Its inheritance relationship is as follows:

java.lang.Object
android.content.Context
android.content.ContextWrapper
android.app.Application

steps

Step 1. Create Application subclass, sample code:

//ApplicationAct Inherited from Application class
public class ApplicationAct extends Application{
 ... // Code ellipsis in a class
}

Step 2, set in the project list < application > The android:name attribute value in the tag was created in step 1

Java class. Sample code:

<application
android:icon= "@drawable/icon"
android:label="@string/app_name"
android:name=".ApplicationAct"
<activity>
... ...
</activity>
</application>