使用WHERE的SQLiteException"+ KEY_Date +"=""+ date +"“"

问题描述

这是在我的mainactivity.java上的selectedDayChange上

This is on my selectedDayChange on my mainactivity.java

date= year +""+ month +""+ dayOfMonth;

                    allfood food = new allfood();
                    food.Date="DATE_"+date;
                    double a = repo.totalFat(food);
                    Toast.makeText(getApplicationContext(), "" +a, Toast.LENGTH_LONG).show();

这是在我的repo.java上

While this is on my repo.java

public double totalFat(allfood date){


        SQLiteDatabase db = dbHelper1.getReadableDatabase();

        String query = "SELECT SUM(Fat) FROM " +allfood.TABLE+ " WHERE " +KEY_Date+"="+date;

        Cursor c = db.rawQuery(query, null);

        c.moveToFirst();
        double i=c.getDouble(0);

        return i;

    }

然后它显示一个错误，顺便说一句，我知道我需要做这样的事情:KEY_Date+"='"+date+"'"

Then it shows an error, by the way, I know I needed to make something like this: KEY_Date+"='"+date+"'"

String query = "SELECT SUM(Fat) FROM " +allfood.TABLE+ " WHERE " +KEY_Date+"='"+date+"'";

此行

应该是

我该如何解决?

推荐答案

1)不要在字符串中添加文字allfood对象. SQL无法解释Java对象.

1) Don't add a literal allfood object to a String. SQL can't interpret a Java object.

该方法应为以下任意一种，因为allfood是整个对象，因此确实需要它作为参数.并将其命名为date简直令人困惑.

The method should be any of the following because allfood is the whole object, you do need it as the parameter. And naming it as date is simply confusing.

• totalFat(Date date)
• totalFat(String date)
• totalFat(Calendar date)
• totalFat(int year, int month, int dayOfMonth)

• totalFat(Date date)
• totalFat(String date)
• totalFat(Calendar date)
• totalFat(int year, int month, int dayOfMonth)

2)不，它确实不应该，因为 Sqlite不支持该日期格式.此外，在前面加上DATE_只是在浪费数据库中的存储空间.

2) No, it really shouldn't because Sqlite does not support that format of dates. Additionally, pre-pending DATE_ is just wasting storage in your database.

3)请不要使用此

date= year +""+ month +""+ dayOfMonth

构建一个Calendar对象，并使用SimpleDateFormat正确获取日期格式的字符串.

Build a Calendar object and use SimpleDateFormat to correctly get a date formatted string.

使用上面的最后一个选项，您将拥有这样的东西

using the last option above, you'd have something like this

SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd");
Calendar calendar = Calendar.getInstance();
calendar.set(year, month, dayOfMonth);
String queryForDate = fmt.format(calendar.getTime());
// db.query(TABLE_NAME, null, new String[] {...  // TODO: Complete this

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