大家好
我为我的android应用程序创建了一个注册表单。mysql数据库在localhost:3306 logcat给了我以下错误，当我尝试注册:
07-27 19:54:13.448 3923-3944/com.burgames.mysqltest E/Buffer Error﹕ Error converting result java.lang.NullPointerException: lock == null
07-27 19:54:13.448 3923-3944/com.burgames.mysqltest E/JSON Parser﹕ Error parsing data org.json.JSONException: End of input at character 0 of
07-27 19:54:13.448 3923-3944/com.burgames.mysqltest E/AndroidRuntime﹕ FATAL EXCEPTION: AsyncTask #2
Process: com.burgames.mysqltest, PID: 3923
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.toString()' on a null object reference
at com.burgames.mysqltest.register$CreateUser.doInBackground(register.java:110)
at com.burgames.mysqltest.register$CreateUser.doInBackground(register.java:73)
at android.os.AsyncTask$2.call(AsyncTask.java:288)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at android.os.AsyncTask$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)
at java.lang.Thread.run(Thread.java:818)
AsynkTas子类如下:
public class register extends ActionBarActivity implements View.OnClickListener {
private EditText user, pass;
private Button mRegister;
// Progress Dialog
private ProgressDialog pDialog;
// JSON parser class
JSONParser jsonParser = new JSONParser();
//php login script
//localhost :
//testing on your device
//put your local ip instead, on windows, run CMD > ipconfig
//or in mac's terminal type ifconfig and look for the ip under en0 or en1
// private static final String LOGIN_URL = "http://xxx.xxx.x.x:1234/webservice/register.php";
//testing on Emulator:
private static final String LOGIN_URL = "http://10.0.2.2:3306/webservice/register.php";
//testing from a real server:
//private static final String LOGIN_URL = "http://www.yourdomain.com/webservice/register.php";
//ids
private static final String TAG_SUCCESS = "success";
private static final String TAG_MESSAGE = "message";
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register);
user = (EditText)findViewById(R.id.username);
pass = (EditText)findViewById(R.id.password);
mRegister = (Button)findViewById(R.id.register);
mRegister.setOnClickListener(this);
}
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
new CreateUser().execute();
}
class CreateUser extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
boolean failure = false;
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(register.this);
pDialog.setMessage("Creating User...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected String doInBackground(String... args) {
// TODO Auto-generated method stub
// Check for success tag
int success;
String username = user.getText().toString();
String password = pass.getText().toString();
try {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("username", username));
params.add(new BasicNameValuePair("password", password));
Log.d("request!", "starting");
//Posting user data to script
JSONObject json = jsonParser.makeHttpRequest(
LOGIN_URL, "POST", params);
// full json response
Log.d("Login attempt", json.toString());
// json success element
success = json.getInt(TAG_SUCCESS);
if (success == 1) {
Log.d("User Created!", json.toString());
finish();
return json.getString(TAG_MESSAGE);
}else{
Log.d("Login Failure!", json.getString(TAG_MESSAGE));
return json.getString(TAG_MESSAGE);
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog once product deleted
pDialog.dismiss();
if (file_url != null){
Toast.makeText(register.this, file_url, Toast.LENGTH_LONG).show();
}
}
}
XML看起来像:
<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"
>
<ImageView
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/textView2"
android:layout_centerHorizontal="true"/>
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/password"
android:layout_centerVertical="true"
android:text="Username" />
<EditText
android:id="@+id/username"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView1"
android:layout_below="@+id/textView1"
android:ems="10" />
<TextView
android:id="@+id/TextView01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/username"
android:layout_below="@+id/username"
android:text="Password" />
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginTop="16dp"
android:gravity="center"
android:text="Android Remote Server Tutorial"
android:textAppearance="?android:attr/textAppearanceLarge"
android:textStyle="bold" />
<EditText
android:id="@+id/password"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/TextView01"
android:layout_centerHorizontal="true"
android:ems="10"
android:inputType="textPassword" />
<Button
android:id="@+id/register"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignRight="@+id/password"
android:layout_below="@+id/password"
android:text="Register" />
</RelativeLayout>
我发现错误可能在登录脚本上:
package com.burgames.mysqltest;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
public class login extends Activity implements OnClickListener{
private EditText user, pass;
private Button mSubmit, mRegister;
// Progress Dialog
private ProgressDialog pDialog;
// JSON parser class
JSONParser jsonParser = new JSONParser();
//php login script location:
//localhost :
//testing on your device
//put your local ip instead, on windows, run CMD > ipconfig
//or in mac's terminal type ifconfig and look for the ip under en0 or en1
// private static final String LOGIN_URL = "http://xxx.xxx.x.x:1234/webservice/login.php";
//testing on Emulator:
private static final String LOGIN_URL = "http://10.0.2.2:3306/webservice/login.php";
//testing from a real server:
//private static final String LOGIN_URL = "http://www.yourdomain.com/webservice/login.php";
//JSON element ids from repsonse of php script:
private static final String TAG_SUCCESS = "success";
private static final String TAG_MESSAGE = "message";
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
//setup input fields
user = (EditText)findViewById(R.id.username_edit_text);
pass = (EditText)findViewById(R.id.password_edit_text);
//setup buttons
mSubmit = (Button)findViewById(R.id.login);
mRegister = (Button)findViewById(R.id.register);
//register listeners
mSubmit.setOnClickListener(this);
mRegister.setOnClickListener(this);
}
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
switch (v.getId()) {
case R.id.login:
new AttemptLogin().execute();
break;
case R.id.register:
Intent i = new Intent(this, register.class);
startActivity(i);
break;
default:
break;
}
}
class AttemptLogin extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
boolean failure = false;
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(login.this);
pDialog.setMessage("Attempting login...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected String doInBackground(String... args) {
// TODO Auto-generated method stub
// Check for success tag
int success;
String username = user.getText().toString();
String password = pass.getText().toString();
try {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("username", username));
params.add(new BasicNameValuePair("password", password));
Log.d("request!", "starting");
// getting product details by making HTTP request
JSONObject json = jsonParser.makeHttpRequest(
LOGIN_URL, "POST", (HashMap<String, String>) params);
// check your log for json response
Log.d("Login attempt", json.toString());
// json success tag
success = json.getInt(TAG_SUCCESS);
if (success == 1) {
Log.d("Login Successful!", json.toString());
Intent i = new Intent(login.this, readComments.class);
finish();
startActivity(i);
return json.getString(TAG_MESSAGE);
}else{
Log.d("Login Failure!", json.getString(TAG_MESSAGE));
return json.getString(TAG_MESSAGE);
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog once product deleted
pDialog.dismiss();
if (file_url != null){
Toast.makeText(login.this, file_url, Toast.LENGTH_LONG).show();
}
}
}
}
我正在浏览这个教程http://www.mybringback.com/android-sdk/13193/android-mysql-php-json-part-5-developing-the-android-application/
到db的端口和登录凭据是正确的。我用模拟器启动它…所以IP也可以。
收到错误后，我已经复制了所有内容。你们知道吗?
Thanks in advance
NullPointerException在这一行:Log.d("Login attempt", json.toString());
第一步是在取消引用json引用之前检查它是否为空:if (json != null)。
我最近写了一篇关于JSONParser类的博文，并将其更新为使用HttpURLConnection而不是旧JSONParser类使用的现在已弃用的方法。
我只是重新工作了一下你的代码，让它与新的JSONParser类一起工作。
首先，这里是新的JSONParser类，用这个替换旧的:
import android.util.Log;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.util.HashMap;
public class JSONParser {
String charset = "UTF-8";
HttpURLConnection conn;
DataOutputStream wr;
StringBuilder result = new StringBuilder();
URL urlObj;
JSONObject jObj = null;
StringBuilder sbParams;
String paramsString;
public JSONObject makeHttpRequest(String url, String method,
HashMap<String, String> params) {
sbParams = new StringBuilder();
int i = 0;
for (String key : params.keySet()) {
try {
if (i != 0){
sbParams.append("&");
}
sbParams.append(key).append("=")
.append(URLEncoder.encode(params.get(key), charset));
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
i++;
}
if (method.equals("POST")) {
// request method is POST
try {
urlObj = new URL(url);
conn = (HttpURLConnection) urlObj.openConnection();
conn.setDoOutput(true);
conn.setRequestMethod("POST");
conn.setRequestProperty("Accept-Charset", charset);
conn.setReadTimeout(10000);
conn.setConnectTimeout(15000);
conn.connect();
paramsString = sbParams.toString();
wr = new DataOutputStream(conn.getOutputStream());
wr.writeBytes(paramsString);
wr.flush();
wr.close();
} catch (IOException e) {
e.printStackTrace();
}
}
else if(method.equals("GET")){
// request method is GET
if (sbParams.length() != 0) {
url += "?" + sbParams.toString();
}
try {
urlObj = new URL(url);
conn = (HttpURLConnection) urlObj.openConnection();
conn.setDoOutput(false);
conn.setRequestMethod("GET");
conn.setRequestProperty("Accept-Charset", charset);
conn.setConnectTimeout(15000);
conn.connect();
} catch (IOException e) {
e.printStackTrace();
}
}
try {
//Receive the response from the server
InputStream in = new BufferedInputStream(conn.getInputStream());
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
String line;
while ((line = reader.readLine()) != null) {
result.append(line);
}
Log.d("JSON Parser", "result: " + result.toString());
} catch (IOException e) {
e.printStackTrace();
}
conn.disconnect();
// try parse the string to a JSON object
try {
jObj = new JSONObject(result.toString());
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON Object
return jObj;
}
}
下面是使用新的JSONParser类的修改过的Register Activity代码。
注意，我做了一些改变。用户名和密码通过变量传递到AsyncTask中，这是一种比以前更简洁的方法，你不应该在后台线程中引用UI元素。
我还将BasicNameValuePair参数切换为使用HashMap，因为BasicNameValuePair在API级别22中已弃用。
下面是完整的类代码:public class Register extends ActionBarActivity implements View.OnClickListener {
private EditText user, pass;
private Button mRegister;
// Progress Dialog
private ProgressDialog pDialog;
// JSON parser class
JSONParser jsonParser = new JSONParser();
private static final String LOGIN_URL = "http://10.0.2.2:3306/webservice/register.php";
private static final String TAG_SUCCESS = "success";
private static final String TAG_MESSAGE = "message";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register);
user = (EditText) findViewById(R.id.username);
pass = (EditText) findViewById(R.id.password);
mRegister = (Button) findViewById(R.id.register);
mRegister.setOnClickListener(this);
}
@Override
public void onClick(View v) {
//send username and password here:
String username = user.getText().toString();
String password = pass.getText().toString();
new CreateUser().execute(username, password);
}
class CreateUser extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
*/
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(Register.this);
pDialog.setMessage("Creating User...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected String doInBackground(String... args) {
// Check for success tag
int success = 0; //initialize to zero
//not needed:
//String username = user.getText().toString();
//String password = pass.getText().toString();
try {
//Remove this code:
/*
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("username", username));
params.add(new BasicNameValuePair("password", password));
*/
//Use a HashMap instead with the varargs:
HashMap<String, String> params = new HashMap<>();
params.put("username", args[0]);
params.put("password", args[1]);
Log.d("request!", "starting");
//Posting user data to script
JSONObject json = jsonParser.makeHttpRequest(
LOGIN_URL, "POST", params);
// full json response
//added null check:
if (json != null) {
Log.d("Login attempt", json.toString());
// json success element
success = json.getInt(TAG_SUCCESS);
if (success == 1) {
Log.d("User Created!", json.toString());
finish();
return json.getString(TAG_MESSAGE);
} else {
Log.d("Login Failure!", json.getString(TAG_MESSAGE));
return json.getString(TAG_MESSAGE);
}
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* *
*/
protected void onPostExecute(String file_url) {
// dismiss the dialog once product deleted
pDialog.dismiss();
if (file_url != null) {
Toast.makeText(Register.this, file_url, Toast.LENGTH_LONG).show();
}
}
}
}
测试上述代码后的结果:
D/JSON Parser﹕ result: {"success":1,"message":"Login successful."}
D/Login attempt﹕ {"message":"Login successful.","success":1}
D/User Created!﹕ {"message":"Login successful.","success":1}
我认为错误可能是这一行参数个数。add(new BasicNameValuePair("username"， username));
改变参数个数。add(new BasicNameValuePair("username="， username));参数个数。add(new BasicNameValuePair("&password="， password));