Question

当尝试从Android应用程序访问RESTful api时，您需要检查两件事：

启用了用户的wifi（并且已经建立了连接）
您的应用实际上可以访问服务器。（我的服务器在本地网络上）

我设法检查了第一个，但我不知道如何检查最新的。

这是我的输出

05-25 15:49:46.929  15485-15999/com.tesis.restapp.restapp E/AndroidRuntime﹕ FATAL EXCEPTION: AsyncTask #1
    java.lang.RuntimeException: An error occured while executing doInBackground()
            at android.os.AsyncTask$3.done(AsyncTask.java:278)
            at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
            at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
            at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
            at java.util.concurrent.FutureTask.run(FutureTask.java:137)
            at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:208)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
            at java.lang.Thread.run(Thread.java:856)
     Caused by: retrofit.RetrofitError: java.net.ConnectException: failed to connect to /192.168.1.25 (port 8080) after 15000ms: isConnected failed: ECONNREFUSED (Connection refused)
            at retrofit.RestAdapter$RestHandler.invokeRequest(RestAdapter.java:385)
            at retrofit.RestAdapter$RestHandler.invoke(RestAdapter.java:241)
            at $Proxy0.logIn(Native Method)
            at com.tesis.restapp.restapp.activities.intro.IntroActivity$SignIn.doInBackground(IntroActivity.java:83)
            at com.tesis.restapp.restapp.activities.intro.IntroActivity$SignIn.doInBackground(IntroActivity.java:70)
            at android.os.AsyncTask$2.call(AsyncTask.java:264)
            at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
            at java.util.concurrent.FutureTask.run(FutureTask.java:137)
            at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:208)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
            at java.lang.Thread.run(Thread.java:856)
     Caused by: java.net.ConnectException: failed to connect to /192.168.1.25 (port 8080) after 15000ms: isConnected failed: ECONNREFUSED (Connection refused)
            at libcore.io.IoBridge.isConnected(IoBridge.java:220)
            at libcore.io.IoBridge.connectErrno(IoBridge.java:158)
            at libcore.io.IoBridge.connect(IoBridge.java:118)
            at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192)
            at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:459)
            at java.net.Socket.connect(Socket.java:849)
            at libcore.net.http.HttpConnection.<init>(HttpConnection.java:77)
            at libcore.net.http.HttpConnection.<init>(HttpConnection.java:50)
            at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:351)
            at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:86)
            at libcore.net.http.HttpConnection.connect(HttpConnection.java:128)
            at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:308)
            at libcore.net.http.HttpEngine.connect(HttpEngine.java:303)
            at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:282)
            at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:232)
            at libcore.net.http.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:80)
            at libcore.net.http.HttpURLConnectionImpl.getOutputStream(HttpURLConnectionImpl.java:188)
            at retrofit.client.UrlConnectionClient.prepareRequest(UrlConnectionClient.java:66)
            at retrofit.client.UrlConnectionClient.execute(UrlConnectionClient.java:37)
            at retrofit.RestAdapter$RestHandler.invokeRequest(RestAdapter.java:322)
            at retrofit.RestAdapter$RestHandler.invoke(RestAdapter.java:241)
            at $Proxy0.logIn(Native Method)
            at com.tesis.restapp.restapp.activities.intro.IntroActivity$SignIn.doInBackground(IntroActivity.java:83)
            at com.tesis.restapp.restapp.activities.intro.IntroActivity$SignIn.doInBackground(IntroActivity.java:70)
            at android.os.AsyncTask$2.call(AsyncTask.java:264)
            at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
            at java.util.concurrent.FutureTask.run(FutureTask.java:137)
            at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:208)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
            at java.lang.Thread.run(Thread.java:856)
     Caused by: libcore.io.ErrnoException: isConnected failed: ECONNREFUSED (Connection refused)
            at libcore.io.IoBridge.isConnected(IoBridge.java:207)
            at libcore.io.IoBridge.connectErrno(IoBridge.java:158)
            at libcore.io.IoBridge.connect(IoBridge.java:118)
            at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192)
            at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:459)
            at java.net.Socket.connect(Socket.java:849)
            at libcore.net.http.HttpConnection.<init>(HttpConnection.java:77)
            at libcore.net.http.HttpConnection.<init>(HttpConnection.java:50)
            at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:351)
            at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:86)
            at libcore.net.http.HttpConnection.connect(HttpConnection.java:128)
            at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:308)
            at libcore.net.http.HttpEngine.connect(HttpEngine.java:303)
            at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:282)
            at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:232)
            at libcore.net.http.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:80)
            at libcore.net.http.HttpURLConnectionImpl.getOutputStream(HttpURLConnectionImpl.java:188)
            at retrofit.client.UrlConnectionClient.prepareRequest(UrlConnectionClient.java:66)
            at retrofit.client.UrlConnectionClient.execute(UrlConnectionClient.java:37)
            at retrofit.RestAdapter$RestHandler.invokeRequest(RestAdapter.java:322)
            at retrofit.RestAdapter$RestHandler.invoke(RestAdapter.java:241)
            at $Proxy0.logIn(Native Method)
            at com.tesis.restapp.restapp.activities.intro.IntroActivity$SignIn.doInBackground(IntroActivity.java:83)
            at com.tesis.restapp.restapp.activities.intro.IntroActivity$SignIn.doInBackground(IntroActivity.java:70)
            at android.os.AsyncTask$2.call(AsyncTask.java:264)
            at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
            at java.util.concurrent.FutureTask.run(FutureTask.java:137)
            at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:208)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
            at java.lang.Thread.run(Thread.java:856)

修改

这是我的界面（目前，它只是尝试登录用户）

public interface RestAppApiInterface {

    @FormUrlEncoded
    @POST(Constants.URL_LOGIN)
    public User logIn(@Field("username") String username, @Field("password") String password);

}

该类返回接口的实例：

public class ApiClient {

    private static final String API_URL = "http://192.168.1.25:8080";

    private static RestAppApiInterface sRestAppService;

    public static RestAppApiInterface getRestAppApiClient() {
        if (sRestAppService == null) {
            RestAdapter restAdapter = new RestAdapter.Builder()
                    .setEndpoint(API_URL)
                    .build();
            sRestAppService = restAdapter.create(RestAppApiInterface.class);
        }
        return sRestAppService;
    }

}

我在像这样的AsynTask中调用服务

RestAppApiInterface apiInterface = ApiClient.getRestAppApiClient();
apiInterface.logIn("username","p@55w0rd");

Answer 1

[未经测试，从我的头脑中]

看起来你可以在这里干预：

Caused by ... yada yada ...
retrofit.client.UrlConnectionClient.execute(UrlConnectionClient.java:37)

改造RestAdapter.Builder可让您使用setClient()方法自定义后端访问方式，因此您可以这样：

RestAdapter restAdapter = new RestAdapter.Builder().setClient(
  new Client.Provider() {
    public Client get() {
      return new UrlConnectionClient() {
          @Override
          public Response execute(Request request) {
            // Test avail. / handle exceptions here,
            // call through to the real implementation
            return super.execute();
          }
      };
    }
  });

对于实际的主机可用性逻辑，您可以尝试this recipe

Answer 2

这是我最终做的事情：我不知道这是否是一个很好的解决方案，但它确实有效。（我每次使用界面时都要记得抓住这个例外。

        try {
            user = apiInterface.logIn(params[0], params[1]);
            if (user != null) {
                return Constants.LOG_IN_OK;
            } else {
                return Constants.LOG_IN_INVALID_CREDENTIALS;
            }
        } catch (RetrofitError e) {
            return Constants.LOG_IN_SERVER_NOT_FOUND;
        }

Answer 3

如果可以，您可以使用异步呼叫。如果使用异步调用，则可以更好地处理Retrofit中的异常。异步执行要求方法的最后一个参数是Callback。（http://square.github.io/retrofit/）所以你的界面看起来像这样：

public interface RestAppApiInterface {

@FormUrlEncoded
@POST(Constants.URL_LOGIN)
void logIn(@Field("username") String username, @Field("password") String password, Callback<User>pCallback);

异常在Callbacks失败方法中处理。而且不需要在单独的线程中执行它。

使用：

apiInterface.logIn("username","p@55w0rd", new Callback<User>() {
                @Override
                public void success(User u, Response response) {
                    //on success
                }

                @Override
                public void failure(RetrofitError error) {
                    //on failure
                }
            });

改造|处理“服务器未找到异常”

3 个答案: