我有一个listView，它从我现有的数据库中显示购物车中的服装项目，在底部显示我购物车中所有商品的总价。当我从购物车中删除商品时，listView确实会更新，它会删除该商品，但是当我删除此商品时，底部显示的总价格不会更新，而此总价格仅来自执行SUM的查询（价格）从我的表中包含我的购物车中的商品。我在下面发布了我的一些代码，如果有人可以提供帮助，那就太棒了。
DatabaseHelper.java
package ankitkaushal.app.healthysizing;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
public class DatabaseHelper extends SQLiteOpenHelper {
public static String DB_PATH = "/data/data/ankitkaushal.app.healthysizing/databases/";
public static String DB_NAME = "FinishDatabase";
public static final int DB_VERSION = 1;
public static final String shoppingCartTable = "OPS_insert";
private SQLiteDatabase myDB;
private Context context;
public DatabaseHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
this.context = context;
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
@Override
public synchronized void close(){
if(myDB!=null){
myDB.close();
}
super.close();
}
// Retrieves all shirt and pant items of the specified brand typed into the search bar
public ArrayList<Item> getAllSearchedItems(String brand, String table_name, String size) {
if (size.equals("null")) {
brand = "\"" + brand + "\"";
ArrayList<Item> itemList = new ArrayList<Item>();
String query = "SELECT * FROM " + table_name + " WHERE Brand LIKE " + brand + " ORDER BY Price ASC"; //query to get all the shirt or pant items for brand typed in
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(query, null);
if (cursor.moveToFirst()){
do {
Item item = new Item();
item.setBrand(cursor.getString(0));
item.setStore(cursor.getString(1));
item.setPrice(cursor.getString(2));
item.setDescription(cursor.getString(3));
item.setSize(cursor.getString(4));
item.setGender(cursor.getString(5));
item.setID(cursor.getString(6));
itemList.add(item);
} while (cursor.moveToNext());
}
return itemList;
}
else {
brand = "\"" + brand + "\"";
ArrayList<Item> itemList = new ArrayList<Item>();
String query = "SELECT * FROM " + table_name + " WHERE Brand LIKE " + brand + " AND Size = '" + size + "' ORDER BY Price ASC"; //query to get all the shirt or pant items for brand typed in
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(query, null);
if (cursor.moveToFirst()){
do {
Item item = new Item();
item.setBrand(cursor.getString(0));
item.setStore(cursor.getString(1));
item.setPrice(cursor.getString(2));
item.setDescription(cursor.getString(3));
item.setSize(cursor.getString(4));
item.setGender(cursor.getString(5));
item.setID(cursor.getString(6));
itemList.add(item);
} while (cursor.moveToNext());
}
return itemList;
}
}
// Retrieves all shirt or pant items from the database
public ArrayList<Item> getAllItems(String table_name, String size) {
if (size.equals("null")) {
ArrayList<Item> itemList = new ArrayList<Item>();
String query = "SELECT * FROM " + table_name + " ORDER BY Price ASC"; //query to get all the shirt or pant items
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(query, null);
if (cursor.moveToFirst()){
do {
Item item = new Item();
item.setBrand(cursor.getString(0));
item.setStore(cursor.getString(1));
item.setPrice(cursor.getString(2));
item.setDescription(cursor.getString(3));
item.setSize(cursor.getString(4));
item.setGender(cursor.getString(5));
item.setID(cursor.getString(6));
itemList.add(item);
} while (cursor.moveToNext());
}
return itemList;
}
else {
ArrayList<Item> itemList = new ArrayList<Item>();
String query = "SELECT * FROM " + table_name + " WHERE Size = '" + size + "' ORDER BY Price ASC"; //query to get all the shirt or pant items
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(query, null);
if (cursor.moveToFirst()){
do {
Item item = new Item();
item.setBrand(cursor.getString(0));
item.setStore(cursor.getString(1));
item.setPrice(cursor.getString(2));
item.setDescription(cursor.getString(3));
item.setSize(cursor.getString(4));
item.setGender(cursor.getString(5));
item.setID(cursor.getString(6));
itemList.add(item);
} while (cursor.moveToNext());
}
return itemList;
}
}
// Retrieves all shoe items from the database
public ArrayList<Item> getAllShoes() {
ArrayList<Item> shoeList = new ArrayList<Item>();
String query = "SELECT * FROM Shoes ORDER BY Price ASC "; // query to get all shoe items
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(query, null);
if (cursor.moveToFirst()){
do {
Item item = new Item();
item.setBrand(cursor.getString(0));
item.setStore(cursor.getString(1));
item.setPrice(cursor.getString(2));
item.setDescription(cursor.getString(3));
item.setGender(cursor.getString(4));
item.setID(cursor.getString(5));
item.setSize("See Description");
shoeList.add(item);
} while (cursor.moveToNext());
}
return shoeList;
}
// Retrieves all shoe items of specified brand typed into the search bar
public ArrayList<Item> getAllSearchedShoes(String brand) {
brand = "\"" + brand + "\"";
ArrayList<Item> shoeList = new ArrayList<Item>();
String query = "SELECT * FROM Shoes WHERE Brand LIKE " + brand + " ORDER BY Price ASC "; //query to get all the shoes for brand typed in
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(query, null);
if (cursor.moveToFirst()){
do {
Item item = new Item();
item.setBrand(cursor.getString(0));
item.setStore(cursor.getString(1));
item.setPrice(cursor.getString(2));
item.setDescription(cursor.getString(3));
item.setGender(cursor.getString(4));
item.setID(cursor.getString(5));
item.setSize("See Description");
shoeList.add(item);
} while (cursor.moveToNext());
}
return shoeList;
}
// Retrieves all outerwear items from the database
public ArrayList<Item> getAllOuterwear() {
ArrayList<Item> outerwearList = new ArrayList<Item>();
String query = "SELECT * FROM Outerwear ORDER BY Price ASC "; // query to get all outerwear items
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(query, null);
if (cursor.moveToFirst()){
do {
Item item = new Item();
item.setBrand(cursor.getString(0));
item.setStore(cursor.getString(1));
item.setPrice(cursor.getString(2));
item.setDescription(cursor.getString(3));
item.setSize(cursor.getString(4));
item.setGender(cursor.getString(5));
item.setID(cursor.getString(6));
outerwearList.add(item);
} while (cursor.moveToNext());
}
return outerwearList;
}
// Retrieves all outerwear items of specified brand typed into the search bar
public ArrayList<Item> getAllSearchedOuterwear(String brand) {
brand = "\"" + brand + "\"";
ArrayList<Item> outerwearList = new ArrayList<Item>();
String query = "SELECT * FROM Outerwear WHERE Brand LIKE " + brand + " ORDER BY Price ASC "; //query to get all the outerwear for brand typed in
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(query, null);
if (cursor.moveToFirst()){
do {
Item item = new Item();
item.setBrand(cursor.getString(0));
item.setStore(cursor.getString(1));
item.setPrice(cursor.getString(2));
item.setDescription(cursor.getString(3));
item.setSize(cursor.getString(4));
item.setGender(cursor.getString(5));
item.setID(cursor.getString(6));
outerwearList.add(item);
} while (cursor.moveToNext());
}
return outerwearList;
}
// Retrieves all the items in the cart
public ArrayList<Item> getItemsInCart() {
ArrayList<Item> cartList = new ArrayList<Item>();
String query = "SELECT * FROM " + shoppingCartTable + " ORDER BY Price ASC"; // query to get all the items in the cart
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(query, null);
if (cursor.moveToFirst()){
do {
Item item = new Item();
item.setBrand(cursor.getString(0));
item.setStore(cursor.getString(1));
item.setPrice(cursor.getString(2));
item.setDescription(cursor.getString(3));
item.setSize(cursor.getString(4));
item.setGender(cursor.getString(5));
item.setID(cursor.getString(6));
cartList.add(item);
} while (cursor.moveToNext());
}
return cartList;
}
// Adds the item chosen from the listView to your shopping cart.
public void addToCart(Item item) {
String description = item.getDescription();
description = description.replaceAll("\"", " inch");
String brand = item.getBrand();
description = "\"" + description + "\"";
brand = "\"" + brand + "\"";
String query = "INSERT INTO " + shoppingCartTable + " (Brand, Store, Price, Description, Size, Gender, ID) " +
"VALUES (" + brand + ", '" + item.getStore() + "', '" + item.getPrice() + "', "
+ description + ", '" + item.getSize() + "', '" + item.getGender() + "', '" + item.getID() + "')";
SQLiteDatabase db = this.getWritableDatabase();
db.execSQL(query);
}
// Deletes the item from the shopping cart
public void deleteItemFromCart(String ID) {
SQLiteDatabase db = this.getWritableDatabase();
db.delete(shoppingCartTable, " ID = '" + ID + "'", null);
}
// Returns total price of items in shopping cart
public String getTotalCartPrice() {
String SQLQuery = "SELECT SUM(Price) FROM OPS_insert";
SQLiteDatabase db = this.getWritableDatabase();
Cursor c = db.rawQuery(SQLQuery, null);
c.moveToFirst();
String priceTotal = c.getString(0);
return priceTotal;
}
public void setLimitPants(String startSize, String currentSize, String limit) {
String SQLQuery = "UPDATE setLimitPants SET startingSize = '" + startSize + "', currentSize = '" + currentSize + "', limitSize = '" + limit + "'";
SQLiteDatabase db = this.getWritableDatabase();
db.execSQL(SQLQuery);
}
public String getLimit(String tableName) {
String SQLQuery = "SELECT limitSize FROM " + tableName;
SQLiteDatabase db = this.getWritableDatabase();
Cursor c = db.rawQuery(SQLQuery, null);
c.moveToFirst();
String limit = c.getString(0);
return limit;
}
public void setLimitShirts(String startSize, String currentSize, String limit) {
String SQLQuery = "UPDATE setLimitShirts SET startingSize = '" + startSize + "', currentSize = '" + currentSize + "', limitSize = '" + limit + "'";
SQLiteDatabase db = this.getWritableDatabase();
db.execSQL(SQLQuery);
}
public String getStartSizePants() {
String SQLQuery = "SELECT startingSize FROM setLimitPants";
SQLiteDatabase db = this.getWritableDatabase();
Cursor c = db.rawQuery(SQLQuery, null);
c.moveToFirst();
String startingSize = c.getString(0);
return startingSize;
}
public String getStartSizeShirts() {
String SQLQuery = "SELECT startingSize FROM setLimitShirts";
SQLiteDatabase db = this.getWritableDatabase();
Cursor c = db.rawQuery(SQLQuery, null);
c.moveToFirst();
String startingSize = c.getString(0);
return startingSize;
}
public String getCurrentShirtSize() {
String SQLQuery = "SELECT currentSize FROM setLimitShirts";
SQLiteDatabase db = this.getWritableDatabase();
Cursor c = db.rawQuery(SQLQuery, null);
c.moveToFirst();
String currentSize = c.getString(0);
return currentSize;
}
public String getCurrentPantsSize() {
String SQLQuery = "SELECT currentSize FROM setLimitPants";
SQLiteDatabase db = this.getWritableDatabase();
Cursor c = db.rawQuery(SQLQuery, null);
c.moveToFirst();
String currentSize = c.getString(0);
return currentSize;
}
public void updateSizeShirts(String newSize) {
String SQLQuery = "UPDATE setLimitShirts SET currentSize = '" + newSize + "'";
SQLiteDatabase db = this.getWritableDatabase();
db.execSQL(SQLQuery);
}
public void updateSizePants(String newSize) {
String SQLQuery = "UPDATE setLimitPants SET currentSize = '" + newSize + "'";
SQLiteDatabase db = this.getWritableDatabase();
db.execSQL(SQLQuery);
}
public void removeLImit(String tableName) {
String SQLQuery = "UPDATE " + tableName + " SET startingSize = 'null', currentSize = 'null', limitSize = 'null'";
SQLiteDatabase db = this.getWritableDatabase();
db.execSQL(SQLQuery);
}
/***
* Open database
* @throws android.database.SQLException
*/
public void openDataBase() throws SQLException {
String myPath = DB_PATH + DB_NAME;
myDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
}
/**
* Copy database from source code assets to device
* @throws java.io.IOException
*/
public void copyDataBase() throws IOException {
try {
InputStream myInput = context.getAssets().open(DB_NAME);
String outputFileName = DB_PATH + DB_NAME;
OutputStream myOutput = new FileOutputStream(outputFileName);
byte[] buffer = new byte[1024];
int length;
while((length = myInput.read(buffer))>0){
myOutput.write(buffer, 0, length);
}
myOutput.flush();
myOutput.close();
myInput.close();
} catch (Exception e) {
Log.e("tle99 - copyDatabase", e.getMessage());
}
}
/***
* Check if the database doesn't exist on device, create new one
* @throws IOException
*/
public void createDataBase() throws IOException {
boolean dbExist = checkDataBase();
if (dbExist) {
} else {
this.getReadableDatabase();
try {
copyDataBase();
} catch (IOException e) {
Log.e("tle99 - create", e.getMessage());
}
}
}
// ---------------------------------------------
// PRIVATE METHODS
// ---------------------------------------------
/***
* Check if the database is exist on device or not
* @return
*/
private boolean checkDataBase() {
SQLiteDatabase tempDB = null;
try {
String myPath = DB_PATH + DB_NAME;
tempDB = SQLiteDatabase.openDatabase(myPath, null,
SQLiteDatabase.OPEN_READWRITE);
} catch (SQLiteException e) {
Log.e("tle99 - check", e.getMessage());
}
if (tempDB != null)
tempDB.close();
return tempDB != null ? true : false;
}
}
CartItemsAdapter.java
package ankitkaushal.app.healthysizing;
import java.util.ArrayList;
import android.content.Context;
import android.graphics.drawable.Drawable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
public final class CartItemsAdapter extends ArrayAdapter<Item> implements View.OnClickListener {
public CartItemsAdapter(Context context, ArrayList<Item> shirtItems) {
super(context, 0, shirtItems);
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
// Get the data item for this position
Item item = getItem(position);
// Check if an existing view is being reused, otherwise inflate the view
if (convertView == null) {
convertView = LayoutInflater.from(getContext()).inflate(R.layout.cart_layout, parent, false);
}
// Lookup view for data population
TextView brand = (TextView) convertView.findViewById(R.id.txt_cart_brand);
TextView price = (TextView) convertView.findViewById(R.id.txt_cart_price);
TextView store = (TextView) convertView.findViewById(R.id.txt_cart_store);
TextView size = (TextView) convertView.findViewById(R.id.txt_cart_size);
TextView description = (TextView) convertView.findViewById(R.id.txt_cart_description);
ImageView shirtsImage = (ImageView) convertView.findViewById(R.id.image_view_cart);
Button deleteFromCartButton = (Button) convertView.findViewById(R.id.deleteItemButton);
// Populate the data into the template view using the data object
brand.setText("Brand:" + " " + item.getBrand());
price.setText("Price:" + " $" + item.getPrice());
store.setText("Store:" + " " + item.getStore());
size.setText("Size:" + " " + item.getSize());
description.setText("Description:" + " " + item.getDescription());
Context context = parent.getContext();
try { // Find the image name from database ID column and link that up with the name of image in drawable folder
String itemName = item.getID();
String uri = "@drawable/"+itemName;
int imageResource = context.getResources().getIdentifier(uri, null, context.getApplicationContext().getPackageName());
Drawable drawable = context.getResources().getDrawable(imageResource);
shirtsImage.setImageDrawable(drawable);
}
catch (Exception e) { // If no image found for item, just set the image to a default image in drawable folder
// TODO Auto-generated catch block
Drawable drawable = context.getResources().getDrawable(R.drawable.shirts); // Default image
shirtsImage.setImageDrawable(drawable);
}
deleteFromCartButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
// To get the item from the listView for which the Add to Cart button is pressed
Item item = getItem(position);
// Delete the item from the cart by pressing the delete item button
DatabaseHelper db = new DatabaseHelper(getContext());
db.deleteItemFromCart(item.getID());
remove(item);
// Update the listView to reflect the changes
notifyDataSetChanged();
}
});
// Return the completed view to render on screen
return convertView;
}
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
}
}
shoppingCart.java
package ankitkaushal.app.healthysizing;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.TextView;
import java.io.IOException;
import java.util.ArrayList;
public class shoppingCart extends ActionBarActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_shopping_cart);
final DatabaseHelper dbhelper;
final ListView listView;
final ListAdapter cartAdapter;
dbhelper = new DatabaseHelper(getApplicationContext());
try {
dbhelper.createDataBase();
} catch (IOException e) {
e.printStackTrace();
}
listView = (ListView) findViewById(R.id.itemsInCartList);
ArrayList<Item> cartList = dbhelper.getItemsInCart();
if (cartList != null) {
cartAdapter = new CartItemsAdapter(getApplicationContext(), cartList);
listView.setAdapter(cartAdapter);
}
listView.setEmptyView(findViewById(R.id.emptyCartMessage));
TextView displayTotalPrice = (TextView) findViewById(R.id.totalCartPrice);
String totalCartPrice = dbhelper.getTotalCartPrice();
if (totalCartPrice != null) {
displayTotalPrice.setText("Total Price: $" + totalCartPrice);
}
else {
displayTotalPrice.setText("Total Price: $0.00");
}
}
}
答案 0 :(得分：2)
在我看来，最快的方法是：
OnItemDeletedListener.java public interface OnItemDeletedListener {
public void onItemDeleted();
}
CartItemsAdapter添加以下代码：
private OnItemDeletedListener onItemDeletedListener;
public void setOnItemDeletedListener(Object object) {
onItemDeletedListener = (OnItemDeletedListener) object;
}
在功能getView(...)中将setOnClickListener替换为：
deleteFromCartButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
// To get the item from the listView for which the Add to Cart button is pressed
Item item = getItem(position);
// Delete the item from the cart by pressing the delete item button
DatabaseHelper db = new DatabaseHelper(getContext());
db.deleteItemFromCart(item.getID());
remove(item);
// Update the listView to reflect the changes
notifyDataSetChanged();
onItemDeletedListener.onItemDeleted();
}
更改shoppingCart课程：
package ankitkaushal.app.healthysizing;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.TextView;
import java.io.IOException;
import java.util.ArrayList;
public class shoppingCart extends ActionBarActivity implements OnItemDeletedListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_shopping_cart);
final DatabaseHelper dbhelper;
final ListView listView;
final ListAdapter cartAdapter;
dbhelper = new DatabaseHelper(getApplicationContext());
try {
dbhelper.createDataBase();
} catch (IOException e) {
e.printStackTrace();
}
listView = (ListView) findViewById(R.id.itemsInCartList);
ArrayList<Item> cartList = dbhelper.getItemsInCart();
if (cartList != null) {
cartAdapter = new CartItemsAdapter(getApplicationContext(), cartList);
cartAdapter.setOnItemDeletedListener(this);
listView.setAdapter(cartAdapter);
}
listView.setEmptyView(findViewById(R.id.emptyCartMessage));
displayTotalPrice();
}
private void displayTotalPrice() {
TextView displayTotalPrice = (TextView) findViewById(R.id.totalCartPrice);
String totalCartPrice = dbhelper.getTotalCartPrice();
if (totalCartPrice != null) {
displayTotalPrice.setText("Total Price: $" + totalCartPrice);
}
else {
displayTotalPrice.setText("Total Price: $0.00");
}
}
@Override
public void onItemDeleted() {
displayTotalPrice();
}
}
[编辑]
将final ListAdapter cartAdapter;替换为final CartItemsAdapter cartAdapter;
答案 1 :(得分：0)
您单击删除按钮时似乎没有通知displayTotalPrice（如果这是您从购物车中删除项目时要更新的TextView）。您的活动应该听取CartItemsAdapter中所做的更改。
将此内部界面添加到CartItemsAdapter。
public static interface ItemDeleteListener {
public void onItemDelete(double price);
}
然后在CartItemsAdapter中引用此接口：
ItemDeleteListener itemDeleteListener;
当您创建新的CartItemsAdapter（将其作为参数传递）时，应初始化此变量：
// 'this' in this case is your Activity passed into Adapter as an argument
cartAdapter = new CartItemsAdapter(getApplicationContext(), cartList, this);
在CartItemsAdapter构造函数中，然后初始化该接口：
this.itemDeleteListener = listener;
然后让您的购物车Activity实现此界面：
public class shoppingCart extends ActionBarActivity implements CartItemsAdapter.ItemDeleteListener {
...
@Override
public void onItemDelete(doublePrice) {
// here you notify displayTotalPrice, doublePrice should be total price
displayTotalPrice.setText(doublePrice);
}
}
发生更改时，请在CartItemsAdapter中调用它，如下所示：
itemDeleteListener.onItemDelete(db.getTotalCartPrice());