android 启动模式(二)

前面我们了解了android的四大启动模式，下面我们以实例来看下各个启动模式：

1、standard:

这里我们定义一个MainActivity和一个ActivityA,点击MainActivity的时候启动ActivityA,点击ActivityA的时候还是启动ActivityA,这里的MainActivity和AcitivtyA都为standard模式：

        <activity
            android:name=".MainActivity"
            android:label="@string/title_activity_main" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
				
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".ActivityA"  
            
          android:label="@string/title_activityA">  
       <intent-filter>  
           <action android:name="com.leaves.ipanel.ActivityA"/>  
           <category android:name="android.intent.category.DEFAULT"/>  
       </intent-filter>  
        </activity> 

部分代码:

MainActivityA中

	public void onClick(View arg0) {
		// TODO Auto-generated method stub
		Log.i(TAG, "--onClick--task id = " + getCurrentTaskId());
		Intent intent = new Intent("com.leaves.ipanel.ActivityA");    
  
	    startActivity(intent); 
	}

ActivityA中：

	public void onClick(View v) {
		// TODO Auto-generated method stub
		Log.i(TAG, "--onClick--task id = " + getCurrentTaskId());	
		
		Intent intent = new Intent("com.leaves.ipanel.ActivityA");  

		startActivity(intent); 
	}

这个时候我们查看堆栈：

ACTIVITY MANAGER ACTIVITIES (dumpsys activity activities)
  Main stack:
    TaskRecord{423d56d0 #15 A com.leaves.ipanel U 0}
    Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.leaves.ipanel/.MainActivity }
      Hist #5: ActivityRecord{41604368 u0 com.leaves.ipanel/.ActivityA}
        Intent { act=com.leaves.ipanel.ActivityA cmp=com.leaves.ipanel/.ActivityA }
        ProcessRecord{413379d8 4999:com.leaves.ipanel/u0a10061}
      Hist #4: ActivityRecord{415d8330 u0 com.leaves.ipanel/.ActivityA}
        Intent { act=com.leaves.ipanel.ActivityA cmp=com.leaves.ipanel/.ActivityA }
        ProcessRecord{413379d8 4999:com.leaves.ipanel/u0a10061}
      Hist #3: ActivityRecord{41403278 u0 com.leaves.ipanel/.ActivityA}
        Intent { act=com.leaves.ipanel.ActivityA cmp=com.leaves.ipanel/.ActivityA }
        ProcessRecord{413379d8 4999:com.leaves.ipanel/u0a10061}
      Hist #2: ActivityRecord{413cc520 u0 com.leaves.ipanel/.ActivityA}
        Intent { act=com.leaves.ipanel.ActivityA cmp=com.leaves.ipanel/.ActivityA }
        ProcessRecord{413379d8 4999:com.leaves.ipanel/u0a10061}
      Hist #1: ActivityRecord{4132a3d0 u0 com.leaves.ipanel/.MainActivity}
        Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.leaves.ipanel/.MainActivity }
        ProcessRecord{413379d8 4999:com.leaves.ipanel/u0a10061}
    TaskRecord{41350f60 #2 A com.android.launcher U 0}
    Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000000 cmp=com.android.launcher/com.android.launcher2.Launcher }
      Hist #0: ActivityRecord{41616790 u0 com.android.launcher/com.android.launcher2.Launcher}
        Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000000 cmp=com.android.launcher/com.android.launcher2.Launcher }
        ProcessRecord{41615818 628:com.android.launcher/1000}

可见即使栈顶是A,也会新建A的实例

查看log:

I/ActivityA( 5226): onUserInteraction
I/ActivityA( 5226): onUserLeaveHint
I/ActivityA( 5226): --onPause--task id = 17
I/ActivityA( 5226): --onCreate--task id = 17
I/ActivityA( 5226): --onStart--task id = 17
I/ActivityA( 5226): --onResume--task id = 17

每次都有onCreate，可见每次都新建了一个ActivityA的实例。

2、singleTop

我们把ActivityA的启动模式改为singleTop:

<activity android:name=".ActivityA"  
            android:launchMode="singleTop"
          android:label="@string/title_activityA">  
       <intent-filter>  
           <action android:name="com.leaves.ipanel.ActivityA"/>  
           <category android:name="android.intent.category.DEFAULT"/>  
       </intent-filter>  

在按 上面的操作一次，查看堆栈：

ACTIVITY MANAGER ACTIVITIES (dumpsys activity activities)
  Main stack:
    TaskRecord{4245b570 #16 A com.leaves.ipanel U 0}
    Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.leaves.ipanel/.MainActivity }
      Hist #2: ActivityRecord{4132a3d0 u0 com.leaves.ipanel/.ActivityA}
        Intent { act=com.leaves.ipanel.ActivityA cmp=com.leaves.ipanel/.ActivityA }
        ProcessRecord{413bccb8 5135:com.leaves.ipanel/u0a10061}
      Hist #1: ActivityRecord{41317bc8 u0 com.leaves.ipanel/.MainActivity}
        Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.leaves.ipanel/.MainActivity }
        ProcessRecord{413bccb8 5135:com.leaves.ipanel/u0a10061}
    TaskRecord{41350f60 #2 A com.android.launcher U 0}
    Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000000 cmp=com.android.launcher/com.android.launcher2.Launcher }
      Hist #0: ActivityRecord{41616790 u0 com.android.launcher/com.android.launcher2.Launcher}
        Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000000 cmp=com.android.launcher/com.android.launcher2.Launcher }
        ProcessRecord{41615818 628:com.android.launcher/1000}

可见无论按多少次，都只有一个Activity的实例。但是当我们查看log,每次都会调用

I/ActivityA( 5135): --onPause--task id = 16
I/ActivityA( 5135): --onNewIntent--task id = 16
I/ActivityA( 5135): --onResume--task id = 16

onNewIntent都被调用。

3、singleTask

我们把A的启动模式设置为singleTask

<activity android:name=".ActivityA"  
           android:launchMode="singleTask"
          android:label="@string/title_activityA">  
       <intent-filter>  
           <action android:name="com.leaves.ipanel.ActivityA"/>  
           <category android:name="android.intent.category.DEFAULT"/>  
       </intent-filter>  
        </activity> 

再按上面的操作，查看堆栈：

ACTIVITY MANAGER ACTIVITIES (dumpsys activity activities)
  Main stack:
    TaskRecord{423fc600 #21 A com.leaves.ipanel U 0}
    Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.leaves.ipanel/.MainActivity }
      Hist #2: ActivityRecord{413c8c70 u0 com.leaves.ipanel/.ActivityA}
        Intent { act=com.leaves.ipanel.ActivityA cmp=com.leaves.ipanel/.ActivityA }
        ProcessRecord{413e6690 5678:com.leaves.ipanel/u0a10061}
      Hist #1: ActivityRecord{4132a3d0 u0 com.leaves.ipanel/.MainActivity}
        Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.leaves.ipanel/.MainActivity }
        ProcessRecord{413e6690 5678:com.leaves.ipanel/u0a10061}
    TaskRecord{41350f60 #2 A com.android.launcher U 0}
    Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000000 cmp=com.android.launcher/com.android.launcher2.Launcher }
      Hist #0: ActivityRecord{41616790 u0 com.android.launcher/com.android.launcher2.Launcher}
        Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000000 cmp=com.android.launcher/com.android.launcher2.Launcher }
        ProcessRecord{41615818 628:com.android.launcher/1000}

可以看到，这中模式也是只有一个实例，仔细看上面的堆栈log,ActivityA并不是该task的根activity，我们在源码中ActivityStack.java的源码中startActivityUncheckedLocked函数也可以发现，当我们以方式启动时，会先在系统中查找属性值affinity等于它的属性值taskAffinity的任务存在；如果存在这样的任务，它就会在这个任务中启动（此后在根据第2条检查），否则就会在新任务中启动。因此，如果我们想要设置了"singleTask"启动模式的Activity在新的任务中启动，就要为它设置一个独立的taskAffinity属性值。再来看一下log:

I/ActivityA( 5321): --onClick--task id = 18
I/ActivityA( 5321): --onPause--task id = 18
I/ActivityA( 5321): --onNewIntent--task id = 18
I/ActivityA( 5321): --onResume--task id = 18

当该activity存在时，每次点击都调用了onNewIntent。

我们设置一下taskAffinity值

<activity android:name=".ActivityA"  
            android:launchMode="singleInstance"
            android:taskAffinity="com.leaves.ipanel.activityA"
          android:label="@string/title_activityA">  
       <intent-filter>  
           <action android:name="com.leaves.ipanel.ActivityA"/>  
           <category android:name="android.intent.category.DEFAULT"/>  
       </intent-filter>  
        </activity> 

重新操作一下，在来看下堆栈：

ACTIVITY MANAGER ACTIVITIES (dumpsys activity activities)
  Main stack:
    TaskRecord{423d8b50 #27 A com.leaves.ipanel.activityA U 0}
    Intent { act=com.leaves.ipanel.ActivityA cmp=com.leaves.ipanel/.ActivityA }
      Hist #2: ActivityRecord{4133b6a0 u0 com.leaves.ipanel/.ActivityA}
        Intent { act=com.leaves.ipanel.ActivityA cmp=com.leaves.ipanel/.ActivityA }
        ProcessRecord{413379d8 6195:com.leaves.ipanel/u0a10061}
    TaskRecord{42328ea0 #26 A com.leaves.ipanel U 0}
    Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.leaves.ipanel/.MainActivity }
      Hist #1: ActivityRecord{4132a3d0 u0 com.leaves.ipanel/.MainActivity}
        Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.leaves.ipanel/.MainActivity }
        ProcessRecord{413379d8 6195:com.leaves.ipanel/u0a10061}
    TaskRecord{41350f60 #2 A com.android.launcher U 0}
    Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000000 cmp=com.android.launcher/com.android.launcher2.Launcher }
      Hist #0: ActivityRecord{41616790 u0 com.android.launcher/com.android.launcher2.Launcher}
        Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000000 cmp=com.android.launcher/com.android.launcher2.Launcher }         ProcessRecord{41615818 628:com.android.launcher/1000}

这时activityA跟MainActivity在一个新的task中启动

我们改一下，在点击ActicityA的时候启动ActivityB,ActivityB的启动模式为standard:

       <activity android:name=".ActivityB"  
          android:label="@string/title_activityB">  
       <intent-filter>  
           <action android:name="com.leaves.ipanel.ActivityB"/>  
           <category android:name="android.intent.category.DEFAULT"/>  
       </intent-filter>  
        </activity> 

在看一下堆栈：

ACTIVITY MANAGER ACTIVITIES (dumpsys activity activities)
  Main stack:
    TaskRecord{416101f8 #29 A com.leaves.ipanel.activityA U 0}
    Intent { act=com.leaves.ipanel.ActivityA cmp=com.leaves.ipanel/.ActivityA }
      Hist #3: ActivityRecord{413c8c70 u0 com.leaves.ipanel/.ActivityB}
        Intent { act=com.leaves.ipanel.ActivityB cmp=com.leaves.ipanel/.ActivityB }
        ProcessRecord{413400d8 6327:com.leaves.ipanel/u0a10061}
      Hist #2: ActivityRecord{4133b6a0 u0 com.leaves.ipanel/.ActivityA}
        Intent { act=com.leaves.ipanel.ActivityA cmp=com.leaves.ipanel/.ActivityA }
        ProcessRecord{413400d8 6327:com.leaves.ipanel/u0a10061}
    TaskRecord{422e7510 #28 A com.leaves.ipanel U 0}
    Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.leaves.ipanel/.MainActivity }
      Hist #1: ActivityRecord{4132a3d0 u0 com.leaves.ipanel/.MainActivity}
        Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.leaves.ipanel/.MainActivity }
        ProcessRecord{413400d8 6327:com.leaves.ipanel/u0a10061}
    TaskRecord{41350f60 #2 A com.android.launcher U 0}
    Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000000 cmp=com.android.launcher/com.android.launcher2.Launcher }
      Hist #0: ActivityRecord{41616790 u0 com.android.launcher/com.android.launcher2.Launcher}
        Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000000 cmp=com.android.launcher/com.android.launcher2.Launcher }
        ProcessRecord{41615818 628:com.android.launcher/1000}

从堆栈信息我们可以看出，ActivityB和ActivityA在同一个task中

在上面的基础上，再修改一下，点击ActivityB时启动ActivityA,这个时候堆栈：

ACTIVITY MANAGER ACTIVITIES (dumpsys activity activities)
  Main stack:
    TaskRecord{41675ee8 #36 A com.leaves.ipanel.ActivityA U 0}
    Intent { act=com.leaves.ipanel.ActivityA flg=0x10000000 cmp=com.leaves.ipanel/.ActivityA }
      Hist #2: ActivityRecord{413c8c70 u0 com.leaves.ipanel/.ActivityA}
        Intent { act=com.leaves.ipanel.ActivityA cmp=com.leaves.ipanel/.ActivityA }
        ProcessRecord{413400d8 6753:com.leaves.ipanel/u0a10061}
    TaskRecord{4163bc50 #35 A com.leaves.ipanel U 0}
    Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.leaves.ipanel/.MainActivity }
      Hist #1: ActivityRecord{4132a3d0 u0 com.leaves.ipanel/.MainActivity}
        Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.leaves.ipanel/.MainActivity }
        ProcessRecord{413400d8 6753:com.leaves.ipanel/u0a10061}
    TaskRecord{41350f60 #2 A com.android.launcher U 0}
    Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000000 cmp=com.android.launcher/com.android.launcher2.Launcher }
      Hist #0: ActivityRecord{41616790 u0 com.android.launcher/com.android.launcher2.Launcher}
        Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000000 cmp=com.android.launcher/com.android.launcher2.Launcher }
        ProcessRecord{41615818 628:com.android.launcher/1000}

可以看到,ActivityA回到前台，ActivityA上面的ActivityB被销毁，原因同样在startActivityUncheckedLocked函数，当启动模式为LAUNCH_SINGLE_TASK，并且该task已经存在时，会调用performClearTaskLocked

4、singleInstance

我们把ActivityA的启动模式改为singleInstance，并把他的taskAffinity属性去掉：

<activity android:name=".ActivityA"  
            android:launchMode="singleInstance"
          android:label="@string/title_activityA">  
       <intent-filter>  
           <action android:name="com.leaves.ipanel.ActivityA"/>  
           <category android:name="android.intent.category.DEFAULT"/>  
       </intent-filter>  
        </activity> 

操作一下，看一下堆栈：

ACTIVITY MANAGER ACTIVITIES (dumpsys activity activities)
  Main stack:
    TaskRecord{413a62c8 #31 A com.leaves.ipanel U 0}
    Intent { act=com.leaves.ipanel.ActivityA cmp=com.leaves.ipanel/.ActivityA }
      Hist #2: ActivityRecord{4133b6a0 u0 com.leaves.ipanel/.ActivityA}
        Intent { act=com.leaves.ipanel.ActivityA cmp=com.leaves.ipanel/.ActivityA }
        ProcessRecord{413379d8 6421:com.leaves.ipanel/u0a10061}
    TaskRecord{41455490 #30 A com.leaves.ipanel U 0}
    Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.leaves.ipanel/.MainActivity }
      Hist #1: ActivityRecord{4132a3d0 u0 com.leaves.ipanel/.MainActivity}
        Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.leaves.ipanel/.MainActivity }
        ProcessRecord{413379d8 6421:com.leaves.ipanel/u0a10061}
    TaskRecord{41350f60 #2 A com.android.launcher U 0}
    Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000000 cmp=com.android.launcher/com.android.launcher2.Launcher }
      Hist #0: ActivityRecord{41616790 u0 com.android.launcher/com.android.launcher2.Launcher}
        Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000000 cmp=com.android.launcher/com.android.launcher2.Launcher }
        ProcessRecord{41615818 628:com.android.launcher/1000}

可以看到，即使没有 taskAffinity属性，我们也会在一个新的task中启动该activity.而不像singleTask，这个原因同样在startActivityUncheckedLocked函数中，以singleInstance启动跟singleTask启动的查找是不一样的，singleInstance启动查找可复用的task是调用findActivityLocked，看这个函数我们就知道原因了，他不会去对比taskAffinity,二十比较ComponentName

相应的Log:

I/ActivityA( 6421): --onClick--task id = 31
I/ActivityA( 6421): --onPause--task id = 31
I/ActivityA( 6421): --onNewIntent--task id = 31
I/ActivityA( 6421): --onResume--task id = 31

我们在ActivityA中启动ActivityB(standard模式)在看看堆栈：

ACTIVITY MANAGER ACTIVITIES (dumpsys activity activities)
  Main stack:
    TaskRecord{422f0e28 #32 A com.leaves.ipanel U 0}
    Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.leaves.ipanel/.MainActivity }
      Hist #3: ActivityRecord{413e6e10 u0 com.leaves.ipanel/.ActivityB}
        Intent { act=com.leaves.ipanel.ActivityB flg=0x400000 cmp=com.leaves.ipanel/.ActivityB }
        ProcessRecord{413400d8 6541:com.leaves.ipanel/u0a10061}
      Hist #2: ActivityRecord{4132a3d0 u0 com.leaves.ipanel/.MainActivity}
        Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.leaves.ipanel/.MainActivity }
        ProcessRecord{413400d8 6541:com.leaves.ipanel/u0a10061}
    TaskRecord{4140fd08 #33 A com.leaves.ipanel U 0}
    Intent { act=com.leaves.ipanel.ActivityA cmp=com.leaves.ipanel/.ActivityA }
      Hist #1: ActivityRecord{4133b6a0 u0 com.leaves.ipanel/.ActivityA}
        Intent { act=com.leaves.ipanel.ActivityA cmp=com.leaves.ipanel/.ActivityA }
        ProcessRecord{413400d8 6541:com.leaves.ipanel/u0a10061}
    TaskRecord{41350f60 #2 A com.android.launcher U 0}
    Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000000 cmp=com.android.launcher/com.android.launcher2.Launcher }
      Hist #0: ActivityRecord{41616790 u0 com.android.launcher/com.android.launcher2.Launcher}
        Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000000 cmp=com.android.launcher/com.android.launcher2.Launcher }
        ProcessRecord{41615818 628:com.android.launcher/1000}

可以看到虽然我们是从ActivityA中启动ActivityB,但Activity并没有放在ActivityA的task中，而是放在了MainActivity的task中，因为两者具有相同的 taskAffinity，虽然ActivityA也具有相同的taskAffinity，但由于启动模式为singleInstance，我们不能不activity加入到里面

总结：

1. 如何决定所属task
“standard”和”singleTop”的activity的目标task，和收到的Intent的发送者在同一个task内，除非intent包括参数FLAG_ACTIVITY_NEW_TASK。
如果提供了FLAG_ACTIVITY_NEW_TASK参数，可能会启动到别的task里。
“singleTask”会查找是否存在合适的task(taskAffinity相同)，有的话则在其中启动，且不一定是根Activity,没有的话新建一个task。
”singleInstance”总是把activity作为一个task的根元素，他们不会被启动到一个其他task里。
 
2. 是否允许多个实例
“standard”和”singleTop”可以被实例化多次，并且可以存在于不同的task中，且一个task可以包括一个activity的多个实例；
“singleTask”和”singleInstance”则限制只生成一个实例，并且singleInstance必须是task的根元素。
singleTop要求如果创建intent的时候栈顶已经有要创建 的Activity的实例，则将intent发送给该实例，而不发送给新的实例。
 
3. 是否允许其它activity存在于本task内
“singleInstance”独占一个task，其它activity不能存在那个task里；如果它启动了一个新的activity，不管新的activity的launch mode 如何，新的activity都将会到别的task里运行（如同加了FLAG_ACTIVITY_NEW_TASK参数）。
而另外三种模式，则可以和其它activity共存。
 
4. 是否每次都生成新实例
“standard”对于没一个启动Intent都会生成一个activity的新实例；
“singleTop”的activity如果在task的栈顶的话，则不生成新的该activity的实例，直接使用栈顶的实例，否则，生成该activity的实例。
比如现在task栈元素为A-B-C-D（D在栈顶），这时候给D发一个启动intent，如果D是 “standard”的，则生成D的一个新实例，栈变为A－B－C－D－D。
如果D是singleTop的话，则不会生产D的新实例，栈状态仍为A-B-C-D
如果这时候给B发Intent的话，不管B的launchmode是”standard” 还是 “singleTop” ，都会生成B的新实例，栈状态变为A-B-C-D-B。
 
“singleInstance”是其所在栈的唯一activity，它会每次都被重用。
 
“singleTask”如果在栈顶，则接受intent，如果不在栈顶，则会把它切换到前台，并销毁其上的Activity。