The technical principles of the technical principles of the VersionedParcelable and Friends frameworks in the Java class library
The technical principles of the technical principles of VersionedParceLABLE and Friends framework in the Java class library
VersionedParceLABLE and FRIENDS frameworks are commonly used in Java libraries to achieve durable data and data transmission in Android applications.This article will outline the technical principles of these two technologies and provide some Java code examples to help readers better understand.
1. The technical principles of VersionedParceLable
VersionedParceLABLE is an interface provided by Android to help developers pass and persist data between classes.By implementing the VersionedParcelable interface, data can be serialized and deepened operations to achieve data preservation and transmission.
VersionedParceLABLE's technical principles are based on the Parcelable interface, but compared to Parcelable, VersionedParceLABLE provides more convenient and flexible data serialization methods.It uses the automatic ParceLABLE.CREATOR interface to create and restore objects.
Below is a simple example, showing how to use VersionedParcelable interface:
import android.os.Parcel;
import android.os.Parcelable;
import androidx.versionedparcelable.VersionedParcelize;
@VersionedParcelize
public class MyData implements VersionedParcelable {
private int value;
public MyData(int value) {
this.value = value;
}
public int getValue() {
return value;
}
public static final Parcelable.Creator<MyData> CREATOR = new Parcelable.Creator<MyData>() {
public MyData createFromParcel(Parcel in) {
MyData data = new MyData();
data.value = in.readInt();
return data;
}
public MyData[] newArray(int size) {
return new MyData[size];
}
};
}
In the above example, by using the `@versionedParcelize` annotation, we instructed the compiler to generate the necessary code for us, including the implementation of the ParceLELABLE.CREATOR interface.Then we can use the MyData class like an ordinary Parcelable interface.
2. Technical principles of FRIENDS framework
The FRIENDS framework is a permissions control mechanism provided by Android. It is used in the Android class library to limit some methods or fields.It is implemented by using Java's private access permissions and restrictions to access to the decorative symbols (Public, Private, ProteCTED).
Friends framework allows divided classes into two types: container classes and authorization classes.Only the authorized class can access the method and field of the container class.
The following is a simple example to illustrate how to use the Friends framework:
package com.example.mylibrary.container;
public class MyClass {
private static String myPrivateField = "Test";
@AllowIfApparentIntent
public static void myMethod() {
System.out.println("Hello Friends!");
}
}
In the above example, we used the MyCLASS class as a container class and marked the `mymethod () method to use @allowifapparentintent annotations. This annotation will declare the method as a friend.Now, only in the authorized class can the `mymethod () method be called.
package com.example.mylibrary.authorized;
import com.example.mylibrary.container.MyClass;
public class MyAuthorizedClass {
public static void main(String[] args) {
MyClass.myMethod (); // The authorized class can call the friendly method
System.out.println (MyClass.MyprivateField); // The authorized class can access the Youyuan field
}
}
In the above example, the MyAutHorizedClass class is an authorized class, which can call the `mymethod ()` method and access `myprivateField` field in MyClass.This is because the MyautHorizedClass class is in the same package as the MyClass class.
Summarize:
VersionedParceLABLE and FRIENDS frameworks are commonly used in Java libraries to achieve durable data and data transmission in Android applications.VersionedParceLABLE realizes the serialization and derivative of the data by implementing the VersionedParceLABLE interface; the Friends framework can be controlled by using access modifications and Youyuan marks. Only the authorized class can access the friendly method and fields.When developing Android applications, these two technologies can greatly facilitate the work of developers.
