Java 登录失败时应用程序崩溃

我正在android studio中制作一个应用程序。当由于密码和电子邮件不匹配或数据库中不存在而导致登录失败时，我希望它只是显示一个警报，但现在它只是崩溃了

这是我的后台任务代码

import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.AsyncTask;
import android.os.Handler;
import android.renderscript.ScriptGroup;
import android.widget.Toast;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;
import java.nio.Buffer;

import javax.net.ssl.HttpsURLConnection;

/**
 * Created by Kelsea
 */
public class BackgroundTask extends AsyncTask<String,Void,String> {




    SharedPreferences preferences;
    SharedPreferences.Editor editor;

    Context context;
    ProgressDialog pDialog;

    BackgroundTask(Context ctx){
        this.context = ctx;
    }

    @Override
    protected String doInBackground(String... params) {

        preferences = context.getSharedPreferences("MYPREFS", Context.MODE_PRIVATE);
        editor = preferences.edit();
        editor.putString("flag","0");
        editor.commit();

        String urlRegistration = "http://biomedengineering.x10host.com/BiomedicalEngineering-register.php";
        String urlLogin  = "http://biomedengineering.x10host.com/BiomedicalEngineering-login.php";
        String task = params[0];

        if(task.equals("register")){
            String regName = params[1];
            String regEmail = params[2];
            String regPassword = params[3];

            try {
                URL url = new URL(urlRegistration);
                HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
                httpURLConnection.setRequestMethod("POST");
                httpURLConnection.setDoOutput(true);
                OutputStream outputStream = httpURLConnection.getOutputStream();
                OutputStreamWriter outputStreamWriter = new OutputStreamWriter(outputStream,"UTF-8");
                BufferedWriter bufferedWriter = new BufferedWriter(outputStreamWriter);
                String myData = URLEncoder.encode("identifier_name","UTF-8")+"="+URLEncoder.encode(regName,"UTF-8")+"&"
                        +URLEncoder.encode("identifier_email","UTF-8")+"="+URLEncoder.encode(regEmail,"UTF-8")+"&"
                        +URLEncoder.encode("identifier_password","UTF-8")+"="+URLEncoder.encode(regPassword,"UTF-8");
                bufferedWriter.write(myData);
                bufferedWriter.flush();
                bufferedWriter.close();
                InputStream inputStream = httpURLConnection.getInputStream();
                inputStream.close();

                editor.putString("flag","register");
                editor.commit();
                return "Successfully Registered " + regName;
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }catch (NullPointerException e) {
            e.printStackTrace();
        }

        }
        if(task.equals("login")){
            String loginEmail = params[1];
            String loginPassword = params[2];
            try {
                URL url = new URL(urlLogin);
                HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
                httpURLConnection.setRequestMethod("POST");
                httpURLConnection.setDoOutput(true);
                httpURLConnection.setDoInput(true);

                //send the email and password to the database
                OutputStream outputStream = httpURLConnection.getOutputStream();
                OutputStreamWriter outputStreamWriter = new OutputStreamWriter(outputStream,"UTF-8");
                BufferedWriter bufferedWriter = new BufferedWriter(outputStreamWriter);
                String myData = URLEncoder.encode("identifier_loginEmail","UTF-8")+"="+URLEncoder.encode(loginEmail,"UTF-8")+"&"
                        +URLEncoder.encode("identifier_loginPassword","UTF-8")+"="+URLEncoder.encode(loginPassword,"UTF-8");
                bufferedWriter.write(myData);
                bufferedWriter.flush();
                bufferedWriter.close();
                outputStream.close();

                //get response from the database
                InputStream inputStream = httpURLConnection.getInputStream();
                InputStreamReader inputStreamReader = new InputStreamReader(inputStream,"UTF-8");
                BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
                String dataResponse = "";
                String inputLine = "";
                while((inputLine = bufferedReader.readLine()) != null){
                    dataResponse += inputLine;
                }
                bufferedReader.close();
                inputStream.close();
                httpURLConnection.disconnect();

                System.out.println("!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");
                System.out.println(dataResponse);

                editor.putString("flag","login");
                editor.commit();
                return  dataResponse;

            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }catch (NullPointerException e) {
            e.printStackTrace();
        }
        }

        return null;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(context);
        pDialog.setMessage("Attempting login...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();
    }

    //This method will be called when doInBackground completes... and it will return the completion string which
    //will display this toast.
    @Override
    protected void onPostExecute(String s) {
        String flag = preferences.getString("flag","0");

        if(flag.equals("register")) {
            Toast.makeText(context,s,Toast.LENGTH_LONG).show();
        }
        if(flag.equals("login")){
            String test = "false";
            String name = "";
            String email = "";
            String[] serverResponse = s.split("[,]");
            test = serverResponse[0];
            name = serverResponse[1];
            email = serverResponse[2];

            if(test.equals("true")){
                editor.putString("name",name);
                editor.commit();
                editor.putString("email",email);
                editor.commit();
                Intent intent = new Intent(context, Home.class);
                context.startActivity(intent);
            }else{
                // Get a handler that can be used to post to the main thread
                Handler mainHandler = new Handler(context.getMainLooper());

                Runnable myRunnable = new Runnable() {
                    @Override
                    public void run() {
                        display("Login failed....", "Something went wrong");
                    } // This is your code
                };
                mainHandler.post(myRunnable);

            }
        }else{

            Handler mainHandler = new Handler(context.getMainLooper());

            Runnable myRunnable = new Runnable() {
                @Override
                public void run() {
                    display("Login failed....", "Something went wrong");
                } // This is your code
            };
            mainHandler.post(myRunnable);

        }
    }


    @Override
    protected void onProgressUpdate(Void... values) {
        super.onProgressUpdate(values);
    }

    public void display(String title, String message){
        AlertDialog.Builder builder = new AlertDialog.Builder(context);
        builder.setCancelable(true);
        builder.setTitle(title);
        builder.setMessage(message);
        builder.show();
    }


}

---

您的问题似乎就在这里，因为您总是希望split方法返回三个条目。正如你所评论的，它可能不是。因此，最好将serverResponse[1]和serverResponse[2]向下移动一个块

 String[] serverResponse = s.split("[,]");
 test = serverResponse[0];
 name = serverResponse[1]; // remove here
 email = serverResponse[2]; // remove here

  if(test.equals("true")){
       editor.putString("name", serverResponse[1]); // put it here
       editor.commit();
       editor.putString("email",serverResponse[2]); // put it here
       editor.commit();
       Intent intent = new Intent(context, Home.class);
       context.startActivity(intent);
      }else{

---

要点是，您必须检查是否有可能的条目。

您需要添加stacktrace。检查您的上下文是getapplicationcontext或activity。这而不是getapplicationcontext use activity。这添加了stack trace@MuratK。您确定此s.split[，]始终返回3个元素吗？因为这是您得到OutOfBondException的地方，如果用户不在数据库中，它可能并不总是返回三个元素database@kelseatomaino好吧，我还是接受这个答案吧。

 String[] serverResponse = s.split("[,]");
 test = serverResponse[0];
 name = serverResponse[1]; // remove here
 email = serverResponse[2]; // remove here

  if(test.equals("true")){
       editor.putString("name", serverResponse[1]); // put it here
       editor.commit();
       editor.putString("email",serverResponse[2]); // put it here
       editor.commit();
       Intent intent = new Intent(context, Home.class);
       context.startActivity(intent);
      }else{