SQlite“删除单行”“并删除所有行”代码不工作

Question

为什么不能在ListView OnItemLongClickListener（）中使用我的SQlite“delete”和“deleteall”代码？ 我尝试了很多代码，但无法使用我的任何代码。 我的错误和方式对我更好吗？ 在此先感谢

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：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！

Answer 1

DatabaseHelper有很多有用的方法。

删除它是更好地为您使用以下命令：

public boolean delete(int ID){ 
    return db.delete(TABLE_NAME, KEY + "=" + ID, null) > 0; 
} 

如果您需要删除所有的行，这是给你：

db.delete(TABLE_NAME, null, null); 

这将删除与KEY = ID所有行， 你可以使用Android studio's提示