Service是Android中一个类,它是Android四大组件之一,使用Service可以在后台执行长时间的操作( perform long-running operations in the background ),Service并不与用户产生UI交互。其他的应用组件可以启动Service,即便用户切换了其他应用,启动的Service仍可在后台运行。一个组件可以与Service绑定并与之交互,甚至是跨进程通信(IPC)。例如,一个Service可以在后台执行网络请求、播放音乐、执行文件读写操作或者与 content provider交互 等。
ps:附上一个service组件介绍的网站:https://blog.****.net/scott2017/article/details/51505801
下面是一个音乐后台播放的例子:
1.Activity类
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button; /**
* Created by cj on 2018/3/28.
*/ public class ServiceDemo extends Activity implements View.OnClickListener{ private static final String TAG = "ServiceDemo";
Button buttonStart, buttonStop; @Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.servicedemo); buttonStart = (Button) findViewById(R.id.buttonStart);
buttonStop = (Button) findViewById(R.id.buttonStop); buttonStart.setOnClickListener(this);
buttonStop.setOnClickListener(this);
} public void onClick(View src) {
switch (src.getId()) {
case R.id.buttonStart:
Log.i(TAG, "onClick: starting service");
startService(new Intent(this, MyService.class));
break;
case R.id.buttonStop:
Log.i(TAG, "onClick: stopping service");
stopService(new Intent(this, MyService.class));
break;
}
} }
2.Service子类:
import android.app.Notification;
import android.app.Service;
import android.content.Intent;
import android.media.MediaPlayer;
import android.os.Build;
import android.os.Debug;
import android.os.IBinder;
import android.support.annotation.Nullable;
import android.util.Log;
import android.widget.Toast; /**
* Created by cj on 2018/3/28.
*/ public class MyService extends Service { private static final String TAG = "MyService";
private final static int GRAY_SERVICE_ID = 1001;
MediaPlayer player; @Nullable
@Override
public IBinder onBind(Intent intent) {
return null;
} @Override
public void onCreate() {
Toast.makeText(this,"MyService Created",Toast.LENGTH_SHORT).show();
Log.i(TAG,"oncreated");
player = MediaPlayer.create(this,R.raw.huanghun); //此处的R.raw.huanghun为要播放的音乐资源。在res文件夹下创建raw目录,huanghun.mp3为音乐资源,放到创建好的raw文件夹下
player.setLooping(false);
} @Override
public int onStartCommand(Intent intent, int flags, int startId) {
//sdk小于18时启动一个状态栏通知
if(Build.VERSION.SDK_INT<18){
startForeground(GRAY_SERVICE_ID,new Notification());
}else{
//sdk大于18 时启动一个状态栏通知
Intent intent1 = new Intent(this,GrayInnerService.class);
startService(intent1);
startForeground(GRAY_SERVICE_ID,new Notification());
}
return super.onStartCommand(intent, flags, startId);
} //给API >= 18 的平台上做灰色保护手段
public class GrayInnerService extends Service {
@Override
public IBinder onBind(Intent intent) {
return null;
} @Override
public int onStartCommand(Intent intent, int flags, int startId) {
startForeground(GRAY_SERVICE_ID, new Notification());
stopForeground(true);
stopSelf(); return super.onStartCommand(intent, flags, startId);
}
} @Override
public void onDestroy() {
Toast.makeText(this, "My Service Stoped", Toast.LENGTH_LONG).show();
Log.i(TAG, "onDestroy");
player.stop();
} @Override
public void onStart(Intent intent, int startId) {
Toast.makeText(this, "My Service Start", Toast.LENGTH_LONG).show();
Log.i(TAG, "onStart");
player.start();
}
}
3.布局文件
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:gravity="center">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content" android:text="@string/servicesdemo" android:gravity="center" android:textSize="20sp" android:padding="20dp"/>
<Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/buttonStart" android:text="@string/start"></Button>
<Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/stop" android:id="@+id/buttonStop"></Button>
</LinearLayout>
4.String.xml文件
<resources>
<string name="app_name">update</string> //此处为运用程序的名称,一般项目创建时自带
<string name="start">播放</string>
<string name="stop">停止</string>
<string name="servicesdemo">Service Demo</string>
</resources>
5.manifest.xml文件中配置
<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=".ServiceDemo">
<intent-filter>
<action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<service android:enabled="true" android:name=".MyService"/> //此处配置,name为service的子类。
</application>