Activity 使用总结

作者: SevChen | 来源:发表于2018-04-27 17:17 被阅读21次

Activity使用详解

LaunchMode

standard

在AndroidManifest中声明

<activity android:name=".lm_standard.ActivityA"
            android:launchMode="standard"/>
            
// java
public class ActivityA extends Activity {

    private static final String TAG = "lm_standard_ActivityA";

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_standard_a);

        Log.d(TAG, "onCreate " + this + " tasksId -> " + getTaskId());
    }

    public void startA(View view) {

        Log.d(TAG, "startA from " + this);

        Intent activity = new Intent(this, ActivityA.class);
        startActivity(activity);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();

        Log.d(TAG, "onDestroy " + this);
    }
}

进入ActivityA后，连续触发了2次startA，然后陆续返回3次：

04-26 17:49:03.065 25218-25218/com.seven.www.activityusage D/lm_standard_ActivityA: onCreate com.seven.www.activityusage.lm_standard.ActivityA@c2ba76d tasksId -> 280
04-26 17:49:04.225 25218-25218/com.seven.www.activityusage D/lm_standard_ActivityA: startA from com.seven.www.activityusage.lm_standard.ActivityA@c2ba76d
04-26 17:49:04.337 25218-25218/com.seven.www.activityusage D/lm_standard_ActivityA: onCreate com.seven.www.activityusage.lm_standard.ActivityA@9990b77 tasksId -> 280
04-26 17:49:05.534 25218-25218/com.seven.www.activityusage D/lm_standard_ActivityA: startA from com.seven.www.activityusage.lm_standard.ActivityA@9990b77
04-26 17:49:05.650 25218-25218/com.seven.www.activityusage D/lm_standard_ActivityA: onCreate com.seven.www.activityusage.lm_standard.ActivityA@286e87b tasksId -> 280

04-26 17:49:11.312 25218-25218/com.seven.www.activityusage D/lm_standard_ActivityA: onDestroy com.seven.www.activityusage.lm_standard.ActivityA@286e87b
04-26 17:49:13.033 25218-25218/com.seven.www.activityusage D/lm_standard_ActivityA: onDestroy com.seven.www.activityusage.lm_standard.ActivityA@9990b77
04-26 17:49:15.450 25218-25218/com.seven.www.activityusage D/lm_standard_ActivityA: onDestroy com.seven.www.activityusage.lm_standard.ActivityA@c2ba76d

可以看出每次都会启动一个全新的Activity，并且放在同一个task里面，返回也是按照创建顺序的倒叙逐个销毁。

singleTop

添加了两个Activity, 分别为ActivityB ActivityC，其中ActivityB launchMode为singleTop, ActivityC 的LaunchMode为standard.

// ActivityB
public class ActivityB extends Activity {

    private static final String TAG = "lm_singleTop";

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_singletop_b);

        Log.d(TAG, "onCreate " + this + "  taskId -> " + getTaskId());
    }

    @Override
    protected void onNewIntent(Intent intent) {
        super.onNewIntent(intent);

        Log.d(TAG, "onNewIntent " + this + " taskId -> " + getTaskId());
    }

    public void startB(View view) {
        Log.d(TAG, "startB");
        Intent activity = new Intent(this, ActivityB.class);
        startActivity(activity);
    }

    public void startC(View view) {
        Log.d(TAG, "startC");
        Intent activity = new Intent(this, ActivityC.class);
        startActivity(activity);
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d(TAG, "onDestroy " + this);
    }
}
// ActivityC
public class ActivityC extends Activity {

    private static final String TAG = "lm_singleTop";

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_singletop_c);

        Log.d(TAG, "onCreate " + this + "  taskId -> " + getTaskId());
    }

    public void startB(View view) {
        Log.d(TAG, "startB");
        Intent activity = new Intent(this, ActivityB.class);
        startActivity(activity);
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d(TAG, "onDestroy " + this);
    }
}

进入ActivityB后触发了一次startB，再点击了一下返回：

04-27 09:10:04.838 25444-25444/com.seven.www.activityusage D/lm_singleTop: onCreate com.seven.www.activityusage.lm_singletop.ActivityB@9a6d920  taskId -> 285
04-27 09:10:08.832 25444-25444/com.seven.www.activityusage D/lm_singleTop: startB
04-27 09:10:08.847 25444-25444/com.seven.www.activityusage D/lm_singleTop: onNewIntent com.seven.www.activityusage.lm_singletop.ActivityB@9a6d920 taskId -> 285

04-27 09:10:15.019 25444-25444/com.seven.www.activityusage D/lm_singleTop: onDestroy com.seven.www.activityusage.lm_singletop.ActivityB@9a6d920 taskId -> 284

进入ActivityB依次触发startC -> startB，再点击3次返回：

04-27 09:11:42.972 25444-25444/com.seven.www.activityusage D/lm_singleTop: onCreate com.seven.www.activityusage.lm_singletop.ActivityB@78d9444  taskId -> 285
04-27 09:11:44.321 25444-25444/com.seven.www.activityusage D/lm_singleTop: startC
04-27 09:11:44.408 25444-25444/com.seven.www.activityusage D/lm_singleTop: onCreate com.seven.www.activityusage.lm_singletop.ActivityC@4d57c36  taskId -> 285
04-27 09:11:46.010 25444-25444/com.seven.www.activityusage D/lm_singleTop: startB
04-27 09:11:46.100 25444-25444/com.seven.www.activityusage D/lm_singleTop: onCreate com.seven.www.activityusage.lm_singletop.ActivityB@33043b3  taskId -> 285
04-27 09:12:16.328 25444-25444/com.seven.www.activityusage D/lm_singleTop: onDestroy com.seven.www.activityusage.lm_singletop.ActivityB@33043b3
04-27 09:12:22.529 25444-25444/com.seven.www.activityusage D/lm_singleTop: onDestroy com.seven.www.activityusage.lm_singletop.ActivityC@4d57c36
04-27 09:12:24.426 25444-25444/com.seven.www.activityusage D/lm_singleTop: onDestroy com.seven.www.activityusage.lm_singletop.ActivityB@78d9444

可以看出，如果ActivityB处于栈顶，那么startB不会新建一个Activity，而是触发栈顶Activity的onNewIntent方法。如果ActivityB不处于栈顶，那么startB的结果
和standard的模式是一致的。

singleTask

添加2个Activity，ActivityD和ActivityE，D为singleTask，E为standard:

// ActivityD
public class ActivityD extends Activity {

    private static final String TAG = "lm_singleTask";

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_singletask_d);

        Log.d(TAG, "onCreate " + this + " taskId -> " + getTaskId());
    }

    @Override
    protected void onNewIntent(Intent intent) {
        super.onNewIntent(intent);
        Log.d(TAG, "onNewIntent " + this + " taskId -> " + getTaskId());
    }

    public void startE(View view) {
        Intent activity = new Intent(this, ActivityE.class);
        startActivity(activity);
    }

    public void startD(View view) {
        Intent activity = new Intent(this, ActivityD.class);
        startActivity(activity);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d(TAG, "onDestroy " + this);
    }
}
// ActivityE
public class ActivityE extends ActivityD {
}

进入D，触发2次startE，再触发startD：

04-27 09:43:07.850 26815-26815/com.seven.www.activityusage D/lm_singleTask: onCreate com.seven.www.activityusage.lm_singletask.ActivityD@7dd0052 taskId -> 287
04-27 09:43:27.325 26815-26815/com.seven.www.activityusage D/lm_singleTask: onCreate com.seven.www.activityusage.lm_singletask.ActivityE@b6edeac taskId -> 287
04-27 09:43:28.259 26815-26815/com.seven.www.activityusage D/lm_singleTask: onCreate com.seven.www.activityusage.lm_singletask.ActivityE@5194736 taskId -> 287
04-27 09:43:34.044 26815-26815/com.seven.www.activityusage D/lm_singleTask: onDestroy com.seven.www.activityusage.lm_singletask.ActivityE@b6edeac
04-27 09:43:34.069 26815-26815/com.seven.www.activityusage D/lm_singleTask: onNewIntent com.seven.www.activityusage.lm_singletask.ActivityD@7dd0052 taskId -> 287
04-27 09:43:34.417 26815-26815/com.seven.www.activityusage D/lm_singleTask: onDestroy com.seven.www.activityusage.lm_singletask.ActivityE@5194736

可以看出，当启动D时，如果D已经在栈内，那么不会重新创建D，而是触发D的onNewIntent，并且全部销毁处于D头上的其他Activity。如果D处于栈顶，则退化成singleTop模式。

singleInstance

添加连个Activity，分别为ActivityF和ActivityG，F为singleInstance，G为standard

// ActivityF
public class ActivityF extends Activity {

    private static final String TAG = "lm_singleInstance";

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_singleinstance_f);
        Log.d(TAG, "onCreate " + this + " taskId -> " + getTaskId());
    }

    @Override
    protected void onNewIntent(Intent intent) {
        super.onNewIntent(intent);
        Log.d(TAG, "onNewIntent " + this + " taskId -> " + getTaskId());
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d(TAG, "onDestroy " + this);
    }

    public void startF(View view) {
        Log.d(TAG, "startF");
        Intent activity = new Intent(this, ActivityF.class);
        startActivity(activity);
    }

    public void startG(View view) {
        Log.d(TAG, "startG");
        Intent activity = new Intent(this, ActivityG.class);
        startActivity(activity);
    }
}
// ActivityG
public class ActivityG extends ActivityF {
}

进入G，触发startF -> startG -> startF -> startG，然后陆续点击返回

04-27 10:52:34.069 29785-29785/com.seven.www.activityusage D/lm_singleInstance: onCreate com.seven.www.activityusage.lm_singleinstance.ActivityG@d2e261f taskId -> 313
04-27 10:52:35.310 29785-29785/com.seven.www.activityusage D/lm_singleInstance: startF
04-27 10:52:35.413 29785-29785/com.seven.www.activityusage D/lm_singleInstance: onCreate com.seven.www.activityusage.lm_singleinstance.ActivityF@372e491 taskId -> 314
04-27 10:52:46.427 29785-29785/com.seven.www.activityusage D/lm_singleInstance: startG
04-27 10:52:46.502 29785-29785/com.seven.www.activityusage D/lm_singleInstance: onCreate com.seven.www.activityusage.lm_singleinstance.ActivityG@233f873 taskId -> 313
04-27 10:54:17.462 29785-29785/com.seven.www.activityusage D/lm_singleInstance: startF
04-27 10:54:17.494 29785-29785/com.seven.www.activityusage D/lm_singleInstance: onNewIntent com.seven.www.activityusage.lm_singleinstance.ActivityF@372e491 taskId -> 314
04-27 10:56:53.108 29785-29785/com.seven.www.activityusage D/lm_singleInstance: startG
04-27 10:56:53.188 29785-29785/com.seven.www.activityusage D/lm_singleInstance: onCreate com.seven.www.activityusage.lm_singleinstance.ActivityG@9e4a99a taskId -> 313

04-27 10:58:05.029 29785-29785/com.seven.www.activityusage D/lm_singleInstance: onDestroy com.seven.www.activityusage.lm_singleinstance.ActivityG@9e4a99a
04-27 10:58:06.689 29785-29785/com.seven.www.activityusage D/lm_singleInstance: onDestroy com.seven.www.activityusage.lm_singleinstance.ActivityG@233f873
04-27 10:58:10.425 29785-29785/com.seven.www.activityusage D/lm_singleInstance: onDestroy com.seven.www.activityusage.lm_singleinstance.ActivityG@d2e261f
04-27 10:58:25.168 29785-29785/com.seven.www.activityusage D/lm_singleInstance: onDestroy com.seven.www.activityusage.lm_singleinstance.ActivityF@372e491

可以看出，启动F时，如果F不存在，那么创建新的task，将F加入新的task中；如果F存在，那么就触发F的onNewIntent。从F启动G时，系统切换到G默认的任务，再重新创建G。
因此可以知道，singleTask的Activity独占一个task，即一个task如果含有一个singleInstance的Activity，那么就不能再存在其他Activity了。

FLAG_ACTIVITY_XXX 标识和 taskAffinity

默认情况下，每个Activity的taskAffinity都是包名，Android的最近任务是按照taskAffinity来进行分组的，不同的task如果taskAffinity相同，那么将放在同一个卡片组里面。也就是说，最近任务不是显示每一个任务，而是按照不同的taskAffinity显示其靠前的任务的最顶层Activity

假设存在3个task：

task1: A -> B -> C (taskAffinity1)

task2: D -> E (taskAffinity2)

task3: G (taskAffinity2)

因为只存在2个taskAffinity，所以在最近任务里面只有2个卡片，卡片1显示的 C，卡片2则需要根据实际情况而定：

如果 task2在task stack中比task3靠前，那么显示的就是E
反之显示的是G

查看那个task靠前，可以通过adb shell dumpsys activity activities查看.

注意：如果我们在最近任务里面选择了某个task，那么系统仅仅是将该task调度到最前面，但是和这个task具有相同的taskAffinity的task被放到了最近任务和系统桌面的下面，也就是说，我们永远无法通过返回按键或者最近任务按键回到那些没显示在最近任务里的task了。因此一般来说，设置taskAffinity都不是什么好事情。尽量避免。

FLAG_ACTIVITY_NEW_TASK

如果目标Activity已经在一个task（不能是默认task）中运行了，并且，这次startActivity查找到的任务就是该task，那么这次操作仅仅是将该任务切换到前台，不会创建新的Activity。
如果目标Activity不存在：

1）如果目标Activity设置了taskAffinity，那么系统将创建一个全新的task，然后创建该Activity放在task的里面。
2）如果没有设置taskAffinity，那么系统不会创建task，而是创建该Activity放在默认task里面。(如果设置了singleInstance，那么还是会创建一个新task)

这个FLAG需要和taskAffinity配合使用。

在Android7.0以前，如果使用Service/Application/Broadcast/类型的Context

FLAG_ACTIVITY_CLEAR_TOP

如果目标Activity在task中存在，那么销毁目标Activity上面的Activty，并触发onNewIntent.
如果不存在，那么创建一个新的，加入task栈顶。

这个FLAG和 launchMode:singleTask类似

FLAG_ACTIVITY_SINGLE_TOP

这个FLAG和 launchMode:singleTop类似

FLAG_ACTIVITY_NO_HISTORY

离开Activity后该Activity即销毁，该Activity的onActivityResult也不会触发。

Activity 使用总结

LaunchMode

standard

singleTop

singleTask

singleInstance

FLAG_ACTIVITY_XXX 标识和 taskAffinity

FLAG_ACTIVITY_NEW_TASK

FLAG_ACTIVITY_CLEAR_TOP

FLAG_ACTIVITY_SINGLE_TOP

FLAG_ACTIVITY_NO_HISTORY

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栏目导航

热点阅读

Activity 使用总结

LaunchMode

standard

singleTop

singleTask

singleInstance

FLAG_ACTIVITY_XXX 标识 和 taskAffinity

FLAG_ACTIVITY_NEW_TASK

FLAG_ACTIVITY_CLEAR_TOP

FLAG_ACTIVITY_SINGLE_TOP

FLAG_ACTIVITY_NO_HISTORY

相关文章

网友评论

延伸阅读

深度阅读

栏目导航

热点阅读

FLAG_ACTIVITY_XXX 标识和 taskAffinity