【问题标题】:Unable to call REST API in android无法在 android 中调用 REST API
【发布时间】:2014-01-04 22:11:06
【问题描述】:

我正在尝试通过手机调用 REST Web 服务。我正在使用以下代码来完成此操作。我只有一个具有按钮和文本视图的活动。每当我单击按钮时,它都会在logcat 中出现以下错误:

AndroidRuntime :: at android.os.Handler.dispatchMessage(Handler.java:92)

我做错了什么?我该如何解决? 以下是我的课程。

rest.java

public class Rest extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.start_rest);

    Button button = (Button) findViewById(R.id.btn);


    button.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            String url = "http://192.168.1.145/tst.php";

            RestService re = new RestService();             
            JSONObject jb =  RestService.doGet(url);

            TextView tv = (TextView) findViewById(R.id.txtView);                
            tv.setText(jb.toString());
        }
    });

  }
}

RestService.java

public class RestService {

public static JSONObject doGet(String url) {
    JSONObject json = null;

    HttpClient httpclient = new DefaultHttpClient();
    // Prepare a request object
    HttpGet httpget = new HttpGet(url);
    // Accept JSON
    httpget.addHeader("accept", "application/json");
    // Execute the request
    HttpResponse response;

    try {
        response = httpclient.execute(httpget);
        // Get the response entity
       // Log.e("myApp", "Issue is here...!");
        HttpEntity entity = response.getEntity();
        // If response entity is not null
        if (entity != null) {
            // get entity contents and convert it to string
            InputStream instream = entity.getContent();
            String result= convertStreamToString(instream);
            // construct a JSON object with result
            json=new JSONObject(result);
            // Closing the input stream will trigger connection release
            instream.close();
        }
    } catch (ClientProtocolException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    // Return the json
    return json;
}

private static String convertStreamToString(InputStream is) {

    BufferedReader br = null;
    StringBuilder sb = new StringBuilder();

    String line;
    try {

        br = new BufferedReader(new InputStreamReader(is));
        while ((line = br.readLine()) != null) {
            sb.append(line);
        }

    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        if (br != null) {
            try {
                br.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    return sb.toString();
}
}

【问题讨论】:

  • 这就是我在 logcat 中得到的全部内容。
  • 你确定吗?也许您已将过滤器应用于 logcat,因此隐藏了其他日志?
  • NetworkOnMainThreadException ???真的???
  • @Lukasz'Severiaan'Grela :是的,我已经检查过了,这就是我在 logcat 中得到的全部内容。没有别的。
  • 我认为 A.S.意思是在 UI 线程上你正在调用网络操作,这将有效地锁定应用程序直到进程完成,这种任务应该在后台线程中使用例如AsyncTask.

标签: android web-services rest


【解决方案1】:

编写一个异步任务并在该线程中执行网络操作。

     public class myTask extends AsyncTask<String, JSONObject, Void> {

        private ProgressDialog dialog;
        private Context mContext;

        public myTask(Context mContext){
            this.mContext = mContext;

        }

        protected void onPreExecute() {
            this.dialog = new ProgressDialog(mContext);
            this.dialog.setCancelable(false);
            this.dialog.setMessage("please wait..");
            this.dialog.show();
        }

        protected JSONObject doInBackground(String... ids) {

            String url = "http://192.168.1.145/tst.php";
            RestService re = new RestService();             
            JSONObject jb =  RestService.doGet(url);

            return jb;
        }

       protected Void onPostExecute(JSONObject jb) {

            //get json data and set
        }
    }

【讨论】:

    【解决方案2】:

    尝试了您发布的代码后,我得到了以下异常(我怀疑如果您查看的话,您会在 logcat 中找到相同的异常)

    12-17 10:28:26.850    2182-2182/com.example.app E/AndroidRuntime﹕ FATAL EXCEPTION: main
        android.os.NetworkOnMainThreadException
                at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1117)
                at java.net.InetAddress.lookupHostByName(InetAddress.java:385)
                at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
                at java.net.InetAddress.getAllByName(InetAddress.java:214)
                at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:137)
                at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
                at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
                at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
                at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
                at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
                at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
                at com.example.app.RestService.doGet(RestService.java:31)
                at com.example.app.MainActivity$1.onClick(MainActivity.java:28)
                at android.view.View.performClick(View.java:4084)
                at android.view.View$PerformClick.run(View.java:16966)
                at android.os.Handler.handleCallback(Handler.java:615)
                at android.os.Handler.dispatchMessage(Handler.java:92)
                at android.os.Looper.loop(Looper.java:137)
                at android.app.ActivityThread.main(ActivityThread.java:4745)
                at java.lang.reflect.Method.invokeNative(Native Method)
                at java.lang.reflect.Method.invoke(Method.java:511)
                at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
                at dalvik.system.NativeStart.main(Native Method)
    

    你得到这个是因为你试图在主线程上通过网络做一些事情,这是不允许的。 (在Google design guidelines here中有提到)

    在这种情况下,最好的解决方案是将服务调用移动到 AsyncTask,它在单独的线程上运行并且不会阻塞 UI。

    试试这个,我把 URL 换成了只返回日期的 freely available JSON web service

    public class MainActivity extends Activity {
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            Button button = (Button) findViewById(R.id.btn);
    
    
            button.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    String url = "http://date.jsontest.com";
                    new MyAsyncTask().execute(url);
                }
            });
    
    
        }
        class MyAsyncTask extends AsyncTask<String,Void,JSONObject> {
    
            @Override
            protected JSONObject doInBackground(String... urls) {
                return RestService.doGet(urls[0]);
            }
    
            @Override
            protected void onPostExecute(JSONObject jsonObject) {
                TextView tv = (TextView) findViewById(R.id.txtView);
                tv.setText(jsonObject.toString());
            }
        }
    
    }
    

    【讨论】:

      猜你喜欢
      • 1970-01-01
      • 2019-10-21
      • 1970-01-01
      • 2021-05-18
      • 2018-09-15
      • 1970-01-01
      • 2019-01-07
      • 2019-08-15
      • 2019-03-21
      相关资源
      最近更新 更多