查看Activity栈

谈起Android程序开发，就需要了解其四个主要的部件：Activity、Service、ContentProvider、 BroadcastReceiver。而其中Activity是唯一直接控制程序界面呈现，直面用户操作的部件（当然BrowadCastReceiver也能通过桌面控件(App Widgets)来呈现有限的操作界面）。Android对于Activity有严格的生命周期控制，以限制开发者在适当的回调函数里的放上合适的代码。对于多个Activity的转换，Android也有非常好的管理和流畅的切换，对此Android还引入了任务栈(Task Stack)的概念，这个概念对于Android设备上得返回按键有极其重要的联系。

(大部分文档都将其表述为Tasks and Back Stack，但从官方文档的描述来看，Android的相对于Activity讲到的Task都视为一个存放Activities的Stack，所以将其称为Task Stack也不为过。)

在AndroidManifest中申明所要用到的Activity时可以设置不同的launchMode来得到不同的Activity“启动”效果。在使用startActivity开启新的Activity时，传入的Intent也可以设置不同的Flag来达到不同的效果。另一方面，在Activity启动时它可能又开启了另一个Activity，或者调用了finish()函数终结了Activity。

这使得Activity栈变得无法掌握，有时候按下返回按钮或者点击关闭当前Activity的操作，都不知道Android系统会把程序带到那个Activity，不确定这是否是最后一个Activity以致退出了整个程序。亦或者一些按钮和操作循环产生Activity而造成内存膨胀。对于这些问题，如果能够在调试期间知道当前任务栈的情况，就能很方便的观察和发现问题存在的原因，进而选择正确的launchMode，设置恰当Intent的Flag来使程序达到预期的效果。

通过ActivityManager获取状态

Android提供了ActivityManger来帮助开发者了解运行期间的状态，通过调用getRunningTasks(int)方法，就可以在得到RunningTaskInfo的列表，其代表着当前Android设备正在运行着的Task。从RunningTaskInfo中又可以进一步得到更多的信息。

[java] view plaincopy

1. 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ertical-align:baseline; color:rgb(51,153,51)">+</span> runningTaskInfo.<span class="me1" style="margin:0px; padding:0px; border:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(0,102,51)">topActivity</span><span class="br0" style="margin:0px; padding:0px; border:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(0,153,0)">)</span><span class="sy0" style="margin:0px; padding:0px; border:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(51,153,51)">;</span></div></li><li class="li1" style="margin:0px; padding:0px; border:0px; font-style:inherit; font-family:inherit; vertical-align:top; list-style-position:outside!important"><div class="de1" style="margin:0px; padding:0px; border:0px; font-size:1em; vertical-align:top; line-height:1.2em; background:none">    log<span class="br0" style="margin:0px; padding:0px; border:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(0,153,0)">(</span><span class="st0" style="margin:0px; padding:0px; border:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(0,0,255)">"baseActivity: "</span> <span class="sy0" style="margin:0px; padding:0px; border:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(51,153,51)">+</span> runningTaskInfo.<span class="me1" style="margin:0px; padding:0px; border:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(0,102,51)">baseActivity</span>.<span class="me1" style="margin:0px; padding:0px; border:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(0,102,51)">toString</span><span class="br0" style="margin:0px; padding:0px; border:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(0,153,0)">(</span><span class="br0" style="margin:0px; padding:0px; border:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(0,153,0)">)</span><span class="br0" style="margin:0px; padding:0px; border:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(0,153,0)">)</span><span class="sy0" style="margin:0px; padding:0px; border:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(51,153,51)">;</span></div></li><li class="li1" style="margin:0px; padding:0px; border:0px; font-style:inherit; font-family:inherit; vertical-align:top; list-style-position:outside!important"><div class="de1" style="margin:0px; padding:0px; border:0px; font-size:1em; vertical-align:top; line-height:1.2em; background:none"><span class="br0" style="margin:0px; padding:0px; border:0px; font-weight:inherit; font-style:inherit; font-family:inherit; vertical-align:baseline; color:rgb(0,153,0)">}</span></div></li></ol>  

例如文中提供的示例程序中定义了4个具有不同launchMode的Activity，每点击一次菜单栏上得选项就会弹出一个新的Activity（或者将指定Singleton的Activity置前）。

Activity上显示的数字则指示startActivity()被第几次调用时开启了这个Activity。有一些Singleton的会显示多个数字，也表明它是被复用的。

因为在onCreate()方法上放置了上述代码，所以观察log就能发现当前有多少个Task在被执行，每个Task又有多少个Activities。

D/IDER    ( 3700): =====================D/IDER    ( 3700): ---------------------D/IDER    ( 3700): id: 25D/IDER    ( 3700): description: nullD/IDER    ( 3700): number of activities: 4D/IDER    ( 3700): topActivity: ComponentInfo{com.iderzheng/com.iderzheng.StandardActivity}D/IDER    ( 3700): baseActivity: ComponentInfo{com.iderzheng/com.iderzheng.SingleTaskActivity}D/IDER    ( 3700): ---------------------D/IDER    ( 3700): id: 24D/IDER    ( 3700): description: nullD/IDER    ( 3700): number of activities: 1D/IDER    ( 3700): topActivity: ComponentInfo{com.iderzheng/com.iderzheng.SingleInstanceActivity}D/IDER    ( 3700): baseActivity: ComponentInfo{com.iderzheng/com.iderzheng.SingleInstanceActivity}D/IDER    ( 3700): ---------------------D/IDER    ( 3700): id: 23D/IDER    ( 3700): description: nullD/IDER    ( 3700): number of activities: 2D/IDER    ( 3700): topActivity: ComponentInfo{com.iderzheng/com.iderzheng.StandardActivity}D/IDER    ( 3700): baseActivity: ComponentInfo{com.iderzheng/com.iderzheng.MainActivity}D/IDER    ( 3700): ---------------------D/IDER    ( 3700): id: 1D/IDER    ( 3700): description: nullD/IDER    ( 3700): number of activities: 1D/IDER    ( 3700): topActivity: ComponentInfo{com.android.launcher/com.android.launcher2.Launcher}D/IDER    ( 3700): baseActivity: ComponentInfo{com.android.launcher/com.android.launcher2.Launcher}

缺点

必须在程序中注入调试代码，因为要控制在发布时代码必须被清理了。RunningTaskInfo虽然能够告诉我们有多少个Activity保存在其上，但是没有提供完整的列表，只能看到头尾两个Activity。给出的两个Activity的属性：topActivity和baseActivity也只是ComponentName类型，并非真实的Activity对象，因此除了类的名字没有其他更多信息。

手动记录和管理Activities栈

Activity的创建和销毁都会有相应的回调函数：onCreate()，onDestroy()。因此可以自建一个静态全局Stack对象，在onCreate()时候讲当前Activity对象加入到Stack中，而在onDestroy()时把它从Stack中移除。这样我们就随时可以知道当前Activity的详细情况了。

缺点

要让所有Activity的onCreate()和onDestroy()方法上有对应的进出栈的方法，要么有统一的基类，要么强制每个Activity都加入这些代码，但两种方式都不完美。另外也很难模拟singleTask这类会创建出新的Task的情况，这时光使用一个Stack就不足够了，要考虑所有的情况又不太可能。再者如同使用ActivityManager一样这些代码也应该只出现在调试阶段

使用adb shell指令

Android还为开发者提供了adb(Android Debug Bridge)，这是非常强大的调试工具。最常用的自然是logcat来显示日志记录。另外一个很强大的指令就是这里要提到的dumpsys。dumpsys还可以添加不同的参数来指示需要输出哪一类Service的信息。对于本文提到的内容，需要查看的就是activity，指令就是：

adb shell dumpsys activity

输入上述指令，就能得到关于设备非常长的一段讯息，单是也能清晰看出它们比较详细的分类

ACTIVITY MANAGER PENDING INTENTS (dumpsys activity intents)  * PendingIntentRecord{42b05f20 com.android.vending startService}  ... ... ... ...ACTIVITY MANAGER BROADCAST STATE (dumpsys activity broadcasts)  Historical broadcasts [foreground]:  #0: BroadcastRecord{430d2fb8 u-1 android.intent.action.TIME_TICK}    act=android.intent.action.TIME_TICK flg=0x50000014 (has extras)    extras: Bundle[{android.intent.extra.ALARM_COUNT=1}]  ... ... ... ...ACTIVITY MANAGER CONTENT PROVIDERS (dumpsys activity providers)  Published single-user content providers (by class):  * ContentProviderRecord{429d18a8 u0 com.android.phone/.IccProvider}    proc=ProcessRecord{429765d8 858:com.android.phone/1001}    singleton=true    authority=icc  ... ... ... ...ACTIVITY MANAGER SERVICES (dumpsys activity services)  User 0 active services:  * ServiceRecord{429f8668 u0 com.android.bluetooth/.hid.HidService}    app=null    created=-1h44m27s317ms started=false connections=0  ... ... ... ...ACTIVITY MANAGER ACTIVITIES (dumpsys activity activities)  Stack #0:    Task id #28      TaskRecord{43525058 #28 A=com.android.systemui U=0 sz=1}      Intent { act=com.android.systemui.recent.action.TOGGLE_RECENTS flg=0x10c00000 cmp=com.android.systemui/.recent.RecentsActivity (has extras) }        Hist #0: ActivityRecord{428d1ae8 u0 com.android.systemui/.recent.RecentsActivity t28}          Intent { act=com.android.systemui.recent.action.TOGGLE_RECENTS flg=0x10800000 cmp=com.android.systemui/.recent.RecentsActivity bnds=[328,886][656,1176] }          ProcessRecord{42968230 695:com.android.systemui/u0a12}  ... ... ... ...ACTIVITY MANAGER RUNNING PROCESSES (dumpsys activity processes)  Process LRU list (sorted by oom_adj, 28 total, non-act at 3, non-svc at 3):    PERS #27: sys   F/ /P  trm: 0 605:system/1000 (fixed)  ... ... ... ...

每一个类别都有一个括号内容，给出了更加详细的指令来查看该类别下更多具体内容。因此再来尝试指令：

db shell dumpsys activity activities

就能看到下边的结果

CTIVITY MANAGER ACTIVITIES (dumpsys activity activities)  Stack #0:    Task id #28    * TaskRecord{43525058 #28 A=com.android.systemui U=0 sz=1}      ... ... ... ...      * Hist #0: ActivityRecord{428d1ae8 u0 com.android.systemui/.recent.RecentsActivity t28}          ... ... ... ...    Task id #1    * TaskRecord{429a35f8 #1 A=com.android.launcher U=0 sz=1}      ... ... ... ...      * Hist #0: ActivityRecord{429a1760 u0 com.android.launcher/com.android.launcher2.Launcher t1}          ... ... ... ...    Running activities (most recent first):      TaskRecord{43525058 #28 A=com.android.systemui U=0 sz=1}        Run #1: ActivityRecord{428d1ae8 u0 com.android.systemui/.recent.RecentsActivity t28}      TaskRecord{429a35f8 #1 A=com.android.launcher U=0 sz=1}        Run #0: ActivityRecord{429a1760 u0 com.android.launcher/com.android.launcher2.Launcher t1}    mLastPausedActivity: ActivityRecord{428d1ae8 u0 com.android.systemui/.recent.RecentsActivity t28}  Stack #1:    Task id #25    * TaskRecord{42b0ee20 #25 I=com.iderzheng/.SingleTaskActivity U=0 sz=5}      numActivities=5 rootWasReset=false userId=0 mTaskType=0 numFullscreen=5 mOnTopOfHome=true      intent={cmp=com.iderzheng/.SingleTaskActivity}      realActivity=com.iderzheng/.SingleTaskActivity      Activities=[ActivityRecord{42a7e160 u0 com.iderzheng/.SingleTaskActivity t25}, ActivityRecord{42bffdf0 u0 com.iderzheng/.StandardActivity t25}, ActivityRecord{42e9e8f8 u0 com.iderzheng/.SingleTopActivity t25}, ActivityRecord{434c2238 u0 com.iderzheng/.StandardActivity t25}, ActivityRecord{4279d2d8 u0 com.iderzheng/.SingleTopActivity t25}]      askedCompatMode=false      lastThumbnail=null lastDescription=null      lastActiveTime=6229735 (inactive for 357s)      * Hist #4: ActivityRecord{4279d2d8 u0 com.iderzheng/.SingleTopActivity t25}          packageName=com.iderzheng processName=com.iderzheng          launchedFromUid=10124 launchedFromPackage=com.iderzheng userId=0          app=ProcessRecord{4312cbb0 3700:com.iderzheng/u0a124}          Intent { cmp=com.iderzheng/.SingleTopActivity bnds=[328,580][656,870] }          frontOfTask=false task=TaskRecord{42b0ee20 #25 I=com.iderzheng/.SingleTaskActivity U=0 sz=5}          taskAffinity=com.iderzheng          realActivity=com.iderzheng/.SingleTopActivity          baseDir=/data/app/com.iderzheng-1.apk          dataDir=/data/data/com.iderzheng          stateNotNeeded=false componentSpecified=true mActivityType=0          compat={320dpi} labelRes=0x7f0a0013 icon=0x7f020057 theme=0x7f0b0000          config={1.0 310mcc?mnc en_US ldltr sw384dp w384dp h567dp 320dpi nrml port finger -keyb/v/h -nav/h s.7}          launchFailed=false launchCount=0 lastLaunchTime=-1h40m33s397ms          haveState=false icicle=null          state=RESUMED stopped=false delayedResume=false finishing=false          keysPaused=false inHistory=true visible=true sleeping=false idle=true          fullscreen=true noDisplay=false immersive=false launchMode=1          frozenBeforeDestroy=false thumbnailNeeded=false forceNewConfig=false          mActivityType=APPLICATION_ACTIVITY_TYPE          thumbHolder: 42b0ee20 bm=null desc=null          waitingVisible=false nowVisible=true lastVisibleTime=-5m56s862ms    ... ... ... ...    Running activities (most recent first):      TaskRecord{42b0ee20 #25 I=com.iderzheng/.SingleTaskActivity U=0 sz=5}        Run #7: ActivityRecord{4279d2d8 u0 com.iderzheng/.SingleTopActivity t25}      TaskRecord{429e9558 #24 A=com.iderzheng U=0 sz=1}        Run #6: ActivityRecord{429d5408 u0 com.iderzheng/.SingleInstanceActivity t24}      TaskRecord{42b0ee20 #25 I=com.iderzheng/.SingleTaskActivity U=0 sz=5}        Run #5: ActivityRecord{434c2238 u0 com.iderzheng/.StandardActivity t25}        Run #4: ActivityRecord{42e9e8f8 u0 com.iderzheng/.SingleTopActivity t25}        Run #3: ActivityRecord{42bffdf0 u0 com.iderzheng/.StandardActivity t25}        Run #2: ActivityRecord{42a7e160 u0 com.iderzheng/.SingleTaskActivity t25}      TaskRecord{4282e508 #23 A=com.iderzheng U=0 sz=2}        Run #1: ActivityRecord{429655d8 u0 com.iderzheng/.StandardActivity t23}        Run #0: ActivityRecord{429564e0 u0 com.iderzheng/.MainActivity t23}   ... ... ... ...  Recent tasks:  ... ... ... ...

整个log显示了当前所有在运行的任务栈，它们的id分别是什么。对于每个Task，也有Activity数量等信息，同时也列出了其中的Activity列表，并且对于每个Activity也有比较详细的描述，比如启动它的Intent的内容。

如果觉得内容过多，只想看看栈的内容，也可以直接跳到”Running activities (most recent first)”那部分，比较简洁而又明了的列出了栈中得Activity列表，就能知道当按下返回键的时候会应该会回到哪个Activity以后是要退出程序。

对于”Running activitie”s的内容在dumpsys activity中就有，并不需要dumpsys activity activities，也可以用下边的指令来限制仅输出”Running activities”列表：

adb shell dumpsys activtiy activities | sed -En -e '/Running activities/,Run #0/p'

[java] view plaincopy

1. <span style="font-family:Arial,Helvetica,sans-serif; font-size:12px; background-color:rgb(240,240,240)">adb shell dumpsys activity activities </span><span class="sy0" style="font-family:inherit; font-size:12px; margin:0px; padding:0px; border:0px; font-weight:inherit; font-style:inherit; vertical-align:baseline; color:rgb(51,153,51)">|</span><span style="font-family:Arial,Helvetica,sans-serif; font-size:12px; background-color:rgb(240,240,240)"> sed </span><span class="sy0" style="font-family:inherit; font-size:12px; margin:0px; padding:0px; border:0px; font-weight:inherit; font-style:inherit; vertical-align:baseline; color:rgb(51,153,51)">-</span><span style="font-family:Arial,Helvetica,sans-serif; font-size:12px; background-color:rgb(240,240,240)">En </span><span class="sy0" style="font-family:inherit; font-size:12px; margin:0px; padding:0px; border:0px; font-weight:inherit; font-style:inherit; vertical-align:baseline; color:rgb(51,153,51)">-</span><span style="font-family:Arial,Helvetica,sans-serif; font-size:12px; background-color:rgb(240,240,240)">e </span><span class="st0" style="font-family:inherit; font-size:12px; margin:0px; padding:0px; border:0px; font-weight:inherit; font-style:inherit; vertical-align:baseline; color:rgb(0,0,255)">'/Running activities/,/Run #0/p'</span>  

缺点

很明显的看出，使用adb shell的相对于之前的方式的明显好处就是不需要添加额外的代码，而且任务栈的信息也更加详尽。但是同样的它只能输出Activity的类名，对于具体属性没有记录。