java - 如何通过在 android 中启动一个新的 Activity 来处理 IOException

Question

我正尝试在抛出异常时启动我的主页 Activity 。现在当异常发生时，应用程序关闭并从主页启动。我想让它无缝地转到主页面应用程序，而不是让用户警告应用程序正在关闭。它给我的错误是这样的:

D/Issue with Http:: IOException
04-19 13:57:31.518 27520-27570/myapp W/System.err: java.io.FileNotFoundException: my webpage
04-19 13:57:31.518 27520-27570/myapp W/System.err:     at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:238)
04-19 13:57:31.518 27520-27570/myapp W/System.err:     at myapp.HttpManager.MyHttpGet.httpDownloadData(MyHttpGet.java:79)
04-19 13:57:31.518 27520-27570/myapp W/System.err:     at myapp.HttpManager.MyHttpGet.doInBackground(MyHttpGet.java:53)
04-19 13:57:31.518 27520-27570/myapp W/System.err:     at myapp.HttpManager.MyHttpGet.doInBackground(MyHttpGet.java:31)
04-19 13:57:31.518 27520-27570/myapp W/System.err:     at android.os.AsyncTask$2.call(AsyncTask.java:295)
04-19 13:57:31.518 27520-27570/myapp W/System.err:     at java.util.concurrent.FutureTask.run(FutureTask.java:237)
04-19 13:57:31.519 27520-27570/myapp W/System.err:     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)
04-19 13:57:31.519 27520-27570/myapp W/System.err:     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
04-19 13:57:31.519 27520-27570/myapp W/System.err:     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
04-19 13:57:31.519 27520-27570/myapp W/System.err:     at java.lang.Thread.run(Thread.java:818)
04-19 13:57:31.538 27520-27520/myapp D/AndroidRuntime: Shutting down VM
04-19 13:57:31.594 27520-27520/myapp E/AndroidRuntime: FATAL EXCEPTION: main
Process: myapp, PID: 27520
java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.contains(java.lang.CharSequence)' on a null object reference
at myapp.JSON.LoginJsonParser.checkUsername(LoginJsonParser.java:41)
at myapp.LoginPage$2.onClick(LoginPage.java:128)
at android.view.View.performClick(View.java:5198)
at android.view.View$PerformClick.run(View.java:21147)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

这对开发人员来说很好，但我想在发生这种情况时开始新的 Activity 。我对这个问题的代码是这样的。

 private String httpDownloadData(String myUrl)

{
    String respone = null;
    HttpURLConnection urlConnection = null;
    try
    {
        URL url = new URL(myUrl);
        //put in the username and pssword for parmas to send to url
        //this is good for login
        if (username!=null)
        {
            Authenticator.setDefault(new Authenticator() {
                @Override
                protected PasswordAuthentication getPasswordAuthentication() {
                    return new PasswordAuthentication(username, password.toCharArray());
                }
            });
        }

        urlConnection = (HttpURLConnection)url.openConnection();
        InputStream inputStream = urlConnection.getInputStream();

        if(inputStream != null)
        {
            respone = streamToString(inputStream);
            inputStream.close();
        }

    }catch (IOException ie)
    {
        //ie.printStackTrace();
        Log.d("Issue with Http: " , "IOException");
        ie.printStackTrace();
        Intent newIntent = new Intent(activity.getApplicationContext(), ECom.class);
        activity.startActivity(newIntent);
    }finally {
        if(urlConnection != null)
        {
            urlConnection.disconnect();
        }
    }
    return respone;
}

感谢您对此的任何帮助。

Answer 1

你不能在 UI 线程中执行任何网络操作，它会给你 networkOnMainThreadException。请使用 AsyncTask 执行网络和长时间运行的操作。你可以找到samples and docs here

或使用 volley处理网络操作的框架