package com.example.shiyan5;

import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;

public class MyService extends Service {
    private final IBinder binder = new MyBinder();
    private Thread workThread;
    private int count=0;
    private boolean c_stop=true;

    public MyService() {

    }
    public void clearcount()
    {
        count=0;
    }
    public void countstop(){
        c_stop=true;
    }
    public void countstart(){
        c_stop=false;
    }

    @Override
    public void onCreate() {
        super.onCreate();
        workThread=new Thread(null,backgroundWork);
        workThread.start();
    }

    @Override
    public boolean onUnbind(Intent intent) {
        return super.onUnbind(intent);
    }

    public class MyBinder extends Binder {
        MyService getService() {
            return MyService.this;
        }
    }

    @Override
    public IBinder onBind(Intent intent) {
        // TODO: Return the communication channel to the service.
        return binder;
        //throw new UnsupportedOperationException("Not yet implemented");

    }

    private Runnable backgroundWork =new Runnable() {
        @Override
        public void run() {
            try {
                while(true)
                {
                    if(c_stop==false)
                    {
                        count++;
                    }
                    MainActivity.UpdateGUI(count);
                    Thread.sleep(10);//10毫秒計(jì)數(shù)一次Z
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    };
}

package com.example.shiyan5;

import androidx.appcompat.app.AppCompatActivity;

import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.Handler;
import android.os.IBinder;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    static TextView textView1,textView2;
    Button bt_clear,bt_stop,bt_start;
    MyService mService;
    boolean mBound;
    static int count;
    static Handler handler=new Handler();

    private ServiceConnection connection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName className, IBinder service) {
            MyService.MyBinder binder = (MyService.MyBinder) service;
            mService = binder.getService();//通過這個(gè)來獲取服務(wù)的實(shí)例
            mBound = true;
        }
        @Override
        public void onServiceDisconnected(ComponentName arg0) {
            mBound = false;
        }
    };

    public static void UpdateGUI(int s_count)
    {
        count=s_count;
        handler.post(RefreshText);
    }

    private static Runnable RefreshText=new Runnable() {
        @Override
        public void run() {
            String sa,sb,sc;
            int a=count%100;
            if(a<10)sa="0"+a;else sa=String.valueOf(a);
            int b=(count/100)%60;
            if(b<10)sb="0"+b;else sb=String.valueOf(b);
            int c=(count/100/60)%60;
            if(c<10)sc="0"+c;else sc=String.valueOf(c);
            textView2.setText(sc+":"+sb+":"+sa);
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mBound=false;
        textView1=(TextView) findViewById(R.id.textview);
        textView2=(TextView) findViewById(R.id.textview_2);
        bt_clear=(Button) findViewById(R.id.bt_clear);
        bt_stop=(Button) findViewById(R.id.bt_stop);
        bt_start=(Button) findViewById(R.id.bt_start);

        bt_clear.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(mBound==true){
                    mService.clearcount();
                    mService.countstop();
                }
            }
        });

        bt_start.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(mBound==true)
                {
                    mService.countstart();
                }
            }
        });

        bt_stop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(mBound==true)
                {
                    mService.countstop();
                }
            }
        });
    }

    @Override
    protected void onStart() {
        super.onStart();
        Intent intent=new Intent(this,MyService.class);
        bindService(intent,connection, Context.BIND_AUTO_CREATE);
    }

    @Override
    protected void onStop() {
        super.onStop();
        unbindService(connection);
        mBound=false;
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    >
    <TextView
        android:id="@+id/textview"
        android:layout_gravity="center_horizontal"
        android:text="計(jì)時(shí)器"
        android:textSize="46sp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
    
    <TextView
        android:id="@+id/textview_2"
        android:gravity="center"
        android:textSize="54sp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

    <LinearLayout
        android:layout_gravity="center_horizontal"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content">
        <Button
            android:id="@+id/bt_clear"
            android:text="清零"
            android:textSize="36sp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>
        <Button
            android:id="@+id/bt_stop"
            android:text="暫停"
            android:textSize="36sp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>
        <Button
            android:id="@+id/bt_start"
            android:text="計(jì)時(shí)"
            android:textSize="36sp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>
    </LinearLayout>

</LinearLayout>