Java 使用php和mysql为android构建登录、注册系统，但应用程序可以运行

我目前正在使用android应用程序的登录和注册系统。我使用mysql作为数据库，php来完成这项工作，但在完成所有系统文件后，当单击“登录”按钮时，应用程序就停止了。请帮助，下面是我编写的所有代码

main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="@drawable/images" >

    <LinearLayout
        android:id="@+id/linearLayout1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_marginBottom="22dp"
        android:layout_marginLeft="19dp"
        android:orientation="vertical" >

        <TextView
            android:id="@+id/textView1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:layout_alignParentLeft="true"
            android:layout_marginBottom="2dp"
            android:text="Plot Out"
            android:textAppearance="?android:attr/textAppearanceLarge" />

        <TextView
            android:id="@+id/textView2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignLeft="@+id/textView1"
            android:layout_alignTop="@+id/textView1"
            android:layout_marginTop="1dp"
            android:text="Bring Me Out"
            android:textAppearance="?android:attr/textAppearanceLarge" />
    </LinearLayout>

    <LinearLayout
        android:id="@+id/linearLayout2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="84dp"
        android:orientation="vertical" >

        <ImageView
            android:id="@+id/imageView1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginBottom="10dp"
            android:layout_marginLeft="53dp"
            android:layout_marginTop="2dp"
            android:src="@drawable/logo" />

        <Button
            android:id="@+id/btnLogin"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_marginBottom="1dp"
            android:layout_marginLeft="40dp"
            android:text="Login"
            android:width="100sp" />

        <Button
            android:id="@+id/btnRegister"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginBottom="10dp"
            android:layout_marginLeft="40dp"
            android:text="Register"
            android:width="100sp" />

        <TextView
            android:id="@+id/link_to_forgotpassword"
            android:clickable="true"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@+id/linearLayout2"
            android:layout_centerHorizontal="true"
            android:text="Forgot Your Password?"
            android:textAppearance="?android:attr/textAppearanceMedium" />
    </LinearLayout>

</RelativeLayout>

RegisterAvtivity.java

package com.plotout.loginandregister;

import java.util.HashMap;

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

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import com.plotout.loginandregister.library.DatabaseHandler;
import com.plotout.loginandregister.library.UserFunctions;

public class LoginActivity extends Activity {
    Button btnLogin;
    EditText inputEmail;
    EditText inputPassword;
    TextView loginErrorMsg;
    TextView link_to_register;

    // JSON Response node names
    private static String KEY_SUCCESS = "success";
    private static String KEY_ERROR = "error";
    private static String KEY_ERROR_MSG = "error_msg";
    private static String KEY_UID = "uid";
    private static String KEY_NAME = "name";
    private static String KEY_EMAIL = "email";
    private static String KEY_CREATED_AT = "created_at";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.login);

        // Importing all assets like buttons, text fields
        inputEmail = (EditText) findViewById(R.id.loginEmail);
        inputPassword = (EditText) findViewById(R.id.loginPassword);
        btnLogin = (Button) findViewById(R.id.btnLogin);
        link_to_register = (TextView) findViewById (R.id.link_to_register);
        loginErrorMsg = (TextView) findViewById(R.id.login_error);

        // Login button Click Event
        btnLogin.setOnClickListener(new View.OnClickListener() {

            public void onClick(View view) {
                String email = inputEmail.getText().toString();
                String password = inputPassword.getText().toString();
                UserFunctions userFunction = new UserFunctions();
                JSONObject json = userFunction.loginUser(email, password);

                // check for login response
                try {
                    if (json.getString(KEY_SUCCESS) != null) {
                        loginErrorMsg.setText("");
                        String res = json.getString(KEY_SUCCESS); 
                        if(Integer.parseInt(res) == 1){
                            // user successfully logged in
                            // Store user details in SQLite Database
                            DatabaseHandler db = new DatabaseHandler(getApplicationContext());
                            JSONObject json_user = json.getJSONObject("user");

                            // Clear all previous data in database
                            userFunction.logoutUser(getApplicationContext());
                            db.addUser(json_user.getString(KEY_NAME), json_user.getString(KEY_EMAIL), json.getString(KEY_UID), json_user.getString(KEY_CREATED_AT));                        

                            // Launch Dashboard Screen
                            Intent dashboard = new Intent(getApplicationContext(), DashboardActivity.class);

                            // Close all views before launching Dashboard
                            dashboard.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                            startActivity(dashboard);

                            // Close Login Screen
                            finish();
                        }else{
                            // Error in login
                            loginErrorMsg.setText("Incorrect username/password");
                        }
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        });

        TextView registerScreen = (TextView) findViewById(R.id.link_to_login);

        // Listening to register new account link
        registerScreen.setOnClickListener(new View.OnClickListener() {

            public void onClick(View v) {
                // Switching to Register screen
                Intent i = new Intent(getApplicationContext(), RegisterActivity.class);
                startActivity(i);
            }
        });
    }
}

package com.plotout.loginandregister;

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

import com.plotout.loginandregister.library.DatabaseHandler;
import com.plotout.loginandregister.library.UserFunctions;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class RegisterActivity extends Activity {
    Button btnRegister;
    TextView link_to_login;
    EditText inputFullName;
    EditText inputEmail;
    EditText inputPassword;
    TextView registerErrorMsg;

    // JSON Response node names
    private static String KEY_SUCCESS = "success";
    private static String KEY_ERROR = "error";
    private static String KEY_ERROR_MSG = "error_msg";
    private static String KEY_UID = "uid";
    private static String KEY_NAME = "name";
    private static String KEY_EMAIL = "email";
    private static String KEY_CREATED_AT = "created_at";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.register);

        // Importing all assets like buttons, text fields
        inputFullName = (EditText) findViewById(R.id.registerName);
        inputEmail = (EditText) findViewById(R.id.registerEmail);
        inputPassword = (EditText) findViewById(R.id.registerPassword);
        btnRegister = (Button) findViewById(R.id.btnRegister);
        link_to_login= (TextView) findViewById(R.id.link_to_login);
        registerErrorMsg = (TextView) findViewById(R.id.register_error);

        // Register Button Click event
        btnRegister.setOnClickListener(new View.OnClickListener() {         
            public void onClick(View view) {
                String name = inputFullName.getText().toString();
                String email = inputEmail.getText().toString();
                String password = inputPassword.getText().toString();
                UserFunctions userFunction = new UserFunctions();
                JSONObject json = userFunction.registerUser(name, email, password);

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

                            // Clear all previous data in database
                            userFunction.logoutUser(getApplicationContext());
                            db.addUser(json_user.getString(KEY_NAME), json_user.getString(KEY_EMAIL), json.getString(KEY_UID), json_user.getString(KEY_CREATED_AT));                        
                            // Launch Dashboard Screen
                            Intent dashboard = new Intent(getApplicationContext(), DashboardActivity.class);
                            // Close all views before launching Dashboard
                            dashboard.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                            startActivity(dashboard);
                            // Close Registration Screen
                            finish();
                        }else{
                            // Error in registration
                            registerErrorMsg.setText("Error occured in registration");
                        }
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        });

        TextView loginScreen = (TextView) findViewById(R.id.link_to_login);

        // Listening to Login Screen link
        loginScreen.setOnClickListener(new View.OnClickListener() {

            public void onClick(View arg0) {
                                // Closing registration screen
                // Switching to Login Screen/closing register screen
                finish();
            }
        });
    }
}

以下是ecplise中显示的日志

我只是更改登录xml中编辑文本的id，以解决ClassCastException错误。。

---

您的按钮不起任何作用，因为LoginActivity中的以下两行抛出ClassCastException，因为您无法从Android.widget.TextView强制转换为Android.widget.EditView

在main.xml中，将前两个更改为：

改为：

<EditText
    android:id="@+id/textView2"
    ...
    android:textAppearance="?android:attr/textAppearanceLarge" />

---

嗯，logcat在哪里？这是一个典型的问题，你在UI线程上做网络工作。使用AsyncTask与服务器进行连接。如果logcat显示ClassCastExcemption中出现错误，请尝试清理项目并重建它。那么我现在应该做什么？我应该重新构建哪个部分？检查xml，我没有注意到这一点。他是对的，在xml中是Textview，而在java代码中是EditText。编辑它，你的问题就解决了，或者需要构建新的public void来转换编辑文本？？我解决了logcat ady..但它变成了另一个新错误..java.lang.NullPointerException..@ken编辑你的问题并添加新的错误，同时更新代码。@JonnyHenly先生，我只是更新了问题ady，以及新的错误..tq

package com.plotout.loginandregister;

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

import com.plotout.loginandregister.library.DatabaseHandler;
import com.plotout.loginandregister.library.UserFunctions;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class RegisterActivity extends Activity {
    Button btnRegister;
    TextView link_to_login;
    EditText inputFullName;
    EditText inputEmail;
    EditText inputPassword;
    TextView registerErrorMsg;

    // JSON Response node names
    private static String KEY_SUCCESS = "success";
    private static String KEY_ERROR = "error";
    private static String KEY_ERROR_MSG = "error_msg";
    private static String KEY_UID = "uid";
    private static String KEY_NAME = "name";
    private static String KEY_EMAIL = "email";
    private static String KEY_CREATED_AT = "created_at";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.register);

        // Importing all assets like buttons, text fields
        inputFullName = (EditText) findViewById(R.id.registerName);
        inputEmail = (EditText) findViewById(R.id.registerEmail);
        inputPassword = (EditText) findViewById(R.id.registerPassword);
        btnRegister = (Button) findViewById(R.id.btnRegister);
        link_to_login= (TextView) findViewById(R.id.link_to_login);
        registerErrorMsg = (TextView) findViewById(R.id.register_error);

        // Register Button Click event
        btnRegister.setOnClickListener(new View.OnClickListener() {         
            public void onClick(View view) {
                String name = inputFullName.getText().toString();
                String email = inputEmail.getText().toString();
                String password = inputPassword.getText().toString();
                UserFunctions userFunction = new UserFunctions();
                JSONObject json = userFunction.registerUser(name, email, password);

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

                            // Clear all previous data in database
                            userFunction.logoutUser(getApplicationContext());
                            db.addUser(json_user.getString(KEY_NAME), json_user.getString(KEY_EMAIL), json.getString(KEY_UID), json_user.getString(KEY_CREATED_AT));                        
                            // Launch Dashboard Screen
                            Intent dashboard = new Intent(getApplicationContext(), DashboardActivity.class);
                            // Close all views before launching Dashboard
                            dashboard.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                            startActivity(dashboard);
                            // Close Registration Screen
                            finish();
                        }else{
                            // Error in registration
                            registerErrorMsg.setText("Error occured in registration");
                        }
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        });

        TextView loginScreen = (TextView) findViewById(R.id.link_to_login);

        // Listening to Login Screen link
        loginScreen.setOnClickListener(new View.OnClickListener() {

            public void onClick(View arg0) {
                                // Closing registration screen
                // Switching to Login Screen/closing register screen
                finish();
            }
        });
    }
}

EditText android:layout_width="fill_parent"
                android:id="@+id/loginEmail"
                android:layout_height="wrap_content"
                android:layout_marginTop="5dip"
                android:layout_marginBottom="20dip"
                android:singleLine="true" />

inputEmail = (EditText) findViewById(R.id.loginEmail);
inputPassword = (EditText) findViewById(R.id.loginPassword);

<TextView
    android:id="@+id/textView1"
    ...
    android:textAppearance="?android:attr/textAppearanceLarge" />

<EditText
    android:id="@+id/textView2"
    ...
    android:textAppearance="?android:attr/textAppearanceLarge" />