我目前正在使用Java Eclipse制作Android应用程序。这个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此数据。我也可以很好地添加项目到这个数据库。我现在要删除数据库中的特定行。但每当我尝试删除所有行时，与用户选择的行相反。
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>
我个人认为错误出现在适配器的这一行：
return db.delete(DATABASE_TABLE, "Pub_Name = '"+ KEY_PUBNAME+"' ", null) > 0;
因为我知道你必须非常具体地说明你放置空间和引语的位置。但我已经改变了几行代码，无法解决我的问题。 任何建议将不胜感激！
答案 0 :(得分：2)
你的功能在这里：
//---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;
}
指定列名而不是值