[英]How to handle a IOException by starting a new Activity in android
引发异常时,我正在尝试启动主页活动。 现在,当发生异常时,该应用程序将关闭并从主页开始。 我希望它无缝进入主页应用程序,而不是警告用户该应用程序已关闭。 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)
对于开发人员来说这很好并且很花哨,但是在发生这种情况时,我想开始一个新的活动。 我对这个问题有代码明智的是这个。
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。
您仅在捕获中处理IOException,否则可能会抛出其他异常,从而导致崩溃。正如我在Log for NPE中所看到的那样,最好确保代码可以通过其他异常或使用base异常类,它将处理所有异常。
您必须在新线程中执行netWorking操作,或使用诸如Volley,Okhhttp之类的框架。Retrofit是我现在使用的最佳框架,其中包含Okhttp和AsyncTask,但您可能希望将RxJava统一起来。
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