服务(Service)全解析(五)--前台Service

MainActivity如下:

package cc.testservice2;
import android.app.Activity;
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.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
/**
 * Demo描述:
 * 前台Service使用示例
 *
 *
 * 主要实现:
 * 1 在Service的onCreate()中调用startForeground()
 * 2 在Service的onDestroy()中调用stopForeground()
 * 3 一个Notification常驻在状态栏,当后台数据变化时需要
 *   更新该通知中的显示内容.在该示例中只用了一个简单的
 *   系统自带Notification来演示,实际项目中多半会用到
 *   自定义的Notification涉及到RemoteView.
 *
 *
 * 前台服务的特点:
 * 1 可尽量避免系统内容不足的时候被系统回收
 * 2 它会有一个图标一直在状态栏显示,拉下状态栏后可见更多信息.
 *   比如有的天气App就采用了该前台服务来实现.
 *
 *
 * 测试环境:
 * 1 该示例测试环境为Android4.4
 * 2 在Android2.3及其以下版本可能报错:
 *   java.lang.IllegalArgumentException: contentIntent required
 *
 *
 * 注意权限:
 *  <uses-permission android:name="android.permission.VIBRATE"/>
 *
 *
 * 参考资料:
 * 1 http://blog.csdn.net/guolin_blog/article/details/11952435
 * 2 http://blog.csdn.net/lfdfhl/article/details/38226523
 * 3 http://blog.csdn.net/vipzjyno1/article/details/25248021
 * 4 http://blog.csdn.net/think_soft/article/details/7299438
 * 5 http://blog.csdn.net/lfdfhl/article/details/10044161
 *   Thank you very much
 */
public class MainActivity extends Activity {
    TextView mNumberTextView;
    TextView mResultTextView;
    Button mSearchButton;
    ServiceConnectionImpl mServiceConnectionImpl;
    QueryInterface  mBinder;
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        //用于接收服务返回的Binder对象
        mServiceConnectionImpl=new ServiceConnectionImpl();
        mNumberTextView=(TextView) findViewById(R.id.numberEditText);
        mResultTextView=(TextView) findViewById(R.id.resultTextView);
        mSearchButton=(Button) findViewById(R.id.searchButton);
        mSearchButton.setOnClickListener(new ButtonOnClickListener());
        Intent intent=new Intent(this,ServiceSubclass.class);
        //当Activity启动的时候就启动服务
        bindService(intent, mServiceConnectionImpl, this.BIND_AUTO_CREATE);
    }

    private class ButtonOnClickListener implements OnClickListener{
		public void onClick(View v) {
			String number=mNumberTextView.getText().toString();
			String result=mBinder.queryByNumber(Integer.valueOf(number));
			mResultTextView.setText(result);
		}
    }

    //绑定服务和解除服务
    private final class ServiceConnectionImpl implements ServiceConnection{
    	//绑定服务时,此方法调用
		public void onServiceConnected(ComponentName name, IBinder service) {
			 mBinder=(QueryInterface) service;
		}
		//解除服务时,此方法调用
		public void onServiceDisconnected(ComponentName name) {
			mBinder=null;
		}
    }

   //解除与服务的连接
	protected void onDestroy() {
		unbindService(mServiceConnectionImpl);
		super.onDestroy();
	}

}

ServiceSubclass如下:

package cc.testservice2;

import android.app.Notification;
import android.app.Notification.Builder;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;

public class ServiceSubclass extends Service {
	private String[] names = new String[] { "小明", "小王", "小杨", "小李", "小强" };
	BinderSubclass mBinderSubclass = new BinderSubclass();
	private String result=null;
	private Context mContext;
	private Builder mBuilder;
	private PendingIntent mPendingIntent;
    private Notification mNotification;
    private NotificationManager mNotificationManager;
    private final int NOTIFICATION_ID=9527;
	@Override
	public void onCreate() {
		super.onCreate();
		mContext=this;
		System.out.println("在onCreate()中---> startForeground()");
		//准备Notification
		initNotification(mContext);
		//开启前台服务
		startForeground(NOTIFICATION_ID, mNotification);
	}

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

	@Override
	public void onDestroy() {
		super.onDestroy();
		//终止前台服务
		stopForeground(true);
		System.out.println("在onDestroy()中---> stopForeground()");
	}

	// queryByNumber就是接口里的业务方法.
	//一般来讲将业务抽象为一个接口,然后去实现接口,比如此处。
	// 注意:BinderSubclass继承自Binder也实现了业务接口
	private final class BinderSubclass extends Binder implements QueryInterface {
		public String queryByNumber(int number) {
			return query(number);
		}
	}

	//服务内部的方法
	public String query(int i) {
		if (i > 0 && i < 6) {
			result=names[i - 1];
			//更新通知
			updateNotification(result);
			return result;
		}
		return "查询错误，请再次输入";
	}

	/**
	 * 发送通知
	 */
	private void initNotification(Context context){
		Intent intent=new Intent(mContext, MainActivity.class);
		mPendingIntent=PendingIntent.getActivity(mContext, 0,intent, PendingIntent.FLAG_UPDATE_CURRENT);
		mNotificationManager=(NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
		mBuilder=new Builder(mContext);
		//通知产生的时间
		mBuilder.setWhen(System.currentTimeMillis());
		//通知首次出现在通知栏时的提示文字
		mBuilder.setTicker("Ticker");
		mBuilder.setContentTitle("ContentTitle");
		mBuilder.setContentInfo("ContentInfo");
		mBuilder.setContentText("ContentText");
		mBuilder.setContentIntent(mPendingIntent);
		//通知的优先级
		mBuilder.setPriority(Notification.PRIORITY_DEFAULT);
		//设置通知的图标.必须要有这句否则通知不显示!!!
		mBuilder.setSmallIcon(R.drawable.ic_launcher);
		//为通知添加声音,闪灯和振动效果等效果
		mBuilder.setDefaults(Notification.DEFAULT_VIBRATE);
		//设置通知是否为一个正在进行的通知.后台任务时常使用true
		mBuilder.setOngoing(false);

		mNotification=mBuilder.build();
		//通知被点击后自动消失
		mNotification.flags = Notification.FLAG_AUTO_CANCEL;
		mNotificationManager.notify(NOTIFICATION_ID, mNotification);
	}

	/**
	 * 更新通知
	 */
	private void updateNotification(String result){
		mBuilder.setContentTitle("Title");
		mBuilder.setContentInfo("Info");
		mBuilder.setContentText(result);
		mNotification=mBuilder.build();
		mNotification.flags = Notification.FLAG_AUTO_CANCEL;
		mNotificationManager.notify(NOTIFICATION_ID, mNotification);
	}

}

QueryInterface如下:

package cc.testservice2;
//业务接口
public interface QueryInterface {
   public String queryByNumber(int number);
}

main.xml如下:

<?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="fill_parent"
    android:orientation="vertical" >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="请输入1到5的数字" />

    <EditText
        android:id="@+id/numberEditText"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/searchButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="查询" />

    <TextView
        android:id="@+id/resultTextView"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

</LinearLayout>