Android关于Task的一些实践之SingleTask, SingleInstance跟TaskAffinity
Android关于Task的一些实践之SingleTask, SingleInstance和TaskAffinity
可以看到三个Activity,都是在同个Task中的。
再来看看其结果,如下:
发现虽然定义了SingleTask,但Second Activity和Main Activity还是在同一个Task中,这跟我们期望的不符,原因其实在于,设置了launchMode = SingleTask启动的Activity,在启动的时候,会去查找跟它的taskAffinity相同的task,如果存在这样一个task,就在这个task中启动,如果不存在这样一个task,才创建一个新的task,并在新task中启动。
下面是结果,启动的顺序是Main Activity->Second Activity->Main Activity -> Second Activity -> Third Activity
在上面的结果中,可以看到在启动Second Activity的时候,的确是在一个新的Task中启动了,Second Activity是这个Task中的根Activity,而由Second Activity启动的Third Activity也是在这个Task中启动的。
下面是结果:
下面来看看结果,如下:
果然,如我们期望的那样,都是在一个新的Task中启动当前的Activity的。
上一篇文章粗略地介绍了一下关于Android中Task的基本知识,不过实践才是检验真理的唯一标准,所以,今天就来试验一下Task中的launchMode是否真的实现了文档所说的那样。
首先,定义三个Activity,MainActivity打开SecondActivity,SecondActivity打开ThirdActivity,如下所示:
下面,我们定义Second Activity的Launch Mode,分别有下面几种情况:
1)Standard(即不定义)
首先是默认情况下,什么都不定义,如下:
<application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" > <activity android:name="com.lms.taskdemo.MainActivity" android:label="@string/app_name" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <activity android:name="com.lms.taskdemo.SecondActivity"> </activity> <activity android:name="com.lms.taskdemo.ThirdActivity" > </activity> </application>顺序打开三个Activity,看看结果:
04-21 15:23:28.373: V/com.lms.taskdemo(20473): Task : 70 04-21 15:23:28.373: V/com.lms.taskdemo(20473): Base activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.MainActivity} 04-21 15:23:28.373: V/com.lms.taskdemo(20473): Current activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.MainActivity} 04-21 15:23:28.373: V/com.lms.taskdemo(20473): Number of activities : 1 04-21 15:23:28.373: V/com.lms.taskdemo(20473): Number of running activities: 1 04-21 15:23:31.336: V/com.lms.taskdemo(20473): Task : 70 04-21 15:23:31.336: V/com.lms.taskdemo(20473): Base activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.MainActivity} 04-21 15:23:31.336: V/com.lms.taskdemo(20473): Current activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.SecondActivity} 04-21 15:23:31.336: V/com.lms.taskdemo(20473): Number of activities : 2 04-21 15:23:31.336: V/com.lms.taskdemo(20473): Number of running activities: 2 04-21 15:23:33.999: V/com.lms.taskdemo(20473): Task : 70 04-21 15:23:33.999: V/com.lms.taskdemo(20473): Base activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.MainActivity} 04-21 15:23:33.999: V/com.lms.taskdemo(20473): Current activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.ThirdActivity} 04-21 15:23:33.999: V/com.lms.taskdemo(20473): Number of activities : 3 04-21 15:23:33.999: V/com.lms.taskdemo(20473): Number of running activities: 3
可以看到三个Activity,都是在同个Task中的。
2)SingleTask
为Second Activity,定义其launch mode 为 “singleTask”,如下:
<application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" > <activity android:name="com.lms.taskdemo.MainActivity" android:label="@string/app_name" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <activity android:name="com.lms.taskdemo.SecondActivity" android:launchMode="singleTask"> </activity> <activity android:name="com.lms.taskdemo.ThirdActivity" > </activity> </application>
再来看看其结果,如下:
04-22 10:31:26.197: V/com.lms.taskdemo(924): Task : 162 04-22 10:31:26.217: V/com.lms.taskdemo(924): Base activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.MainActivity} 04-22 10:31:26.217: V/com.lms.taskdemo(924): Current activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.MainActivity} 04-22 10:31:26.217: V/com.lms.taskdemo(924): Number of activities : 1 04-22 10:31:26.217: V/com.lms.taskdemo(924): Number of running activities: 1 04-22 10:31:31.112: V/com.lms.taskdemo(924): Task : 162 04-22 10:31:31.112: V/com.lms.taskdemo(924): Base activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.MainActivity} 04-22 10:31:31.112: V/com.lms.taskdemo(924): Current activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.SecondActivity} 04-22 10:31:31.112: V/com.lms.taskdemo(924): Number of activities : 2 04-22 10:31:31.112: V/com.lms.taskdemo(924): Number of running activities: 2 04-22 10:31:32.884: V/com.lms.taskdemo(924): Task : 162 04-22 10:31:32.884: V/com.lms.taskdemo(924): Base activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.MainActivity} 04-22 10:31:32.884: V/com.lms.taskdemo(924): Current activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.ThirdActivity} 04-22 10:31:32.884: V/com.lms.taskdemo(924): Number of activities : 3 04-22 10:31:32.884: V/com.lms.taskdemo(924): Number of running activities: 2
发现虽然定义了SingleTask,但Second Activity和Main Activity还是在同一个Task中,这跟我们期望的不符,原因其实在于,设置了launchMode = SingleTask启动的Activity,在启动的时候,会去查找跟它的taskAffinity相同的task,如果存在这样一个task,就在这个task中启动,如果不存在这样一个task,才创建一个新的task,并在新task中启动。
而在这里,因为没有为各个activity定义taskAffinity,那么默认的affinity值就是包名,那么几个Activity都是一样的,所以就在同样的Task中启动了。
3)Single Task Different Task Affinity
下面,我们分别为Main Activity和 Second Activity设置不同的TaskAffinity值,如下:
<application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" > <activity android:name="com.lms.taskdemo.MainActivity" android:label="@string/app_name" android:taskAffinity="com.lms.taskdemo.MainActivity" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <activity android:name="com.lms.taskdemo.SecondActivity" android:launchMode="singleTask" android:taskAffinity="com.lms.taskdemo.SecondActivity" > </activity> <activity android:name="com.lms.taskdemo.ThirdActivity" > </activity> </application>
下面是结果,启动的顺序是Main Activity->Second Activity->Main Activity -> Second Activity -> Third Activity
04-22 10:26:27.818: V/com.lms.taskdemo(32677): Task : 151 04-22 10:26:27.818: V/com.lms.taskdemo(32677): Base activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.MainActivity} 04-22 10:26:27.818: V/com.lms.taskdemo(32677): Current activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.MainActivity} 04-22 10:26:27.818: V/com.lms.taskdemo(32677): Number of activities : 1 04-22 10:26:27.818: V/com.lms.taskdemo(32677): Number of running activities: 1 04-22 10:26:31.362: V/com.lms.taskdemo(32677): Task : 152 04-22 10:26:31.362: V/com.lms.taskdemo(32677): Base activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.SecondActivity} 04-22 10:26:31.362: V/com.lms.taskdemo(32677): Current activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.SecondActivity} 04-22 10:26:31.372: V/com.lms.taskdemo(32677): Number of activities : 1 04-22 10:26:31.372: V/com.lms.taskdemo(32677): Number of running activities: 1 04-22 10:26:36.558: V/com.lms.taskdemo(32677): Task : 151 04-22 10:26:36.558: V/com.lms.taskdemo(32677): Base activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.MainActivity} 04-22 10:26:36.558: V/com.lms.taskdemo(32677): Current activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.MainActivity} 04-22 10:26:36.558: V/com.lms.taskdemo(32677): Number of activities : 1 04-22 10:26:36.558: V/com.lms.taskdemo(32677): Number of running activities: 1 04-22 10:26:39.401: V/com.lms.taskdemo(32677): Task : 153 04-22 10:26:39.401: V/com.lms.taskdemo(32677): Base activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.SecondActivity} 04-22 10:26:39.401: V/com.lms.taskdemo(32677): Current activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.SecondActivity} 04-22 10:26:39.401: V/com.lms.taskdemo(32677): Number of activities : 1 04-22 10:26:39.401: V/com.lms.taskdemo(32677): Number of running activities: 1 04-22 10:26:41.123: V/com.lms.taskdemo(32677): Task : 153 04-22 10:26:41.123: V/com.lms.taskdemo(32677): Base activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.SecondActivity} 04-22 10:26:41.123: V/com.lms.taskdemo(32677): Current activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.ThirdActivity} 04-22 10:26:41.123: V/com.lms.taskdemo(32677): Number of activities : 2 04-22 10:26:41.123: V/com.lms.taskdemo(32677): Number of running activities: 2
在上面的结果中,可以看到在启动Second Activity的时候,的确是在一个新的Task中启动了,Second Activity是这个Task中的根Activity,而由Second Activity启动的Third Activity也是在这个Task中启动的。
4)Single Instance
下面,我们再来看看Single Instance,同样的,先不定义Task Affinity,在AndroidManifest文件中定义如下:
<application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" > <activity android:name="com.lms.taskdemo.MainActivity" android:label="@string/app_name"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <activity android:name="com.lms.taskdemo.SecondActivity" android:launchMode="singleInstance"> </activity> <activity android:name="com.lms.taskdemo.ThirdActivity" > </activity> </application>
04-22 10:29:43.207: V/com.lms.taskdemo(682): Task : 159 04-22 10:29:43.207: V/com.lms.taskdemo(682): Base activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.MainActivity} 04-22 10:29:43.207: V/com.lms.taskdemo(682): Current activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.MainActivity} 04-22 10:29:43.207: V/com.lms.taskdemo(682): Number of activities : 1 04-22 10:29:43.207: V/com.lms.taskdemo(682): Number of running activities: 1 04-22 10:29:46.580: V/com.lms.taskdemo(682): Task : 160 04-22 10:29:46.580: V/com.lms.taskdemo(682): Base activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.SecondActivity} 04-22 10:29:46.580: V/com.lms.taskdemo(682): Current activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.SecondActivity} 04-22 10:29:46.580: V/com.lms.taskdemo(682): Number of activities : 1 04-22 10:29:46.580: V/com.lms.taskdemo(682): Number of running activities: 1 04-22 10:29:48.202: V/com.lms.taskdemo(682): Task : 159 04-22 10:29:48.202: V/com.lms.taskdemo(682): Base activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.MainActivity} 04-22 10:29:48.202: V/com.lms.taskdemo(682): Current activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.ThirdActivity} 04-22 10:29:48.202: V/com.lms.taskdemo(682): Number of activities : 2 04-22 10:29:48.202: V/com.lms.taskdemo(682): Number of running activities: 1 04-22 10:29:57.112: V/com.lms.taskdemo(682): Task : 160 04-22 10:29:57.112: V/com.lms.taskdemo(682): Base activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.SecondActivity} 04-22 10:29:57.112: V/com.lms.taskdemo(682): Current activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.SecondActivity} 04-22 10:29:57.112: V/com.lms.taskdemo(682): Number of activities : 1 04-22 10:29:57.112: V/com.lms.taskdemo(682): Number of running activities: 1可以看到启动Second Activity的时候,是在新的Task中,而当启动Third Activity的时候,它又跑回原来的Task中去了,这是跟文档描述中符合的,的确是新建的Task中只能有且仅有一个Activity。而由于我们没有定义Task Affinity,所以当启动Third Activity的时候,它就会去找相同Affinity的task,所以就会找到原来的Task,也即是说,如果定义了TaskAffinity的话,那以Third Activity就应该在新的Task中创建了,下面就来验证一下。
5)Single Instance Different Affinity
在配置文件中定义如下:
<application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" > <activity android:name="com.lms.taskdemo.MainActivity" android:label="@string/app_name" android:taskAffinity="com.lms.taskdemo.MainActivity" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <activity android:name="com.lms.taskdemo.SecondActivity" android:launchMode="singleInstance" android:taskAffinity="com.lms.taskdemo.SecondActivity" > </activity> <activity android:name="com.lms.taskdemo.ThirdActivity" > </activity> </application>
下面来看看结果,如下:
04-22 10:27:58.866: V/com.lms.taskdemo(391): Task : 155 04-22 10:27:58.866: V/com.lms.taskdemo(391): Base activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.MainActivity} 04-22 10:27:58.866: V/com.lms.taskdemo(391): Current activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.MainActivity} 04-22 10:27:58.866: V/com.lms.taskdemo(391): Number of activities : 1 04-22 10:27:58.866: V/com.lms.taskdemo(391): Number of running activities: 1 04-22 10:28:00.677: V/com.lms.taskdemo(391): Task : 156 04-22 10:28:00.677: V/com.lms.taskdemo(391): Base activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.SecondActivity} 04-22 10:28:00.677: V/com.lms.taskdemo(391): Current activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.SecondActivity} 04-22 10:28:00.677: V/com.lms.taskdemo(391): Number of activities : 1 04-22 10:28:00.677: V/com.lms.taskdemo(391): Number of running activities: 1 04-22 10:28:02.309: V/com.lms.taskdemo(391): Task : 157 04-22 10:28:02.309: V/com.lms.taskdemo(391): Base activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.ThirdActivity} 04-22 10:28:02.309: V/com.lms.taskdemo(391): Current activity : ComponentInfo{com.lms.taskdemo/com.lms.taskdemo.ThirdActivity} 04-22 10:28:02.309: V/com.lms.taskdemo(391): Number of activities : 1 04-22 10:28:02.309: V/com.lms.taskdemo(391): Number of running activities: 1
果然,如我们期望的那样,都是在一个新的Task中启动当前的Activity的。
总结:
当使用Launch Mode 来改变系统默认的任务调度的时候,如果是用到Single Task或者Single Instance的时候,还要注意到Affinity的使用,要跟Affinity配合使用,可能才能达到我们期望中的效果。而Affinity,其实是Android提供的一个表从属意义的参数,类似于一个Tag值,它表明当前Activity属于哪一个Tag,相当的Affinity值的Activity,如果不使用其他的标志,如Single Instance之类,那么都会在存在于同一个task中。一般情况下,我们并不定义Task
Affinity值,则其默认的值就是当前App的包名。
结束。