Question

我有一个SQLdatabase，我希望使用列表视图中每个条目旁边的按钮删除列表视图中显示的条目。但目前它并没有让我删除。

此问题位于selectionargs变量中，如下所示。如果我输入一个数字，例如1，手动进入selectionargs它将起作用，但我一直试图通过代表每个条目的变量来做到这一点。这不会导致错误但只是直接向toast消息无法删除。 ac.ID指的是适配器类和列表项条目的ID。

书签类：

public class Bookmark extends AppCompatActivity {

myAdapter myAdapter;
DBManager db;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_bookmark);
    db = new DBManager(this);

    onLoadAttraction();
   // onLoadTransport();


}

public void onLoadAttraction() {
    ArrayList<Adapter> listData = new ArrayList<Adapter>();
    listData.clear();
    Cursor cursor = db.Query("BookmarkAttraction",null, null, null, DBManager.ColId);

    if (cursor.moveToFirst()) {
        do {
            listData.add(new Adapter(
                    cursor.getString(cursor.getColumnIndex(DBManager.ColType))
                    , cursor.getString(cursor.getColumnIndex(DBManager.ColName))
                    , cursor.getString(cursor.getColumnIndex(DBManager.ColLocation))
                    , cursor.getString(cursor.getColumnIndex(DBManager.ColOpening))
                    , cursor.getString(cursor.getColumnIndex(DBManager.ColClosing))
                    , cursor.getString(cursor.getColumnIndex(DBManager.ColNearbyStop))
            ,null,null,null, null, null));
        } while (cursor.moveToNext());
    }

    myAdapter = new myAdapter(listData);
    ListView ls = (ListView) findViewById(R.id.listView);
    ls.setAdapter(myAdapter);
}

public void onLoadTransport(){
    ArrayList<Adapter> listData = new ArrayList<Adapter>();
    listData.clear();
    Cursor cursor = db.Query("BookmarkTransport",null, null, null, DBManager.ColId);

    if (cursor.moveToFirst()) {
        do {
            listData.add(new Adapter(
                    cursor.getString(cursor.getColumnIndex(DBManager.ColType))
                    , cursor.getString(cursor.getColumnIndex(DBManager.ColName))
                    , cursor.getString(cursor.getColumnIndex(DBManager.ColLocation))
                    , null
                    , null
                    , null
                    ,cursor.getString(cursor.getColumnIndex(DBManager.ColTime))
                    ,cursor.getString(cursor.getColumnIndex(DBManager.ColNextStop))
                    , cursor.getString(cursor.getColumnIndex(DBManager.ColPhoneNumber))
                    ,null,null));
        } while (cursor.moveToNext());
    }

    myAdapter = new myAdapter(listData);
    ListView ls = (ListView) findViewById(R.id.listView);
    ls.setAdapter(myAdapter);
}

  class myAdapter extends BaseAdapter {
    public ArrayList<Adapter> listItem;
    Adapter ac;
    public myAdapter(ArrayList<Adapter> listItem) {
        this.listItem = listItem;

    }

    @Override
    public int getCount() {
        return listItem.size();
    }

    @Override
    public Object getItem(int position) {
        return null;
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View view, ViewGroup viewGroup) {
        LayoutInflater myInflator = getLayoutInflater();
        final View myView = myInflator.inflate(R.layout.list_bookmark, null);

       ac = listItem.get(position);


        TextView Type = (TextView) myView.findViewById(R.id.BMType);
        Type.setText(ac.Type);

        TextView Name = (TextView) myView.findViewById(R.id.BMName);
        Name.setText(ac.Name);

        TextView Location = (TextView) myView.findViewById(R.id.BMLocation);
        Location.setText(ac.Location);

        TextView Opening = (TextView) myView.findViewById(R.id.BMOpen);
        Opening.setText(ac.Opening);


        TextView Closing = (TextView) myView.findViewById(R.id.BMClose);


            Closing.setText(ac.Closing);


        TextView NearbyStop1 = (TextView) myView.findViewById(R.id.BMNearbyStop);

            NearbyStop1.setText(ac.NearbyStop);


        Button buttonDelete = (Button)myView.findViewById(R.id.buttonDelete);
        buttonDelete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String[] selectionArgs = {ac.ID};
                int count = db.Delete("BookmarkAttraction","ID=? ",selectionArgs);
                if (count > 0) {
                    onLoadAttraction();
                    Toast.makeText(getApplicationContext(),"Data deleted", Toast.LENGTH_LONG).show();
                }else{
                    Toast.makeText(getApplicationContext(),"Cannnot delete", Toast.LENGTH_LONG).show();
                }

            }
        });



        return myView;
    }
}
}

DBManager类：

 public class DBManager  {

private SQLiteDatabase sqlDB;
static final String ColId = "ID";
static final String DBName = "InternalDB";
static final String TableName = "BookmarkAttraction";
static final String TableName2 = "BookmarkTransport";
static final String TableName3 = "Itinerary";
static final String ColItineraryName = "ItineraryName";
static final String ColDate = "Date";
static final String ColType = "Type";
static final String ColName = "Name";
static final String ColLocation = "Location";
static final String ColOpening = "OpeningTime";
static final String ColClosing = "ClosingTime";
static final String ColNearbyStop = "NerbyStop1";


static final String ColTime = "Time";
static final String ColNextStop = "NextStop";
static final String ColPhoneNumber = "PhoneNumber";

static final int DBVersion = 1;

static final String CreateTable = "CREATE TABLE IF NOT EXISTS " + TableName + "(ID INTEGER PRIMARY KEY AUTOINCREMENT," + ColType+ " TEXT," +
        ColName+ " TEXT," + ColLocation+ " TEXT," + ColOpening+ " TEXT," +ColClosing+ " TEXT," + ColNearbyStop+ " TEXT);";

static  final String CreateTabe2 = "CREATE TABLE IF NOT EXISTS " +TableName2 + "(ID INTEGER PRIMARY KEY AUTOINCREMENT,"
        + ColType + " TEXT,"
        + ColName + " TEXT,"
        + ColLocation + " TEXT,"
        + ColTime+ " TEXT,"
        + ColNextStop + " TEXT,"
        + ColPhoneNumber + " TEXT);";

static final String CreateTable3 = "CREATE TABLE IF NOT EXISTS " + TableName3 + "(ID INTEGER PRIMARY KEY AUTOINCREMENT," + ColItineraryName + " TEXT,"
        + ColDate + " TEXT," + ColName + " TEXT," + ColLocation + " TEXT," + ColTime + " TEXT);";


static class DBHelper extends SQLiteOpenHelper{
    Context context;

    DBHelper(Context context){
        super(context, DBName, null, DBVersion);
        this.context = context;
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        Toast.makeText(context,DBName,Toast.LENGTH_LONG).show();
        db.execSQL(CreateTable);
        Toast.makeText(context,"Table is created ", Toast.LENGTH_LONG).show();
        db.execSQL(CreateTabe2);
        Toast.makeText(context,"Transport table created", Toast.LENGTH_LONG).show();
        db.execSQL(CreateTable3);
        Toast.makeText(context,"Itin table created", Toast.LENGTH_LONG).show();
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int i, int i1) {
        db.execSQL("DROP TABLE IF EXISTS" + TableName);
        db.execSQL("DROP TABLE IF EXISTS" + TableName2);
        db.execSQL("DROP TABLE IF EXISTS" + TableName3);
        onCreate(db);
    }
}


public DBManager(Context context){
    DBHelper db = new DBHelper(context);
    sqlDB = db.getWritableDatabase();
}

public long Insert(String tablename,ContentValues values){
    long ID =  sqlDB.insert(tablename,"",values);
    return ID;
}

public Cursor Query(String tablename, String [] projection, String selection, String [] selectionArgs, String sortOrder){
    SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
    qb.setTables(tablename);
    Cursor cursor = qb.query(sqlDB,projection, selection, selectionArgs,null,null,sortOrder);
    return cursor;
}

public int Delete(String tablename,String selection, String[] selectionArgs){
    int count = sqlDB.delete(tablename,selection,selectionArgs);
    return count;
}

}

适配器类：

 public class Adapter {

public String ID;
public String Type;
public String Name;
public String Location;
public String Opening;
public String Closing;
public String NearbyStop;
public String Time;
public String NextStop;
public String PhoneNumber;
public String Latitude;
public String Longitude;

public Adapter(String type, String name, String location, String opening, String closing,
               String nearbyStop, String time, String nextStop, String phoneNumber, String Latitude,
               String Longitude) {
    this.Type = type;
    this.Name = name;
    this.Location = location;
    this.Opening = opening;
    this.Closing = closing;
    this.NearbyStop = nearbyStop;
    this.Time = time;
    this.NextStop = nextStop;
    this.PhoneNumber = phoneNumber;
    this.Latitude = Latitude;
    this.Longitude = Longitude;
}
}

删除按钮的代码位于我的书签类中，DBManager保存了实际的删除代码。如果有人可以提供帮助，我们将不胜感激。

Answer 1

删除ac类的myAdapter字段，并将其用作getView方法中的方法变量。

然后使用ListView.setOnItemClickListener方法添加具有位置感知功能的点击侦听器。（在设置适配器后只执行一次）这样，您可以listItem.get(position)将项目置于该位置。

SQLIte数据库无法删除条目

1 个答案: