android - 在Android轮播上重新启动活动(Activity restart on rotation Android)

Question

In my Android application, when I rotate the device (slide out the keyboard) then my Activity is restarted ( onCreate is called).

(在我的Android应用程序中，当我旋转设备（滑出键盘）时，我的Activity将重新启动（调用onCreate ）。)

Now, this is probably how it's supposed to be, but I do a lot of initial setting up in the onCreate method, so I need either:

(现在，这大概应该是这样，但是我在onCreate方法中做了很多初始设置，所以我需要：)

1. Put all the initial setting up in another function so it's not all lost on device rotation or

   (将所有初始设置都放在另一个功能中，这样就不会因设备旋转或)

2. Make it so onCreate is not called again and the layout just adjusts or

   (使其不再被onCreate再次调用，布局只是调整或)

3. Limit the app to just portrait so that onCreate is not called.

   (将应用程序限制为仅纵向模式，以便不调用onCreate 。)

  ask by Isaac Waller translate from so

Answer 1

Using the Application Class

(使用应用程序类)

Depending on what you're doing in your initialization you could consider creating a new class that extends Application and moving your initialization code into an overridden onCreate method within that class.

(根据您在初始化过程中所执行的操作，可以考虑创建一个扩展Application的新类，并将初始化代码移动到该类中重写的onCreate方法中。)

public class MyApplicationClass extends Application {
  @Override
  public void onCreate() {
    super.onCreate();
    // TODO Put your application initialization code here.
  }
}

The onCreate in the application class is only called when the entire application is created, so the Activity restarts on orientation or keyboard visibility changes won't trigger it.

(仅在创建整个应用程序时才调用应用程序类中的onCreate ，因此Activity在方向上重新启动，否则键盘可见性更改不会触发它。)

It's good practice to expose the instance of this class as a singleton and exposing the application variables you're initializing using getters and setters.

(优良作法是将此类的实例公开为单例，并使用getter和setter公开要初始化的应用程序变量。)

NOTE: You'll need to specify the name of your new Application class in the manifest for it to be registered and used:

(注意：您需要在清单中指定新Application类的名称，以便注册和使用它：)

<application
    android:name="com.you.yourapp.MyApplicationClass"

Reacting to Configuration Changes [UPDATE: this is deprecated since API 13;

(对配置更改做出反应 [更新：自API 13起不推荐使用；)

see the recommended alternative ]

(请参阅推荐的替代方法 ])

As a further alternative, you can have your application listen for events that would cause a restart – like orientation and keyboard visibility changes – and handle them within your Activity.

(作为另一种选择，您可以让您的应用程序监听会导致重启的事件（例如方向和键盘可见性更改），并在Activity中处理它们。)

Start by adding the android:configChanges node to your Activity's manifest node

(首先将android:configChanges节点添加到“活动”的清单节点中)

 <activity android:name=".MyActivity"
      android:configChanges="orientation|keyboardHidden"
      android:label="@string/app_name">

or for Android 3.2 (API level 13) and newer :

(或适用于Android 3.2（API级别13）及更高版本 ：)

<activity android:name=".MyActivity"
      android:configChanges="keyboardHidden|orientation|screenSize"
      android:label="@string/app_name">

Then within the Activity override the onConfigurationChanged method and call setContentView to force the GUI layout to be re-done in the new orientation.

(然后在Activity中重写onConfigurationChanged方法并调用setContentView以强制以新方向重新完成GUI布局。)

@Override
public void onConfigurationChanged(Configuration newConfig) {
  super.onConfigurationChanged(newConfig);
  setContentView(R.layout.myLayout);
}