Question

不要没有问题，只是每次我输入用户名和密码对话框显示尝试登录和应用程序崩溃。使用的服务器：Wamp 以下是使用的代码。任何帮助都会很明显。谢谢。

LoginActivity.java：

package com.sam.kiet;    
import android.app.Activity;   
import android.app.ProgressDialog;   
import android.content.Intent;     
import android.os.AsyncTask;     
import android.os.Bundle;     
import android.view.View;      
import android.widget.Button;      
import android.widget.EditText;      
import android.widget.Toast;      
import android.util.Log;            


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.List;      

/**       
 * Created by Vaibhav on 10/2/2015.     
*/      


public class LoginActivity extends Activity implements View.OnClickListener                  {
   private EditText user, pass;       
   private Button bLogin;       
   private ProgressDialog pDialog;         
   JSONParser jsonParser = new JSONParser();            
   private static final String LOGIN_URL = "http://192.168.43.1/login.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.login);
    user = (EditText) findViewById(R.id.username);
    pass = (EditText) findViewById(R.id.password);
    bLogin = (Button) findViewById(R.id.Blogin);
    bLogin.setOnClickListener(this);

}

@Override    
public void onClick(View v) {
    switch (v.getId()) {
        case R.id.Blogin:
            new AttemptLogin().execute();

        default:
            break;
    }
}

class AttemptLogin extends AsyncTask<String, String, String> {
    //boolean failure = false;
    private String username,password;

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(LoginActivity.this);
        pDialog.setMessage("Attempting for login...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();
        username = user.getText().toString();
        password = pass.getText().toString();



    }

    @Override
    protected String doInBackground(String... args) {
        int success;

        try {
            List<NameValuePair> params = new ArrayList<NameValuePair>();


            params.add(new BasicNameValuePair("username", username));
            params.add(new BasicNameValuePair("password", password));
            Log.d("request!", "starting");

            JSONObject json = jsonParser.makeHttpRequest(LOGIN_URL, "POST", params);
            Log.d("Login attempt", json.toString());
            success = json.getInt(TAG_SUCCESS);
            if (success == 1) {
                Log.d("Successfully Login!", json.toString());

                Intent main_activity = new Intent(LoginActivity.this, MainActivity.class);
                finish();
                startActivity(main_activity);
                return json.getString(TAG_MESSAGE);
            } else {
                return json.getString(TAG_MESSAGE);


            }

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

    @Override
    protected void onPostExecute(String message) {
        super.onPostExecute(message);
        pDialog.dismiss();
        if (message != null){
            Toast.makeText(LoginActivity.this, message, Toast.LENGTH_LONG).show();

    }
  }
 }
}

JasonParsor.java：

package com.sam.kiet;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader; 
import java.io.UnsupportedEncodingException;
import java.util.List;

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.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URLEncodedUtils;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException; 
import org.json.JSONObject;

import android.util.Log;

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;

}

public JSONObject getJSONFromUrl(final String url) {

    // Making HTTP request
    try {
        // Construct the client and the HTTP request.
        DefaultHttpClient httpClient = new DefaultHttpClient();
        HttpPost httpPost = new HttpPost(url);

        // Execute the POST request and store the response locally.
        HttpResponse httpResponse = httpClient.execute(httpPost);
        // Extract data from the response.
        HttpEntity httpEntity = httpResponse.getEntity();
        // Open an inputStream with the data content.
        is = httpEntity.getContent();

    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    try {
        // Create a BufferedReader to parse through the inputStream.
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);
        // Declare a string builder to help with the parsing.
        StringBuilder sb = new StringBuilder();
        // Declare a string to store the JSON object data in string form.
        String line = null;

        // Build the string until null.
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }

        // Close the input stream.
        is.close();
        // Convert the string builder data to an actual string.
        json = sb.toString();
    } catch (Exception e) {
        Log.e("Buffer Error", "Error converting result " + e.toString());
    }

    // Try to 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 the JSON Object.
    return jObj;

   }
}

Login.xml：

    <LinearLayout 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:gravity="center_horizontal"
android:orientation="vertical"
android:paddingBottom="16dp"
android:paddingLeft="16dp"
android:paddingRight="16dp"
android:paddingTop="16dp"
tools:context=".LoginActivity"
>

<!-- Login progress -->
<ProgressBar
    android:id="@+id/login_progress" style="?android:attr/progressBarStyleLarge"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginBottom="8dp"
    android:visibility="gone"
    />

<ScrollView
    android:id="@+id/login_form"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        >


        <LinearLayout
            android:id="@+id/email_login_form"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical">

            <AutoCompleteTextView
                android:id="@+id/username"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:hint="Username"
                android:inputType="text"
                android:maxLines="1"
                android:singleLine="true" />

            <EditText android:id="@+id/password"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:hint="Password"
                android:imeActionId="@+id/login"
                android:imeActionLabel="Login"
                android:imeOptions="actionUnspecified"
                android:inputType="textPassword"
                android:maxLines="1"
                android:singleLine="true" />

            <Button
                android:id="@+id/Blogin"
                style="?android:textAppearanceSmall"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginTop="16dp"
                android:text="Login"
                android:textStyle="bold" />

        </LinearLayout>
    </LinearLayout>
</ScrollView>

logcat的（错误）：

10-12 09:02:22.084    1804-1819/com.sam.kiet E/Buffer Error﹕ Error converting 

result java.lang.NullPointerException: lock == null
10-12 09:02:22.084    1804-1819/com.sam.kiet E/JSON Parser﹕ Error parsing data org.json.JSONException: End of input at character 0 of
10-12 09:02:22.094    1804-1819/com.sam.kiet E/AndroidRuntime﹕ FATAL EXCEPTION: AsyncTask #2
    Process: com.sam.kiet, PID: 1804
    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.sam.kiet.LoginActivity$AttemptLogin.doInBackground(LoginActivity.java:92)
            at com.sam.kiet.LoginActivity$AttemptLogin.doInBackground(LoginActivity.java:60)
            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)
            at java.lang.Thread.run(Thread.java:841)
10-12 09:02:23.744    1804-1804/com.sam.kiet E/WindowManager﹕ android.view.WindowLeaked: Activity com.sam.kiet.LoginActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{b1402280 V.E..... R......D 0,0-1026,288} that was originally added here
            at android.view.ViewRootImpl.<init>(ViewRootImpl.java:346)
            at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:248)
            at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
            at android.app.Dialog.show(Dialog.java:286)
            at com.sam.kiet.LoginActivity$AttemptLogin.onPreExecute(LoginActivity.java:71)
            at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:587)
            at android.os.AsyncTask.execute(AsyncTask.java:535)
            at com.sam.kiet.LoginActivity.onClick(LoginActivity.java:53)
            at android.view.View.performClick(View.java:4438)
            at android.view.View$PerformClick.run(View.java:18422)
            at android.os.Handler.handleCallback(Handler.java:733)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5001)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
            at dalvik.system.NativeStart.main(Native Method)

新LOGCAT：

10-12 10:40:56.083    5644-5658/com.sam.kiet E/JSON Parser﹕ Error parsing data org.json.JSONException: Value success of type java.lang.String cannot be converted to JSONObject
10-12 10:40:56.093    5644-5658/com.sam.kiet E/AndroidRuntime﹕ FATAL EXCEPTION: AsyncTask #2
    Process: com.sam.kiet, PID: 5644
    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.sam.kiet.LoginActivity$AttemptLogin.doInBackground(LoginActivity.java:85)
            at com.sam.kiet.LoginActivity$AttemptLogin.doInBackground(LoginActivity.java:60)
            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)
            at java.lang.Thread.run(Thread.java:841)
10-12 10:40:58.003    5644-5644/com.sam.kiet E/WindowManager﹕ android.view.WindowLeaked: Activity com.sam.kiet.LoginActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{b1401ef8 V.E..... R......D 0,0-1026,288} that was originally added here
            at android.view.ViewRootImpl.<init>(ViewRootImpl.java:346)
            at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:248)
            at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
            at android.app.Dialog.show(Dialog.java:286)
            at com.sam.kiet.LoginActivity$AttemptLogin.onPreExecute(LoginActivity.java:71)
            at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:587)
            at android.os.AsyncTask.execute(AsyncTask.java:535)
            at com.sam.kiet.LoginActivity.onClick(LoginActivity.java:53)
            at android.view.View.performClick(View.java:4438)
            at android.view.View$PerformClick.run(View.java:18422)
            at android.os.Handler.handleCallback(Handler.java:733)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5001)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
            at dalvik.system.NativeStart.main(Native Method)

Answer 1

好吧我认为你得到的是NullPointer：

if(method == "POST"){

将其更改为

if("POST".equals(method)){

您将对象引用与==的值进行比较。这就是方法makeHttpRequest返回null的原因。

当然你也必须改变它：

}else if(method == "GET"){

Answer 2

这部分代码

Intent main_activity = new Intent(LoginActivity.this, MainActivity.class);
finish();
startActivity(main_activity);
return json.getString(TAG_MESSAGE);

您创建Intent然后finish()活动，然后运行startActivity()并最终返回。

逻辑顺序错误，尝试这种方法：

class AttemptLogin extends AsyncTask<String, String, JSONObject> {
    //boolean failure = false;
    private String username,password;

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(LoginActivity.this);
        pDialog.setMessage("Attempting for login...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();
        username = user.getText().toString();
        password = pass.getText().toString();



    }

    @Override
    protected JSONObject doInBackground(String... args) {
            List<NameValuePair> params = new ArrayList<NameValuePair>();
            params.add(new BasicNameValuePair("username", username));
            params.add(new BasicNameValuePair("password", password));
            Log.d("request!", "starting");
            JSONObject json = jsonParser.makeHttpRequest(LOGIN_URL, "POST", params);
            Log.d("Login attempt", json.toString());
            return json;
    }

    @Override
    protected void onPostExecute(JSONObject json) {
        super.onPostExecute(json);
        pDialog.dismiss();
        if (json != null){
            try {
                int success = json.getInt(TAG_SUCCESS);
                String message = json.getString(TAG_MESSAGE);
                if (success == 1) {
                    Log.d("Successfully Login!", json.toString());
                    Toast.makeText(LoginActivity.this,"Login successful" + message, Toast.LENGTH_LONG).show();
                    Intent main_activity = new Intent(LoginActivity.this, MainActivity.class);
                    startActivity(main_activity);
                    finish();//only at the end!!!
                } else {
                    Toast.makeText(LoginActivity.this, "Login failed = " + message, Toast.LENGTH_LONG).show();
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }

        }
    }
}

Answer 3

尝试更改

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

到

 try {
        jObj = new JSONObject(json);
    } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data",e);
    } catch (Exception e) {
        Log.e("JSON Parser", "Error parsing data",e);
    }

我的猜测是你得到一个JSONException没有捕获的空指针异常。

一般情况下，我建议在try-＆gt; catch之前检查null对象，因为它的价格更便宜＆＃34;比try-＆gt; catch机制（非常昂贵＆＃34;）。

Answer 4

JSONObject json = jsonParser.makeHttpRequest(LOGIN_URL, "POST", params);

将此更改为此

JSONObject json = jsonParser.makeHttpRequest(LOGIN_URL, "GET", params);

你收到错误是因为你没有得到Json所以改变你的类型并再次调用方法

Answer 5

观察您的代码和logcat报告......

最初你有一个错误，将你用try catch处理的InputStream转换为String ，因为Log.e("Buffer Error", "Error converting result " + e.toString());你可以在第一个logcat报告中看到它。此错误是InputStream is的NPE。但最后你的方法返回null jsonObject这会导致传播多个错误 解决方案修复此问题由@Stefan Beike提供，答案是错误的字符串比较

现在你的json形成有错误，所以你在下面的代码中提到了错误

try {
        jObj = new JSONObject(json); //LINE THROWING ERROR...
        //check properly String json if properly formatted json....so request for String json in question
    } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data " + e.toString()); 
        //Above line is visible in the second logcat report i.e new logcat.
    }

但是你的方法再次返回jObj，这是null ...所以在你的doInBackground中你再次遇到多个错误从新的logcat报告

Error parsing data org.json.JSONException: Value success of type java.lang.String cannot be converted to JSONObject

所以，如果你想与其他程序员有更多的帮助，那么我会要求你转换InputStream后发布json字符串即字符串有问题的字符串。或者你自己可以检查字符串是否格式正确JSON。

LoginActivity在登录期间崩溃

5 个答案: