Question

我在bundle中保存实例的代码正在运行，但我不明白它是如何工作的。

如果我旋转设备，点击保存在捆绑中的按钮后的学生姓名。

这是我的班级

package com.example.app;

import android.os.Parcel;
import android.os.Parcelable;

public class Student implements Parcelable {

   private String firstName;

   private String lastName;


   public Student(String firstName, String lastName) {
       this.firstName = firstName;
       this.lastName = lastName;
   }

   public String getDisplayedName()
   {
       return lastName + " " + firstName;
   }

   @Override
   public int describeContents() {
       return 0;
   }

   @Override
   public void writeToParcel(Parcel dest, int flags) {

   }
}

你可以在这里看到我没有在方法writeToParcel中编写任何代码，也没有在类中创建CREATOR字段。但它正在我的所有设备上工作，包括模拟器设备

这是我的活动代码

package com.example.app;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import java.util.Random;

public class MainActivity extends Activity {

private Student student;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Button generateButton = (Button) findViewById(R.id.generate);
    generateButton.setOnClickListener(generateStudentName);
    if (savedInstanceState != null) {
        student = savedInstanceState.getParcelable("student");
        writeStudent();
    }
}

@Override
protected void onSaveInstanceState(Bundle outState) {
    outState.putParcelable("student", student);
    super.onSaveInstanceState(outState);
}

private void writeStudent() {
    final TextView studentName = (TextView) findViewById(R.id.student_name);
    studentName.setText(student.getDisplayedName());
}

private View.OnClickListener generateStudentName = new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        Random randomGenerator = new Random();
        student = new Student(String.valueOf(randomGenerator.nextInt(10000)), String.valueOf(randomGenerator.nextInt(10000)));
        writeStudent();
    }
};


}

为什么会这样？

奇怪的Parcelable实现

0 个答案: