java.lang.IllegalArgumentException: column '_id' does not exist

package com.example.user.acconting;import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;public class MainActivity2 extends AppCompatActivity implements AdapterView.OnItemClickListener{
    String db_name="db_name";
    String tb_name="tb_name";
    static  final int MAX=8;
    static  final String[] FROM=new String[] {"amount","idcategory","date"};
    SQLiteDatabase db;
    Cursor cur;
    SimpleCursorAdapter adapter;
    EditText etDate,etAmount,etCategory;
    Button btInsert,btUpdate,btDelete,btQuery;
    ListView lv;
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
        etDate=(EditText)findViewById(R.id.editText3);
        etAmount=(EditText)findViewById(R.id.editText5);
        etCategory=(EditText)findViewById(R.id.editText4);
        btInsert=(Button)findViewById(R.id.button);
        btDelete=(Button)findViewById(R.id.button1);
        btUpdate=(Button)findViewById(R.id.button2);
        btQuery=(Button)findViewById(R.id.button3);
        lv=(ListView)findViewById(R.id.lv);
        db=openOrCreateDatabase(db_name, Context.MODE_PRIVATE,null);
        String createTable="CREATE TABLE IF NOT EXISTS  "+tb_name
                + "(_id INTEGER PRIMARY KEY AUTOINCREMENT,"
                + "amount VARCHAR(16),"
                + "category VARCHAR(32),"
                + "date VARCHAR(32))";
        db.execSQL(createTable);
        addDate("100", "生活用品", "20170915");
        addDate("100","生活用品","20170915");
        cur=db.rawQuery("SELECT * FROM tb_name",null);
        adapter=new SimpleCursorAdapter(this,R.layout.item,cur,
                FROM,
                new int[]{R.id.amount,R.id.category,R.id.date},0);
        lv=(ListView)findViewById(R.id.lv);
        lv.setAdapter(adapter);
        lv.setOnItemClickListener(this);    }
    public void onItemClick (AdapterView<?> parent, View v, int position,long id){
        cur.moveToPosition(position);
        etAmount.setText(cur.getInt(cur.getColumnIndex(FROM[0])));
        etCategory.setText(cur.getString(cur.getColumnIndex(FROM[1])));
        etDate.setText(cur.getInt(cur.getColumnIndex(FROM[2])));
    }
    private void addDate(String amount,String category,String  date){
        ContentValues cv=new ContentValues(3);
        cv.put("amount",amount);
        cv.put("category",category);
        cv.put("date",date);
        db.insert(tb_name,null,cv);
    }}
总显示这个错误： java.lang.IllegalArgumentException: column '_id' does not exist，但我数据库有_id啊，这是为什么？我搜索了一下，也是要加_id,求大佬帮帮忙