我正在寻找一个服务,我可以使用它来调用基于web的REST API。

我想在app init上启动一个服务然后我想让这个服务请求一个url并返回结果。与此同时,我希望能够显示一个进度窗口或类似的东西。

我目前创建了一个使用IDL的服务,我在某处读到过,你只需要它来跨应用程序通信,所以认为这些需求剥离,但不确定如何做回调没有它。另外,当我点击帖子(Config.getURL(“login”),值)时,应用程序似乎暂停了一段时间(看起来很奇怪-以为服务背后的想法是它在不同的线程上运行!)

目前,我有一个服务与post和获取http方法在里面,一对AIDL文件(双向通信),一个ServiceManager处理启动,停止,绑定等到服务,我动态创建一个处理器与特定的代码回调需要。

我不希望任何人给我一个完整的代码库来工作,但一些指针将非常感激。

代码(大部分)完整:

public class RestfulAPIService extends Service  {

final RemoteCallbackList<IRemoteServiceCallback> mCallbacks = new RemoteCallbackList<IRemoteServiceCallback>();

public void onStart(Intent intent, int startId) {
    super.onStart(intent, startId);
}
public IBinder onBind(Intent intent) {
    return binder;
}
public void onCreate() {
    super.onCreate();
}
public void onDestroy() {
    super.onDestroy();
    mCallbacks.kill();
}
private final IRestfulService.Stub binder = new IRestfulService.Stub() {
    public void doLogin(String username, String password) {

        Message msg = new Message();
        Bundle data = new Bundle();
        HashMap<String, String> values = new HashMap<String, String>();
        values.put("username", username);
        values.put("password", password);
        String result = post(Config.getURL("login"), values);
        data.putString("response", result);
        msg.setData(data);
        msg.what = Config.ACTION_LOGIN;
        mHandler.sendMessage(msg);
    }

    public void registerCallback(IRemoteServiceCallback cb) {
        if (cb != null)
            mCallbacks.register(cb);
    }
};

private final Handler mHandler = new Handler() {
    public void handleMessage(Message msg) {

        // Broadcast to all clients the new value.
        final int N = mCallbacks.beginBroadcast();
        for (int i = 0; i < N; i++) {
            try {
                switch (msg.what) {
                case Config.ACTION_LOGIN:
                    mCallbacks.getBroadcastItem(i).userLogIn( msg.getData().getString("response"));
                    break;
                default:
                    super.handleMessage(msg);
                    return;

                }
            } catch (RemoteException e) {
            }
        }
        mCallbacks.finishBroadcast();
    }
    public String post(String url, HashMap<String, String> namePairs) {...}
    public String get(String url) {...}
};

几个AIDL文件:

package com.something.android

oneway interface IRemoteServiceCallback {
    void userLogIn(String result);
}

and

package com.something.android
import com.something.android.IRemoteServiceCallback;

interface IRestfulService {
    void doLogin(in String username, in String password);
    void registerCallback(IRemoteServiceCallback cb);
}

服务经理:

public class ServiceManager {

    final RemoteCallbackList<IRemoteServiceCallback> mCallbacks = new RemoteCallbackList<IRemoteServiceCallback>();
    public IRestfulService restfulService;
    private RestfulServiceConnection conn;
    private boolean started = false;
    private Context context;

    public ServiceManager(Context context) {
        this.context = context;
    }

    public void startService() {
        if (started) {
            Toast.makeText(context, "Service already started", Toast.LENGTH_SHORT).show();
        } else {
            Intent i = new Intent();
            i.setClassName("com.something.android", "com.something.android.RestfulAPIService");
            context.startService(i);
            started = true;
        }
    }

    public void stopService() {
        if (!started) {
            Toast.makeText(context, "Service not yet started", Toast.LENGTH_SHORT).show();
        } else {
            Intent i = new Intent();
            i.setClassName("com.something.android", "com.something.android.RestfulAPIService");
            context.stopService(i);
            started = false;
        }
    }

    public void bindService() {
        if (conn == null) {
            conn = new RestfulServiceConnection();
            Intent i = new Intent();
            i.setClassName("com.something.android", "com.something.android.RestfulAPIService");
            context.bindService(i, conn, Context.BIND_AUTO_CREATE);
        } else {
            Toast.makeText(context, "Cannot bind - service already bound", Toast.LENGTH_SHORT).show();
        }
    }

    protected void destroy() {
        releaseService();
    }

    private void releaseService() {
        if (conn != null) {
            context.unbindService(conn);
            conn = null;
            Log.d(LOG_TAG, "unbindService()");
        } else {
            Toast.makeText(context, "Cannot unbind - service not bound", Toast.LENGTH_SHORT).show();
        }
    }

    class RestfulServiceConnection implements ServiceConnection {
        public void onServiceConnected(ComponentName className, IBinder boundService) {
            restfulService = IRestfulService.Stub.asInterface((IBinder) boundService);
            try {
            restfulService.registerCallback(mCallback);
            } catch (RemoteException e) {}
        }

        public void onServiceDisconnected(ComponentName className) {
            restfulService = null;
        }
    };

    private IRemoteServiceCallback mCallback = new IRemoteServiceCallback.Stub() {
        public void userLogIn(String result) throws RemoteException {
            mHandler.sendMessage(mHandler.obtainMessage(Config.ACTION_LOGIN, result));

        }
    };

    private Handler mHandler;

    public void setHandler(Handler handler) {
        mHandler = handler;
    }
}

服务初始化和绑定:

// this I'm calling on app onCreate
servicemanager = new ServiceManager(this);
servicemanager.startService();
servicemanager.bindService();
application = (ApplicationState)this.getApplication();
application.setServiceManager(servicemanager);

服务函数调用:

// this lot i'm calling as required - in this example for login
progressDialog = new ProgressDialog(Login.this);
progressDialog.setMessage("Logging you in...");
progressDialog.show();

application = (ApplicationState) getApplication();
servicemanager = application.getServiceManager();
servicemanager.setHandler(mHandler);

try {
    servicemanager.restfulService.doLogin(args[0], args[1]);
} catch (RemoteException e) {
    e.printStackTrace();
}

...later in the same file...

Handler mHandler = new Handler() {
    public void handleMessage(Message msg) {

        switch (msg.what) {
        case Config.ACTION_LOGIN:

            if (progressDialog.isShowing()) {
                progressDialog.dismiss();
            }

            try {
                ...process login results...
                }
            } catch (JSONException e) {
                Log.e("JSON", "There was an error parsing the JSON", e);
            }
            break;
        default:
            super.handleMessage(msg);
        }

    }

};

当前回答

如果您的服务将成为应用程序的一部分,那么您将使它比实际需要的复杂得多。由于您有一个从rest式Web服务获取数据的简单用例,您应该研究ResultReceiver和IntentService。

这个Service + ResultReceiver模式的工作原理是,当你想要执行某些操作时,使用startService()启动或绑定到服务。你可以指定要执行的操作,并通过Intent中的extras传入ResultReceiver (activity)。

在服务中实现onHandleIntent来执行Intent中指定的操作。当操作完成时,使用ResultReceiver传递的消息向Activity发送消息,此时onReceiveResult将被调用。

例如,您希望从Web服务中提取一些数据。

创建意图并调用startService。 服务中的操作启动,并向活动发送消息,称其已启动 活动处理消息并显示进度。 服务完成操作并将一些数据发送回您的活动。 您的活动处理数据并将其放入列表视图中 该服务向你发送消息,说它已经完成了,然后它就自杀了。 活动获取完成消息并隐藏进度对话框。

我知道你提到过你不想要一个代码库,但开源谷歌I/O 2010应用程序以我描述的这种方式使用服务。

更新后添加了示例代码:

的活动。

public class HomeActivity extends Activity implements MyResultReceiver.Receiver {

    public MyResultReceiver mReceiver;

    public void onCreate(Bundle savedInstanceState) {
        mReceiver = new MyResultReceiver(new Handler());
        mReceiver.setReceiver(this);
        ...
        final Intent intent = new Intent(Intent.ACTION_SYNC, null, this, QueryService.class);
        intent.putExtra("receiver", mReceiver);
        intent.putExtra("command", "query");
        startService(intent);
    }

    public void onPause() {
        mReceiver.setReceiver(null); // clear receiver so no leaks.
    }

    public void onReceiveResult(int resultCode, Bundle resultData) {
        switch (resultCode) {
        case RUNNING:
            //show progress
            break;
        case FINISHED:
            List results = resultData.getParcelableList("results");
            // do something interesting
            // hide progress
            break;
        case ERROR:
            // handle the error;
            break;
    }
}

服务:

public class QueryService extends IntentService {
    protected void onHandleIntent(Intent intent) {
        final ResultReceiver receiver = intent.getParcelableExtra("receiver");
        String command = intent.getStringExtra("command");
        Bundle b = new Bundle();
        if(command.equals("query") {
            receiver.send(STATUS_RUNNING, Bundle.EMPTY);
            try {
                // get some data or something           
                b.putParcelableArrayList("results", results);
                receiver.send(STATUS_FINISHED, b)
            } catch(Exception e) {
                b.putString(Intent.EXTRA_TEXT, e.toString());
                receiver.send(STATUS_ERROR, b);
            }    
        }
    }
}

ResultReceiver扩展-编辑关于实现MyResultReceiver。接收机

public class MyResultReceiver implements ResultReceiver {
    private Receiver mReceiver;

    public MyResultReceiver(Handler handler) {
        super(handler);
    }

    public void setReceiver(Receiver receiver) {
        mReceiver = receiver;
    }

    public interface Receiver {
        public void onReceiveResult(int resultCode, Bundle resultData);
    }

    @Override
    protected void onReceiveResult(int resultCode, Bundle resultData) {
        if (mReceiver != null) {
            mReceiver.onReceiveResult(resultCode, resultData);
        }
    }
}

其他回答

当我点击 帖子(Config.getURL(“登录”), 值)应用程序似乎暂停了一个 虽然(看起来很奇怪——这个想法想 服务的背后是它运行在 不同的线程!)

不,你必须自己创建一个线程,默认情况下本地服务运行在UI线程中。

我强烈推荐REST客户端Retrofit。

我发现这篇写得很好的博客文章非常有用,它还包含简单的示例代码。 作者使用了Retrofit进行网络调用,Otto实现了一个数据总线模式:

http://www.mdswanson.com/blog/2014/04/07/durable-android-rest-clients.html

另外,当我点击帖子(Config.getURL(“login”),值)时,应用程序似乎暂停了一段时间(看起来很奇怪-以为服务背后的想法是它在不同的线程上运行!)

在这种情况下,最好使用asynctask,它在不同的线程上运行,并在完成时将结果返回给ui线程。

如果您的服务将成为应用程序的一部分,那么您将使它比实际需要的复杂得多。由于您有一个从rest式Web服务获取数据的简单用例,您应该研究ResultReceiver和IntentService。

这个Service + ResultReceiver模式的工作原理是,当你想要执行某些操作时,使用startService()启动或绑定到服务。你可以指定要执行的操作,并通过Intent中的extras传入ResultReceiver (activity)。

在服务中实现onHandleIntent来执行Intent中指定的操作。当操作完成时,使用ResultReceiver传递的消息向Activity发送消息,此时onReceiveResult将被调用。

例如,您希望从Web服务中提取一些数据。

创建意图并调用startService。 服务中的操作启动,并向活动发送消息,称其已启动 活动处理消息并显示进度。 服务完成操作并将一些数据发送回您的活动。 您的活动处理数据并将其放入列表视图中 该服务向你发送消息,说它已经完成了,然后它就自杀了。 活动获取完成消息并隐藏进度对话框。

我知道你提到过你不想要一个代码库,但开源谷歌I/O 2010应用程序以我描述的这种方式使用服务。

更新后添加了示例代码:

的活动。

public class HomeActivity extends Activity implements MyResultReceiver.Receiver {

    public MyResultReceiver mReceiver;

    public void onCreate(Bundle savedInstanceState) {
        mReceiver = new MyResultReceiver(new Handler());
        mReceiver.setReceiver(this);
        ...
        final Intent intent = new Intent(Intent.ACTION_SYNC, null, this, QueryService.class);
        intent.putExtra("receiver", mReceiver);
        intent.putExtra("command", "query");
        startService(intent);
    }

    public void onPause() {
        mReceiver.setReceiver(null); // clear receiver so no leaks.
    }

    public void onReceiveResult(int resultCode, Bundle resultData) {
        switch (resultCode) {
        case RUNNING:
            //show progress
            break;
        case FINISHED:
            List results = resultData.getParcelableList("results");
            // do something interesting
            // hide progress
            break;
        case ERROR:
            // handle the error;
            break;
    }
}

服务:

public class QueryService extends IntentService {
    protected void onHandleIntent(Intent intent) {
        final ResultReceiver receiver = intent.getParcelableExtra("receiver");
        String command = intent.getStringExtra("command");
        Bundle b = new Bundle();
        if(command.equals("query") {
            receiver.send(STATUS_RUNNING, Bundle.EMPTY);
            try {
                // get some data or something           
                b.putParcelableArrayList("results", results);
                receiver.send(STATUS_FINISHED, b)
            } catch(Exception e) {
                b.putString(Intent.EXTRA_TEXT, e.toString());
                receiver.send(STATUS_ERROR, b);
            }    
        }
    }
}

ResultReceiver扩展-编辑关于实现MyResultReceiver。接收机

public class MyResultReceiver implements ResultReceiver {
    private Receiver mReceiver;

    public MyResultReceiver(Handler handler) {
        super(handler);
    }

    public void setReceiver(Receiver receiver) {
        mReceiver = receiver;
    }

    public interface Receiver {
        public void onReceiveResult(int resultCode, Bundle resultData);
    }

    @Override
    protected void onReceiveResult(int resultCode, Bundle resultData) {
        if (mReceiver != null) {
            mReceiver.onReceiveResult(resultCode, resultData);
        }
    }
}

Lets say I want to start the service on an event - onItemClicked() of a button. The Receiver mechanism would not work in that case because :- a) I passed the Receiver to the service (as in Intent extra) from onItemClicked() b) Activity moves to the background. In onPause() I set the receiver reference within the ResultReceiver to null to avoid leaking the Activity. c) Activity gets destroyed. d) Activity gets created again. However at this point the Service will not be able to make a callback to the Activity as that receiver reference is lost. The mechanism of a limited broadcast or a PendingIntent seems to be more usefull in such scenarios- refer to Notify activity from service