Android開發學習筆記整理（15）-BroadcastReceive和Service

Service

什麼是Service?

Service是Android四大組件之一，它能夠在後臺執行一些比較耗時較長的操作，並且不提供用戶界面。應用場景：後臺播放音樂等。簡單理解爲沒有界面的Activity。

Service的創建

繼承Service類並重寫bind方法，並在Manifest.xml中註冊。

Service的兩種啓用方式

• （1）startService方式
• （2）bindService方式

Service的生命週期

使用Service完成計算案例

代碼部分：

part1：

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/button"
        android:layout_width="0dp"
        android:layout_height="50dp"
        android:onClick="showLocal"
        android:text="演示本地廣播"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

效果圖：

LocalBroadcast.java

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.widget.Toast;
/**
 * 用於演示本地廣播
 */
public class LocalBroadcast extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context, "接收到了本地廣播", Toast.LENGTH_SHORT).show();
    }

}

activity_local.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".LocalActivity">

    <Button
        android:id="@+id/button2"
        android:layout_width="0dp"
        android:layout_height="50dp"
        android:onClick="sendBroadcast"
        android:text="發送廣播"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/btn_color"
        android:layout_width="0dp"
        android:layout_height="50dp"
        android:onClick="jumpNext"
        android:text="按鈕"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button2" />
    
</androidx.constraintlayout.widget.ConstraintLayout>

效果圖：

activity_next.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".NextActivity">

    <Button
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="changeColor"
        android:text="改變顏色"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/et_color"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="58dp"
        android:ems="10"
        android:hint="請輸入顏色"
        android:inputType="textPersonName"
        app:layout_constraintBottom_toTopOf="@+id/button3"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent" />
    
</androidx.constraintlayout.widget.ConstraintLayout>

效果圖：

NextActivity.java

import androidx.appcompat.app.AppCompatActivity;
import androidx.localbroadcastmanager.content.LocalBroadcastManager;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
/**
 * 演示發送廣播更改上一頁按鈕顏色
 */
public class NextActivity extends AppCompatActivity {

    private EditText et_color;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_next);

        et_color = findViewById(R.id.et_color);
    }

    /**
     * 更改顏色按鈕
     * @param view
     */
    public void changeColor(View view) {
        // 1.發送廣播
        Intent intent = new Intent("day14.local.color");
        String color = et_color.getText().toString().trim();
        intent.putExtra("color", color);
        LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
        // 2.關閉界面
        finish();
    }

}

LocalActivity.java

import androidx.appcompat.app.AppCompatActivity;
import androidx.localbroadcastmanager.content.LocalBroadcastManager;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.graphics.Color;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
public class LocalActivity extends AppCompatActivity {

    /*
     * 廣播的使用步驟：
     *   1.創建廣播
     *   2.註冊廣播和取消註冊廣播
     *   3.發送廣播
     * */

    private LocalBroadcast localBroadcast;

    private ColorBroadcast colorBroadcast;

    private Button button;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_local);

        // 獲取按鈕
        button = findViewById(R.id.btn_color);

        // 註冊廣播
        localBroadcast = new LocalBroadcast();
        IntentFilter filter = new IntentFilter("day14.local.broadcast");
        LocalBroadcastManager.getInstance(this).registerReceiver(localBroadcast, filter);

        colorBroadcast = new ColorBroadcast();
        IntentFilter colorFilter = new IntentFilter("day14.local.color");
        LocalBroadcastManager.getInstance(this).registerReceiver(colorBroadcast, colorFilter);
    }

    // 取消廣播位置需要注意時機
//    @Override
//    protected void onPause() {
//        super.onPause();
//        LocalBroadcastManager.getInstance(this).unregisterReceiver(colorBroadcast);
//        Log.i("LocalActivity","廣播已取消註冊");
//    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        // 取消廣播註冊
        LocalBroadcastManager.getInstance(this).unregisterReceiver(localBroadcast);
//        LocalBroadcastManager.getInstance(this).unregisterReceiver(colorBroadcast);
    }

    /**
     * 發送廣播
     * @param view
     */
    public void sendBroadcast(View view) {
        Intent intent = new Intent("day14.local.broadcast");
        LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
    }

    /**
     * 演示通過廣播進行按鈕顏色更改
     */
    public void jumpNext(View view) {
        // 1.拿到按鈕 2.定義更改按鈕的廣播 3.註冊和取消註冊廣播 4.發送廣播
        Intent intent = new Intent(this, NextActivity.class);
        startActivity(intent);
    }

    /**
     * 更改按鈕顏色的廣播（內部類）
     */
    class ColorBroadcast extends BroadcastReceiver{
        @Override
        public void onReceive(Context context, Intent intent) {
            String color = intent.getStringExtra("color"); // #FFFFFF
            button.setBackgroundColor(Color.parseColor("#"+color));
        }
    }

}

MainActivity.java

import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
public class MainActivity extends AppCompatActivity {

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

    /**
     * 演示本地廣播
     * @param view
     */
    public void showLocal(View view) {
        Intent intent = new Intent(this, LocalActivity.class);
        startActivity(intent);
    }

}

效果圖：

點擊發送廣播

點擊按鈕

part2：

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/button"
        android:layout_width="0dp"
        android:layout_height="50dp"
        android:onClick="showLocal"
        android:text="演示本地廣播"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button4"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:onClick="showService"
        android:text="演示service"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button" />
    
</androidx.constraintlayout.widget.ConstraintLayout>

效果圖：

MyService.java

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;
import androidx.annotation.Nullable;
/**
 * Service使用startService啓用的時候：onCreate方法只調用一次，
 * 在銷燬之前，再次調用startService，只會觸發onStartCommand
 */
public class MyService extends Service {

    private static final String TAG = "MyService";

    @Override
    public void onCreate() {
        super.onCreate();
        Log.i(TAG,"MyService正在onCreate");
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.i(TAG, "MyService正在onDestroy");
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        // 執行service業務的方法
        Log.i(TAG, "MyService正在onStartCommand");
        return super.onStartCommand(intent, flags, startId);
    }

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

}

MyService2.java

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;
import androidx.annotation.Nullable;
public class MyService2 extends Service {

    private static final  String TAG = "MyService2";

    @Override
    public void onCreate() {
        super.onCreate();
        Log.i(TAG,"bindService方式啓用Service正在onCreate");
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.i(TAG,"bindService方式啓用Service正在onDestroy");
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        Log.i(TAG,"bindService方式啓用Service正在onBind");
        return null;
    }

    @Override
    public boolean onUnbind(Intent intent) {
        Log.i(TAG,"bindService方式啓用Service正在onUnbind");
        return super.onUnbind(intent);
    }
    
}

AndroidMainfest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.day14">

    <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=".ServiceActivity"></activity>
        <activity android:name=".NextActivity" />
        <activity android:name=".LocalActivity" />
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity> <!-- service註冊 -->
        <service android:name=".MyService" />
        <service android:name=".MyService2" />
    </application>

</manifest>

activity_service.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ServiceActivity">

    <Button
        android:id="@+id/button5"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="59dp"
        android:layout_marginLeft="59dp"
        android:layout_marginTop="108dp"
        android:onClick="startService"
        android:text="啓動Service"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button6"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="104dp"
        android:layout_marginEnd="57dp"
        android:layout_marginRight="57dp"
        android:onClick="stopService"
        android:text="停止Service"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button7"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="57dp"
        android:layout_marginLeft="57dp"
        android:onClick="bindStart"
        android:text="bind方式啓用"
        app:layout_constraintBaseline_toBaselineOf="@+id/button8"
        app:layout_constraintStart_toStartOf="parent" />

    <Button
        android:id="@+id/button8"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="262dp"
        android:layout_marginEnd="60dp"
        android:layout_marginRight="60dp"
        android:onClick="unBindService"
        android:text="取消綁定"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
    
</androidx.constraintlayout.widget.ConstraintLayout>

效果圖：

ServiceActivity.java

import androidx.appcompat.app.AppCompatActivity;
import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.view.View;
public class ServiceActivity extends AppCompatActivity {

    private ServiceConnection serviceConnection;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_service);

        serviceConnection = new ServiceConnection() {
            @Override
            public void onServiceConnected(ComponentName name, IBinder service) {
                // 鏈接完成後
            }

            @Override
            public void onServiceDisconnected(ComponentName name) {
                // 當結束鏈接後
            }
        };
    }

    /**
     * 開是Service
     * @param view
     */
    public void startService(View view) {
        Intent intent = new Intent(this, MyService.class);
        startService(intent);
    }

    /**
     * 結束Service
     * @param view
     */
    public void stopService(View view) {
        Intent intent = new Intent(this, MyService.class);
        stopService(intent);
    }

    /**
     * 綁定service啓動
     * @param view
     */
    public void bindStart(View view) {
        Intent intent = new Intent(this, MyService2.class);
        bindService(intent, serviceConnection, BIND_AUTO_CREATE);
    }

    /**
     * 取消綁定service
     * @param view
     */
    public void unBindService(View view) {
        unbindService(serviceConnection);
    }

}

MainActivity.java

import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
public class MainActivity extends AppCompatActivity {

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

    /**
     * 演示本地廣播
     * @param view
     */
    public void showLocal(View view) {
        Intent intent = new Intent(this, LocalActivity.class);
        startActivity(intent);
    }

    /**
     * 演示service
     * @param view
     */
    public void showService(View view) {
        Intent intent = new Intent(this, ServiceActivity.class);
        startActivity(intent);
    }

}

效果圖：

點擊啓動SERVICE

點擊停止SERVICE

BIND方式啓用

取消綁定

part3：

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/button"
        android:layout_width="0dp"
        android:layout_height="50dp"
        android:onClick="showLocal"
        android:text="演示本地廣播"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button4"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:onClick="showService"
        android:text="演示service"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button" />

    <Button
        android:id="@+id/button9"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:onClick="showDownload"
        android:text="演示模擬下載"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button4" />

</androidx.constraintlayout.widget.ConstraintLayout>

效果圖：

DownloadService.java

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import androidx.annotation.Nullable;
import androidx.localbroadcastmanager.content.LocalBroadcastManager;
public class DownloadService extends Service {

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        // 執行邏輯
        int percent = intent.getIntExtra("percent", 0); // 下載百分比
        while(true) {
            percent++;
            try {
                Thread.sleep(20);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            if (percent == 100) {
                // 1.發起通知，告訴其他下載完成
                LocalBroadcastManager.getInstance(this).sendBroadcast(new Intent("day14.download"));
                // 跳出循環
                break;
            }
        }
        // 2.結束Service
        stopSelf();
        return START_STICKY;
    }

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

}

DownloadBroadcast.java

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.widget.Toast;
public class DownloadBroadcast extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context, "下載完成", Toast.LENGTH_SHORT).show();
    }
    
}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.day14">

    <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=".ServiceActivity" />
        <activity android:name=".NextActivity" />
        <activity android:name=".LocalActivity" />
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity> <!-- service註冊 -->
        <service android:name=".MyService" />
        <service android:name=".MyService2" />
        <service android:name=".DownloadService" />
    </application>

</manifest>

MainActivity.java

import androidx.appcompat.app.AppCompatActivity;
import androidx.localbroadcastmanager.content.LocalBroadcastManager;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.view.View;
public class MainActivity extends AppCompatActivity {

    private DownloadBroadcast downloadBroadcast;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // 註冊廣播
        downloadBroadcast = new DownloadBroadcast();
        IntentFilter intentFilter = new IntentFilter("day14.download");
        LocalBroadcastManager.getInstance(this).registerReceiver(downloadBroadcast, intentFilter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        LocalBroadcastManager.getInstance(this).unregisterReceiver(downloadBroadcast);
    }

    /**
     * 演示本地廣播
     * @param view
     */
    public void showLocal(View view) {
        Intent intent = new Intent(this, LocalActivity.class);
        startActivity(intent);
    }

    /**
     * 演示service
     * @param view
     */
    public void showService(View view) {
        Intent intent = new Intent(this, ServiceActivity.class);
        startActivity(intent);
    }

    /**
     * 演示下載案例
     * @param view
     */
    public void showDownload(View view) {
        /*
         *   點擊下載模擬按鈕，啓用一個Service，傳遞下載進度，每隔幾毫秒，下載進度+1，
         *   直到100，提示下載完成並結束service
         * */

        //1.創建service 2.完成service中不斷加1的方法 3.發起廣播 4.創建廣播並註冊廣播、註銷廣播
        Intent intent = new Intent(this, DownloadService.class);
        intent.putExtra("percent", 0);
        startService(intent);

    }

}

效果圖：

part4：

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/button"
        android:layout_width="0dp"
        android:layout_height="50dp"
        android:onClick="showLocal"
        android:text="演示本地廣播"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button4"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:onClick="showService"
        android:text="演示service"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button" />

    <Button
        android:id="@+id/button9"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:onClick="showDownload"
        android:text="演示模擬下載"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button4" />

    <Button
        android:id="@+id/button10"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:onClick="showCompute"
        android:text="演示計算數據"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button9" />
    
</androidx.constraintlayout.widget.ConstraintLayout>

效果圖：

activity_compute.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ComputeActivity">

    <EditText
        android:id="@+id/et_math"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="55dp"
        android:ems="10"
        android:hint="請輸入數學成績"
        android:inputType="textPersonName"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/et_chinese"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="47dp"
        android:ems="10"
        android:hint="請輸入語文成績"
        android:inputType="textPersonName"
        app:layout_constraintStart_toStartOf="@+id/et_math"
        app:layout_constraintTop_toBottomOf="@+id/et_math" />

    <TextView
        android:id="@+id/tv_avg"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="26dp"
        android:layout_marginEnd="14dp"
        android:layout_marginRight="14dp"
        app:layout_constraintEnd_toEndOf="@+id/button11"
        app:layout_constraintTop_toBottomOf="@+id/et_chinese" />

    <Button
        android:id="@+id/button11"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="33dp"
        android:onClick="submit"
        android:text="確定"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/tv_avg" />
    
</androidx.constraintlayout.widget.ConstraintLayout>

效果圖：

ComputeService.java

import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;
import androidx.annotation.Nullable;
public class ComputeService extends Service {
    
    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return new MyBinder();
    }

    public double caculate(double math, double chinese) {
        double result = (math+chinese)/2;
        return result;
    }

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

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.day14">

    <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=".ComputeActivity"></activity>
        <activity android:name=".ServiceActivity" />
        <activity android:name=".NextActivity" />
        <activity android:name=".LocalActivity" />
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity> <!-- service註冊 -->
        <service android:name=".MyService" />
        <service android:name=".MyService2" />
        <service android:name=".DownloadService" />
        <service android:name=".ComputeService" />
    </application>

</manifest>

ComputeActivity.java

import androidx.appcompat.app.AppCompatActivity;
import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;
public class ComputeActivity extends AppCompatActivity {

    private ServiceConnection serviceConnection;

    private ComputeService.MyBinder myBinder;

    private EditText et_math;
    private EditText et_chinese;
    private TextView tx_avg;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_compute);
        // 視圖控件
        et_math = findViewById(R.id.et_math);
        et_chinese = findViewById(R.id.et_chinese);
        tx_avg = findViewById(R.id.tv_avg);

        serviceConnection = new ServiceConnection() {
            @Override
            public void onServiceConnected(ComponentName name, IBinder service) {
                myBinder = (ComputeService.MyBinder) service;
            }
            @Override
            public void onServiceDisconnected(ComponentName name) {
            }
        };

        Intent intent = new Intent(this, ComputeService.class);
        bindService(intent,serviceConnection, BIND_AUTO_CREATE);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unbindService(serviceConnection);
    }

    /**
     * 確定計算
     * @param view
     */
    public void submit(View view) {
        String math = et_math.getText().toString();
        String chinese = et_chinese.getText().toString();

        ComputeService computeService = myBinder.getService();
        double result = computeService.caculate(Double.parseDouble(math), Double.parseDouble(chinese));
        tx_avg.setText(result+"");
    }

}

MainActivity.java

import androidx.appcompat.app.AppCompatActivity;
import androidx.localbroadcastmanager.content.LocalBroadcastManager;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.view.View;
public class MainActivity extends AppCompatActivity {

    private DownloadBroadcast downloadBroadcast;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // 註冊廣播
        downloadBroadcast = new DownloadBroadcast();
        IntentFilter intentFilter = new IntentFilter("day14.download");
        LocalBroadcastManager.getInstance(this).registerReceiver(downloadBroadcast, intentFilter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        LocalBroadcastManager.getInstance(this).unregisterReceiver(downloadBroadcast);
    }

    /**
     * 演示本地廣播
     * @param view
     */
    public void showLocal(View view) {
        Intent intent = new Intent(this, LocalActivity.class);
        startActivity(intent);
    }

    /**
     * 演示service
     * @param view
     */
    public void showService(View view) {
        Intent intent = new Intent(this, ServiceActivity.class);
        startActivity(intent);
    }

    /**
     * 演示下載案例
     * @param view
     */
    public void showDownload(View view) {
        /*
         *   點擊下載模擬按鈕，啓用一個Service，傳遞下載進度，每隔幾毫秒，下載進度+1，
         *   直到100，提示下載完成並結束service
         * */

        //1.創建service 2.完成service中不斷加1的方法 3.發起廣播 4.創建廣播並註冊廣播、註銷廣播
        Intent intent = new Intent(this, DownloadService.class);
        intent.putExtra("percent", 0);
        startService(intent);

    }

    /**
     * 計算
     * @param view
     */
    public void showCompute(View view) {
        startActivity(new Intent(this, ComputeActivity.class));
    }
    
}

效果圖：