SQLite和android
我是android新手，我正在创建一个存储学生信息的应用程序。我无法使用SQLITE验证登录。当我运行下面的代码时，它会将我引导到登录页面，但我会收到错误“不幸的是，yourapp已停止” 下面是DBAdapter.javaSQLite和android,android,sqlite,Android,Sqlite,我是android新手，我正在创建一个存储学生信息的应用程序。我无法使用SQLITE验证登录。当我运行下面的代码时，它会将我引导到登录页面，但我会收到错误“不幸的是，yourapp已停止” 下面是DBAdapter.java public class DBAdapter { private static final String DATABASE_NAME = "Student_Info"; private static final int DATABASE_VE
public class DBAdapter {
private static final String DATABASE_NAME = "Student_Info";
private static final int DATABASE_VERSION = 2;
private static final String DATABASE_CREATE_STUDENTS = "create table Students (ID integer primary key autoincrement, "
+ "USN varchar, Password varchar);";
private static final String DATABASE_SELECT_STUDENTS="students";
public static final String Student_ID = "ID";
public static final String Student_USN = "USN";
public static final String Student_PASSWORD = "Password ";
private final Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
public DBAdapter(Context ctx)
{
this.context = ctx;
DBHelper = new DatabaseHelper(context);
}
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
public void onCreate(SQLiteDatabase db)
{
System.out.println("Creating table");
db.execSQL(DATABASE_CREATE_STUDENTS);
//I commented this line after my initial run since
//I wanted to add users using SQLite Browser and the
//table need only be created once.
}
public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
//empty method
}
}
public DBAdapter open() throws SQLException
{
db = DBHelper.getWritableDatabase();
return this;
}
public void close()
{
DBHelper.close();
}
public Cursor fetchStudent(String usn, String password)
{
Cursor myCursor = db.query(DATABASE_SELECT_STUDENTS,
new String[] { Student_ID, Student_USN, Student_PASSWORD },
Student_USN + "='" + usn + "' AND " +
Student_PASSWORD + "='" + password + "'", null, null, null, null);
if (myCursor != null) {
myCursor.moveToFirst();
}
return myCursor;
}
public void InsertData(String usn, String password)
{
String sql="INSERT INTO students (USN,Password) VALUES('"+usn+"','"+password+"')";
db.execSQL(sql);
}
}
This Is The Error shown by logcat
04-18 02:04:33.010: W/dalvikvm(757): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
04-18 02:04:33.110: E/AndroidRuntime(757): FATAL EXCEPTION: main
04-18 02:04:33.110: E/AndroidRuntime(757): java.lang.IllegalStateException: Could not execute method of the activity
04-18 02:04:33.110: E/AndroidRuntime(757): at android.view.View$1.onClick(View.java:3591)
04-18 02:04:33.110: E/AndroidRuntime(757): at android.view.View.performClick(View.java:4084)
04-18 02:04:33.110: E/AndroidRuntime(757): at android.view.View$PerformClick.run(View.java:16966)
04-18 02:04:33.110: E/AndroidRuntime(757): at android.os.Handler.handleCallback(Handler.java:615)
04-18 02:04:33.110: E/AndroidRuntime(757): at android.os.Handler.dispatchMessage(Handler.java:92)
04-18 02:04:33.110: E/AndroidRuntime(757): at android.os.Looper.loop(Looper.java:137)
04-18 02:04:33.110: E/AndroidRuntime(757): at android.app.ActivityThread.main(ActivityThread.java:4745)
04-18 02:04:33.110: E/AndroidRuntime(757): at java.lang.reflect.Method.invokeNative(Native Method)
04-18 02:04:33.110: E/AndroidRuntime(757): at java.lang.reflect.Method.invoke(Method.java:511)
04-18 02:04:33.110: E/AndroidRuntime(757): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
04-18 02:04:33.110: E/AndroidRuntime(757): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
04-18 02:04:33.110: E/AndroidRuntime(757): at dalvik.system.NativeStart.main(Native Method)
04-18 02:04:33.110: E/AndroidRuntime(757): Caused by: java.lang.reflect.InvocationTargetException
04-18 02:04:33.110: E/AndroidRuntime(757): at java.lang.reflect.Method.invokeNative(Native Method)
04-18 02:04:33.110: E/AndroidRuntime(757): at java.lang.reflect.Method.invoke(Method.java:511)
04-18 02:04:33.110: E/AndroidRuntime(757): at android.view.View$1.onClick(View.java:3586)
04-18 02:04:33.110: E/AndroidRuntime(757): ... 11 more
04-18 02:04:33.110: E/AndroidRuntime(757): Caused by: java.lang.NullPointerException
04-18 02:04:33.110: E/AndroidRuntime(757): at com.abhineel.studentinfo.LoginActivity.loginListener(LoginActivity.java:39)
04-18 02:04:33.110: E/AndroidRuntime(757): ... 14 more
04-18 02:04:33.250: W/ActivityManager(163): Force finishing activity com.abhineel.studentinfo/.LoginActivity
04-18 02:04:33.310: W/WindowManager(163): Failure taking screenshot for (164x246) to layer 21015
04-18 02:04:33.850: W/ActivityManager(163): Activity pause timeout for ActivityRecord{4132cda8 com.abhineel.studentinfo/.LoginActivity}
loginListener您需要查看那里。如果发生崩溃，logcat中会出现异常stacktrace。把它包括在你的问题中。另外，请注意代码格式以使其可读。我是stackoverflow.com的新手。我正在发布logcat错误，下次发布时我一定会保持“正确格式化代码”。很抱歉给您带来不便
public class DBAdapter {
private static final String DATABASE_NAME = "Student_Info";
private static final int DATABASE_VERSION = 2;
private static final String DATABASE_CREATE_STUDENTS = "create table Students (ID integer primary key autoincrement, "
+ "USN varchar, Password varchar);";
private static final String DATABASE_SELECT_STUDENTS="students";
public static final String Student_ID = "ID";
public static final String Student_USN = "USN";
public static final String Student_PASSWORD = "Password ";
private final Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
public DBAdapter(Context ctx)
{
this.context = ctx;
DBHelper = new DatabaseHelper(context);
}
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
public void onCreate(SQLiteDatabase db)
{
System.out.println("Creating table");
db.execSQL(DATABASE_CREATE_STUDENTS);
//I commented this line after my initial run since
//I wanted to add users using SQLite Browser and the
//table need only be created once.
}
public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
//empty method
}
}
public DBAdapter open() throws SQLException
{
db = DBHelper.getWritableDatabase();
return this;
}
public void close()
{
DBHelper.close();
}
public Cursor fetchStudent(String usn, String password)
{
Cursor myCursor = db.query(DATABASE_SELECT_STUDENTS,
new String[] { Student_ID, Student_USN, Student_PASSWORD },
Student_USN + "='" + usn + "' AND " +
Student_PASSWORD + "='" + password + "'", null, null, null, null);
if (myCursor != null) {
myCursor.moveToFirst();
}
return myCursor;
}
public void InsertData(String usn, String password)
{
String sql="INSERT INTO students (USN,Password) VALUES('"+usn+"','"+password+"')";
db.execSQL(sql);
}
}
This Is The Error shown by logcat
04-18 02:04:33.010: W/dalvikvm(757): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
04-18 02:04:33.110: E/AndroidRuntime(757): FATAL EXCEPTION: main
04-18 02:04:33.110: E/AndroidRuntime(757): java.lang.IllegalStateException: Could not execute method of the activity
04-18 02:04:33.110: E/AndroidRuntime(757): at android.view.View$1.onClick(View.java:3591)
04-18 02:04:33.110: E/AndroidRuntime(757): at android.view.View.performClick(View.java:4084)
04-18 02:04:33.110: E/AndroidRuntime(757): at android.view.View$PerformClick.run(View.java:16966)
04-18 02:04:33.110: E/AndroidRuntime(757): at android.os.Handler.handleCallback(Handler.java:615)
04-18 02:04:33.110: E/AndroidRuntime(757): at android.os.Handler.dispatchMessage(Handler.java:92)
04-18 02:04:33.110: E/AndroidRuntime(757): at android.os.Looper.loop(Looper.java:137)
04-18 02:04:33.110: E/AndroidRuntime(757): at android.app.ActivityThread.main(ActivityThread.java:4745)
04-18 02:04:33.110: E/AndroidRuntime(757): at java.lang.reflect.Method.invokeNative(Native Method)
04-18 02:04:33.110: E/AndroidRuntime(757): at java.lang.reflect.Method.invoke(Method.java:511)
04-18 02:04:33.110: E/AndroidRuntime(757): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
04-18 02:04:33.110: E/AndroidRuntime(757): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
04-18 02:04:33.110: E/AndroidRuntime(757): at dalvik.system.NativeStart.main(Native Method)
04-18 02:04:33.110: E/AndroidRuntime(757): Caused by: java.lang.reflect.InvocationTargetException
04-18 02:04:33.110: E/AndroidRuntime(757): at java.lang.reflect.Method.invokeNative(Native Method)
04-18 02:04:33.110: E/AndroidRuntime(757): at java.lang.reflect.Method.invoke(Method.java:511)
04-18 02:04:33.110: E/AndroidRuntime(757): at android.view.View$1.onClick(View.java:3586)
04-18 02:04:33.110: E/AndroidRuntime(757): ... 11 more
04-18 02:04:33.110: E/AndroidRuntime(757): Caused by: java.lang.NullPointerException
04-18 02:04:33.110: E/AndroidRuntime(757): at com.abhineel.studentinfo.LoginActivity.loginListener(LoginActivity.java:39)
04-18 02:04:33.110: E/AndroidRuntime(757): ... 14 more
04-18 02:04:33.250: W/ActivityManager(163): Force finishing activity com.abhineel.studentinfo/.LoginActivity
04-18 02:04:33.310: W/WindowManager(163): Failure taking screenshot for (164x246) to layer 21015
04-18 02:04:33.850: W/ActivityManager(163): Activity pause timeout for ActivityRecord{4132cda8 com.abhineel.studentinfo/.LoginActivity}