Question

抱歉，我只是学习使用AsyncTask，但运行代码时出现问题..

我有三节课 RestClient的第一个类

public class LoginPembayaran {

private static final String urlServer = "https://webservicetagihan.herokuapp.com";

RestTemplate restTemplate = new RestTemplate();

public void login(String username, String password) throws GagalLoginException{
    Map<String, String> logindata = new HashMap<>();
    logindata.put("username",username);
    logindata.put("password",password);

    Map<String,Object> hasil = restTemplate.postForObject(urlServer + "/api/login",logindata,Map.class,new Object[]{});

    if (hasil == null ){
        throw new GagalLoginException("Respon valid");
    }

    if (!(Boolean)hasil.get("sukses")){
        throw new GagalLoginException("user name / password salah");
    }


}

AsyncTask的第二课..

public class loginAktifity extends Fragment {
private LoginPembayaran loginPembayaran = new LoginPembayaran();

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    final View fragment = inflater.inflate(R.layout.fr_login,container,false);

    Button button = (Button)fragment.findViewById(R.id.BtnLogin);
    button.setOnClickListener(
            new View.OnClickListener() {
                @Override
                public void onClick(View v) {

                    String username = ((EditText)fragment.findViewById(R.id.Etusernama)).getText().toString();
                    String password = ((EditText)fragment.findViewById(R.id.EtPassword)).getText().toString();

                    new AsyncTask<String,Void,Boolean>(){

                        String ErrorMassage;
                        @Override
                        protected Boolean doInBackground(String... params) {

                            try {
                                loginPembayaran.login(params[0], params[1]);
                                return true;
                            }catch (GagalLoginException err){
                                ErrorMassage = err.getMessage();
                                return false;
                            }
                        };


                        @Override
                        protected void onPostExecute(Boolean sukses) {
                            if(sukses){
                                Intent intent = new Intent(getContext(),SesudahLoginActivity.class);
                                startActivity(intent);
                            }
                            else {
                                Toast.makeText(getContext(),ErrorMassage,Toast.LENGTH_LONG).show();
                            }
                        }
                    }.execute(username,password);


                }
            }
    );
    return fragment;
}

}

异常的类树

public class GagalLoginException extends Exception {
public GagalLoginException(String message) {
    super(message);
}

}

我的logcat ..

    03-18 09:57:35.780 30964-31227/com.khoiron.apptagihan E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1
  Process: com.khoiron.apptagihan, PID: 30964
  java.lang.RuntimeException: An error occured while executing doInBackground()
      at android.os.AsyncTask$3.done(AsyncTask.java:300)
      at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
      at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
      at java.util.concurrent.FutureTask.run(FutureTask.java:242)
      at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
      at java.lang.Thread.run(Thread.java:841)
   Caused by: java.lang.NullPointerException
      at com.khoiron.apptagihan.RestClient.LoginPembayaran.login(LoginPembayaran.java:31)
      at com.khoiron.apptagihan.Fragment.loginAktifity$1$1.doInBackground(loginAktifity.java:48)
      at com.khoiron.apptagihan.Fragment.loginAktifity$1$1.doInBackground(loginAktifity.java:41)
      at android.os.AsyncTask$2.call(AsyncTask.java:288)
      at java.util.concurrent.FutureTask.run(FutureTask.java:237)
      at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231) 
      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112) 
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587) 
      12q
      at java.lang.Thread.run(Thread.java:841)

请帮帮我。请指导我......

Answer 1

如果是第31行

if (!(boolean)hasil.get("sukses")){

所以你用标签做了拼写错误，get（）返回null并将其强制转换为布尔值导致NPE。

Answer 2

从异常日志中，您可以看到异常来自{31}的LoginPembayaran.login。

Caused by: java.lang.NullPointerException
      at com.khoiron.apptagihan.RestClient.LoginPembayaran.login(LoginPembayaran.java:31)

正如在其他答案中已经提到的，地图hasil可能不包含关键项sukses，因此例外。

要调试此问题，您可以使用Android Studio的调试器（请参阅official guide）并在第31行设置断点，以检查地图hasil是否确实包含密钥{{ 1}}。

致命异常：AsyncTask＃1怎么修复？

2 个答案: