我有一个sqlite，列名，学分，缺席。我想通过在显示所有sqlite数据的回收视图中单击按钮来增加缺少的值。你能帮忙吗？
预先感谢。
我的SqliteHelper-
public class Myhelper extends SQLiteOpenHelper {
public static final String DATABASE_NAME="mydatabase.db";
public static final String TABLE_NAME="mytable";
public static final String COLUMN_ID="_id";
public static final String COL_1="NAME";
public static final String COL_2="CREDIT";
public static final String COL_3="BUNKS";
public static final String[] COLUMNS ={COLUMN_ID,COL_1,COL_2,COL_3};
Context con;
public Myhelper(Context context) {
super(context, DATABASE_NAME, null, 1);
con = context;
}
@Override
public void onCreate(SQLiteDatabase db) {
String createTable= "CREATE TABLE " + TABLE_NAME + " (" + COLUMN_ID +" INTEGER PRIMARY KEY AUTOINCREMENT, " + " NAME TEXT, CREDIT TEXT, BUNKS INTEGER )";
db.execSQL(createTable);
Toast.makeText(con,"table created",Toast.LENGTH_SHORT).show();
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS "+ TABLE_NAME);
onCreate(db);
}
public boolean insertData(String x,String y,int z){
SQLiteDatabase db=this.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put(COL_1, String.valueOf(x));
contentValues.put(COL_2,String.valueOf(y));
contentValues.put(COL_3,z);
long result = db.insert(TABLE_NAME, null, contentValues);
if (result == -1) {
return false;
} else {
return true;
}
}
public ArrayList<String> queryXdata(){
ArrayList<String> xnewdata= new ArrayList<String>();
String query = "SELECT "+ COL_1 + " FROM " + TABLE_NAME;
SQLiteDatabase db=this.getWritableDatabase();
Cursor cursor= db.rawQuery(query,null);
for (cursor.moveToFirst(); !cursor.isAfterLast(); cursor.moveToNext()){
xnewdata.add(cursor.getString(cursor.getColumnIndex(COL_1)));
}
cursor.close();
return xnewdata;
}
public ArrayList<Integer> queryYdata(){
ArrayList<Integer> ynewdata= new ArrayList<Integer>();
String query = "SELECT "+ COL_3+ " FROM " + TABLE_NAME;
SQLiteDatabase db=this.getWritableDatabase();
Cursor cursor= db.rawQuery(query,null);
for (cursor.moveToFirst(); !cursor.isAfterLast(); cursor.moveToNext()){
ynewdata.add(cursor.getInt(cursor.getColumnIndex(COL_3)));
}
cursor.close();
return ynewdata;
}
public ArrayList<Integer> queryZdata(){
ArrayList<Integer> znewdata= new ArrayList<Integer>();
String query = "SELECT "+ COL_2+ " FROM " + TABLE_NAME;
SQLiteDatabase db=this.getWritableDatabase();
Cursor cursor= db.rawQuery(query,null);
for (cursor.moveToFirst(); !cursor.isAfterLast(); cursor.moveToNext()){
znewdata.add(((cursor.getColumnIndex(COL_2))));
}
cursor.close();
return znewdata;
}
public attendence getdetails(long id){
SQLiteDatabase db = this.getWritableDatabase();
String query= "SELECT" + COL_2+" FROM " + TABLE_NAME +" WHERE _id=" + id;
Cursor cursor= db.rawQuery(query,null);
attendence attendence1= new attendence();
if (cursor.getCount()>0){
cursor.moveToFirst();
attendence1.setSubname(cursor.getString(cursor.getColumnIndex(COL_1)));
attendence1.setCredit(cursor.getString(cursor.getColumnIndex(COL_2)));
attendence1.setBunks(cursor.getInt(cursor.getColumnIndex(COL_3)));
}
return attendence1;
}
public void delete(long id,Context context){
SQLiteDatabase db=this.getWritableDatabase();
db.execSQL("DELETE FROM "+TABLE_NAME+" WHERE _id='"+id+"'");
Toast.makeText(context,"delted",Toast.LENGTH_SHORT).show();
}
public List<attendence> list(String filter){
String query;
if (filter.equals("")){
query = "SELECT * FROM " + TABLE_NAME ;
}
else {
query= " SELECT * FROM " + TABLE_NAME ;
}
List<attendence> linkedlist = new LinkedList<>();
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(query,null);
attendence attendence;
if (cursor.moveToFirst()){
do {
attendence = new attendence();
attendence.setId(cursor.getLong(cursor.getColumnIndex(COLUMN_ID)));
attendence.setSubname(cursor.getString(cursor.getColumnIndex(COL_1)));
attendence.setCredit(cursor.getString(cursor.getColumnIndex(COL_2)));
attendence.setBunks(cursor.getInt(cursor.getColumnIndex(COL_3)));
linkedlist.add(attendence);
}
while (cursor.moveToNext());
}
return linkedlist;
}
public int getbunk(int id){
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.query(TABLE_NAME, COLUMNS,"_id=?",new String[]{String.valueOf(id)},null,null,null,null );
if (cursor!=null){cursor.moveToFirst();}
int output = cursor.getInt(cursor.getColumnIndex(COL_3));
cursor.close();
return output;
}
public void updatebunk(int id){
SQLiteDatabase db = this.getWritableDatabase();
int bunk = getbunk(id);
int bunkinc= ++bunk;
ContentValues contentValues= new ContentValues();
contentValues.put(COL_3,bunkinc);
db.update(TABLE_NAME,contentValues,COLUMN_ID+" =?",new String[]{String.valueOf(id)});
db.close();
}
}
myRecycleViewAdapter
public class attendence_recycleadapter extends RecyclerView.Adapter<attendence_recycleadapter.ViewHolder> {
private List<attendence> mattendence_list;
private Context mcontext;
public RecyclerView mrecycleview;
@NonNull
@Override
public attendence_recycleadapter.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
LayoutInflater inflater= LayoutInflater.from(parent.getContext());
View v=inflater.inflate(R.layout.attendence_recycleview_card,parent,false);
ViewHolder viewHolder = new ViewHolder(v);
return viewHolder;
}
@Override
public void onBindViewHolder(@NonNull attendence_recycleadapter.ViewHolder holder, final int position) {
final attendence attendence= mattendence_list.get(position);
holder.subname.setText("Name: " + attendence.getSubname());
holder.subcredit.setText("CREDIT: " + attendence.getCredit());
holder.bunks.setText("BUNKS: " + attendence.getBunks());
holder.deletesub.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Myhelper myhelper = new Myhelper(mcontext);
myhelper.delete(attendence.getId(),mcontext);
// mattendence_list.remove(position);
// mrecycleview.removeViewAt(position);
notifyItemRemoved(position);
notifyItemRangeChanged(position,mattendence_list.size());
notifyDataSetChanged();
delete(position);
}
});
holder.addbunk.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Myhelper myhelper = new Myhelper(mcontext);
myhelper.updatebunk(position);
notifyDataSetChanged();
}
});
}
@Override
public int getItemCount() {
return mattendence_list.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
public TextView subname;
public TextView subcredit;
public TextView bunks;
public View layout;
public Button addbunk;
public Button deletesub;
public ViewHolder(View itemView) {
super(itemView);
layout=itemView;
subname=(TextView)itemView.findViewById(R.id.attendernce_subname);
subcredit=(TextView)itemView.findViewById(R.id.attendernce_credit);
bunks=(TextView)itemView.findViewById(R.id.attendernce_bunks);
addbunk = (Button)itemView.findViewById(R.id.attendence_addbunk);
deletesub = (Button)itemView.findViewById(R.id.attendence_deletesub);
}
}
public void add(int position,attendence attendence2){
mattendence_list.add(position,attendence2);
notifyItemInserted(position);
}
public void delete(int position){
mattendence_list.remove(position);
notifyItemRemoved(position);
}
public attendence_recycleadapter(List<attendence> mydataset, Context context, RecyclerView recyclerView){
mattendence_list = mydataset;
mcontext = context;
mrecycleview= recyclerView;
}
}
当我单击addbunk按钮时，我在getBunk（）中遇到了错误。由于光标无法找到任何值，因此getbunk（）中存在问题。
错误消息：android.database.CursorIndexOutOfBoundsException：请求索引0，大小为0
答案 0 :(得分：0)
您的代码中有几个错误。
我改写了两种方法。
现在，如果找不到getbunk，则-1返回id。
我希望我没有错别字。
请尝试以下代码，如果需要解释，请询问：
public int getbunk(int id){
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery("SELECT " + COL_3 + " FROM " + TABLE_NAME + " WHERE " + COLUMN_ID + " = " + String.valueOf(id), null);
int output = -1;
if (cursor != null){
if (cursor.moveToFirst()) {
output = cursor.getInt(0);
}
cursor.close();
}
db.close();
return output;
}
public void updatebunk(int id){
SQLiteDatabase db = this.getWritableDatabase();
int bunk = getbunk(id);
if (bunk < 0) {
Log.i("Error:", "Id=" + id + " not found!");
return;
}
int bunkinc = ++bunk;
ContentValues contentValues= new ContentValues();
contentValues.put(COL_3, bunkinc);
db.update(TABLE_NAME, contentValues,COLUMN_ID + "=?", new String[]{String.valueOf(id)});
db.close();
}