我有一个MyDBAdapter类，可以做一些简单的选择，但现在我需要一个特殊的选择。我需要实现这个选择：
SELECT * FROM position WHERE fk_email='given value by variable'
但我的android的dbadapter技能非常低......我不知道该怎么做。
我必须添加两个新方法：
public Cursor fetchPositionsByEmail(String fk_email)
public List<Position> retrievePositionsByEmail(String fk_email)
我试过这些实现，但它们没有用，它们给我一个空位置：
public Cursor fetchPositionsByEmail(String email) throws SQLException {
Cursor mCursor = mDb.query(true, "position", new String[] {"idposition", "latitude", "longitude", "timestamp", "fk_email"}
, "fk_email" + "='" + email+"'", null, null, null, null, null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
public List<Position> retrievePositionsByEmail(String email)
{
List <Position> positions=new ArrayList<Position>();
Cursor result=fetchPositionsByEmail(email);
if( result.moveToFirst() ){
do{
positions.add(new Position(result.getString(result.getColumnIndexOrThrow("idposition")),
result.getString(result.getColumnIndexOrThrow("latitude")),
result.getString(result.getColumnIndexOrThrow("longitude")),
result.getString(result.getColumnIndexOrThrow("timestamp")),
result.getString(result.getColumnIndexOrThrow("fk_email"))));
}while( result.moveToNext() );
}
return positions;
}
有人可以帮助我在这个MyDBAdapter类上实现这两个方法吗？
这是班级：
public class MyDbAdapter {
private static final String TAG = "NotesDbAdapter";
private DatabaseHelper mDbHelper;
private SQLiteDatabase mDb;
private static final String DATABASE_NAME = "gpslocdb";
private static final String PERMISSION_TABLE_CREATE = "CREATE TABLE permission ( fk_email1 varchar, fk_email2 varchar, validated tinyint, hour1 time default '08:00:00', hour2 time default '20:00:00', date1 date, date2 date, weekend tinyint default '0', fk_type varchar, PRIMARY KEY (fk_email1,fk_email2))";
private static final String USER_TABLE_CREATE = "CREATE TABLE user ( email varchar, password varchar, fullName varchar, mobilePhone varchar, mobileOperatingSystem varchar, PRIMARY KEY (email))";
private static final String POSITION_TABLE_CREATE = "CREATE TABLE position (idposition bigint, latitude varchar, longitude varchar, timestamp datetime, fk_email varchar, PRIMARY KEY (idposition))";
private static final int DATABASE_VERSION = 2;
private final Context mCtx;
private static class DatabaseHelper extends SQLiteOpenHelper {
DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("DROP TABLE IF EXISTS user");
db.execSQL("DROP TABLE IF EXISTS permission");
db.execSQL("DROP TABLE IF EXISTS position");
db.execSQL(PERMISSION_TABLE_CREATE);
db.execSQL(USER_TABLE_CREATE);
db.execSQL(POSITION_TABLE_CREATE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
//db.execSQL("DROP TABLE IF EXISTS user");
//db.execSQL("DROP TABLE IF EXISTS permission");
//onCreate(db);
}
@Override
public void onOpen(SQLiteDatabase db) {
super.onOpen(db);
//onCreate(db);
}
public void clearDb(SQLiteDatabase db){
db.execSQL("DROP TABLE IF EXISTS user");
db.execSQL("DROP TABLE IF EXISTS permission");
db.execSQL("DROP TABLE IF EXISTS position");
onCreate(db);
}
public void deleteUser(SQLiteDatabase db, String email)
{
db.execSQL("DELETE FROM user Where email='"+email+"'");
}
public void deletePermission(SQLiteDatabase db, String email)
{
db.execSQL("DELETE FROM permission Where fk_email2='"+email+"'");
}
}
/**
* Constructor - takes the context to allow the database to be
* opened/created
*
* @param ctx the Context within which to work
*/
public MyDbAdapter(Context ctx) {
this.mCtx = ctx;
}
/**
* Open the 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 MyDbAdapter open() throws SQLException {
mDbHelper = new DatabaseHelper(mCtx);
mDb = mDbHelper.getWritableDatabase();
return this;
}
public void close() {
//clearDB();
mDbHelper.close();
}
public long createUser(String email, String password, String fullName, String mobilePhone, String mobileOperatingSystem)
{
ContentValues initialValues = new ContentValues();
initialValues.put("email",email);
initialValues.put("password",password);
initialValues.put("fullName",fullName);
initialValues.put("mobilePhone",mobilePhone);
initialValues.put("mobileOperatingSystem",mobileOperatingSystem);
return mDb.insert("user", null, initialValues);
}
public long createPermission(String email1, String email2, String validated, String hour1, String hour2,
String date1, String date2, String weekend, String fk_type)
{
ContentValues initialValues = new ContentValues();
initialValues.put("fk_email1",email1);
initialValues.put("fk_email2",email2);
initialValues.put("validated",validated);
initialValues.put("hour1",hour1);
initialValues.put("hour2",hour2);
initialValues.put("date1",date1);
initialValues.put("date2",date2);
initialValues.put("weekend",weekend);
initialValues.put("fk_type",fk_type);
return mDb.insert("permission", null, initialValues);
}
public long createPosition(String idposition, String latitude, String longitude, String timestamp, String fk_email)
{
ContentValues initialValues = new ContentValues();
initialValues.put("idposition",idposition);
initialValues.put("latitude",latitude);
initialValues.put("longitude",longitude);
initialValues.put("timestamp",timestamp);
initialValues.put("fk_email",fk_email);
return mDb.insert("position", null, initialValues);
}
public void clearDB() {
mDbHelper.clearDb(mDb);
}
public Cursor fetchAllUsers() {
return mDb.query("user", new String[] {"email", "password", "fullName", "mobilePhone", "mobileOperatingSystem"}, null, null, null, null, null);
}
public Cursor fetchAllPermissions() {
return mDb.query("permission", new String[] {"fk_email1", "fk_email2", "validated", "hour1", "hour2", "date1", "date2", "weekend", "fk_type"}, null, null, null, null, null);
}
public Cursor fetchUser(String email) throws SQLException {
Cursor mCursor = mDb.query(true, "user", new String[] {"email", "password", "fullName", "mobilePhone", "mobileOperatingSystem"}
, "email" + "=" + email, null, null, null, null, null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
public List<Friend> retrieveAllFriends()
{
List <Friend> friends=new ArrayList<Friend>();
Cursor result=fetchAllUsers();
if( result.moveToFirst() ){
do{
friends.add(new Friend(result.getString(result.getColumnIndexOrThrow("email")),result.getString(result.getColumnIndexOrThrow("password")), result.getString(result.getColumnIndexOrThrow("fullName")),result.getString(result.getColumnIndexOrThrow("mobilePhone")),result.getString(result.getColumnIndexOrThrow("mobileOperatingSystem"))));
}while( result.moveToNext() );
}
return friends;
}
public List<Permission> retrieveAllPermissions()
{
List <Permission> permissions=new ArrayList<Permission>();
Cursor result=fetchAllPermissions();
if( result.moveToFirst() ){
do{
permissions.add(new Permission(result.getString(result.getColumnIndexOrThrow("fk_email1")),
result.getString(result.getColumnIndexOrThrow("fk_email2")),
Integer.parseInt(result.getString(result.getColumnIndexOrThrow("validated"))),
result.getString(result.getColumnIndexOrThrow("hour1")),
result.getString(result.getColumnIndexOrThrow("hour2")),
result.getString(result.getColumnIndexOrThrow("date1")),
result.getString(result.getColumnIndexOrThrow("date2")),
Integer.parseInt(result.getString(result.getColumnIndexOrThrow("weekend"))),
result.getString(result.getColumnIndexOrThrow("fk_type"))));
}while( result.moveToNext() );
}
return permissions;
}
public void deleteUser(String email) throws SQLException
{
mDbHelper.deleteUser(mDb, email);
}
public void deletePermission(String email) throws SQLException
{
mDbHelper.deletePermission(mDb, email);
}
}
答案 0 :(得分：1)
尝试使用占位符而不是连接值。
Cursor mCursor = mDb.query(true, "position", new String[] {"idposition", "latitude", "longitude", "timestamp", "fk_email"}
, "fk_email=?", new String[] { email } , null, null, null, null);
由于您通过串联传递电子邮件地址，因此问题可能来自@符号。
我发现this post关于sql中的@