android - 自定义游标适配器运行时出错，非法参数异常

Question

我已经用更改更新了我的帖子，插入了“_id”，一切都正常工作

我希望有人可以帮助解决我的问题，因为我对 android 和 java 很陌生。我创建了一个使用 SQLite 数据库的应用程序，我使用自定义光标适配器打印数据库的一行以及 2 个按钮和一个 editText。我认为我有正确的代码，但是当我尝试运行该应用程序时，我收到了 IllegalArgumentException，我已经浏览这个论坛几天了，但我仍然很困惑。如果有人能指出我的错误并帮助我修复它那就太好了!

这是我的主要 Activity

import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.os.Handler;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;
import com.pinchtapzoom.R;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class MyActivity extends Activity {

private CustomCursorAdapter customAdapter;
//private com.example.rory.dbtest.DBAdapter databaseHelper;
public ListView list1;

com.example.rory.dbtest.DBAdapter db = new com.example.rory.dbtest.DBAdapter(this);
//CustomCursorAdapter c = new CustomCursorAdapter(this,c);

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

    list1 = (ListView)findViewById(R.id.data_list);
    db.open();


    Button addBtn = (Button)findViewById(R.id.add);
    addBtn.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            Intent i = new Intent(MyActivity.this, addassignment.class);
            startActivity(i);
        }
    });

    Button deleteBtn = (Button)findViewById(R.id.delete);
    deleteBtn.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            Intent i = new Intent(MyActivity.this, Delete.class);
            startActivity(i);
        }
    });

    Button updateBtn = (Button)findViewById(R.id.update);
    updateBtn.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            Intent i = new Intent(MyActivity.this, Update.class);
            startActivity(i);
        }
    });


    try {
        String destPath = "/data/data/" + getPackageName() + "/databases/AssignmentDB";
        File f = new File(destPath);
        if (!f.exists()) {
            CopyDB( getBaseContext().getAssets().open("mydb"),
                    new FileOutputStream(destPath));
        }
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }


   new Handler().post(new Runnable() {
        @Override
        public void run() {
            //Log.d("test", "customadapter is " + customAdapter.toString());
            //Log.d("test", "databaseHelper is " + databaseHelper.toString());
            customAdapter = new CustomCursorAdapter(MyActivity.this, db.getAllRecords());
            list1.setAdapter(customAdapter);
        }
    });


}

private class DBAdapter extends BaseAdapter {
    private LayoutInflater mInflater;
    //private ArrayList<>

    @Override
    public int getCount() {

        return 0;
    }

    @Override
    public Object getItem(int arg0) {

        return null;
    }

    @Override
    public long getItemId(int arg0) {

        return 0;
    }

    @Override
    public View getView(int arg0, View arg1, ViewGroup arg2) {

        return null;
    }

}

public void CopyDB(InputStream inputStream, OutputStream outputStream)
        throws IOException {
    //---copy 1K bytes at a time---
    byte[] buffer = new byte[1024];
    int length;
    while ((length = inputStream.read(buffer)) > 0) {
        outputStream.write(buffer, 0, length);
    }
    inputStream.close();
    outputStream.close();
}
}

这是我的数据库类

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 KEY_ROWID = "_id";
public static final String KEY_ITEM = "item";
public static final String KEY_LITRES = "litres";
private static final String TAG = "DBAdapter";

private static final String DATABASE_NAME = "DripDrop";
private static final String DATABASE_TABLE = "assignments";
private static final int DATABASE_VERSION = 1;

private static final String DATABASE_CREATE =
        "create table if not exists assignments (_id integer primary key autoincrement, "
                + "item VARCHAR not null, litres date );";

private final Context context;

private DatabaseHelper DBHelper;
private SQLiteDatabase db;

public DBAdapter(Context ctx)
{
    this.context = ctx;
    DBHelper = new DatabaseHelper(context);
}

private static class DatabaseHelper extends SQLiteOpenHelper
{
    DatabaseHelper(Context context)
    {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db)
    {
        try {
            db.execSQL(DATABASE_CREATE);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    @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 contacts");
        onCreate(db);
    }
}

//---opens the database---
public DBAdapter open() throws SQLException
{
    db = DBHelper.getWritableDatabase();
    return this;
}

//---closes the database---
public void close()
{
    DBHelper.close();
}

//---insert a record into the database---
public long insertRecord(String item, String litres)
{
    ContentValues initialValues = new ContentValues();
    initialValues.put(KEY_ITEM, item);
    initialValues.put(KEY_LITRES, litres);
    return db.insert(DATABASE_TABLE, null, initialValues);
}

//---deletes a particular record---
public boolean deleteContact(long rowId)
{
    return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}

//---retrieves all the records---
public Cursor getAllRecords()
{
    return db.query(DATABASE_TABLE, new String[] {KEY_ROWID, KEY_ITEM,
            KEY_LITRES}, null, null,null, null, null);
}



//---retrieves a particular record---
public Cursor getRecord(long rowId) throws SQLException
{
    Cursor mCursor =
            db.query(true, DATABASE_TABLE, new String[] {KEY_ROWID,
                            KEY_ITEM, KEY_LITRES},
                    KEY_ROWID + "=" + rowId, null, null, null, null, null);
    if (mCursor != null) {
        mCursor.moveToFirst();
    }
    return mCursor;
}

//---updates a record---
public boolean updateRecord(String item, String litres)
{
    db.execSQL("UPDATE "+DATABASE_TABLE+" SET "+KEY_LITRES+"='"+litres+"' WHERE "+KEY_ITEM+"='"+item+"'");
    return true;
}
}

这是我的自定义光标类 导入 android.content.Context； 导入 android.database.Cursor; 导入 android.view.LayoutInflater; 导入 android.view.View； 导入 android.view.ViewGroup; 导入 android.widget.CursorAdapter; 导入 android.widget.TextView; 导入 com.pinchtapzoom.R;

public class CustomCursorAdapter extends CursorAdapter {

public CustomCursorAdapter(Context context, Cursor c) {
    super(context, c);
}

@Override
public View newView(Context context, Cursor cursor, ViewGroup parent) {
    // when the view will be created for first time,
    // we need to tell the adapters, how each item will look
    LayoutInflater inflater = LayoutInflater.from(parent.getContext());
    View retView = inflater.inflate(R.layout.row, parent, false);

    return retView;
}

@Override
public void bindView(View view, Context context, Cursor cursor) {
    // here we are setting our data
    // that means, take the data from the cursor and put it in views

    TextView textViewPersonName = (TextView) view.findViewById(R.id.item1);
    textViewPersonName.setText(cursor.getString(cursor.getColumnIndex(cursor.getColumnName(1))));

}
}

这是我运行应用程序时遇到的 logcat 错误

    4501-4501/com.example.rory.dbtest E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.example.rory.dbtest, PID: 4501
    java.lang.IllegalArgumentException: column '_id' does not exist
        at android.database.AbstractCursor.getColumnIndexOrThrow(AbstractCursor.java:303)
        at android.widget.CursorAdapter.init(CursorAdapter.java:172)
        at android.widget.CursorAdapter.<init>(CursorAdapter.java:120)
        at com.example.rory.dbtest.CustomCursorAdapter.<init>(CustomCursorAdapter.java:19)
        at com.example.rory.dbtest.MyActivity$4.run(MyActivity.java:94)

Answer 1

CursorAdapter 始终需要一个名为 _id 的列，您必须为 CursoAdapter 提供它，将表列 id 更改为 _id ，或者当您从表中查询时，创建一个id 列的别名为 _id