Question

我正在为学校开发一个需要登录系统的应用程序。它以前可以工作，但是我在在线数据库中添加了一些新行，并且还修改了应用程序内的Java代码来存储这些数据，但是现在当我单击“登录”按钮时，什么也没做，它不会将活动更改为我的仪表板活动，不会显示登录成功或错误的消息，它不会执行任何操作。这是我的调试控制台：

W/System.err: org.json.JSONException: Value <br of type java.lang.String cannot be converted to JSONObject
        at org.json.JSON.typeMismatch(JSON.java:112)
W/System.err:     at org.json.JSONObject.<init>(JSONObject.java:163)
W/System.err:     at org.json.JSONObject.<init>(JSONObject.java:176)
W/System.err:     at quizonwheels.quizonwheels.LoginActivity$3.onResponse(LoginActivity.java:74)
W/System.err:     at quizonwheels.quizonwheels.LoginActivity$3.onResponse(LoginActivity.java:69)
W/System.err:     at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:78)
W/System.err:     at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:30)
W/System.err:     at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:106)
W/System.err:     at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
W/System.err:     at android.os.Looper.loop(Looper.java:193)
W/System.err:     at android.app.ActivityThread.main(ActivityThread.java:6669)
        at java.lang.reflect.Method.invoke(Native Method)
W/System.err:     at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
W/System.err:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

我是Java的新手，我们的老师没有向我们解释太多，我也不明白为什么它不起作用。

这是我的登录功能和SharedPrefManager类

private void userLogin(){
        final String username = UsernameEt.getText().toString().trim();
        final String password = PasswordEt.getText().toString().trim();
       progressDialog.show();
        StringRequest stringRequest = new StringRequest(
                Request.Method.POST, Constants.URL_LOGIN, new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                progressDialog.dismiss();
                try {
                    JSONObject obj = new JSONObject(response);
                    if (!obj.getBoolean("error")){
                        SharedPrefManager.getInstance(getApplicationContext()).userLogin(
                                obj.getInt("id"),
                                obj.getString("username"),
                                obj.getString("email"),
                                obj.getString("firstname"),
                                obj.getString("lastname"),
                                obj.getString("country"),
                                obj.getString("points")
                        );
                        startActivity(new Intent(getApplicationContext(),DashboardActivity.class));
                        finish();
                    }else
                    {
                        Toast.makeText(getApplicationContext(), obj.getString("message"), Toast.LENGTH_LONG).show();
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
               progressDialog.dismiss();
                Toast.makeText(getApplicationContext(), error.getMessage(), Toast.LENGTH_LONG).show();
            }
        }
        ){
            @Override
            protected Map<String, String> getParams() throws AuthFailureError {
                Map<String,String> params = new HashMap<>();
                params.put("username",username);
                params.put("password",password);
                return params;
            }
        };

        RequestHandler.getInstance(this).addToRequestQueue(stringRequest);

和我的SharedPrefManager类

package quizonwheels.quizonwheels;
import android.content.Context;
import android.content.SharedPreferences;




public class SharedPrefManager {
    private static SharedPrefManager mInstance;

    private static Context mCtx;
    private static final String SHARED_PREF_NAME ="mysharedpref12";
    private static final String KEY_USERNAME="username";
    private static final String KEY_USER_EMAIL="email";
    private static final String KEY_USER_ID="id";
    private static final String KEY_USER_FIRSTNAME="firstname";
    private static final String KEY_USER_LASTNAME="lastname";
    private static final String KEY_USER_COUNTRY="country";
    private static final String KEY_USER_POINTS="points";

    private SharedPrefManager(Context context) {
        mCtx = context;

    }

    public static synchronized SharedPrefManager getInstance(Context context) {
        if (mInstance == null) {
            mInstance = new SharedPrefManager(context);
        }
        return mInstance;
    }

    public boolean userLogin(int id, String username, String email, String firstname, String lastname, String country, String points) {
        SharedPreferences sharedPreferences= mCtx.getSharedPreferences(SHARED_PREF_NAME,Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = sharedPreferences.edit();
        editor.putInt(KEY_USER_ID,id);
        editor.putString(KEY_USER_EMAIL,email);
        editor.putString(KEY_USERNAME,username);
        editor.putString(KEY_USER_LASTNAME,lastname);
        editor.putString(KEY_USER_FIRSTNAME,firstname);
        editor.putString(KEY_USER_COUNTRY,country);
        editor.putString(KEY_USER_POINTS,points);

        editor.apply();
        return true;
    }

    public boolean isLoggedIn(){
        SharedPreferences sharedPreferences = mCtx.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
        if(sharedPreferences.getString(KEY_USERNAME,null)!=null){
            return true;
        }
        return false;
    }

    public boolean logout(){
        SharedPreferences sharedPreferences = mCtx.getSharedPreferences(SHARED_PREF_NAME, Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = sharedPreferences.edit();
        editor.clear();
        editor.apply();
        return true;
    }
}

我的php代码是：

<?php 

require_once '../includes/DbConnect.php';

$response =array(); 

if($_POST['username'] && $_POST['password']){
    $username = $_POST['username'];
    $password = $_POST['password'];

    $sql = "SELECT * FROM users WHERE username=?";
    $stmt = mysqli_stmt_init($con);
    mysqli_stmt_bind_param($stmt,"s",$username);
    mysqli_stmt_execute($stmt);
    $result = mysqli_stmt_get_result($stmt);
    if($user = mysqli_fetch_assoc($result))
    {
        $passwordCheck = password_verify($password,$user['password']);
        if($passwordCheck == false){
            $response['error'] = true; 
            $response['message'] = "Invalid username or password";  
        }
        else if($passwordCheck == true) {

            $response['error'] = false; 
            $response['id'] = $user['idUsers'];
            $response['email'] = $user['email'];
            $response['username'] = $user['username'];
            $response['country']= $user['country'];
             $response['firstname']= $user['firstname'];
              $response['lastname']= $user['lastname'];
               $response['points']= $user['points'];
        }
    }
}



echo json_encode($response);

?>

Answer 1

在此行设置断点：

JSONObject obj = new JSONObject(response);

复制response字符串值，并检查它是否为有效的JSON字符串。

online JSON validate website很好。

Answer 2

请注意此代码

 @Override
        public void onResponse(String response) {
            progressDialog.dismiss();
            try {
                JSONObject obj = new JSONObject(response);

将“响应”修复为“ response.toString（）”，即可享受。

@Override
    public void onResponse(String response) {
        progressDialog.dismiss();
        try {
            JSONObject obj = new JSONObject(response.toString());

使用String Request和JSONObject解析数据时出错

2 个答案: