我创建了一个ListView，并用数据库中的项填充它。目前我正在努力使它能够长时间点击一个项目并将它从ListView和数据库中一起删除，但似乎出现了问题。一切正常，直到删除部分。我有它所以它通过获取其ID来删除该项，这是我认为它出错的地方。我找到了一种方法来显示id并且每次它返回0.我不知道它为什么这样做。我没有得到任何错误，但它没有按照我希望的那样工作。如果有人能指出我正确的方向，这将是非常棒的。
这是我的databaseHelper类：
public class HabitDbHelper extends SQLiteOpenHelper{
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_NAME="habits";
public static final String TABLE_HABITS = "habit_names";
public static final String KEY_NAME = "hname";
public static final String KEY_ID = "id";
public static final String KEY_STARTDATE = "start_date";
public static final String KEY_ENDDATE = "end_date";
public static final String KEY_DAYCOUNT = "day_count";
public HabitDbHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
// Creating Tables
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE "+TABLE_HABITS+" ("
+KEY_ID+" INTEGER PRIMARY KEY AUTOINCREMENT, "
+KEY_NAME+" TEXT, "
+KEY_STARTDATE+" TEXT, "
+KEY_ENDDATE+" TEXT, "
+KEY_DAYCOUNT+" INTEGER);");
}
// Upgrading Database
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS "+TABLE_HABITS);
onCreate(db);
}
//Adding new habit
public void addHabit(Habit habit) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_NAME, habit.getName()); // Habit Name
values.put(KEY_STARTDATE, habit.getStartDate()); // Start Date
values.put(KEY_ENDDATE, habit.getEndDate()); // End Date
values.put(KEY_DAYCOUNT, habit.getDayCount());
// Inserting Row
db.insert(TABLE_HABITS, null, values);
db.close(); // Closing database connection
}
// Fetching 1 Habit
public Habit getHabit(int id) {
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.query(TABLE_HABITS, new String[] { KEY_ID,
KEY_NAME, KEY_STARTDATE ,KEY_ENDDATE, KEY_DAYCOUNT }, KEY_ID + "=?",
new String[] { String.valueOf(id) }, null, null, null, null);
if (cursor != null)
cursor.moveToFirst();
Habit habit = new Habit(Integer.parseInt(cursor.getString(0)), cursor.getString(1), cursor.getString(2), cursor.getString(3), Integer.parseInt(cursor.getString(4)));
// return contact
return habit;
}
// Fetching all Habits
public ArrayList<Habit> getAllHabits() {
ArrayList<Habit> habitList = new ArrayList<Habit>();
// Select All Query
String selectQuery = "SELECT * FROM " + TABLE_HABITS;
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
Habit habit = new Habit();
habit.setID(Integer.parseInt(cursor.getString(cursor.getColumnIndex(KEY_ID))));
habit.setName(cursor.getString(cursor.getColumnIndex(KEY_NAME)));
habit.setStartDate(cursor.getString(cursor.getColumnIndex(KEY_STARTDATE)));
habit.setEndDate(cursor.getString(cursor.getColumnIndex(KEY_ENDDATE)));
habit.setDayCount(Integer.parseInt(cursor.getString(cursor.getColumnIndex(KEY_DAYCOUNT))));
// Adding contact to list
habitList.add(habit);
} while (cursor.moveToNext());
}
return habitList;
}
//Updating single habit
public int updateHabit(Habit habit) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_NAME, habit.getName());
values.put(KEY_STARTDATE, String.valueOf(habit.getStartDate())); // Start Date
values.put(KEY_ENDDATE, habit.getEndDate()); // End Date
values.put(KEY_DAYCOUNT, habit.getDayCount()); // Day Count
// updating row
return db.update(TABLE_HABITS, values, KEY_ID + " = ?",
new String[] { String.valueOf(habit.getID()) });
}
// Deleting Single Habit
public void deleteHabit(Habit habit) {
SQLiteDatabase db = this.getWritableDatabase();
db.delete(TABLE_HABITS, KEY_ID + " = ?",
new String[] { Integer.toString(habit.getID()) });
db.close();
}
// Getting habits count
public int getHabitsCount() {
String countQuery = "SELECT * FROM " + TABLE_HABITS;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(countQuery, null);
cursor.close();
// return count
return cursor.getCount();
}
}
我的mainActivity我用delete方法调用onItemLongClickListener：
public class fourtyMain extends Activity
{
private HabitDbHelper mDB;
private ListView mList;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.fourty_main);
mList = (ListView)findViewById(R.id.habit_list);
mDB = new HabitDbHelper(this);
getActionBar().setDisplayShowTitleEnabled(false);
//long click to delete data
mList.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
public boolean onItemLongClick(AdapterView<?> parent, final View view, int position, long id) {
final Habit habit = (Habit) parent.getAdapter().getItem(position);
deleteHabitInListView(habit);
return true;
}
private void deleteHabitInListView(final Habit habit){
Builder deleteDialog = new AlertDialog.Builder(fourtyMain.this);
deleteDialog.setTitle("Delete " + habit.getName() + "?");
deleteDialog.setMessage("Are you sure you want to delete this habit? All your progress will be lost!");
deleteDialog.setPositiveButton("Yes", new AlertDialog.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
mDB.deleteHabit(habit);
displayData();
}
});
deleteDialog.setNegativeButton("No", new AlertDialog.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
deleteDialog.show();
}
});
}
我的ListView适配器类：
public class HabitAdapter extends BaseAdapter {
private ArrayList<Habit> habits;
private Context context;
private int layoutId, id1;
public HabitAdapter(Context c, int LayoutId,ArrayList<Habit> habits) {
this.context = c;
this.layoutId = LayoutId;
this.habits = habits;
}
@Override
public int getCount() {
return habits.size();
}
@Override
public Habit getItem(int position) {
return habits.get(position);
}
@Override
public long getItemId(int position) {
Habit habit = (Habit)habits.get(position);
Long idInt = Long.parseLong(habit.getIDString());
return id1;
}
public View getView(int pos, View child, ViewGroup parent) {
Holder mHolder;
LayoutInflater layoutInflater;
Habit habit = habits.get(pos);
if (child == null) {
layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
child = layoutInflater.inflate(R.layout.fragment_start_habit_item, null);
mHolder = new Holder();
mHolder.title = (TextView)child.findViewById(R.id.fragment_title);
mHolder.dayCount = (TextView)child.findViewById(R.id.fragment_days_left);
mHolder.startDate = (TextView)child.findViewById(R.id.fragment_start_date);
child.setTag(mHolder);
} else {
mHolder = (Holder) child.getTag();
}
mHolder.title.setText(habit.getName());
mHolder.dayCount.setText("Days Completed: " + habit.getDayCountString());
mHolder.startDate.setText("Date Started: " + habit.getStartDate());
return child;
}
public class Holder {
TextView title;
TextView dayCount;
TextView startDate;
}
}
最后我的习惯对象类：
public class Habit {
private int day_count;
private int _id;
private String habit_name, date_started, end_date, day_count_string, id_string;
public Habit(){
}
public Habit(int id, String name, String startDate, String endDate, int dayCount){
this._id = id;
this.habit_name = name;
this.date_started = startDate;
this.end_date = endDate;
this.day_count = dayCount;
}
public Habit(String name, String startDate, String endDate, int dayCount){
this.habit_name = name;
this.date_started = startDate;
this.end_date = endDate;
this.day_count = dayCount;
}
public int getID()
{
return _id;
}
public int setID(int id)
{
return this._id;
}
public String getIDString()
{
id_string = "" + this._id;
return id_string;
}
public int getDayCount()
{
return this.day_count;
}
public String getDayCountString()
{
day_count_string = "" + this.day_count;
return day_count_string;
}
public int setDayCount(int dayCount)
{
return this.day_count;
}
public String getName()
{
return this.habit_name;
}
public void setName(String name)
{
this.habit_name = name;
}
public String getStartDate()
{
return this.date_started;
}
public void setStartDate(String startDate)
{
this.date_started = startDate;
}
public String getEndDate()
{
return this.end_date;
}
public void setEndDate(String endDate)
{
this.end_date = endDate;
}
}
现在我认为我从我的Habit对象类或Listview适配器检索id错误。我不确定，我完全失去了这个。非常感谢任何帮助！
答案 0 :(得分：0)
你如何填充你的ArrayList？你如何设置每个习惯的id？这只是一个猜测，但也许您使用Listview中的位置作为ID，它与数据库ID不匹配？另外，你能否澄清一下＆＃34;不工作＆＃34;？是删除吗？不删除？
答案 1 :(得分：0)
尝试在适配器上调用notifyDataSetChanged（）或尝试在列表视图上调用invalidateViews（）。
答案 2 :(得分：0)
数据库没有删除，因为表中的id与listview中的id不同。每次创建条目时，都会使用新的唯一ID建立，而不是像listview那样按表中的顺序建立。 所以将此方法添加到habitDbHelper类：
public void delete(int orderInList){//orederInList is the position in your listView
SQLiteDatabase db = this.getWritableDatabase();
List<Integer> database_ids = new ArrayList<Integer>();
Cursor c = db.rawQuery("SELECT*FROM "+TABLE_HABITS,null);
while(c.moveToNext){
database_ids.add(Integer.parseInt(c.getString(0)));
}
db.delete(TABLE_HABITS,KEY_ID + " =?",new String[]{String.valueOf(database_ids.get(orderInList)});
如果你想删除它OnLongClick添加：
ListView lv = (ListView)findViewById(R.id.your_id);
lv.setLongClickable(true);
lv.setOnLongClickListener(new OnLongClickListener(){
@Override
public boolean onItemLongClick(AdapterView<?> parent, View view,
int position, long id) {
AlertDialog.Builder aat = new AlertDialog.Builder(this);
aat.setTitle("Delete?")
.setMessage("Are you sure you want to delete "+parent.getItemAtPosition(position).toString()+"?")
.setCancelable(true)
.setNegativeButton("Cancel", new DialogInterface.OnClickListener(){
@Override
public void onClick(DialogInterface dialog, int which) {
// TODO Auto-generated method stub
dialog.cancel();
}
})
.setPositiveButton("Delete", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
// TODO Auto-generated method stub
HabitDbHelper helper = new HabitDBHelper(this);
helper.delete(position);
helper.close();
onCreate(null);//call it here to refresh listView upon delete
}
});
AlertDialog art = aat.create();
art.show();
}
});
希望这会有所帮助。