java - 错误: deleting all rows instead of 1 row Android

Question

我目前正在使用 Java Eclipse 制作 Android 应用程序。该应用程序有一个包含数据的 SQLite 数据库。我可以在列表中查看这些数据。我还可以将项目添加到该数据库中。我现在尝试从数据库中删除特定行。但每当我尝试删除所有行，而不是用户选择的行。

这是我的适配器:

package com.example.beer_budget3;

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;
import android.widget.EditText;

public class DatabaseSetup2
{

        // These are the names of the columns the table will contain
        public static final String KEY_ROWID = "_id";
        public static final String KEY_PUBNAME = "Pub_Name";
        public static final String KEY_LOCATION = "Location";
        public static final String KEY_PRICE = "Price"; 

        private static final String DATABASE_NAME = "CillinsAssignment";
        private static final String DATABASE_TABLE = "Beer_Budget";
        private static final int DATABASE_VERSION = 1;

        // This is the string containing the SQL database create statement
        private static final String DATABASE_CREATE = "CREATE TABLE " + DATABASE_TABLE + 
                "( " +KEY_ROWID + " integer primary key autoincrement, "+KEY_PUBNAME +" text not null, "+KEY_LOCATION+" text not null, "+KEY_PRICE+ " text not null);";

     private final Context context; 

     private DatabaseHelper DBHelper;// utility class that makes it easy to create and maintain an SQLLite database
     private SQLiteDatabase db;//Class containing methods to manage a local SQLLite Database file 

     // constructor for your class 
     public DatabaseSetup2(Context ctx) 
     {
         // Context is a way that Android transfers info about Activities and apps. 
         this.context = ctx;
         DBHelper = new DatabaseHelper(context);
     }

    // This is the helper class that will create the dB if it doesn’t exist and 
    //upgrades it if the structure has changed. It needs a constructor, an 
    //onCreate() method and an onUpgrade() method

     private static class DatabaseHelper extends SQLiteOpenHelper 
     {
        // constructor for your dB helper class. This code is standard. You’ve set 
        //up the parameter values for the constructor already…database name,etc
        DatabaseHelper(Context context) 
        {
            super(context, DATABASE_NAME, null, 1);
        }

        @Override
         public void onCreate(SQLiteDatabase db)
         {
            // The “Database_create” string below needs to contain the SQL 
            //statement needed to create the dB
            try 
            { 
                db.execSQL(DATABASE_CREATE);        
            } 
            catch (SQLException e) 
            {   
                e.printStackTrace();        
            }

         }
         @Override
         public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) 
         {
             // If you want to change the structure of your database, e.g. 
             // Add a new column to a table, the code will go head..
             //This method only triggers if the database version number has 
             //increased 
             Log.w("test", "Upgrading database from version " + oldVersion + " to "                    
             + newVersion + ", which will destroy all old data");            
             db.execSQL("DROP TABLE IF EXISTS Beer_Budget");           
             onCreate(db);

         }
     }// end of the help class

         // from here on, include whatever methods will be used to access or change data 
        //in the database
         //---opens the database--- any activity that uses the dB will need to do this
         public DatabaseSetup2 open() throws SQLException 
         {
             db = DBHelper.getWritableDatabase();
             return this;
         }

         //---closes the database--- any activity that uses the dB will need to do this 
         public void close() 
         {
             DBHelper.close();
         }

         //---insert a pub into the database---
         public long insertPub(String Pub_Name, String Location, String Price) 
         {
             ContentValues initialValues = new ContentValues();
             initialValues.put(KEY_PUBNAME, Pub_Name);
             initialValues.put(KEY_LOCATION, Location);
             initialValues.put(KEY_PRICE, Price);
             return db.insert(DATABASE_TABLE, null, initialValues);
         }

         //---deletes a particular pub---
         public boolean deletePub(String Pub_Name) 
         {
            //delete statement. If any rows deleted (i.e. >0), returns true
            return db.delete(DATABASE_TABLE, "Pub_Name = '"+ KEY_PUBNAME+"' ", null) > 0;
            //return db.delete(DB_TABLE, "name='"+ name+"'", null) > 0;
         }

        //---retrieves all the rows---
         public Cursor getAllPubs() 
         {
         return db.query(DATABASE_TABLE, new String[] 
         {
            KEY_ROWID, 
            KEY_PUBNAME,
            KEY_LOCATION,
            KEY_PRICE}, 
            null, 
            null, 
            null, 
            null,
            null);
         }
         //---retrieves a particular row---
         public Cursor getPub(int _id) throws SQLException 
         {
         Cursor mCursor = db.query(DATABASE_TABLE, new String[] 
         {
            KEY_ROWID,
            KEY_PUBNAME, 
            KEY_LOCATION,
            KEY_PRICE
         }, 
         KEY_ROWID + "=" + _id,
         null,
         null,
         null,
         null
         );
         if (mCursor != null) {
         mCursor.moveToFirst();
         }
         return mCursor;
         }

}

这是我的删除页面:

package com.example.beer_budget3;


import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import android.content.Intent;

//Need to update delete layout after deleting row
public class Delete extends Activity
{
    //Creating an object name for my database
    DatabaseSetup2 db = new DatabaseSetup2(this);

    public void onCreate(Bundle savedInstanceState) 
     {
        super.onCreate(savedInstanceState);
        //This page layout is located in the delete XML file
        setContentView(R.layout.delete);//Put one of these in each class

        //Delete button that has been created in the delete XML file
        Button delete = (Button)findViewById(R.id.deletepub);
        delete.setOnClickListener(new View.OnClickListener() 
        { 
            @Override 
            public void onClick(View v) 
            {
                //This page links back to the MainMenu page
                Intent i = new Intent(Delete.this, MainMenu.class); 
                //Calling the deleting function
                deleting(v);
                //Activating the intent
                startActivity(i);
            }
        });
     }


    public void deleting(View v)
    {
        //Save user input into rowId
        EditText pnametxt = (EditText)findViewById(R.id.delete1);
        //Open the database
        db.open();
        String pname2 = pnametxt.getText().toString();

        db.deletePub(pname2);
        db.close();
    }
}

这是我用于删除页面的 XML 文件:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="@color/background"
    tools:context="com.example.beer_budget3.delete" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="85dp"
        android:layout_marginBottom="20dp"
        android:text="@string/app_name"
        android:textColor="@color/blue"
        android:textStyle="bold"
        android:textSize="30sp" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/details"
        android:layout_marginLeft="50dp"
        android:layout_marginBottom="30dp" 
        android:textSize="25sp"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/pub"
        android:textSize="20sp"/>

    <EditText
        android:id="@+id/delete1"
        android:inputType="text"
        android:layout_width="200dp"
        android:layout_height="wrap_content"
        />

    <Button
        android:id="@+id/deletepub"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="300dp"
        android:layout_marginLeft="130dp"
        android:onClick="delete"
        android:text="@string/delete" />


</LinearLayout>

我个人认为错误出在适配器中的这一行:

return db.delete(DATABASE_TABLE, "Pub_Name = '"+ KEY_PUBNAME+"' ", null) > 0;

因为我知道您必须非常具体地确定放置空间和引用的位置。但我已经更改了这行代码几次并且无法解决我的问题。任何建议将不胜感激!

Answer 1

您的功能在这里:

    //---deletes a particular pub---
     public boolean deletePub(String Pub_Name) 
     {
        //delete statement. If any rows deleted (i.e. >0), returns true
        return db.delete(DATABASE_TABLE, "Pub_Name = '"+ KEY_PUBNAME+"' ", null) > 0;
        //return db.delete(DB_TABLE, "name='"+ name+"'", null) > 0;
     }

应该是

    //---deletes a particular pub---
     public boolean deletePub(String Pub_Name) 
     {
        //delete statement. If any rows deleted (i.e. >0), returns true
        return db.delete(DATABASE_TABLE, "Pub_Name = '"+ Pub_Name+"' ", null) > 0;
        //return db.delete(DB_TABLE, "name='"+ name+"'", null) > 0;
     }

您指定列名称而不是值