Question

我尝试过多次修改我的代码，但仍然无法将变量从UIViewController传递给UIView，变量总是返回（null）。

// BPGraphView.h

   @interface BPGraphView : UIView

    @property (nonatomic, retain) NSString *test;

    @end

// BPGraphView.m

#import "BPGraphView.h"

@implementation BPGraphView
@synthesize test;

- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];

    NSLog(@"test %@",test);

    if (self) {
        // Initialization code
    }
    return self;
}


- (void)drawRect:(CGRect)rect
{    

    NSLog(@"draw %@", test); // always return (null)

    if ([test isEqual:@"something"])  {
    [self drawOutLine];
    }
}

@end

// BloodPressureViewController.m

- (void)viewDidLoad
{
BPGraphView * graphview=[[BPGraphView alloc] init];
graphview.test = @"something";
}

Answer 1

在您的代码中：

- (void)viewDidLoad
{
BPGraphView * graphview=[[BPGraphView alloc] init];
graphview.test = @"dd";
}

运行graphview完成后，变量viewDidLoad基本上被销毁。永远不会有机会运行drawRect。

现在的问题是如何在UIViewController中定义BPGraphView的实例变量。最简单的方法是将BPGraphView添加到视图的xib文件中，并链接到UIViewController中的IBOutlet。通过这种方式，您应该能够分配到测试

@IBOutlet BPGraphView graphview;


- (void)viewDidLoad
{
    graphview.test = @"dd";
}

Answer 2

如果不设置框架，则不会调用drawRect。

BPGraphView * graphview=[[BPGraphView alloc] initWithFrame:CGRectMake(0, 0, 200, 200)];
graphview.test = @"something";
[self.view addSubview:graphview];

Answer 3

我试过这个，它运行良好，在你的代码中，drawRect不被称为

 BPGraphView * graphview=[[BPGraphView alloc] init];
    graphview.test = @"dd";
    [graphview drawRect:CGRectMake(0, 0, 0, 0)];

将变量从UIViewController传递给UIView

3 个答案: