java捆绑包丢失值

Question

我是java新手。 我试图在屏幕旋转时将变量从OnSaveInstanceState保存到OnCreate。 我已将保存的值记录到savedInstanceState包中。 当屏幕旋转时，OnCreate(Bundle savedInstanceState)中的捆绑值在日志中显示为0，但在日志中显示为OnSaveInstanceState的正确值

我的活动是Java

package com.hfad.stopwatch;

import 安卓.app.Activity;
import 安卓.os.Bundle;
import 安卓.os.Handler;
import 安卓.util.Log;
import 安卓.view.View;
import 安卓.widget.TextView;

public class StopwatchActivity extends Activity {

    private static final String TAG = StopwatchActivity.class.getSimpleName();
    private int seconds;
    private boolean running;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_stopwatch);
        if(savedInstanceState != null){
            Log.d(TAG, "onCreate() Restoring previous state");
            /* restore state */
            seconds = savedInstanceState.getInt("seconds");
            running = savedInstanceState.getBoolean("running");
            String tmpStr = String.valueOf(seconds);
            Log.d(TAG,tmpStr);
            Log.d(TAG, "onCreate() ending");
        } else {
            Log.d(TAG, "onCreate() No saved state available");
            /* initialize app */
        }
        runTimer();
    }

    @Override
    public void onSaveInstanceState(Bundle savedInstanceState){
        super.onSaveInstanceState(savedInstanceState);
        Log.d(TAG,"onSaveInstanceState() saving state");
        savedInstanceState.putInt("Seconds", seconds);
        savedInstanceState.putBoolean("running", running);
        String tmpStr = String.valueOf(savedInstanceState.getInt("Seconds"));
        Log.d(TAG,tmpStr);
        Log.d(TAG,"onSaveInstanceState() ending");
    }

    //Start the stopwatch running when the start button is clicked
    public void onClickStart(View view){
        running = true;
    }

    //Stop the stopwatch running when the stop button is clicked
    public void onClickStop(View view){
        running = false;
    }

    //Start the stopwatch running when the start button is clicked
    public void onClickReset(View view){
        running = false;
        seconds = 0;
    }

    private void runTimer(){
        final TextView timeView = (TextView)findViewById(R.id.time_view);
        final Handler handler = new Handler();
        handler.post(new Runnable(){
            @Override
            public void run(){
                int hours = seconds/3600;
                int minutes = (seconds%3600)/60;
                int secs = seconds%60;
                String time = String.format("%d:%02d:%02d",hours,minutes,secs);
                timeView.setText(time);
                if(running){
                    seconds++;
                }
                handler.postDelayed(this, 1000);
            }
        });
    }

}

这是日志

07-26 21:02:19.880 6124-6124/com.hfad.stopwatch D/StopwatchActivity: onSaveInstanceState() saving state

07-26 21:02:19.880 6124-6124/com.hfad.stopwatch D/StopwatchActivity: 11

07-26 21:02:19.880 6124-6124/com.hfad.stopwatch D/StopwatchActivity: onSaveInstanceState() ending

07-26 21:02:19.940 6124-6124/com.hfad.stopwatch D/StopwatchActivity: onCreate() Restoring previous state

07-26 21:02:19.940 6124-6124/com.hfad.stopwatch D/StopwatchActivity: 0

07-26 21:02:19.940 6124-6124/com.hfad.stopwatch D/StopwatchActivity: onCreate() ending

我正在一本书中学习课程，但这并不像我解释的那样有效，我也无法在网上找到解决方案

Answer 1

设置要保存的值后，应该调用super.onSaveInstanceState(savedInstanceState)

你可以看到更多in the documentations

Answer 2

Bundle区分大小写。你正在输入“秒”并检索“秒”。好的做法是将键定义为常量，这样就不会出现这样的错误

Bundle - is key case sensitive?

Answer 3

您使用了错误的键来查找值。你的钥匙上有一个大写字母S。aBundle中的键区分大小写

这里的一个好做法是将密钥字符串声明为最终静态，并使用它们来存储和检索。例如

public static final String SECONDS_KEY = "seconds";
public static final String RUNNING_KEY = "running"