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이 문제가 발생했습니다. 나는 ListActivity를 가지고 있는데, 이후에 내 목록에서보고자하는 모든 데이터베이스 항목을 가져 오려고합니다.데이터베이스 항목을 커서에 입력하는 방법
이제 내 테이블에서 모든 데이터를 가져올 때 Nullpointer 예외 문제가 발생합니다. 2 단계에서 확인하십시오.
가 여기에 ListActivity의 코드입니다 :
package de.retowaelchli.filterit.stats;
import de.retowaelchli.filterit.database.ADFilterDBAdapter;
import android.app.ListActivity;
import android.database.Cursor;
import android.os.Bundle;
import android.widget.ArrayAdapter;
public class CreatedADFilters extends ListActivity {
//Variablen deklaration
private ADFilterDBAdapter mDbHelper;
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
//Hier wir die Datenbank aufgerufen
mDbHelper = new ADFilterDBAdapter(this);
mDbHelper.open();
System.out.println("STEP1"); //Until here it works
Cursor c = mDbHelper.getAllADFilter();
startManagingCursor(c);
System.out.println("STEP2"); //Here's the problem I don't get.
}
}
그래서 여기 내 DB-어댑터의 코드 부분 : 나는 내가 잘못 것을 얻을하지 않습니다
public Cursor getAllADFilter() {
return this.mDb.query(DATABASE_TABLE, new String[] { ROW_ID,
NAME, KEYWORD, CACHE }, null, null, null, null, null);
}
, 제발 조언 좀 해줘.
미리 감사드립니다.
그래서 여기에이 표에 대한 전체 DB-어댑터의 :
package de.retowaelchli.filterit.database;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class ADFilterDBAdapter {
public static final String ROW_ID = "_id";
public static final String NAME = "name";
public static final String KEYWORD = "keyword";
public static final String CACHE = "cache";
private static final String DATABASE_TABLE = "adfilter";
private DatabaseHelper mDbHelper;
private SQLiteDatabase mDb;
private final Context mCtx;
private static class DatabaseHelper extends SQLiteOpenHelper {
DatabaseHelper(Context context) {
super(context, DBAdapter.DATABASE_NAME, null, DBAdapter.DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
/**
* Constructor - takes the context to allow the database to be
* opened/created
*
* @param ctx
* the Context within which to work
*/
public ADFilterDBAdapter(Context ctx) {
this.mCtx = ctx;
}
/**
* Open the ADFilter database. If it cannot be opened, try to create a new
* instance of the database. If it cannot be created, throw an exception to
* signal the failure
*
* @return this (self reference, allowing this to be chained in an
* initialization call)
* @throws SQLException
* if the database could be neither opened or created
*/
public ADFilterDBAdapter open() throws SQLException {
this.mDbHelper = new DatabaseHelper(this.mCtx);
this.mDb = this.mDbHelper.getWritableDatabase();
return this;
}
/**
* close return type: void
*/
public void close() {
this.mDbHelper.close();
}
/**
* Create a new ADFilter. If the car is successfully created return the new
* rowId for that ADFilter, otherwise return a -1 to indicate failure.
*
* @param name
* @param keyword
* @param cache
* @return rowId or -1 if failed
*/
public long createADFilter(String name, String keyword, String cache){
ContentValues initialValues = new ContentValues();
initialValues.put(NAME, name);
initialValues.put(KEYWORD, keyword);
initialValues.put(CACHE, cache);
return this.mDb.insert(DATABASE_TABLE, null, initialValues);
}
/**
* Delete the ADFilter with the given rowId
*
* @param rowId
* @return true if deleted, false otherwise
*/
public boolean deleteADFilter(long rowId) {
return this.mDb.delete(DATABASE_TABLE, ROW_ID + "=" + rowId, null) > 0; //$NON-NLS-1$
}
/**
* Return a Cursor over the list of all ADFilter in the database
*
* @return Cursor over all ADFilters
*/
public Cursor getAllADFilter() {
return this.mDb.query(DATABASE_TABLE, new String[] { ROW_ID,
NAME, KEYWORD, CACHE }, null, null, null, null, null);
}
/**
* Return a Cursor positioned at the ADFilter that matches the given rowId
* @param rowId
* @return Cursor positioned to matching ADFilter, if found
* @throws SQLException if ADFilter could not be found/retrieved
*/
public Cursor getADFilter(long rowId) throws SQLException {
Cursor mCursor =
this.mDb.query(true, DATABASE_TABLE, new String[] { ROW_ID, NAME,
KEYWORD, CACHE}, ROW_ID + "=" + rowId, null, null, null, null, null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
/**
* Update the ADFilter
*
* @param rowId
* @param name
* @param keyword
* @param cache
* @return true if the note was successfully updated, false otherwise
*/
public boolean updateADFilter(long rowId, String name, String keyword,
String cache){
ContentValues args = new ContentValues();
args.put(NAME, name);
args.put(KEYWORD, keyword);
args.put(CACHE, cache);
return this.mDb.update(DATABASE_TABLE, args, ROW_ID + "=" + rowId, null) >0;
}
}
그리고 여기에 글로벌 DB-어댑터의 : 나는 희망
package de.retowaelchli.filterit.database;
import android.content.Context;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DBAdapter {
public static final String DATABASE_NAME = "filterit"; //$NON-NLS-1$
public static final int DATABASE_VERSION = 1;
public static final String CREATE_TABLE_ADFILTER =
"create table adfilter (_id integer primary key autoincrement, " //$NON-NLS-1$
+ ADFilterDBAdapter.NAME+ " TEXT," //$NON-NLS-1$
+ ADFilterDBAdapter.KEYWORD+ " TEXT," //$NON-NLS-1$
+ ADFilterDBAdapter.CACHE+ " TEXT" + ");"; //$NON-NLS-1$ //$NON-NLS-2$
private static final String CREATE_TABLE_SFILTER = "create table sfilter (_id integer primary key autoincrement, " //$NON-NLS-1$
+SFilterDBAdapter.NAME+" TEXT," //$NON-NLS-1$
+SFilterDBAdapter.KEYWORD+" TEXT," //$NON-NLS-1$
+SFilterDBAdapter.COLOR+" TEXT,"//$NON-NLS-1$ //$NON-NLS-2$
+SFilterDBAdapter.SMILEY+" TEXT"+ ");";
private static final String CREATE_TABLE_ADMESSAGES = "create table admessages (_id integer primary key autoincrement, " //$NON-NLS-1$
+ADMessagesDBAdapter.PHONENUMBER+" TEXT," //$NON-NLS-1$
+ADMessagesDBAdapter.MESSAGE+" TEXT,"+ ");"; //$NON-NLS-1$ //$NON-NLS-2$
private final Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
/**
* Constructor
* @param ctx
*/
public DBAdapter(Context ctx)
{
this.context = ctx;
this.DBHelper = new DatabaseHelper(this.context);
}
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL(CREATE_TABLE_ADFILTER);
db.execSQL(CREATE_TABLE_SFILTER);
db.execSQL(CREATE_TABLE_ADMESSAGES);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion,
int newVersion)
{
// Adding any table mods to this guy here
}
}
/**
* open the db
* @return this
* @throws SQLException
* return type: DBAdapter
*/
public DBAdapter open() throws SQLException
{
this.db = this.DBHelper.getWritableDatabase();
return this;
}
/**
* close the db
* return type: void
*/
public void close()
{
this.DBHelper.close();
}
}
그 .. =) 밖으로 당신을 도와줍니다
데이터베이스에 데이터가 없기 때문에 커서가 null 일 수 있습니다. – ingsaurabh
어떻게 테스트 할 수 있습니까? 내가 어떻게 고칠 수, 그래서 nullpointer 예외가 없습니까? – safari
데이터베이스 또는 테이블이 생성 되었습니까? 데이터베이스와 테이블이 있는지 확인하십시오. – WindsurferOak