaredField("activity");
                activityField.setAccessible(true);
                Activity activity = (Activity) activityField.get(activityRecord);
                if (topActivity == null) {
                    Field pausedField = activityClientRecordClass.getDeclaredField("paused");
                    pausedField.setAccessible(true);
                    if (!pausedField.getBoolean(activityRecord)) {
                        topActivity = activity;
                    } else {
                        list.add(activity);
                    }
                } else {
                    list.add(activity);
                }
            }
        } catch (Exception e) {
            Log.e("UtilsActivityLifecycle", "getActivitiesByReflect: " + e.getMessage());
        }
        if (topActivity != null) {
            list.addFirst(topActivity);
        }
        return list;
    }
}

0x6.调用LeakHelper.getTopActivity() 绕过UtilsActivityLifecycleImpl因为调用时机不正确引起的内存泄漏