Flutter-TextFormField的异步验证器 [英] Flutter - Async Validator of TextFormField
问题描述
在我的应用程序中,用户必须在textformfield中插入一个名称。当用户编写查询时,应该对数据库进行查询,该查询控制名称是否已经存在。该查询返回名称存在的次数。到现在,按一下按钮我就可以做到这一点。
In my app the user has to insert a name in the textformfield. While the user is writing a query should be made to the database, that controls if the name already exists. This query returns the number of how many times the name exists. Till now I am able to make it when I press a button.
这是返回名称计数的函数:
This is the function that returns the count of the names:
checkRecipe(String name) async{
await db.create();
int count = await db.checkRecipe(name);
print("Count: "+count.toString());
if(count > 0) return "Exists";
}
这是TextFormField,应该异步验证:
And this is the TextFormField, which should be validated async:
TextField(
controller: recipeDescription,
decoration: InputDecoration(
hintText: "Beschreibe dein Rezept..."
),
keyboardType: TextInputType.multiline,
maxLines: null,
maxLength: 75,
validator: (text) async{ //Returns an error
int count = await checkRecipe(text);
if (count > 0) return "Exists";
},
)
代码错误是:
自变量类型Future无法分配给参数类型
字符串
The argument type Future can't be assigned to the parameter type String
我确实知道错误的含义。但是我不知道该如何解决。
I do know what the error means. But I do not know how to work around could look like. It would be awesome if somebody could help me.
我的代码现在看起来像这样:
My Code looks now like this:
//My TextFormField validator
validator: (value) => checkRecipe(value) ? "Name already taken" : null,
//the function
checkRecipe<bool>(String name) {
bool _recExist = false;
db.create().then((nothing){
db.checkRecipe(name).then((val){
if(val > 0) {
setState(() {
_recExist = true;
});
} else {
setState(() {
_recExist = false;
});
}
});
});
return _recExist;
}
推荐答案
也许您可以运行 async
使用 onChange
处理程序进行检查,并设置一个本地变量来存储结果。
Perhaps you could run your async
check using the onChange
handler and set a local variable to store the result.
类似的东西:
TextFormField(
controller: recipeDescription,
decoration: InputDecoration(hintText: "Beschreibe dein Rezept..."),
keyboardType: TextInputType.multiline,
maxLines: null,
maxLength: 75,
onChanged: (text) async {
final check = await checkRecipe(text);
setState(() => hasRecipe = check);
},
validator: (_) => (hasRecipe) ? "Exists" : null,
)
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