我正在使用SQLite数据库，我希望在加载时在Spinner中检索来自一列（USER_NAME）的数据。
当我运行应用程序时，它会崩溃。
这是我到目前为止的情况。在我的UserDBHelper类中，与微调器相关的方法称为getAllNames（），并且在Mark类中我将代码放在OnCreate（）
中UserContract：
public class UserContract {
public static abstract class NewUserInfo{
public static final String USER_NAME = "user_name";
public static final String USER_SURNAME = "user_surname";
public static final String USER_MARK = "user_mark";
public static final String TABLE_NAME = "user_info";
}
}
UserDBHelper
public class UserDBHelper extends SQLiteOpenHelper {
public static final String DATABASE_NAME = "USERINFO.DB";
private static final int DATABASE_VERSION = 1;
private static final String CREATE_QUERY =
"CREATE TABLE " + UserContract.NewUserInfo.TABLE_NAME + "(" + UserContract.NewUserInfo.USER_NAME + " TEXT,"
+ UserContract.NewUserInfo.USER_SURNAME + " TEXT,"
+ UserContract.NewUserInfo.USER_MARK + " TEXT);";
SQLiteDatabase db;
UserDBHelper helper;
Context c;
public UserDBHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
Log.e("DATABASE OPERATION", "Database created / opened...");
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_QUERY);
Log.e("DATABASE OPERATION", "Table created...");
}
public ArrayList<String> getAllNames(){
ArrayList<String> list=new ArrayList<String>();
// Open the database for reading
SQLiteDatabase db = this.getReadableDatabase();
// Start the transaction.
db.beginTransaction();
try
{
String selectQuery = "SELECT * FROM "+ UserContract.NewUserInfo.TABLE_NAME;
Cursor cursor = db.rawQuery(selectQuery, null);
if(cursor.getCount() >0)
{
while (cursor.moveToNext()) {
// Add province name to arraylist
String name= cursor.getString(cursor.getColumnIndex("USER_NAME"));
list.add(name);
}
}
db.setTransactionSuccessful();
}
catch (SQLiteException e)
{
e.printStackTrace();
}
finally
{
db.endTransaction();
// End the transaction.
db.close();
// Close database
}
return list;
}
//GET ALL VALUES
public Cursor getAllValues()
{
String[] columns={UserContract.NewUserInfo.USER_NAME,UserContract.NewUserInfo.USER_SURNAME,UserContract.NewUserInfo.USER_MARK};
return db.query(UserContract.NewUserInfo.TABLE_NAME, columns, null, null, null, null, null);
}
public void addInformations(String name, String surname, String mark, SQLiteDatabase db) {
ContentValues contentValues = new ContentValues();
contentValues.put(UserContract.NewUserInfo.USER_NAME, name);
contentValues.put(UserContract.NewUserInfo.USER_SURNAME, surname);
contentValues.put(UserContract.NewUserInfo.USER_MARK, mark);
db.insert(UserContract.NewUserInfo.TABLE_NAME, null, contentValues);
Log.e("DATABASE OPERATION", "One row inserted...");
}
@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
}
public boolean updateData (String name, String surname, String mark){
SQLiteDatabase db = this.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put(UserContract.NewUserInfo.USER_NAME,name);
contentValues.put(UserContract.NewUserInfo.USER_SURNAME,surname);
contentValues.put(UserContract.NewUserInfo.USER_MARK,mark);
db.update(UserContract.NewUserInfo.TABLE_NAME, contentValues, " USER_NAME = ?", new String[] { name });
return true;
}
}
标记
public class Mark extends Activity {
Spinner spin;
EditText uname, usurname, umark;
Context context =this;
UserDBHelper userDbHelper ;
SQLiteDatabase sqLiteDatabase;
ArrayList<String> names=new ArrayList<String>();
ArrayAdapter<String> adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.mark);
uname = (EditText) findViewById(R.id.txtName);
usurname = (EditText) findViewById(R.id.txtSurname);
umark = (EditText) findViewById(R.id.txtMark);
spin=(Spinner) findViewById(R.id.spinner);
userDbHelper = new UserDBHelper(this);
ArrayList<String> list=userDbHelper.getAllNames();
ArrayAdapter<String> adapter=new ArrayAdapter<String>(this, R.layout.mark, R.id.text, list);
spin.setAdapter(adapter);
}
public void insertUpdate(View view){
userDbHelper = new UserDBHelper(getApplicationContext());
sqLiteDatabase = userDbHelper.getReadableDatabase();
Cursor cursor = updateData();
if(cursor.moveToFirst()) {
userDbHelper.updateData(uname.getText().toString(),
usurname.getText().toString(),
umark.getText().toString());
Toast.makeText(Mark.this, "Data updated", Toast.LENGTH_LONG).show();
}else{
String name = uname.getText().toString();
String surname = usurname.getText().toString();
String mark = umark.getText().toString();
userDbHelper = new UserDBHelper(context);
sqLiteDatabase = userDbHelper.getWritableDatabase();
userDbHelper.addInformations(name, surname, mark, sqLiteDatabase);
Toast.makeText(getBaseContext(),"Data Saved",Toast.LENGTH_LONG).show();
userDbHelper.close();
}
}
public Cursor updateData(){
SQLiteDatabase db = this.userDbHelper.getWritableDatabase();
Cursor res = db.rawQuery("select * from "+TABLE_NAME.trim()+" WHERE "+USER_NAME.trim()+ " = " + "'"+ uname.getText().toString() + "'" ,null);
return res;
}
public void viewAll(View view) {
{
userDbHelper = new UserDBHelper(getApplicationContext());
sqLiteDatabase = userDbHelper.getReadableDatabase();
Cursor cursor = getAllData();
if (cursor.moveToFirst()) {
String name = cursor.getString(0);
String surname = cursor.getString(1);
String mark = cursor.getString(2);
uname.setText(name);
usurname.setText(surname);
umark.setText(mark);
// s_surname.setVisibility(View.VISIBLE);
// s_mark.setVisibility(View.VISIBLE);
}
}
}
public Cursor getAllData() {
SQLiteDatabase db = this.userDbHelper.getWritableDatabase();
//Cursor res = db.rawQuery("select * from "+TABLE_NAME.trim()+" WHERE "+COL_2.trim()+" = 'Lyubo'" , null);
Cursor res = db.rawQuery("select * from "+TABLE_NAME.trim()+" WHERE "+USER_NAME.trim()+ " = " + "'"+ uname.getText().toString() + "'" ,null);
return res;
}}
这是我的Log CAT：
FATAL EXCEPTION: main
Process: com.example.lyubo.datatrial, PID: 6056
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.lyubo.datatrial/com.example.lyubo.datatrial.Mark}: java.lang.IllegalStateException: Couldn't read row 0, col -1 from CursorWindow. Make sure the Cursor is initialized correctly before accessing data from it.
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: java.lang.IllegalStateException: Couldn't read row 0, col -1 from CursorWindow. Make sure the Cursor is initialized correctly before accessing data from it.
at android.database.CursorWindow.nativeGetString(Native Method)
at android.database.CursorWindow.getString(CursorWindow.java:438)
at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:51)
at com.example.lyubo.datatrial.UserDBHelper.getAllNames(UserDBHelper.java:69)
at com.example.lyubo.datatrial.Mark.onCreate(Mark.java:44)
at android.app.Activity.performCreate(Activity.java:6679)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
答案 0 :(得分：1)
您的代码似乎很好，但缺少一件事。
试试这个：
String selectQuery = "SELECT * FROM "+ UserContract.NewUserInfo.TABLE_NAME;
Cursor cursor = db.rawQuery(selectQuery, null);
if(cursor.getCount() >0)
{
cursor.moveToFirst(); //missing
while (cursor.moveToNext()) {
// Add province name to arraylist
String name= cursor.getString(cursor.getColumnIndex("USER_NAME"));
list.add(name);
}
}
这应该按预期工作，因为cursor.moveToFirst();将光标放在第一个位置而不是第0个位置。
答案 1 :(得分：0)
这解决了我的问题：
UserDBHelper
public List<String> getAllNames(){
List<String> labels = new ArrayList<String>();
// Select All Query
String selectQuery = "SELECT * FROM " + UserContract.NewUserInfo.TABLE_NAME;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
labels.add(cursor.getString(0));
} while (cursor.moveToNext());
}
// closing connection
cursor.close();
db.close();
// returning lables
return labels;
}
Mark Class（主要活动）：
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.mark);
uname = (EditText) findViewById(R.id.txtName);
usurname = (EditText) findViewById(R.id.txtSurname);
umark = (EditText) findViewById(R.id.txtMark);
spin=(Spinner) findViewById(R.id.spinner);
loadSpinnerData();
}
private void loadSpinnerData() {
// database handler
UserDBHelper db = new UserDBHelper(getApplicationContext());
// Spinner Drop down elements
List<String> lables = db.getAllNames();
// Creating adapter for spinner
ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_item, lables);
// Drop down layout style - list view with radio button
dataAdapter
.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
// attaching data adapter to spinner
spin.setAdapter(dataAdapter);
}