Android 如何避免同一活动的多个实例？
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How to avoid multiple instances of same Activity?
提问by Debojit
In my PoC, I have some Activities, HomeActivity, CreateActivity, SearchActivity, ResultsActivity, ResultDetailsActivity, and UpdateActivity.
在我的 PoC 中，我有一些活动HomeActivity、CreateActivity、SearchActivity、ResultsActivity、ResultDetailsActivity、 和UpdateActivity。
I have two main navigation paths: Createand Search.
我有两个主要的导航路径：Create和Search。
Navigation for the Createpath is as follows: HomeActivity--> CreateActivity-(on complete)-> HomeActivity
创建路径的导航如下：HomeActivity--> CreateActivity-（完成时）->HomeActivity
Navigation for Searchis as follows: HomeActivity--> SearchActivity--> ResultsActivity(ListActivity) --> ResultDetailsActivity--> UpdateActivity-(on complete)-> ResultDetailsActivity(with updated data).
搜索导航如下：HomeActivity--> SearchActivity--> ResultsActivity( ListActivity) --> ResultDetailsActivity--> UpdateActivity-（完成时）-> ResultDetailsActivity（更新数据）。
Currently, navigation to a new Activityis via startActivity(intent)method. However, this is causing multiple instances of each Activityto be opened.
目前，导航到新Activity的startActivity(intent)方法是通过方法。但是，这会导致Activity打开每个实例的多个实例。
I'm rather new to Android. Could someone please suggest how I could avoid this?
我对 Android 比较陌生。有人可以建议我如何避免这种情况吗？
回答by Sherif elKhatib
In your android manifest, Add to your <activity>tag the android:launchMode="singleTask"
在您的 android 清单中，添加到您的<activity>标签android:launchMode="singleTask"
For a full list, check the documentation of activity
如需完整列表，请查看活动文档
In your manifest:
在您的清单中：
<activity android:name=".YourActivity"
android:launchMode="singleTask"
android:label="@string/app_name" />
Note: don't use singleton.
注意：不要使用单例。
回答by waqaslam
Setting either the following flags may help you to resolve your issue:
设置以下任一标志可能会帮助您解决问题：
Intent.FLAG_ACTIVITY_CLEAR_TOPIntent.FLAG_ACTIVITY_REORDER_TO_FRONT
Intent.FLAG_ACTIVITY_CLEAR_TOPIntent.FLAG_ACTIVITY_REORDER_TO_FRONT
回答by Joonsung Kim
Use Intentflag when startActivity:
在以下情况下使用Intent标志startActivity：
Intent intent = new Intent(this, MyActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
startActivity(intent);
there are many kinds of flag.
国旗有很多种。
This will be helpful: android singleton activity
这会有所帮助： android singleton activity
回答by Aracem
The best form to manage the Activities is use
管理活动的最佳形式是使用
startActivityForRestult(Intent,ID)
startActivityForRestult(Intent,ID)
With this method to call Activities your HomeActivity can manage a result for the other activities in the Override method
使用此方法调用活动，您的 HomeActivity 可以管理 Override 方法中其他活动的结果
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// TODO Auto-generated method stub
super.onActivityResult(requestCode, resultCode, data);
}
You can send known result for the diferents Activities and manage it. For example:
(Allways with startActivityForResult)
您可以发送不同活动的已知结果并对其进行管理。例如：（
始终与 startActivityForResult）
HomeActivity --> SearchActivity --> ResultsActivity(ListActivity) --> ResultDetailsActivity --> UpdateActivity -(on complete)-> ResultDetailsActivity (with updated data). Press Return and send SEARCH_fINISHED -->UpdateActivity catch this and send the same result in the onActivityResult method and finish() --> The same with searchActivity --> Home
HomeActivity --> SearchActivity --> ResultsActivity(ListActivity) --> ResultDetailsActivity --> UpdateActivity -（完成时）-> ResultDetailsActivity（更新数据）。按 Return 并发送 SEARCH_fINISHED -->UpdateActivity 捕获此并在 onActivityResult 方法和 Finish() 中发送相同的结果 --> 与 searchActivity 相同 --> Home
This can help you too:
这也可以帮助您：
Intent.FLAG_ACTIVITY_CLEAR_TOP
Intent.FLAG_ACTIVITY_REORDER_TO_FRONT
Intent.FLAG_ACTIVITY_CLEAR_TOP
Intent.FLAG_ACTIVITY_REORDER_TO_FRONT
http://blog.akquinet.de/2010/04/15/android-activites-and-tasks-series-intent-flags/
http://blog.akquinet.de/2010/04/15/android-activites-and-tasks-series-intent-flags/
回答by Kugan Kumar
Few things to add on to the answer posted by JoonSung Kim, change the addFlag method which will throw "cannot resolve error"
对 JoonSung Kim 发布的答案添加的内容很少，更改将抛出“无法解决错误”的 addFlag 方法
change: intent.addFlag(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
改变： intent.addFlag(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
to: intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
到： intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
code should be:
代码应该是：
Intent intent = new Intent(this, MyActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
startActivity(intent);
To prevent multiple instance of a same Activity change the flag
为了防止同一活动的多个实例更改标志
from : intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
从 ： intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
to: intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
到： intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
code should be:
代码应该是：
Intent intent = new Intent(this, MyActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
回答by Salman Khalid
My problem was setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);in onCreate(...) method of Activity.
我的问题出setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);在 Activity 的 onCreate(...) 方法中。
