在Android平台上启动服务

Question

我正在使用startService（Intent intent）方法启动服务。 当我调用此函数时，它会到达服务的onCreate ，但无法调用onStartCommand 。 这是我的代码-

@Override
public void onReceive(Context context, Intent intent) {
    // Send a text notification to the screen.
    Log.e("mudit", "Action: " + intent.getAction());

    try {
        ConnectivityManager connManager = (ConnectivityManager) context
                .getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo info = connManager.getActiveNetworkInfo();
        Log.e("mudit", "getType: " + info.getType());
        Log.e("mudit", "isConnected: " + info.isConnected());
        if (info.isConnected()) {

            Intent newinIntent = new Intent(context, service.class);
            context.startService(newinIntent);
        }

    } catch (Exception e) {
        e.printStackTrace();
        Intent newinIntent = new Intent(context, service.class);
        context.stopService(newinIntent);

    }

}

服务代码-

package com.android.service;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.widget.Toast;

public class service extends Service {

    @Override
    public IBinder onBind(Intent arg0) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public void onCreate() {
        super.onCreate();
        Toast.makeText(this, "Service created...", Toast.LENGTH_LONG).show();
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Toast.makeText(this, "Service destroyed ...", Toast.LENGTH_LONG).show();
    }

    public int onStartCommand(Intent intent, int flags, int startId) {

        Toast.makeText(this, "onStartCommand...", Toast.LENGTH_LONG).show();
        return 1;
    }

}  

Manifest.xml-

<receiver class=".AReceiver" android:name=".AReceiver">
        <intent-filter>
            <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
        </intent-filter>
    </receiver>
    <service class=".service" android:name=".service"
        android:enabled="true" android:icon="@drawable/icon">
    </service>

Answer 1

1. Unbound Service：无限期地在后台运行，即使已启动的活动也随服务结束。
2. 绑定服务：它将一直运行到活动的生命周期。

活动可以通过startService()启动服务，而将通过stopService()停止。 如果活动要与服务进行交互，则可以使用bindService() 。

首先调用onCreate() ，然后使用活动提供的意图数据调用onStartCommand 。

资源

Answer 2

larsVogel 在这篇出色的文章中解决了这个问题（以及许多其他类似的问题）。

这就是我修改他的代码以创建连接性接收器的方式，该连接器可以监视用户何时连接到WIFI网络，以便批量上传使用情况数据：

在清单文件中，在您的</ application>的结束标记之前放置一个接收器并声明一个服务：

    <receiver android:name=".ConnMonitor" android:enabled="true">
        <intent-filter>
            <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
        </intent-filter>
    </receiver>
    <service android:name=".BatchUploadGpsData" ></service>

</application>

在名为ConnMonitor.java的单独文件中创建广播接收器类（请取消注释Log调用以能够正确监视流）

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.util.Log;

public class ConnMonitor extends BroadcastReceiver {
    private String TAG = "TGtracker";

    @Override
    public void onReceive(Context context, Intent intent) {
        //String typeName = "";
        String state = "";
        int type = -1;
        ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService( Context.CONNECTIVITY_SERVICE );
        NetworkInfo test = (NetworkInfo) connectivityManager.getActiveNetworkInfo();
        //Log.v(TAG,"there has been a CONNECTION CHANGE -> "+intent.getExtras().get(ConnectivityManager.EXTRA_NETWORK_INFO));
        try {
            //typeName = test.getTypeName().toString();
            type = test.getType();
            state = test.getState().toString();
            //Log.i(TAG,"type -> '"+typeName +"'  state -> '"+state+"'"   );
        } catch (Exception e) {
            //typeName = "null";
            type = -1;
            state = "DISCONNECTED";
            //Log.i(TAG,"type -> error1 "+e.getMessage()+ "   cause = "+e.getCause()   );
        }

        if ( (type == 1)  &&  (state == "CONNECTED") ) {
            //Log.i(TAG, "I am soooo friggin uploadin on this beautiful WIFI connection ");
            Intent batchUploadDataService = new Intent(context, BatchUploadGpsData.class);
            context.startService(batchUploadDataService);
        } else {
            //Log.e(TAG,"NO FOUND MATCH type -> '"+typeName +"'  state -> '"+state+"'"   );
        }
    }
}

最后，创建服务BatchUploadGpsData.java，如下所示：

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.util.Log;

public class BatchUploadGpsData extends Service {
    final String TAG = "TGtracker";

    @Override
    public void onCreate() {
        Log.e(TAG, "here i am, rockin like a hurricane.   onCreate service");
    // this service tries to upload and terminates itself whether it is successful or not 
    // but it only effectively DOES anything while it is created 
    // (therefore, you can call 1 million times if uploading isnt done, nothing happens)
    // if you comment this next line, you will be able to see that it executes onCreate only the first it is called
    // the reason i do this is that the broadcast receiver is called at least twice every time you have a new change of connectivity state with successful connection to wifi
        this.stopSelf();
    }
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        //Log.i(TAG, "Received start id " + startId + ": " + intent);
        Log.e(TAG, "call me redundant BABY!  onStartCommand service");
        // this service is NOT supposed to execute anything when it is called
        // because it may be called inumerous times in repetition
        // all of its action is in the onCreate - so as to force it to happen ONLY once
        return 1;
    }
    @Override
    public IBinder onBind(Intent intent) {
        // TODO Auto-generated method stub
        return null;
    }

}

这不是伪代码，这是实际代码，已在android 2.2及更高版本上测试并运行。

测试该服务的方法是关闭并重新启动android上的WIFI服务（关闭wifi路由器电源也可以解决问题）。 但是此代码无法验证您是否已有效连接到网络。 为此，我建议您提出一个httpclient请求并检查呼叫结果。 超出了本讨论范围。

注意：由于服务在与UI相同的线程上运行，因此我强烈建议您根据您的特定需求，在单独的线程或asynctask上实现正确的上传。 您也可以在单独的线程上运行整个服务，但是尽管在这些情况下是标准做法，但这也不是本文讨论的范围。

Answer 3

首先，你应该添加@Override之前onStartCommand(..)然后确保为Android项目的目标是高于2.0。

Answer 4

我相信，您无法访问服务中的任何UI组件，例如Dialog甚至Toast。

尝试这个。

public int onStartCommand(Intent intent, int flags, int startId) {

/*    Toast.makeText(this, "onStartCommand...", Toast.LENGTH_LONG).show();
    return 1; */

    Log.i("YourService", "Yes this works.");
}

Answer 5

首先，我建议您将班级命名为其他名称，以免造成混乱。 其次，这是我明显调用我拥有的服务的示例。 我在调用服务等时使用完整路径名，因为它们与我的应用程序不在同一个程序包中。

<service android:name="com.public.service.UploaderService" android:icon="@drawable/vgbio"></service>

这是我服务等级的要点，

package com.public.service;
....
public class UploaderService extends Service{
....
}

第三，确保对onStartCommand（）使用@Override。