Question

所以这是我的代码：

public void onItemClick(AdapterView<?> listView, View view, int position, long id)
{
    Cursor cursor = (Cursor) listView.getItemAtPosition(position);

    int _id = cursor.getInt(0);
    String _recipe = cursor.getString(1);
    Intent intent = new Intent(Luzon1Activity.this,RecipeInstruction.class);
    intent.putExtra("id", _id);
    intent.putExtra("recipe", _recipe);
    startActivity(intent);
}

这是我下一个活动的代码：

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.recipeinstruction);

    dbHelper = new Dbadapter(this);
    dbHelper.open();
    bg = (RelativeLayout) findViewById(R.id.relativeLayout1);

    Bundle extras = getIntent().getExtras();
    if (extras != null) {
        id = extras.getInt("id");   
        recipe = extras.getString("recipe");
    }
    Toast.makeText(this, id+"\n"+recipe, Toast.LENGTH_SHORT).show();
    bg.setBackgroundResource(getImageId(this, recipe));
}

我的问题在于这一部分：String _recipe = cursor.getString(1)。它总是给我错误的数据。我试图更改数字，但它仍然给我错误的数据。

这是我的数据库：

package com.pinoycookbook;

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 ROWID = "_id";
    public static final String NAME = "foodname";
    public static final String ORIGIN = "origin";

    public static final String RECIPE = "recipe";

    public static final String CATEGORY = "category";

    private static final String TAG = "Dbadapter";
    private DatabaseHelper mDbHelper;
    private SQLiteDatabase mDb;

    private static final String DATABASE_NAME = "PinoyCookbook.sqlite";
    public static final String SQLITE_TABLE = "Food";
    private static final int DATABASE_VERSION = 1;

    private final Context mCtx;

    private static final String DATABASE_CREATE =
        "CREATE TABLE if not exists " + SQLITE_TABLE + " (" +
                ROWID + " integer PRIMARY KEY autoincrement," +
                NAME + " TEXT," +
                RECIPE + " TEXT," +
                ORIGIN + " TEXT," + 
                CATEGORY+ " TEXT,"+
                " UNIQUE (" + ROWID +"));";

    private static class DatabaseHelper extends SQLiteOpenHelper
    {

        DatabaseHelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
        }

        @Override
        public void onCreate(SQLiteDatabase db) {
            Log.w(TAG, DATABASE_CREATE);
            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 " + SQLITE_TABLE);
            onCreate(db);
        }
    }

    public Dbadapter(Context ctx) {
        this.mCtx = ctx;
    }

    public Dbadapter open() throws SQLException {
        mDbHelper = new DatabaseHelper(mCtx);
        mDb = mDbHelper.getWritableDatabase();
        return this;
    }

    public void close() {
        if (mDbHelper != null) {
            mDbHelper.close();
        }
    }

    public long createData(String foodname, String recipe, String origin,  int i) {
        ContentValues initialValues = new ContentValues();
        initialValues.put(NAME, foodname);
        initialValues.put(RECIPE, recipe);
        initialValues.put(ORIGIN, origin);

        initialValues.put(CATEGORY, i);

        return mDb.insert(SQLITE_TABLE, null, initialValues);
    }

    public boolean deleteAllData() {
        int doneDelete = 0;
        doneDelete = mDb.delete(SQLITE_TABLE, null , null);
        Log.w(TAG, Integer.toString(doneDelete));
        return doneDelete > 0;
    }

    public void insertData() {
        createData("Adobong Manok","adobongmanok","Manila",1);
        createData("Lechon","lechon","Cebu",2);
        createData("Crispy Pata","crispypata","Cebu",2);
        createData("Bulalo","bulalo","Batangas",1);
        createData("Taba ng Talangka Rice","talangkarice","Roxas",2);
        createData("Arroz Caldo","arrozcaldo","Roxas",2);
        createData("Sinigang","sinigang","Manila",1);
    }
}

Answer 1

所以我建议你使用getColumnIndex()方法而不是硬编码。

String _recipe = cursor.getString(cursor.getColumnIndex(Dbadapter.RECIPE));

它将确保您永远得到正确的领域。如果它仍然出错，那么查询中的数据问题不在Cursor

中

注意：使用包含列名称的静态字段始终是最佳做法。

更新

我之前尝试过，它给了我这个错误： java.lang.IllegalArgumentException：列'recipe'不存在

您需要找出实际的表结构。尝试执行此声明：

PRAGMA table_info(Dbadapter.SQLITE_TABLE);

说文档（source）：

此pragma为指定表中的每列返回一行。结果集中的列包括列名，数据类型，是否或者不是列可以为NULL，以及列的默认值。对于不是的列，结果集中的“pk”列为零主键的一部分，是主键中列的索引作为主键一部分的列的键。

实施例

我在这里为您创建了通过PRAGMA获取tableinfo的方法：

public String getTableInfo() {
    StringBuilder b = new StringBuilder("");
    Cursor c = null;
    try {
        db = helper.getReadableDatabase();
        String query = "pragma table_info(" + Dbadapter.SQLITE_TABLE + ")";
        c = db.rawQuery(query, null);
        if (c.moveToFirst()) {
            do {
                b.append("Col:" + c.getString(c.getColumnIndex("name")) + " ");                     
                b.append(c.getString(c.getColumnIndex("type")));
                b.append("\n");
            } while (c.moveToNext());
        }
        return b.toString();
    }
    finally {
        if (c != null) {
            c.close();
        }
        if (db != null) {
            db.close();
        }
    }
}

输出将是这样的：

Column: type text
Column: date text

只有想象力，我会给你屏幕：

Pragram Android Example Screenshot

Answer 2

你可以这样试试：

cursor.getString(cursor.getColumnIndex("recipe"));

它会返回正确的索引，并返回正确的值。

cursor.getstring（）在数据库中获取了错误的字段

2 个答案:

更新

实施例