[英]Android App crashes whenever i try to login using JSONParser but i can sucessfully login with my browser
我已经使用wampserver建立了数据库进行登录，并创建了适当的php文件，并且可以通过浏览器成功登录。 但是我使用JSONParser创建了一个应用程序并连接了数据库，现在每当我尝试登录时，我的应用程序就会崩溃。 这是logcat屏幕显示的内容。
06-29 11:51:37.044 15586-15889/com.zaid.sling.mysqltest E/AndroidRuntime﹕ FATAL EXCEPTION: AsyncTask #1
java.lang.RuntimeException: An error occured while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:299)
.....
Caused by: java.lang.NullPointerException
at com.zaid.sling.mysqltest.Login$AttemptLogin.doInBackground(Login.java:125)
这是我的JSONParser.java
public class JSONParser {
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
// constructor
public JSONParser() {
}
// function get json from url
// by making HTTP POST or GET mehtod
public JSONObject makeHttpRequest(String url, String method,
List<NameValuePair> params) {
// Making HTTP request
try {
// check for request method
if(method == "POST"){
// request method is POST
// defaultHttpClient
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();
}else if(method == "GET"){
// request method is GET
DefaultHttpClient httpClient = new DefaultHttpClient();
String paramString = URLEncodedUtils.format(params, "utf-8");
url += "?" + paramString;
HttpGet httpGet = new HttpGet(url);
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
}
这是我的Login.java
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:
private static final String LOGIN_URL "http://10.0.2.2/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);
pass = (EditText)findViewById(R.id.password);
//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", 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, ReadComment.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();
}
}
}
}
在我的php文件中也有html表单，并且使用浏览器可以正常进行登录过程
这是用@Daniel Nugent的代码更新以上代码后的日志猫
06-30 12:19:30.579 26905-26960/com.zaid.sling.mysqltest E/AndroidRuntime﹕ FATAL EXCEPTION: AsyncTask #1
java.lang.RuntimeException: An error occured while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:299)
..........
at java.lang.Thread.run(Thread.java:856)
Caused by: java.lang.ArrayIndexOutOfBoundsException: length=0; index=0
at com.zaid.sling.mysqltest.Login$AttemptLogin.doInBackground(Login.java:107)
请帮助提前感谢
您的代码中存在多个问题。 首先，您在doInBackground()方法中调用finish() ，这可能导致窗口泄漏。 不管您是否显示ProgressDialog，都不应在AsyncTask运行时完成Activity。
您还使用了不推荐使用的DefaultHttpClient ，它将在Android 5.0及更高版本中不起作用。
我刚刚有了一个可以在服务器上使用的PHP页面工作并经过测试的解决方案。
首先，这是一个修改后的JSONParser类，它使用HttpURLConnection ：
import android.util.Log;
import org.apache.http.NameValuePair;
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.net.HttpURLConnection;
import java.net.URL;
import java.util.List;
/**
* Created by daniel on 6/29/15.
*/
public class JSONParser {
HttpURLConnection conn;
DataOutputStream wr;
StringBuilder result = new StringBuilder();
URL urlObj;
static JSONObject jObj = null;
static String json = "";
public JSONParser() {
}
public JSONObject makeHttpRequest(String url,
List<NameValuePair> params) {
try {
urlObj = new URL(url);
conn = (HttpURLConnection) urlObj.openConnection();
conn.setDoOutput(true); //moved here
conn.setRequestMethod("POST");
conn.connect();
} catch (IOException e) {
e.printStackTrace();
}
conn.setReadTimeout(10000);
conn.setConnectTimeout(15000);
StringBuilder sbCert = new StringBuilder();
for (int i = 0; i < params.size(); i++){
if (i != 0){
sbCert.append("&");
}
NameValuePair nvp = params.get(i);
sbCert.append(nvp.getName()).append("=").append(nvp.getValue());
}
String cert=sbCert.toString();
try {
wr = new DataOutputStream(conn.getOutputStream());
wr.writeBytes(cert);
wr.flush();
wr.close();
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;
}
}
接下来，这是您的AsyncTask的修改版本：
class AttemptLogin extends AsyncTask<String, String, String> {
boolean failure;
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(MainActivity.this);
pDialog.setMessage("Attempting login...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected String doInBackground(String... args) {
int success;
String username = args[0];
String password = args[1];
try {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("name", username));
params.add(new BasicNameValuePair("password", password));
Log.d("request!", "starting");
// getting product details by making HTTP request
JSONObject json = jsonParser.makeHttpRequest(
LOGIN_URL, params);
// check your log for json response
Log.d("Login attempt", json.toString());
// json success tag
success = json.getInt(TAG_SUCCESS);
if (success == 1) {
failure = false;
Log.d("Login Successful!", json.toString());
}else{
failure = true;
Log.d("Login Failure!", json.getString(TAG_MESSAGE));
}
return json.getString(TAG_MESSAGE);
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
protected void onPostExecute(String file_url) {
// dismiss the dialog once product deleted
pDialog.dismiss();
if (file_url != null){
Toast.makeText(MainActivity.this, file_url, Toast.LENGTH_LONG).show();
}
if (failure == false) {
Intent i = new Intent(Login.this, ReadComment.class);
//finish();
Login.this.startActivity(i);
}
}
}
并这样称呼它：
new AttemptLogin().execute( user.getText().toString(), pass.getText().toString());
当然，还要确保您在AndroidManifest.xml中具有INTERNET权限：
<uses-permission android:name="android.permission.INTERNET" />
通过服务器上的PHP页面运行代码的日志：
D/JSON Parser﹕ result: {"success":1,"message":"Message successfully created."}
D/Login attempt﹕ {"message":"Message successfully created.","success":1}
D/Login Successful!﹕ {"message":"Message successfully created.","success":1}
从堆栈跟踪看来，异常发生在：
06-29 11:51:40.064 15586-15586/com.zaid.sling.mysqltest E/WindowManager﹕ Activity com.zaid.sling.mysqltest.Login has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@41d684b0 that was originally added here
android.view.WindowLeaked: Activity com.zaid.sling.mysqltest.Login has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@41d684b0 that was originally added here
...
at android.app.Dialog.show(Dialog.java:277)
at com.zaid.sling.mysqltest.Login$AttemptLogin.onPreExecute(Login.java:103)
at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586)
at android.os.AsyncTask.execute(AsyncTask.java:534)
at com.zaid.sling.mysqltest.Login.onClick(Login.java:77)
...
并且发生的异常是android.view.WindowLeaked异常。
当您尝试退出活动后显示对话框时，会发生这种情况。
请阅读以下信息：
更新的代码：
class AttemptLogin extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
boolean failure = false;
int success;
@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
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", 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());
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 (success == 1) {
Log.d("Login Successful!", json.toString());
Intent i = new Intent(Login.this, ReadComment.class);
startActivity(i);
finish();
}else{
Log.d("Login Failure!", "your Message");
}
if (file_url != null){
Toast.makeText(Login.this, file_url, Toast.LENGTH_LONG).show();
}
}
}
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