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每当我启动我的应用程序时，我的java.lang.IllegalArgumentException: column '_id' does not existLogCat 都会出现错误。我已经创建了 column '_id'，但它仍然抛出这个。这是我的主要.java：

package com.gantt.shoppinglist;

import android.app.Dialog;
import android.app.ListActivity;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;

public class ShoppingList extends ListActivity {
    
    private DataHelper DataHelper;
    /** Called when the activity is first created. */
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        DataHelper = new DataHelper(this);
        
        Cursor c = (Cursor) DataHelper.selectAll();
        long id = c.getLong(c.getColumnIndex("_id"));
        startManagingCursor(c);

        ListView lv = (ListView) findViewById(android.R.id.list);
        
        String[] from = new String[] { com.gantt.shoppinglist.DataHelper.getDatabaseName() };
        int[] to = new int[] { android.R.id.text1 };
        
        SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,
                android.R.layout.simple_list_item_1, c, from, to);       
        lv.setAdapter(adapter);
        
        Button button1main = (Button) findViewById(R.id.add);
        button1main.setOnClickListener(new OnClickListener()  {
            @Override
            public void onClick(View v)  {
            final Dialog additem = new Dialog(ShoppingList.this);
            additem.setContentView(R.layout.maindialog);
            final EditText et = (EditText)additem.findViewById(R.id.edittext);
            additem.setTitle("Type your item");
            additem.setCancelable(true);
            et.setHint("Type the name of an item...");

            Button button = (Button) additem.findViewById(R.id.cancel);
            button.setOnClickListener(new OnClickListener()  {
                @Override
                public void onClick(View v)  {
                    additem.dismiss();
                }
            });
            additem.show();

            Button ok = (Button) additem.findViewById(R.id.ok);
            ok.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {
                    final String text = et.getText().toString();
                    additem.dismiss();
                    et.setText("");
                }
            });
       }
        });
    }
}

这是我的 DataHelper 类：

package com.gantt.shoppinglist;

import java.util.ArrayList;
import java.util.List;

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

public class DataHelper {

       private static final String DATABASE_NAME = "items.db";
       private static final int DATABASE_VERSION = 1;
       private static final String TABLE_NAME = "table1";
       public static final String KEY_ROWID = "_id";

       private Context context;
       private SQLiteDatabase db;

       private SQLiteStatement insertStmt;
       private static final String INSERT = "insert into " 
          + TABLE_NAME + "(name) values (?)";

       public DataHelper(Context context) {
          this.context = context;
          OpenHelper openHelper = new OpenHelper(this.context);
          this.db = openHelper.getWritableDatabase();
          this.insertStmt = this.db.compileStatement(INSERT);
       }

       public long insert(String name) {
          this.insertStmt.bindString(1, name);
          return this.insertStmt.executeInsert();
       }

       public void deleteAll() {
          this.db.delete(TABLE_NAME, null, null);
       }

       public Cursor selectAll() {
          List<String> list = new ArrayList<String>();
          Cursor cursor = this.db.query(TABLE_NAME, new String[] { "name" }, 
            null, null, null, null, "name desc");
          if (cursor.moveToFirst()) {
             do {
                list.add(cursor.getString(0)); 
             } while (cursor.moveToNext());
          }
          if (cursor != null && !cursor.isClosed()) {
             cursor.close();
          }
          return cursor;
       }

       public static String getDatabaseName() {
        return DATABASE_NAME;
    }

    private static class OpenHelper extends SQLiteOpenHelper {

          OpenHelper(Context context) {
             super(context, getDatabaseName(), null, DATABASE_VERSION);
          }

          @Override
          public void onCreate(SQLiteDatabase db) {
              db.execSQL("CREATE TABLE " + TABLE_NAME + "(id INTEGER PRIMARY KEY, name TEXT");
              
          }

          @Override
          public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
             Log.w("Example", "Upgrading database, this will drop tables and recreate.");
             db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
             onCreate(db);
          }
       }
    }
4

2 回答 2

50

我有一个类似的问题 - 我认为这是一个必须“选择”（或“选择为”）的情况，_id因为SimpleCursorAdapter需要它。

从文档中：

处理内容 URI ID

按照惯例，提供者通过接受内容 URI 来提供对表中单行的访问，该内容 URI 具有 URI 末尾的行的 ID 值。同样按照惯例，提供者将 ID 值与表的 _ID列进行匹配，并对匹配的行执行请求的访问。

此约定有助于应用程序访问提供程序的通用设计模式。该应用程序对提供者进行查询，Cursor并ListView使用CursorAdapter. 的定义需要toCursorAdapter中的列之一。Cursor_ID

就我而言，我的表中有一个名为“oid”的自动编号列，因此我将 SELECT 命令更改为（例如）...

SELECT oid as _id, name, number FROM mytable

这解决了我的问题。

编辑以显示更广泛的代码...

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.channel_selector);

    GridView channel_selector_grid = (GridView) findViewById(R.id.channel_grid);
    sca = getGuideAdapter();
    channel_selector_grid.setAdapter(sca);
}

public SimpleCursorAdapter getGuideAdapter() {
    SimpleCursorAdapter adapter = null;
    SQLiteDatabase db = SQLiteDatabaseHelper.getReadableDatabase();
    Cursor cursor = db.rawQuery("SELECT DISTINCT oid as _id, name, number FROM CHAN_TABLE ORDER BY number", null);
    if (cursor.moveToFirst()) {
        String[] columnNames = { "name" };
        int[] resIds = { R.id.channel_name };
        adapter = new SimpleCursorAdapter(this, R.layout.channel_selector_item, cursor, columnNames, resIds);
    }
    return adapter; 
}
于 2011-02-11T23:02:59.877 回答
1

嗯，不知道你是不是贴错了，但是：

 DataHelper = new DataHelper(this);
 Cursor c = (Cursor) DataHelper.selectAll();

是错的。您需要将其声明为一个对象并在初始化的 DataBase 对象上调用您的方法：

 DataHelper dataHelper = new DataHelper(this);
 Cursor c = (Cursor) dataHelper.selectAll();

哦，我的错，你刚刚用大写的 D 声明了你的变量名，这既不是推荐的，也不是标准的 java 编码风格。

http://java.about.com/od/javasyntax/a/nameconventions.htm

于 2011-02-11T22:58:58.473 回答