Question

以下是调查应用程序中Andoird中SQLite的数据库。每次调查都是一个存储在数据库中的记录。

我已成功创建数据库（并且数据库存在 - 我使用SQLite浏览器浏览所有不同的记录）。

但是，在进行一些调查后，我有一个问题显示所有记录。只有第一次调查才会显示在活动中。即使它们存在于内存中，也不会显示其他记录。我的简单游标适配器有问题吗？

这是我的数据库类：

package nidhin.survey;


import android.app.Activity;
import android.app.ListActivity;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.widget.TextView;

public class Database extends Activity {
    private static final SimpleCursorAdapter SimpleCursorAdapter = null;


    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.database);

        ListView lv=(ListView)findViewById(R.id.mylist);
        lv.setClickable(true);

        Button button1 = (Button)findViewById(R.id.button1);
        button1.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {


        Intent intent=new Intent(Database.this,MainMenu.class);
            startActivity(intent);

            }
         });


        Intent sender=getIntent();

        DatabaseHelper dbh = new DatabaseHelper(this);

        Cursor c = dbh.getReadableDatabase().rawQuery("SELECT _id, " + 
                        DatabaseHelper.COL_NAME + 
                ", " + DatabaseHelper.VALUE1 + 
                ", " + DatabaseHelper.VALUE2 + 
                " FROM " +
                DatabaseHelper.TABLE_NAME, null); // initializing 

        String[] dataFrom ={DatabaseHelper.COL_NAME, DatabaseHelper.VALUE1, DatabaseHelper.VALUE2};//, DatabaseHelper.VALUE3, DatabaseHelper.VALUE4, DatabaseHelper.VALUE5, DatabaseHelper.VALUE6, DatabaseHelper.VALUE7, DatabaseHelper.VALUE8, DatabaseHelper.VALUE9, DatabaseHelper.VALUE10, DatabaseHelper.VALUE11};
        int[] dataTo = {R.id.name, R.id.value1, R.id.value2};//, R.id.value3, R.id.value4, R.id.value5, R.id.value6, R.id.value7, R.id.value8, R.id.value9, R.id.value10, R.id.value11};

        SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, 
                R.layout.row, c, dataFrom, dataTo);

        lv.setAdapter(adapter);

    }

    public void onListItemClick()
    {

    }


}

数据库助手：

package nidhin.survey;

import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

import android.content.ContentValues;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

public class DatabaseHelper extends SQLiteOpenHelper {

static final String TABLE_NAME = "mygrades";
static final String COL_NAME = "name";
static final String VALUE1 = "ClassNumber";
static final String VALUE2 = "value2";
static final String VALUE3 = "value3";
static final String VALUE4 = "value4";
static final String VALUE5 = "value5";
static final String VALUE6 = "value6";
static final String VALUE7 = "value7";
static final String VALUE8 = "value8";
static final String VALUE9 = "value9";
static final String VALUE10 = "value10";
static final String VALUE11 = "value11";


DatabaseHelper(Context context)
{
    super(context, "grades.sqlite", null, 20);
}

@Override
public void onCreate(SQLiteDatabase db) 
{


    db.execSQL("CREATE TABLE " + TABLE_NAME +
               "(_id INTEGER PRIMARY KEY AUTOINCREMENT, " +
               COL_NAME + " TEXT, " + 
               VALUE1 + " TEXT, " +
               VALUE2 + " TEXT, " +
               VALUE3 + " TEXT, " +
               VALUE4 + " TEXT, " +
               VALUE5 + " TEXT, " +
               VALUE6 + " TEXT, " +
               VALUE7 + " TEXT, " +
               VALUE8 + " TEXT, " +
               VALUE9 + " TEXT, " +
               VALUE10 + " TEXT, " +
               VALUE11 + " TEXT);");

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) 
{
    android.util.Log.w("cars", "Upgrading database, all table info will be lost");
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
    onCreate(db);
}

}

Answer 1

让我们再试一次

试试这个：

在数据库助手中（注意应该有5个空值）：

public Cursor fetchAllSurveys() {
    return mDb.query(TABLE_NAME, new String[] { "_id", COL_NAME, VALUE1,VALUE2 }, null, null, null, null, null);
}

在你的onCreate中，它会像这样使用：

Cursor c = dbh.fetchAllSurveys();
String[] dataFrom ={DatabaseHelper.COL_NAME, DatabaseHelper.VALUE1, DatabaseHelper.VALUE2};
int[] dataTo = {R.id.name, R.id.value1, R.id.value2};
SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, R.layout.row, c, dataFrom, dataTo); 
lv.setAdapter(adapter);

希望这有帮助！

Answer 2

调用Cursor.moveToFirst，如：

if (c !=null)
{
    c.moveToFirst();
}

在分配此行之前：

SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, 
                R.layout.row, c, dataFrom, dataTo);

问题显示数据库中的条目

2 个答案: