如何创建一个Dalvik不会杀死的Android服务?
在进入示例之前,我们应该了解Android中的服务是什么。服务将在后台运行而无需与UI交互,即使活动销毁后它也能继续工作。
此示例演示了如何创建一个Dalvik不会杀死的Android服务。
步骤 1 - 在Android Studio中创建一个新项目,转到文件⇒新建项目,并填写所有必要的信息以创建新项目。
步骤 2 - 将以下代码添加到res/layout/activity_main.xml中。
<?xml version = "1.0" encoding = "utf-8"?> <android.support.constraint.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"> <TextView android:id = "@+id/text" android:layout_width = "wrap_content" android:layout_height = "wrap_content" android:text = "Start Service" android:textSize = "25sp" app:layout_constraintBottom_toBottomOf = "parent" app:layout_constraintLeft_toLeftOf = "parent" app:layout_constraintRight_toRightOf = "parent" app:layout_constraintTop_toTopOf = "parent" /> </android.support.constraint.ConstraintLayout>
在上面的代码中,我们使用了TextView,当用户点击TextView时,它将启动和停止服务。
步骤 3 - 将以下代码添加到src/MainActivity.java中
package com.example.andy.myapplication; import android.app.ActivityManager; import android.content.Context; import android.content.Intent; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.util.Log; import android.view.View; import android.widget.TextView; public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); final TextView text = findViewById(R.id.text); text.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { if (isMyServiceRunning(service.class)) { text.setText("Stoped"); stopService(new Intent(MainActivity.this, service.class)); } else { text.setText("Started"); startService(new Intent(MainActivity.this, service.class)); } } }); } private boolean isMyServiceRunning(Class<?> serviceClass) { ActivityManager manager = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE); for (ActivityManager.RunningServiceInfo service : manager.getRunningServices(Integer.MAX_VALUE)) { if (serviceClass.getName().equals(service.service.getClassName())) { return true; } } return false; } }
在上面的代码中,启动和停止服务。我们使用了Intent并传递了上下文和服务类。现在在包文件夹中创建一个服务类,如service.class,并添加以下代码 -
package com.example.andy.myapplication; import android.annotation.SuppressLint; import android.annotation.TargetApi; import android.app.Notification; import android.app.NotificationChannel; import android.app.NotificationManager; import android.app.PendingIntent; import android.app.Service; import android.content.Context; import android.content.Intent; import android.graphics.Color; import android.media.MediaPlayer; import android.os.Build; import android.os.IBinder; import android.os.PowerManager; import android.support.annotation.RequiresApi; import android.support.v4.app.NotificationCompat; import android.util.Log; import android.widget.Toast; public class service extends Service { PowerManager pm; @SuppressLint("InvalidWakeLockTag") PowerManager.WakeLock wl; @Override public IBinder onBind(Intent intent) { return null; } @SuppressLint("InvalidWakeLockTag") @Override public void onCreate() { super.onCreate(); pm = (PowerManager) getSystemService(Context.POWER_SERVICE); wl = pm.newWakeLock(PowerManager.SCREEN_DIM_WAKE_LOCK, "My Tag"); } @TargetApi(Build.VERSION_CODES.O) @RequiresApi(api = Build.VERSION_CODES.JELLY_BEAN) @Override public int onStartCommand(Intent intent, int flags, int startId) { wl.acquire(); //Do some task Toast.makeText(this, "Notification Service started by user.", Toast.LENGTH_LONG).show(); return START_STICKY; } @RequiresApi(api = Build.VERSION_CODES.N) @Override public void onDestroy() { super.onDestroy(); wl.release(); Toast.makeText(this, "Notification Service destroyed by user.", Toast.LENGTH_LONG).show(); } }
在上面的代码中,我们调用了电源管理器来停止屏幕锁定,因此Android线程不会停止服务线程,如下所示 -
@SuppressLint("InvalidWakeLockTag") @Override public void onCreate() { super.onCreate(); pm = (PowerManager) getSystemService(Context.POWER_SERVICE); wl = pm.newWakeLock(PowerManager.SCREEN_DIM_WAKE_LOCK, "My Tag"); } @TargetApi(Build.VERSION_CODES.O) @RequiresApi(api = Build.VERSION_CODES.JELLY_BEAN) @Override public int onStartCommand(Intent intent, int flags, int startId) { wl.acquire(); //Do some task Toast.makeText(this, "Notification Service started by user.", Toast.LENGTH_LONG).show(); return START_STICKY; } @RequiresApi(api = Build.VERSION_CODES.N) @Override public void onDestroy() { super.onDestroy(); wl.release(); Toast.makeText(this, "Notification Service destroyed by user.", Toast.LENGTH_LONG).show(); }
步骤 4 - 将以下代码添加到manifest.xml中
<?xml version = "1.0" encoding = "utf-8"?> <manifest xmlns:android = "http://schemas.android.com/apk/res/android" package = "com.example.andy.myapplication"> <uses-permission android:name = "android.permission.WAKE_LOCK"/> <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 = ".service"/> </application> </manifest>
让我们尝试运行您的应用程序。我假设您已将您的实际Android移动设备连接到您的计算机。要从Android Studio运行应用程序,请打开项目的其中一个活动文件,然后单击工具栏中的运行 图标。选择您的移动设备作为选项,然后检查您的移动设备,它将显示您的默认屏幕 -
以上结果是初始屏幕,点击TextView,它将启动通知服务,如下所示 -
在以上结果中,服务已启动,现在点击TextView,它将停止通知服务,如下所示 -
点击这里下载项目代码
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