java - onSaveInstanceState 和 onRestoreInstanceState 似乎不起作用

Question

我正在尝试创建一个计数器，并尝试在您离开应用程序时保存当前值，因此我尝试使用 onSaveInstanceState 和 onRestoreInstanceState 但似乎不上类

代码如下

package com.example.taekwondobuddy.util;

import android.app.Activity;

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

public class Counter extends Activity {

int counter;
Button add;
Button sub;
TextView display;


public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.counter);

    counter = 0;
    add = (Button) findViewById(R.id.button1);
    sub = (Button) findViewById(R.id.button2);
    display = (TextView) findViewById(R.id.tvDisplay);
    add.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            counter++;
            display.setText("Counter: " + counter);
        }
    });
    sub.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            counter--;
            display.setText("Counter: " + counter);
        }
    });
}

public void onSaveInstanceState(Bundle savedInstanceState) {
      super.onSaveInstanceState(savedInstanceState);


      savedInstanceState.putInt("counter", counter);


    }

@Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
  super.onRestoreInstanceState(savedInstanceState);


  counter = savedInstanceState.getInt("counter");

   }



  }

这是我第一次超过 savedInstanceState 所以我想知道语法是否正确以及我是否以正确的方式使用它？如果是这样我的代码有什么问题吗？感谢帮助和提示

Answer 1

您需要交换方法中的顺序，因为父级的实现方法将从方法中返回，并且您的代码将不会运行。另外，您还需要检查 onRestoreInstanceState 中的参数是否不为 null。

public void onSaveInstanceState(Bundle savedInstanceState) {
    savedInstanceState.putInt("counter", counter);
    super.onSaveInstanceState(savedInstanceState);
}

@Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
    if (savedInstanceState != null) {
        counter = savedInstanceState.getInt("counter");
    }
    super.onRestoreInstanceState(savedInstanceState);
}

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你也说了

I'm trying to make a counter and trying to save the current value when you leave the application

仅当应用程序位于内存中时，保存实例状态才有效(尽管离开应用程序并不会将其删除)。如果它被杀了，国家就会消失。