轉換結果java.lang.NullPointerException時出錯：lock == null，並且解析數據org.json.JSONException時出錯：輸入的字符0的結尾

Question

以下是相關的日志貓信息：

11-09 16:45:47.354    5149-5149/com.example.apex.apex E/Buffer Error﹕ Error converting result      java.lang.NullPointerException: lock == null
11-09 16:45:47.354    5149-5149/com.example.apex.apex E/JSON Parser﹕ Error parsing data org.json.JSONException: End of input at character 0 of
11-09 16:45:47.354    5149-5149/com.example.apex.apex D/AndroidRuntime﹕ Shutting down VM
11-09 16:45:47.354    5149-5149/com.example.apex.apex W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x41bd9ce0)
    Process: com.example.apex.apex, PID: 5149
    java.lang.NullPointerException
            at com.example.apex.apex.RegisterActivity$1.onClick(RegisterActivity.java:70)
            at android.view.View.performClick(View.java:4445)
            at android.view.View$PerformClick.run(View.java:18446)
            at android.os.Handler.handleCallback(Handler.java:733)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5146)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)
            at dalvik.system.NativeStart.main(Native Method)
11-09 16:46:36.686    5149-5149/com.example.apex.apex I/Process﹕ Sending signal. PID: 5149 SIG: 9

RegisterActivity.java：

我是Java和Android開發的新手，因此最初是對數據進行硬編碼以通過PHP與遠程服務器進行通信。

import android.app.Activity;
import android.os.Build;
import android.os.Bundle;
import android.os.StrictMode;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

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

import java.sql.Date;
import java.text.ParseException;
import java.text.SimpleDateFormat;


public class RegisterActivity extends Activity {

private static String KEY_SUCCESS = "success";
private static String KEY_ERROR = "error";
private static String KEY_ERROR_MSG = "error_msg";

Button btnRegister;
TextView registerErrorMsg;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_register);

    if(Build.VERSION.SDK_INT > 8)
    {
        StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
        StrictMode.setThreadPolicy(policy);
    }

    // import all assets
    btnRegister = (Button) findViewById(R.id.btnRegister);

    btnRegister.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            // inputs
            String fName = "John";
            String lName = "Smith";
            String email = "someone@example.com";
            String password  = "123345";
            String location = "Sligo";
            String dob = "07-10-1993";
            SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy");
            java.util.Date date = null;
            try {
                date = sdf.parse(dob);
            } catch (ParseException e) {
                e.printStackTrace();
            }
            java.sql.Date sqlDob = new Date(date.getTime());
            String gender = "Male";
            int height = 128;
            double weight = 78.5;
            CyclistFunctions cyclistFunction = new CyclistFunctions();
            JSONObject json = cyclistFunction.registerCyclist(fName, lName, email, password,
                    location, sqlDob, gender, height, weight);

            // check for register response
            try {
                if (json.getString(KEY_SUCCESS) != null) {
                    registerErrorMsg.setText("");
                    String res = json.getString(KEY_SUCCESS);
                    if(Integer.parseInt(res) == 1) {
                        // user successfully registered
                        // store user details in SQLite DB
                        DatabaseHandler db = new DatabaseHandler(getApplicationContext());
                        JSONObject json_user = json.getJSONObject("user");

                        // clear all previous data in database
                        finish();
                    } else {
                        registerErrorMsg.setText("Error in registration occurred! :/");
                    }
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
    });
}


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

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}
}

activity_register.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context="com.example.apex.apex.RegisterActivity">

<Button
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:id="@+id/btnRegister"
    android:text="Click!"/>

<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_below="@id/btnRegister"
    android:layout_marginTop="50dp"/>

JSONParser.java

package com.example.apex.apex;

import android.util.Log;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.protocol.HTTP;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.List;


public class JSONParser {

static InputStream is = null;
static JSONObject jObj = null;
static String json = "";

// constructor
public JSONParser() {

}

public JSONObject getJSONFromUrl(String url, List<NameValuePair> params) {

    // make HTTP request
    try {
        // creates a new HTTP client from parameters and a connection manager
        DefaultHttpClient httpClient = new DefaultHttpClient();
        HttpPost httpPost = new HttpPost(url);
        httpPost.setEntity(new UrlEncodedFormEntity(params));

        HttpResponse httpResponse = httpClient.execute(httpPost);
        HttpEntity httpEntity = httpResponse.getEntity();
        is = httpEntity.getContent();
    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    try {
        // buffer input from is
        BufferedReader reader = new BufferedReader(new InputStreamReader
                (is, HTTP.UTF_8), 8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }
        is.close();
        json = sb.toString();
        Log.e("JSON", json);
    } catch (Exception e) {
        Log.e("Buffer Error", "Error converting result " + e.toString());
    }

    // try to parse the string to JSON object
    try {
        jObj = new JSONObject(json);
    } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data " + e.toString());
    }

    // return JSON String
    return jObj;
}
}

CyclistFunctions.java

package com.example.apex.apex;

import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONObject;

import java.sql.Date;
import java.util.ArrayList;
import java.util.List;


public class CyclistFunctions {

private JSONParser jsonParser;

private static final String registerURL = "http://127.0.0.1/apexdb/include/db_functions.php/";

private static String register_tag = "register";

// constructor
public CyclistFunctions() {
    jsonParser = new JSONParser();
}

/**
 * make register request
 */
public JSONObject registerCyclist(String first_name, String last_name, String email_address,
                                  String password, String location, Date birth_date, String gender,
                                  int height_cm, double weight_kg) {

    // build parameters
    List<NameValuePair> params = new ArrayList<NameValuePair>();
    params.add(new BasicNameValuePair("tag", register_tag));
    params.add(new BasicNameValuePair("first_name", first_name));
    params.add(new BasicNameValuePair("last_name", last_name));
    params.add(new BasicNameValuePair("email_address", email_address));
    params.add(new BasicNameValuePair("password", password));
    params.add(new BasicNameValuePair("location", location));
    params.add(new BasicNameValuePair("birth_date", String.valueOf(birth_date)));
    params.add(new BasicNameValuePair("gender", gender));
    params.add(new BasicNameValuePair("height_cm", String.valueOf(height_cm)));
    params.add(new BasicNameValuePair("weight_kg", String.valueOf(weight_kg)));

    // fetch JSON object
    JSONObject json = jsonParser.getJSONFromUrl(registerURL, params);
    // return json
    return json;
}
}

db_functions.php

<?php

class DB_Functions {

private $db;
// constructor
function __construct() {
    require_once 'db_connect.php';
    // connecting to database
    $this->db = new db_connect();
    $this->db->connect();
}

// destructor
function __destruct() {

}

/**
Storing new cyclist
return user details
**/
public function storeCyclist($first_name, $last_name, $email_address,
    $password, $birth_date, $gender, $height_cm, $weight_kg) { 

    $hash = $this->hashSSHA($password);
    $encrypted_password = $hash["encrypted"]; // password
    $salt = $hash["salt"]; // salt
    $result = mysqli_query("INSERT INTO cyclist (first_name, last_name, email_address, 
        encrypted_password, salt, birth_date, gender, height_cm, weight_kg, date_created) 
        VALUES ('$first_name', '$last_name', '$email_address', '$encrypted_password', '$salt', '$birth_date',
        '$gender', '$height_cm', '$weight_kg', NOW())"); 

        if($result) {
            // successfully inserted cyclist into database
            $response["success"] = 1;
            $response["message"] = "Cyclist succesfully created";

            // echo JSON response
            echo json_encode($response);
        } else {
            // insert fail
            $response["success"] = 1;
            $response["message"] = "Woops, something went wrong - failed to create new cyclist! :(";

        }
}

public function userExists($email_address) {
    $result = mysqli_query("SELECT email_address from cyclist WHERE email_address = '$email_address'");
    $no_of_rows = mysqli_num_rows($result);
    if($no_of_rows > 0) {
        // user exists
        return true;
    } else {
        // user exists
        return false;
    }

}
/**
encrypt password
@param password
returns salt
**/

public function hashSSHA($password) {

    $salt = sha1(rand());
    $salt = substr($salt, 0, 10);
    $encrypted = base64_encode(sha1($password . $salt, true) . $salt);
    $hash = array("salt" => $salt, "encrypted" => $encrypted);
    return $hash;
}

/**
decrypting password
@params salt, password
returns hash string
**/
public function checkSSHA($salt, $password) {

    $hash = base64_encode(sha1($password . $salt, true) . $salt);

    return $hash;
}
}
?>

DB_Connect.php

<?php

class DB_Connect {

// constructor
function __construct() {

}

// destructor
function __destruct() {
    // $this->close();
}

// connecting to database
public function connect() {
    require_once 'config.php';
    // connecting to mysqli
    $con = new mysqli_connect($db_host, $db_user, $db_password, $db_name);
    // check connection
    if(mysqli_connect_errno())
    {
        echo "Failed to connect to MySQL: " .mysqli_connect_errno();
    }

    // return db handler
    return $con;
}

public function close() {
    // close connection
    mysqli_close();
} 
}
?>

Answer 1

由於這個原因，您沒有給registerErrorMsg賦值，所以您得到的是空指針。

registerErrorMsg =  (TextView) findViewById(R.id.registerErrorMsg);

我認為這將解決您的問題。

Answer 2

您必須發布json模型和循環功能，以識別確切的問題。

這行造成錯誤

       JSONObject json = cyclistFunction.registerCyclist(fName, lName, email, password,
                location, sqlDob, gender, height, weight);

一定是這樣

         String result_json = cyclistFunction.registerCyclist(fName, lName, email, password,location, sqlDob, gender, height, weight);
    if (result_json != null) {
    try {
    JSONObject jsonObj = new JSONObject(result_json );

    if (jsonObj != null) {

     String res = json.getString(KEY_SUCCESS);
    } 
    } catch (JSONException e) {
    e.printStackTrace();

    }
    } else {

    Log.e("JSON Data", "Didn't receive any data from server!");
    }