Ios UIPickerView以编程方式选择第一行

有很多这样的问题，但我相信我的案例是独一无二的

我有一个pickerview，当在里面点击一个文本框时会弹出。用户在pickerview中选择他们的位置，并将其放入文本框中

打开pickerview时，滑块位于第一个元素上，但如果我单击“完成”按钮以最小化pickerview，则不会选择任何元素，即必须向下和向上滚动以选择第一个元素

我试过了

    [pickerView selectRow:0 inComponent:0 animated:YES];

和它的各种组合，但它只将滑块放在该元素上，而不是实际选择它

一些答案说在viewDidLoad方法中应用了上述代码，但不幸的是，我正在从web服务中提取位置数组，无法做到这一点

理想情况下，我想做这样的工作——用户在文本框中单击，pickerview会正常弹出，如果此时单击“完成”按钮，则会选择第一项

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提前谢谢

以下是您可以尝试的：

在@interface中设置一个var，类似于NSString*selectedString

在pickerView:titleForRow:forComponent:中初始化UIPickerView时，设置行0的标题时，请使用与行0标题相同的字符串设置selectedString。然后，在pickerView:didSelectRow:Incomonent:中，使用适当的字符串设置selectedString：

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {

    // Some stuff

    // Assuming "yourDataArray" contains your strings
    selectedString = [yourDataArray objectAtIndex:row];

}

然后，当您调用由按下“完成”按钮触发的方法时，使用selectedString设置文本

希望这对你有用

/为textfield创建一个iAction，事件编辑已开始，函数应检查字段是否为空，如下所示/

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我也有同样的问题。我的解决办法是：

-(void)textFieldDidBeginEditing:(UITextField *)textField
{
    // Only for the text field with the picker
    if (textField == self.yourTextField)
    {
        // Select the first row programmatically 
        [self.categoriesPicker selectRow:0 inComponent:0 animated:YES];
        // The delegate method isn't called if the row is selected programmatically
        [self pickerView:self.categoriesPicker didSelectRow:0 inComponent:0];
    }



}

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
    //Do all the stuff to populate the TextField

}

斯威夫特3+

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如果textfield不是空的，还需要设置一个条件。我们不必忘记textfield的委托。yourTextField.delegate=self

-(void)textFieldDidBeginEditing:(UITextField *)textField
{
    // Only for the text field with the picker
    if (textField == self.yourTextField)
    {
        // Select the first row programmatically 
        [self.categoriesPicker selectRow:0 inComponent:0 animated:YES];
        // The delegate method isn't called if the row is selected programmatically
        [self pickerView:self.categoriesPicker didSelectRow:0 inComponent:0];
    }



}

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
    //Do all the stuff to populate the TextField

}

-(void)textFieldDidBeginEditing:(UITextField *)textField
{
    // Only for the text field with the picker
    if (textField == self.yourTextField && [textField length]!=0)
    {
        // Select the first row programmatically 
        [self.categoriesPicker selectRow:0 inComponent:0 animated:YES];
        // The delegate method isn't called if the row is selected programmatically
        [self pickerView:self.categoriesPicker didSelectRow:0 inComponent:0];
    }



}

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
    //Do all the stuff to populate the TextField
}

func textFieldDidBeginEditing(_ textField: UITextField) {
    if textField == yourTextField{
        self.yourPickerView.selectRow(0, inComponent: 0, animated: true)
        self.pickerView(yourPickerView, didSelectRow: 0, inComponent: 0)
    }
}

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {

//Do all the stuff to populate the TextField

}