IOS，如何将自定义SelectionIndicator添加到UIPickerView？

Question

我想添加一个复选标记，而不是 UIPickerView 的默认 SelectionIndicator。

我正在尝试将图像添加为子视图，

 UIImageView * checkMark = [[[UIImageView alloc] initWithFrame:CGRectMake(0, 102, 13, 13)] autorelease];
[checkMark setImage:[UIImage imageNamed:@"pickerChechmark.png"]];
checkMark.layer.borderColor = [[UIColor redColor] CGColor];
checkMark.layer.borderWidth = 2;
 [picker addSubview:checkMark];

但它已添加到选择器后面，请参阅下图。

x =0 时的图像 1，x =5 时的图像 2，x = 10 时的图像 3 （复选标记的 x 位置） 另请参阅左上角的红色矩形，以澄清我的问题

UIView * redblock = [[[UIView alloc] initWithFrame:CGRectMake(0, -20, 50, 40)] autorelease];
redblock.backgroundColor = [UIColor redColor];
[picker addSubview:redblock];
[picker bringSubviewToFront:redblock];

如何解决此问题？

Answer 1

我还需要自定义选择指示器，因为我使用高于标准指示器的自定义视图（它们类似于表视图单元格）填充选择器。

我最初尝试指定一个半透明视图在创建时叠加到 UIPickerView 上，但得到了相同的结果。在跟踪时，我注意到选择器视图在创建时还没有子视图，这可能是自定义选择指示器被发送到视觉层次结构后面的原因。

我的解决方案包括在第一次调用委托方法 pickerView:viewForRow:forComponent:reusingView: 时为选择指示器指定自定义视图。那时，UIPickerView 已准备好其所有子视图，并且我的新自定义视图已正确附加在其余视图之上。如果您不需要对内容使用自定义视图，则可以使用其他数据源方法 pickerView:titleForRow:forComponent: 执行相同操作。

以下代码片段显示了我的解决方案。

注意：如果委托方法服务于多个 UIPickerView，则需要以不同的方式处理该标志； SLPickerCell 是我自己的单元格类，只是 UIView 的子类。

- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view
{
    SLPickerCell        *pickerCell = nil;
    NSArray             *topLevelObjects;
    const CGFloat       kPickerBorderSize = 10;
    const CGFloat       kIndicatorVerticalMargin = 2;

    // if this is the first time we enter the function, add selection indicator view on top of everything else
    if ( ![self pickerSelectionIndicatorInstalled] )
    {
        UIView          *customSelectionIndicator;
        CGRect          selectionIndicatorFrame;
        CGRect          pickerViewFrame;

        pickerViewFrame = [pickerView frame];

        // Create and add a custom selection indicator (a superimposed semi-transparent view)
        // Use the cell height as reference for the height of the indicator
        selectionIndicatorFrame = CGRectMake(kPickerBorderSize, (pickerViewFrame.size.height - ( [SLPickerCell height] + kIndicatorVerticalMargin )) / 2, pickerViewFrame.size.width - (2 * kPickerBorderSize), ( [SLPickerCell height] + kIndicatorVerticalMargin ));

        customSelectionIndicator = [[UIView alloc] initWithFrame:selectionIndicatorFrame];
        [customSelectionIndicator setUserInteractionEnabled:NO];
        [customSelectionIndicator setAlpha:0.25];
        [customSelectionIndicator setBackgroundColor:[UIColor lightGrayColor]];
        [[customSelectionIndicator layer]setBorderWidth:1.0];
        [[customSelectionIndicator layer]setBorderColor:[[UIColor darkGrayColor]CGColor]];          

        // Add the indicator on top of the picker
        [pickerView addSubview:customSelectionIndicator];

        // set the flag; remember to reset it upon creation of a new UIPickerView
        [self setPickerSelectionIndicatorInstalled:YES];
    }
    // [...]

Answer 2

试试这个代码，我在我的选择器视图中添加了复选标记和标签

- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)theView{

    UIView *pickerviewtemp=[[UIView alloc] initWithFrame:CGRectZero];

    UILabel *lbl=[[UILabel alloc] initWithFrame:CGRectMake(-105, -15, 240, 30)];
    [lbl setBackgroundColor:[UIColor clearColor]];
    [lbl setText:[self.folderNameArray objectAtIndex:row]];
    [lbl setFont:[UIFont boldSystemFontOfSize:20]];
    [pickerviewtemp addSubview:lbl];
    UIImageView *imgView=[[UIImageView alloc]initWithFrame:CGRectMake(-130, -5, 15, 15)];
if ([self.folderCheckArray containsObject:[NSString stringWithFormat:@"%d",row]]) {
        [imgView setImage:[UIImage imageNamed:@"tick.png"]];
    }
    else {      
        [imgView setImage:nil];
    }   

    [pickerviewtemp addSubview:imgView];
    return pickerviewtemp;
}

Answer 3

尝试添加复选标记以查看自身，如下所示：

[self.view addSubview:checkMark];

您将不得不摆弄坐标，但您应该能够在选择器视图上看到它。