为什么不在ListView OnItemLongClickListener（）中使用我的SQlite“delete”和“deleteall”代码？ 我尝试了很多代码，但无法处理任何代码。 我的错误和方式对我来说哪个方面更好？ 提前致谢
这是我的编码。
DBclass
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;
import android.util.Log;
public class DBclass {
public static final String KEY_ROWID = "_id";
public static final String KEY_COL1 = "col1";
public static final String KEY_COL2 = "col2";
private static final String DATABASE_NAME = "mydb";
private static final String DATABASE_TABLE = "mytable";
private static final int DATABASE_VERSION = 1;
private final Context ourContext;
private DbHelper dbh;
private SQLiteDatabase odb;
private static final String USER_MASTER_CREATE =
"CREATE TABLE IF NOT EXISTS " + DATABASE_TABLE+ "("
+ KEY_ROWID + " INTEGER PRIMARY KEY AUTOINCREMENT,"
+ KEY_COL1 + " VARCHAR(15) UNIQUE, " + KEY_COL2 + " VARCHAR(15) )";
private static class DbHelper extends SQLiteOpenHelper {
public DbHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(USER_MASTER_CREATE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// if DATABASE VERSION changes
// Drop old tables and call super.onCreate()
}
}
public DBclass(Context c) {
ourContext = c;
dbh = new DbHelper(ourContext);
}
public DBclass open() throws SQLException {
odb = dbh.getWritableDatabase();
return this;
}
public void close() {
dbh.close();
}
public long insertmaster(String col1, String col2) throws SQLException{
Log.d("", col1);
Log.d("", col2);
ContentValues IV = new ContentValues();
IV.put(KEY_COL1, col1);
IV.put(KEY_COL2, col2);
return odb.insert(DATABASE_TABLE, null, IV);
// returns a number >0 if inserting data is successful
}
public void updateRow(long rowID, String col1, String col2) {
ContentValues values = new ContentValues();
values.put(KEY_COL1, col1);
values.put(KEY_COL2, col2);
try {
odb.update(DATABASE_TABLE, values, KEY_ROWID + "=" + rowID, null);
} catch (Exception e) {
}
}
public void delete(){
//??????????????????????????????????????????????????????????
//????????????????????????????????????????????????????????
//?????????????????????????????????????????????????????
}
public void deleteall(){
//??????????????????????????????????????????????????????????
//????????????????????????????????????????????????????????
//?????????????????????????????????????????????????????
}
// public void deleteEntry(long row,String key_name) {
// odb.delete(DATABASE_TABLE, KEY_ROWID + "=" + row + " and " + KEY_COL1 + "=" + key_name, null);
/*if you just have key_name to select a row,you can ignore passing rowid(here-row) and use:
db.delete(DATABASE_TABLE, KEY_NAME + "=" + key_name, null);
*/
// }
// private static final String mname = "'KEY_COL1'";
// public void deleteContact()
// {
// odb.delete(DATABASE_TABLE, KEY_COL1 + "=" + mname, null);
// }
// public boolean deleteSingleRow(String rowId)
// {
// return odb.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
// }
// public void deleteRowFromTable(String tableName, String columnName, String keyValue) {
// String whereClause = columnName + "=?";
// String[] whereArgs = new String[]{String.valueOf(keyValue)};
// odb.delete(tableName, whereClause, whereArgs);
// }
// public boolean delete(String value){
// return odb.delete(DATABASE_TABLE,KEY_COL1+"="+value+";",null)>0;
// }
// public void delete(long rowid){
// odb.delete(DATABASE_TABLE,KEY_COL1+"="+rowid,null);
// }
// public void delete(String value){
// odb.delete(DATABASE_TABLE,KEY_COL1+"=?",new String[]{String.valueOf(value)} ) ;
// }
public Cursor queueAll(String id)throws SQLException{
String[] columns = new String[]{KEY_COL1, KEY_COL2};
Cursor mCursor = odb.query(DATABASE_TABLE, columns,
null, null, null, null, null);
return mCursor;
}
public Cursor getAllTitles() {
// using simple SQL query
return odb.rawQuery("select * from " + DATABASE_TABLE, null);
}
public Cursor getallCols(String id) throws SQLException {
Cursor mCursor = odb.query(DATABASE_TABLE, new String[] { KEY_COL1,
KEY_COL2 }, null, null, null, null, null);
Log.e("getallcols zmv", "opening successfull");
return mCursor;
}
public Cursor getColsById(String id) throws SQLException {
Cursor mCursor = odb.query(DATABASE_TABLE, new String[] { KEY_COL1,
KEY_COL2 }, KEY_ROWID + " = " + id, null, null, null, null);
Log.e("getallcols zmv", "opening successfull");
return mCursor;
}
}
这是我的：MainActivity
public class MainActivity extends Activity {
private ListView list_lv;
private EditText col1_ed;
private Button sub_btn;
private DBclass db;
private ArrayList<String> collist_1;
private ArrayList<String> collist_2;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
collist_1 = new ArrayList<String>();
collist_2 = new ArrayList<String>();
items();
getData();
AnimationSet anim2 = (AnimationSet) AnimationUtils.loadAnimation(getBaseContext(), R.anim.rotate);
sub_btn.startAnimation(anim2);
}
private void items() {
sub_btn = (Button) findViewById(R.id.submit_btn);
col1_ed = (EditText) findViewById(R.id.ed1);
list_lv = (ListView) findViewById(R.id.dblist);
sub_btn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
submitData();
}
});
}
protected void submitData() {
String a = col1_ed.getText().toString();
db = new DBclass(this);
long num;
if(a.length()>0){
col1_ed.setText("");
db.open();
num = db.insertmaster(a, "");
getData();
db.close();
}
}
public void getData() {
collist_1.clear();
collist_2.clear();
db = new DBclass(this);
try {
db.open();
Cursor cur = db.getAllTitles();
while (cur.moveToNext()) {
String valueofcol1 = cur.getString(1);
String valueofcol2 = cur.getString(2);
// Log.e("---****---", "*********** col 1 = " + valueofcol1);
// Log.e("---****---", "*********** col 2 = " + valueofcol2);
collist_1.add(valueofcol1);
collist_2.add(valueofcol2);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
db.close();
}
printList();
setDataIntoList();
}
private void printList() {
for (int i = 0; i < collist_1.size(); i++) {
Log.e("***************",
collist_1.get(i) + " --- " + collist_2.get(i));
}
}
private void setDataIntoList() {
// create the list item mapping
String[] from = new String[] { "col_1", "col_2" };
int[] to = new int[] { R.id.col1tv};
// prepare the list of all records
List<HashMap<String, String>> fillMaps = new ArrayList<HashMap<String, String>>();
for (int i = 0; i < collist_1.size(); i++) {
HashMap<String, String> map = new HashMap<String, String>();
map.put("col_1", collist_1.get(i));
map.put("col_2", collist_2.get(i));
fillMaps.add(map);
}
// fill in the grid_item layout
SimpleAdapter adapter = new SimpleAdapter(this, fillMaps,
R.layout.custom, from, to);
list_lv.setAdapter(adapter);
}
}
谢谢！
答案 0 :(得分：1)
DatabaseHelper有很多有用的方法。
要删除它，最好使用以下内容：
public boolean delete(int ID){
return db.delete(TABLE_NAME, KEY + "=" + ID, null) > 0;
}
如果您需要删除所有行，这适合您：
db.delete(TABLE_NAME, null, null);
这将删除KEY = ID的所有行，您可以使用Android studio's提示