我的AsyncTask中什么变量读取为null?

时间:2015-01-16 03:55:08

标签: java android json android-asynctask

每次按下登录按钮调用AsyncTask时,应用程序都会崩溃。我无法弄清楚我是否错误地传递了字符串或是什么。任何想法将不胜感激。另外,如果我没有提供足够的信息,请告诉我。对不起,这是我的第一篇文章。谢谢

package com.carrcodes.getgathering;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import org.json.JSONException;
import org.json.JSONObject;

public class LoginActivity extends Activity {

    EditText usernameField,passwordField;
    Button login,register;
    TextView loginErrorMsg;

    // JSON Response node names
    private static String KEY_SUCCESS = "success";
    private static String KEY_ERROR = "error";
    private static String KEY_ERROR_MSG = "error_msg";
    private static String KEY_UID = "uid";
    private static String KEY_NAME = "name";
    private static String KEY_EMAIL = "email";
    private static String KEY_CREATED_AT = "created_at";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        setTitle("Login");

        usernameField = (EditText) findViewById(R.id.StudentEmailBox);
        passwordField = (EditText) findViewById(R.id.PasswordBox);
        login = (Button) findViewById(R.id.sign_in_button);
        register = (Button) findViewById(R.id.register_button);
        loginErrorMsg = (TextView) findViewById(R.id.login_error);

        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
             /*   Intent intent = new Intent(LoginActivity.this, GetGatheringActivity.class);
                Bundle login_info = new Bundle();
                String username = usernameField.getText().toString();
                String password = passwordField.getText().toString();
                login_info.putString("Username", username);
                login_info.putString("Password", password);
                intent.putExtras(login_info);
                UserFunctions userFunction = new UserFunctions();
                JSONObject json = userFunction.loginUser(username, password); */


                Async task = new Async();
                task.execute(KEY_SUCCESS);
            }});
/*

                StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
                StrictMode.setThreadPolicy(policy);
                // check for login response
                try {
                    if (json.getString(KEY_SUCCESS) != null) {
                        loginErrorMsg.setText("");
                        String res = json.getString(KEY_SUCCESS);
                        if (Integer.parseInt(res) == 1) {
                            // user successfully logged in
                            // Store user details in SQLite Database
                            DatabaseHandler db = new DatabaseHandler(getApplicationContext());
                            JSONObject json_user = json.getJSONObject("user");

                            // Clear all previous data in database
                            userFunction.logoutUser(getApplicationContext());
                            db.addUser(json_user.getString(KEY_EMAIL)
                                    , json.getString(KEY_UID), json_user.getString(KEY_CREATED_AT));

                            // Launch Dashboard Screen
                            Intent dashboard = new Intent(getApplicationContext(),
                                    GetGatheringActivity.class);

                            // Close all views before launching Dashboard
                            dashboard.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                            startActivity(dashboard);

                            // Close Login Screen
                            finish();
                        } else {
                            // Error in login
                            loginErrorMsg.setText("Incorrect username/password");
                        }
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        });*/


                register.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        Intent registerIntent = new Intent(getApplicationContext(),
                                RegisterActivity.class);

                        startActivity(registerIntent);
                        finish();
                    }
                });
            }


    private class Async extends AsyncTask<String, Void, Void>{

        private Context context;

        @Override
        protected Void doInBackground(String... sUrl) {

            Intent intent = new Intent (LoginActivity.this, GetGatheringActivity.class);
            Bundle login_info = new Bundle();
            String username = usernameField.getText().toString();
            String password = passwordField.getText().toString();
            login_info.putString("Username", username);
            login_info.putString("Password", password);
            intent.putExtras(login_info);
            UserFunctions userFunction = new UserFunctions();
            JSONObject json = userFunction.loginUser(username, password);


            // check for login response
            try {
                if (json.getString(KEY_SUCCESS) != null) {
                    loginErrorMsg.setText("");
                    String res = json.getString(KEY_SUCCESS);
                    if(Integer.parseInt(res) == 1){
                        // user successfully logged in
                        // Store user details in SQLite Database
                        DatabaseHandler db = new DatabaseHandler(getApplicationContext());
                        JSONObject json_user = json.getJSONObject("user");

                        // Clear all previous data in database
                        userFunction.logoutUser(getApplicationContext());
                        db.addUser(json_user.getString(KEY_EMAIL)
                                , json.getString(KEY_UID), json_user.getString(KEY_CREATED_AT));



                        // Launch Dashboard Screen
                        Intent dashboard = new Intent(getApplicationContext(),
                                GetGatheringActivity.class);

                        // Close all views before launching Dashboard
                        dashboard.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                        startActivity(dashboard);

                        // Close Login Screen
                        finish();

                    }else{
                        // Error in login
                        loginErrorMsg.setText("Incorrect username/password");
                    }

                }
            } catch (JSONException e) {
                e.printStackTrace();
            }
            return null;
        }
        }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

这是我的Logcat

01-15 21:31:25.642    1777-1777/com.carrcodes.getgathering D/InputEventConsistencyVerifier﹕ KeyEvent: ACTION_UP but key was not down.
    in android.widget.EditText{3cd680a VFED..CL .F...... 64,221-1376,378 #7f090004 app:id/PasswordBox}
    0: sent at 2748595000000, KeyEvent { action=ACTION_UP, keyCode=KEYCODE_TAB, scanCode=15, metaState=0, flags=0x8, repeatCount=0, eventTime=2748595, downTime=2748451, deviceId=0, source=0x101 }
01-15 21:31:28.647    1777-1798/com.carrcodes.getgathering E/JSON﹕ [ 01-15 21:31:28.655  1777: 1798 E/JSON Parser ]
    Error parsing data org.json.JSONException: End of input at character 0 of
01-15 21:31:28.665    1777-1798/com.carrcodes.getgathering E/AndroidRuntime﹕ FATAL EXCEPTION: AsyncTask #1
    Process: com.carrcodes.getgathering, PID: 1777
    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:818)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String org.json.JSONObject.getString(java.lang.String)' on a null object reference
            at com.carrcodes.getgathering.LoginActivity$Async.doInBackground(LoginActivity.java:151)
            at com.carrcodes.getgathering.LoginActivity$Async.doInBackground(LoginActivity.java:130)
            at android.os.AsyncTask$2.call(AsyncTask.java:288)
            at java.util.concurrent.FutureTask.run(FutureTask.java:237)

2 个答案:

答案 0 :(得分:0)

JSONObject json = userFunction.loginUser(username, password);

我怀疑json将返回null,因为在此之后您在其上调用了几个getString()方法。你可以将它打印到日志或使用调试器一步一步吗?

这是引起问题的线路,我认为(没有行号,很难确定):

if (json.getString(KEY_SUCCESS) != null) {

答案 1 :(得分:0)

我认为问题是空指针异常。 问题发生在 JSONObject json = userFunction.loginUser(用户名,密码);

在调用任何方法之前进行if(json!= null)之类的检查。