NumberFormatException：null（Android Studio中的错误）

Question

我在下面得到这个错误。我正在从firebase和sqlite浏览器检索我的数据库。希望你们能帮我解决这件事。

public class Database extends SQLiteAssetHelper {

    private static final String DB_NAME="coolblogDB.db";
    private static final int DB_VER=1;


    public Database(Context context) { super(context, DB_NAME, null, DB_VER); }

    public List<Order> getCarts() {
        SQLiteDatabase db = getReadableDatabase();
        SQLiteQueryBuilder qb = new SQLiteQueryBuilder();

        String[] sqlSelect = {"ProductId", "ProductName", "Quantity", "Price", "Discount"};
        String sqlTable = "OrderDetail";

        qb.setTables(sqlTable);
        Cursor c = qb.query(db, sqlSelect, null, null, null, null, null);

        final List<Order> result = new ArrayList<>();
        if (c.moveToFirst()) {
            do {
                result.add(new Order(c.getString(c.getColumnIndex("ProductId")),
                        c.getString(c.getColumnIndex("ProductName")),
                        c.getString(c.getColumnIndex("Quantity")),
                        c.getString(c.getColumnIndex("Price")),
                        c.getString(c.getColumnIndex("Discount"))
                ));
            } while (c.moveToNext());
        }
        return result;
    }

    public void addToCart(Order order)
    {
        SQLiteDatabase db = getReadableDatabase();
        String query = String.format("INSERT INTO OrderDetail(ProductId,ProductName,Quantity,Price,Discount) VALUES('%s','%s','%s','%s','%s');",
                order.getProductId(),
                order.getProductName(),
                order.getQuantity(),
                order.getPrice(),
                order.getDiscount());
        db.execSQL(query);
    }

    public void cleanCart()
    {
        SQLiteDatabase db = getReadableDatabase();
        String query = String.format("DELETE FROM OrderDetail");
        db.execSQL(query);
    }
}

10-15 13:48:34.439 128 60-12860/com.example.mariamsyafiqah.coolblog2 e/androidruntime：致命异常：main process:com.example.mariamsyafiqah.coolblog2,pid:12860 java.lang.runtimeexception：无法启动活动ComponentInfo{com.example.mariamsyafiqah.coolblog2/com.example.mariamsyafiqah.coolblog2.cart}activity(activityThread.java:2726)，android.app.activityThread.-wrap12(activityThread.java)，android.app.activityThread.$h.handleMessage(activityThread.java:1477)，android.os.handler.dispatchMessage(handler.java:102)，android.os.handler.dispatchMessage(handler.java:154)，android.app.activityThread.main java:886)在com.android.internal.os.zygoteinit.main（zygoteinit.java:776)casedby：java.lang.NumberFormatException：null at java.lang.Integer.ParseInt(Integer.java:483)at java.lang.Integer.ParseInt(Integer.java:556)at com.example.mariamsyafiqah.coolblog2.cart.loadlistDrink(cart.java:128)at com.example.mariamsyafiqah.coolblog2.cart.oncreate(cart.java:71)at Android.app.activitythread.java:2618)的chactivity（activitythread.java:2726)在Android.app.activitythread.-Wrap12(activitythread.java) 在Android.app.activitythread$h.handleMessage(activitythread.java:1477) 在Android.os.handler.DispatchMessage(Handler.java:102) 在Android.os.looper.loop(looper.java:154) 在Android.app.activitythread.main(activitythread.java:6119) 在java.lang.reflect.Method.invoke（本机方法） 在com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:886) 在com.android.internal.os.zygoteinit.main(zygoteinit.java:776)

Answer 1

检查cart.java第128行，如下错误所示：

java.lang.NumberFormatException：在java.lang.Integer.ParseInt(Integer.java:483)，java.lang.Integer.ParseInt(Integer.java:556)，com.example.Mariamsyafiqah.Coolblog2.cart.LoadListDrink(cart.java:128)，at ；

有一句台词是这样的：

int val = Integer.parseInt(stringValue);

如果stringValue为空或为空，则会引发错误。您需要首先检查字符串是否是正确的数字