Question

如果我的设备未连接到互联网，那么它应该在Toast中提供互联网连接错误。但我的应用程序崩溃了。它没有捕获无Internet连接错误。我的代码完全适用于互联网连接。请帮帮我

private class MyAsyncTask extends AsyncTask<String, Integer, String>{


        @Override
        protected String doInBackground(String... params) {
            // TODO Auto-generated method stub
            String s=postData();
            return s;
        }

        protected void onPostExecute(String result){
            pb.setVisibility(View.GONE);
            Toast.makeText(getApplicationContext(), result, Toast.LENGTH_LONG).show();
        }
        protected void onProgressUpdate(Integer... progress){
            pb.setProgress(progress[0]);
        }

        public String postData() {
            // Create a new HttpClient and Post Header


            String origresponseText="";
            try {
                  DefaultHttpClient httpclient = new DefaultHttpClient();
                HttpPost httppost = new HttpPost("http://localhost/ServletParams/AndroidServlet");

                // Add your data  cnic,mobileNo,name,address,nextkin
                List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
                nameValuePairs.add(new BasicNameValuePair("param1",cnic));
                nameValuePairs.add(new BasicNameValuePair("param2", mobileNo));
                nameValuePairs.add(new BasicNameValuePair("param3", name));
                nameValuePairs.add(new BasicNameValuePair("param4", address));
                nameValuePairs.add(new BasicNameValuePair("param5", nextkin));
                nameValuePairs.add(new BasicNameValuePair("param6", sendImages));


                httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
         /* execute */

                HttpResponse response = httpclient.execute(httppost);
                  HttpEntity rp = response.getEntity();
origresponseText=readContent(response);

            } 
      catch (ClientProtocolException e) {
                // TODO Auto-generated catch block
          Toast.makeText(getBaseContext(), "No Internet Connection", Toast.LENGTH_SHORT).show();
            } 
      catch (IOException e) {
                // TODO Auto-generated catch block
          Toast.makeText(getBaseContext(), "sorry", Toast.LENGTH_SHORT).show();
            }
            String responseText = origresponseText.substring(7, origresponseText.length());
            return responseText;

        }


    }
    String readContent(HttpResponse response)
    {
        String text = "";
        InputStream in =null;

        try {
            in = response.getEntity().getContent();
            BufferedReader reader = new BufferedReader(new InputStreamReader(in));
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                  sb.append(line);
                }
                text = sb.toString();
        } catch (IllegalStateException e) {
            Toast.makeText(getBaseContext(), "sorry", Toast.LENGTH_SHORT).show();

        } catch (IOException e) {
            Toast.makeText(getBaseContext(), "Sorry", Toast.LENGTH_SHORT).show();
        }
        finally {
            try {

              in.close();
            } catch (Exception ex) {
                Toast.makeText(getBaseContext(), "Sorry", Toast.LENGTH_SHORT).show();
            }
            }

return text;
    }

这是一个日志：

10-17 19:45:05.061: E/AndroidRuntime(22597): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
10-17 19:45:05.061: E/AndroidRuntime(22597):    at android.os.Handler.<init>(Handler.java:121)
10-17 19:45:05.061: E/AndroidRuntime(22597):    at android.widget.Toast$TN.<init>(Toast.java:322)
10-17 19:45:05.061: E/AndroidRuntime(22597):    at android.widget.Toast.<init>(Toast.java:91)
10-17 19:45:05.061: E/AndroidRuntime(22597):    at android.widget.Toast.makeText(Toast.java:238)
10-17 19:45:05.061: E/AndroidRuntime(22597):    at com.example.androidufoneapp.CustomerRegistrationL0$MyAsyncTask.postData(CustomerRegistrationL0.java:647)
10-17 19:45:05.061: E/AndroidRuntime(22597):    at com.example.androidufoneapp.CustomerRegistrationL0$MyAsyncTask.doInBackground(CustomerRegistrationL0.java:602)
10-17 19:45:05.061: E/AndroidRuntime(22597):    at com.example.androidufoneapp.CustomerRegistrationL0$MyAsyncTask.doInBackground(CustomerRegistrationL0.java:1)
10-17 19:45:05.061: E/AndroidRuntime(22597):    at android.os.AsyncTask$2.call(AsyncTask.java:287)
10-17 19:45:05.061: E/AndroidRuntime(22597):    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
10-17 19:45:05.061: E/AndroidRuntime(22597):    ... 4 more

Answer 1

我认为，你有Window Leak，因为当没有互联网连接时，你的代码正在访问doInBackground方法中的UI线程。在ReadContent方法中查看Toast消息。你的Toast消息将访问UI线程，如果没有互联网并且它有异常。但是当你的应用程序在后台线程当时，所以你会得到窗口泄漏错误，应用程序将崩溃，因为你无法访问App UI背景线程。

Ok ..要修复此问题，请从PostData方法中删除Toast消息。如果要显示toast，则在onPostExecute方法中显示它。我建议另一个好方法。

使用此方法使用以下方法检查连接是否可用

public boolean isOnline() {
        ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo netInfo = cm.getActiveNetworkInfo();
        if (netInfo != null && netInfo.isConnectedOrConnecting()
                && cm.getActiveNetworkInfo().isAvailable()
                && cm.getActiveNetworkInfo().isConnected()) {
            return true;
        }
        return false;
    }

然后当您启动AsyncTask时，请执行此操作

if(isOnline()){
   // Start your AsyncTask
} else{
  // Show internet not available alert
}

您还需要添加ACCESS_NETWORK_STATE权限才能使用此方法。希望它有所帮助。

Answer 2

问题是您在Toast.makeText调用的方法中调用doInBackground。此方法触及在doInBackground内禁止的UI线程，您应根据查询结果从Toast.makeText调用onPostExecute。

你可以这样做：

protected void onPostExecute(String result){
    if (!result.equals("")){ // Check to see if String result contains a result or in case or error, is still your empty String you assigned it
        pb.setVisibility(View.GONE);
        Toast.makeText(getApplicationContext(), result, Toast.LENGTH_LONG).show();
    }else{
        Toast.makeText(getApplicationContext(), errorMessage, Toast.LENGTH_LONG).show();
        // errorMessage can be a String that you keep track of inside your catch clauses or a generic error message
    }
}

您还需要从Toast.makeText方法中的catch子句中删除对readContent的所有来电。

此外，最好在启动AsyncTask之前检查之前的网络连接，并且只处理AsyncTask代码中的IO错误等。 Ayon的解决方案将适用于此。

Answer 3

你必须把你的祝酒词放在主ui线程中，如下所示：

runOnUiThread(new Runnable() {
    public void run() {
        // runs on UI thread
          Toast.makeText(getBaseContext(), "No Internet Connection", Toast.LENGTH_SHORT).show();

    }
});

将两者都放在这样，你的问题就会解决！ ;）

Answer 4

在调用AsyncTask之前，首先检查连接。

创建一个名为AppUtility的类。

public class AppUtility {
    /**
         * Determine connectivity. a utility method to determine Internet
         * connectivity this is invoked before every web request
         * 
         * @param ctx
         *            the context
         * @return true, if successful
         */
        public static boolean determineConnectivity(Context context) {
            ConnectivityManager manager = (ConnectivityManager) context
                    .getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo info = manager.getActiveNetworkInfo();
            return info != null && info.getState() == NetworkInfo.State.CONNECTED;
        } 

}

并检查这样的连接

if (AppUtility.determineConnectivity(this))
  new MyAsyncTask().execute();
else
Toast.makeText(this, "sorry! No Internet Connection", Toast.LENGTH_SHORT).show();

希望这会对你有所帮助。

应用程序崩溃而不是提供Internet连接错误

4 个答案: