在sq lite中传递字符串变量，android程序 [英] Passing string variable in sq lite,android programs

问题描述

Hai，



如何解决此错误。我是Android应用程序的新手。请帮忙。



我的代码就像是

Hai,

How can i solve this error. I'm new in android apps. please help.

my code is like

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 DBAdapter {
    public static final String KEY_ROWID = "_id";
    public static final String KEY_USERNAME = "username";
    public static final String KEY_PWDL = "pwdl";
    public static final String KEY_PWDD = "pwdd";
    public static final String KEY_ROLE = "role";
    
    private static final String TAG = "DBAdap";	
    private static final String DATABASE_NAME = "Paydb";
    private static final String DATABASE_TABLE = "table1";
    private static final int DATABASE_VERSION = 1;
    private static final String DATABASE_CREATE = "create table table1 (_id integer primary key, " + "username text not null,"+ " pwdl text not null, "
    		+ "pwdd text not null,"+  "role integer not null);"; 
    
    private final Context context;
    private DatabaseHelper DBHelper;
    private SQLiteDatabase db;
    public DBAdapter(Context ctx) 
    {
    	this.context = ctx;
    	DBHelper = new DatabaseHelper(context);
    }
    public static class DatabaseHelper extends SQLiteOpenHelper 
        {
    	DatabaseHelper(Context context) {
    		super(context, DATABASE_NAME, null, DATABASE_VERSION);
    	}
    	@Override
    	public void onCreate(SQLiteDatabase db) 
    	{
    		db.execSQL(DATABASE_CREATE);
    	}
    	@Override
    	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
    	+ newVersion + ", which will destroy all old data");
    		db.execSQL("DROP TABLE IF EXISTS table1");
    		onCreate(db);
    	}
    }
    
    // ---opens the database---
    public DBAdapter open() throws SQLException 
    {
    	db = DBHelper.getWritableDatabase();
    	return this;
    }
    
    // ---closes the database---
    public void close() 
    {
    	DBHelper.close();
    }
    // ---insert a table1into the database---
    public long insertUser(Integer id, String name, String pwdl,String pwdd,Integer role) 
    {
    	ContentValues initialValues = new ContentValues();
    	initialValues.put(KEY_ROWID, id);
    	initialValues.put(KEY_USERNAME, name);
    	initialValues.put(KEY_PWDL, pwdl);
    	initialValues.put(KEY_PWDD, pwdd);
    	initialValues.put(KEY_ROLE, role);
    	return db.insert(DATABASE_TABLE, null, initialValues);
    }
    
	// ---retrieves a particular table1--- 

//In here I'm passing an integer variable and this function working smoothly
    public Cursor getUser1(Integer Role) throws SQLException
    {
        Cursor mCursor = db.query(true, DATABASE_TABLE, new String[] {KEY_ROWID, KEY_USERNAME, KEY_PWDL, KEY_PWDD,KEY_ROLE },  KEY_ROLE +"="+ Role, null, null, null, null, null);

        if (mCursor != null)
                {
            mCursor.moveToFirst();
        }
        return mCursor;
    }
 
//in here I'm passing a string variable and this function find the error.
    public Cursor getUser2(String user) throws SQLException
    {
                Cursor mCursor = db.query(true, DATABASE_TABLE, new String[] {KEY_ROWID, KEY_USERNAME, KEY_PWDL, KEY_PWDD,KEY_ROLE },  KEY_USERNAME +"=" + user, null, null, null, null, null);
        if (mCursor != null)
                {
            mCursor.moveToFirst();
        }
        return mCursor;
    }


}

问候

vani

regards
vani

推荐答案

尝试类似：

Try something like:

public Cursor getUser2(String user) throws SQLException
    Cursor cursor = null;
    String[] columns = null; // select all columns
    String selection = KEY_USERNAME + "=?";
    String[] selectionArgs = new String[1];
    selectionArgs[0] = user;
    String groupBy = null;
    String having = null;
    String orderBy = null;
    cursor = db.query(DATABASE_TABLE,
    		columns,
    		selection, 
    		selectionArgs,
    		groupBy,
    		having,
    		orderBy
    		);
    
    return cursor;
    }

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