Android计时器

熟悉和掌握Android线程的使用

实验要求：

完成一个秒表，具备启停功能，正确使用工作线程完成界面刷新

分析秒表的计时是否准确，原因是什么，如何保证秒表计时准确

代码实现：

（1）Activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:gravity="center">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="秒表"
        android:textSize="30dp"
        android:paddingTop="80dp"/>

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:gravity="center">

        <TextView
            android:id="@+id/tv_min"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="25dp"
            android:text="00"/>
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="25dp"
            android:text=":"/>
        <TextView
            android:id="@+id/tv_seconds"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="25dp"
            android:text="00"/>
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="25dp"
            android:text=":"/>
        <TextView
            android:id="@+id/tv_ms"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="25dp"
            android:text="00"/>

    </LinearLayout>

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content">

        <Button
            android:id="@+id/btn_clean"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="清零"
            android:textSize="20dp"/>

        <Button
            android:id="@+id/btn_count"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="计时"
            android:textSize="20dp"/>

        <Button
            android:id="@+id/btn_stop"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="停止"
            android:textSize="20dp"/>

    </LinearLayout>
</LinearLayout>

（2）MainActivity.java文件

package com.example.administrator.myapplication5;

import android.app.Activity;
import android.content.Intent;
import android.os.Handler;
import android.os.IBinder;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends Activity {
    private static Handler handler=new Handler();

    private static TextView tv_minus;
    private static TextView tv_seconds;
    private static TextView tv_ms;
    public static int minuts;
    public static int seconds;
    public static int mseconds;


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        tv_minus=(TextView)findViewById(R.id.tv_min);
        tv_seconds=(TextView)findViewById(R.id.tv_seconds);
        tv_ms=(TextView)findViewById(R.id.tv_ms);
        final Button btn_clean=(Button)findViewById(R.id.btn_clean);
        final Button btn_count=(Button)findViewById(R.id.btn_count);
        final Button btn_stop=(Button)findViewById(R.id.btn_stop);
        final Intent serviceIntent=new Intent(this,CountService.class);

        btn_clean.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View view)
            {
                System.out.println("thisisatestsssss");
                tv_minus.setText("00");
                tv_seconds.setText("00");
                tv_ms.setText("00");
            }
        });
        btn_count.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View view)
            {
                startService(serviceIntent);//显示启动service
            }
        });

        btn_stop.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View view)
            {
                stopService(serviceIntent);//停止service
            }
        });
    }

    public static void UpdateGUI(int m,int s,int ms){
        minuts=m;
        seconds=s;
        mseconds=ms;
        handler.post(RefreshLable);
    }

    static Runnable RefreshLable=new Runnable() {
        @Override
        public void run() {
            try {
                Thread.sleep(50);
                tv_minus.setText(String.format("%02d",minuts));
                tv_seconds.setText(String.format("%02d",seconds));
                tv_ms.setText(String.format("%02d",mseconds%100));

            } catch (InterruptedException e) {
                e.printStackTrace();
            }

        }
    };
}

（3）CountService.Java文件

package com.example.administrator.myapplication5;

import android.app.Service;
import android.content.Intent;
//import android.icu.util.Calendar;
import android.os.IBinder;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.TextView;

import java.util.Calendar;

/**
 * Created by lh on 2018/10/22.
 */

public class CountService extends Service {
    private Thread workThread;
    long startTime=System.currentTimeMillis();

    @Override
    public void onCreate() {
        super.onCreate();
        workThread=new Thread(null,backgroundThread,"workThread");

    }

    @Override
    public void onStart(Intent intent,int startId) {
        super.onStart(intent,startId);
        if(!workThread.isAlive()){
            workThread.start();
        }
    } 
    @Override
    public void onDestroy() {
        super.onDestroy();
        workThread.interrupt();
    }

    @Override
    public IBinder onBind(Intent intent){
        return null;

    }
    private Runnable backgroundThread=new Runnable() {
        @Override
        public void run() {

            try{
                while(!Thread.interrupted()){
                    long currentTime=System.currentTimeMillis();
                    long time=currentTime-startTime;
                    long m=time/(1000*60);
                    long s=time/1000;
                    long ms=time%1000;
                    int mi=(int)m;
                    int si=(int)s;
                    int msi=(int)ms;
                    MainActivity.UpdateGUI(mi,si,msi);
                    workThread.sleep(50);

                }
            }catch (InterruptedException e){
                e.printStackTrace();
            }
        }
    };
}

（4）AndroidManifest.xml文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.administrator.myapplication5">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <service android:name=".CountService"/>

    </application>

</manifest>

总结：

setText()括号内应该是String类型

System.currentTimeMillis()函数来获取系统时间