Question

我的数据库活动遇到了一些问题。我无法使用以下代码写入数据库并查看数据库。

我的数据库活动：

package com.jacob.eindproject;

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.database.sqlite.SQLiteDatabase.CursorFactory;

import java.sql.*;

import com.readystatesoftware.sqliteasset.SQLiteAssetHelper;

public class Database extends SQLiteAssetHelper {

    public static final String KEY_PRODUCT = "Product";
    public static final String KEY_EENHEID = "Eenheid";
    public static final String KEY_KCAL = "Kcal";

    private static final String DATABASE_NAME = "Voedsel";
    private static final String DATABASE_TABLE = "Voeding";
    private static final int DATABASE_VERSION = 1;

    private DbHelper ourHelper;
    private final Context ourContext;
    private SQLiteDatabase ourDatabase;

    private static class DbHelper extends SQLiteAssetHelper{

        public DbHelper(Context context) {
            super(context, DATABASE_NAME, context.getExternalFilesDir(null).getAbsolutePath(), null, DATABASE_VERSION);
            // TODO Auto-generated constructor stub
        }

    }

        @Override
        public void onUpgrade(SQLiteDatabase Voedsel, int oldVersion, int newVersion) {
            Voedsel.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
            onCreate(Voedsel);
        }

        public void close(Database database) {
            // TODO Auto-generated method stub

        }




    public Database(Context c){
        ourContext = c;
    }

    public Database open() throws SQLException{
        ourHelper = new DbHelper(ourContext);
        ourDatabase = ourHelper.getWritableDatabase();
        return this;        
    }

    public void close() {

    ourHelper.close();
}



    public long createEntry(String product, String kcal, String eenheid) {
        ContentValues cv = new ContentValues();
        cv.put(KEY_PRODUCT, product);
        cv.put(KEY_EENHEID, eenheid);
        cv.put(KEY_KCAL, kcal);
        return ourDatabase.insert(DATABASE_TABLE, null, cv);

    }

    public String getData() {
        // TODO Auto-generated method stub
        String[] columns = new String[]{ KEY_PRODUCT, KEY_EENHEID, KEY_KCAL};
        Cursor c = ourDatabase.query(DATABASE_TABLE, columns, null, null, null, null, null);
        String result = "";

        int iRow = c.getColumnIndex(KEY_PRODUCT);
        int iName = c.getColumnIndex(KEY_EENHEID);
        int iHotness = c.getColumnIndex(KEY_KCAL);

        for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()){
            result = result + c.getString(iRow) + " " + c.getString(iName) + " " + c.getString(iHotness) + "\n";


        }

        return result;
    }
}

我的SQLView活动：

package com.jacob.eindproject;

import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;

public class SQLView extends Activity{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.sqlview);
        TextView tv = (TextView) findViewById(R.id.tvSQLinfo);
        Database info = new Database(this);
        info.open();
        String data = info.getData();
        info.close();
        tv.setText(data);





    }

}

SQLite活动：

package com.jacob.eindproject;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.app.Activity;
import android.app.Dialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.view.View.OnClickListener;


public class SQLite extends Activity implements View.OnClickListener {

    Button sqlUpdate, sqlView;
    EditText sqlVoeding, sqlKcal, sqlEenheid;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.sqllite);
        sqlUpdate = (Button) findViewById(R.id.bSQLUpdate);
        sqlVoeding = (EditText) findViewById(R.id.etSQLVoeding);
        sqlEenheid = (EditText) findViewById(R.id.etSQLEenheid);
        sqlKcal = (EditText) findViewById(R.id.etSQLKcal);

        sqlView = (Button) findViewById(R.id.bSQLopenView);
        sqlView.setOnClickListener((android.view.View.OnClickListener) this);
        sqlUpdate.setOnClickListener((android.view.View.OnClickListener) this);
    }

    public void onClick(View arg0) {
        switch (arg0.getId()) {
        case R.id.bSQLUpdate:


            boolean didItWork = true;
            try{            
            String voeding = sqlVoeding.getText().toString();
            String Kcal = sqlKcal.getText().toString();
            String eenheid = sqlEenheid.getText().toString();

            Database entry = new Database(SQLite.this);
            entry.open();
            entry.createEntry(voeding, Kcal, eenheid);
            entry.close();

            }catch (Exception e ){
                didItWork = false;

            }finally{
                if (didItWork){
                    Dialog d = new Dialog(this);
                    d.setTitle("Heak Yeay");
                    TextView tv = new TextView(this);
                    tv.setText("Succes");
                    d.setContentView(tv);
                    d.show();
            }
        }

            break;
        case R.id.bSQLopenView:
            Intent i = new Intent(this, SQLView.class);
            startActivity(i);


        }
        }

    public void onClick(DialogInterface arg0, int arg1) {
        // TODO Auto-generated method stub

    }

    }

我正在使用我的数据库文件（Voedsel.rar），位于 assets / databases / Voedsel.rar 。

Answer 1

要写入数据库，请尝试以下方法：

public void insertVoeding(String product, String eenheid, String kcal) {
    ourDatabase.execSQL("INSERT INTO Voeding (Product, Eenheid, Kcal) VALUES (?, ?, ?)",
              new String[] {product, eenheid, kcal});
}

问号由字符串数组中的值替换。无法使用字符串数组插入列名，因为execSQL方法会在这些值周围加上引号。如果您尝试，查询将失败。

有两种方法可以从数据库中读取（甚至可能有两种方式来写入数据库）。我个人更喜欢使用原始查询，比如这个获取整个数据库：

public Cursor getEntireDB() {
    return ourDatabase.rawQuery("SELECT * FROM Voeding");
}

然后，您可以使用CursorAdapter中的光标创建列表。

SQLiteAssetHelper和getWritableDatabase

1 个答案: