我在byethost服务器上创建了数据库和表，生成了我从教程（http://www.androidhive.info/2012/01/android-login-and-registration-with-php-mysql-and-sqlite/）看到的代码的apk，然后将其安装在我的设备上。但每当我尝试注册时，我只会收到一条错误消息，这是UI的一部分。当我尝试单击登录页面中的登录按钮时，应用程序崩溃。
布局代码：
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:padding="10dip" >
<!-- View Title Label -->
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="10dip"
android:text="LOGIN"
android:textSize="25dip"
android:textStyle="bold" />
<!-- Email Label -->
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Email" />
<!-- Email TextField -->
<EditText
android:id="@+id/loginEmail"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
<!-- Password Label -->
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginTop="15dip"
android:text="Password" />
<!-- Password TextField -->
<EditText
android:id="@+id/loginPassword"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:password="true" />
<!-- Error message -->
<TextView android:id="@+id/login_error"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textColor="#e30000"
android:padding="10dip"
android:textStyle="bold"/>
<!-- Login Button -->
<Button
android:id="@+id/btnLogin"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginTop="20dip"
android:text="Login" />
<!-- Link to Registration Screen -->
<Button
android:id="@+id/btnLinkToRegisterScreen"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginTop="40dip"
android:background="@null"
android:text="I don't have account. Register Me!"
android:textColor="#21dbd4"
android:textStyle="bold" />
</LinearLayout>
</ScrollView>
java文件的代码：
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.example.androidhive.library.DatabaseHandler;
import com.example.androidhive.library.UserFunctions;
public class LoginActivity extends Activity {
Button btnLogin;
Button btnLinkToRegister;
EditText inputEmail;
EditText inputPassword;
TextView loginErrorMsg;
// 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);
btnLinkToRegister = (Button) findViewById(R.id.btnLinkToRegisterScreen);
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();
Log.d("Button", "Login");
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();
}
}
});
// Link to Register Screen
btnLinkToRegister.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Intent i = new Intent(getApplicationContext(),
RegisterActivity.class);
startActivity(i);
finish();
}
});
}
}
编辑：按下登录按钮时的logcat
07-30 15:32:15.488: I/Choreographer(867): Skipped 81 frames! The application may be doing too much work on its main thread.
07-30 15:32:31.938: D/Button(867): Login
07-30 15:32:35.650: E/JSON(867): No database selected
07-30 15:32:35.670: E/JSON Parser(867): Error parsing data org.json.JSONException: Value No of type java.lang.String cannot be converted to JSONObject
07-30 15:32:35.679: D/AndroidRuntime(867): Shutting down VM
07-30 15:32:35.690: W/dalvikvm(867): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
07-30 15:32:35.753: E/AndroidRuntime(867): FATAL EXCEPTION: main
07-30 15:32:35.753: E/AndroidRuntime(867): java.lang.NullPointerException
07-30 15:32:35.753: E/AndroidRuntime(867): at com.example.androidhive.LoginActivity$1.onClick(LoginActivity.java:65)
07-30 15:32:35.753: E/AndroidRuntime(867): at android.view.View.performClick(View.java:4204)
07-30 15:32:35.753: E/AndroidRuntime(867): at android.view.View$PerformClick.run(View.java:17355)
07-30 15:32:35.753: E/AndroidRuntime(867): at android.os.Handler.handleCallback(Handler.java:725)
07-30 15:32:35.753: E/AndroidRuntime(867): at android.os.Handler.dispatchMessage(Handler.java:92)
07-30 15:32:35.753: E/AndroidRuntime(867): at android.os.Looper.loop(Looper.java:137)
07-30 15:32:35.753: E/AndroidRuntime(867): at android.app.ActivityThread.main(ActivityThread.java:5041)
07-30 15:32:35.753: E/AndroidRuntime(867): at java.lang.reflect.Method.invokeNative(Native Method)
07-30 15:32:35.753: E/AndroidRuntime(867): at java.lang.reflect.Method.invoke(Method.java:511)
07-30 15:32:35.753: E/AndroidRuntime(867): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
07-30 15:32:35.753: E/AndroidRuntime(867): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
07-30 15:32:35.753: E/AndroidRuntime(867): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：0)
首先，您应该了解有关AsyncTask的更多信息。这是一个教程：http://www.vogella.com/tutorials/AndroidBackgroundProcessing/article.html
在UI Thread上做这种工作并不好。
您的JSON代码必须改进。 这是其他教程： http://www.vogella.com/tutorials/AndroidJSON/article.html
尝试创建一个类，它将为您创建连接，并从您传递的URL获取JSONObject。你必须处理这个例外。