重要的：
我已经发现了问题，但版主出于某种原因删除了它：
我尝试直接从按钮调用该函数，而不是在视图控制器中使用该函数。
我仍然不完全理解为什么它不起作用，所以我会接受这个问题的任何答案。
主帖
按下 UIButton 后，我正在尝试做一些绘图。我的绘图是在 UIView 的子类中完成的。我的 ViewController 中有这个子类的实例。我的 ViewController 中还有一个 UIButton 调用子类的函数。在我调用的那个函数中
[self setNeedsDisplay];
当我加载我的应用程序时，drawRect 在视图加载时被调用一次，但永远不会再次调用，尽管每次按下按钮时都会调用 setNeedsDisplay。我查看了许多类似的问题，但没有找到解决方案。
我将在这里发布我的所有代码：
AEViewController.h
#import <UIKit/UIKit.h>
#import "AEGraphView.h"
@interface AEViewController : UIViewController{
IBOutlet AEGraphView *theView;
}
-(IBAction)updateAEGraphView:(id)sender;
@end
AEViewController.m
#import "AEViewController.h"
@interface AEViewController ()
@end
@implementation AEViewController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
theView = [[AEGraphView alloc] init];
}
- (void)viewDidUnload
{
[super viewDidUnload];
// Release any retained subviews of the main view.
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone) {
return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}
else {
return YES;
}
}
-(IBAction)updateAEGraphView:(id)sender{
[theView UpdateView];
}
@end
AEGraphView.h
#import <UIKit/UIKit.h>
@interface AEGraphView : UIView{
CGContextRef mainContext;
int power;
int multiplier;
}
-(void)prepareGraphics;
- (void) drawLineFrom:(CGPoint)p1 To:(CGPoint)p2;
-(void)UpdateView;
@end
AEGraphView.m
#import "AEGraphView.h"
@implementation AEGraphView
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
return self;
}
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
[self prepareGraphics];
// Drawing code
NSLog(@"called");
if (power == 0) {
[self drawLineFrom:CGPointMake(100,100) To:CGPointMake(-50, -2)];
}
else {
[self drawLineFrom:CGPointMake(0, 0) To:CGPointMake(150, 150)];
}
[super drawRect:rect];
}
-(void)prepareGraphics{
mainContext = UIGraphicsGetCurrentContext();
CGContextSetShouldAntialias(mainContext, TRUE);
CGContextSetLineWidth(mainContext, 2);
CGContextSetLineCap(mainContext, kCGLineCapRound);
}
- (void) drawLineFrom:(CGPoint)p1 To:(CGPoint)p2{
NSLog(@"%f,%f to %f,%f", p1.x,p1.y,p2.x,p2.y);
// Begin a path.
CGContextBeginPath(mainContext);
// Add a line to the path.
CGContextMoveToPoint(mainContext, p1.x, p1.y);
CGContextAddLineToPoint(mainContext, p2.x, p2.y);
// Stroke and reset the path.
CGContextStrokePath(mainContext);
}
-(void)UpdateView{
if (power == 0) {
power = 1;
}
else {
power = 0;
}
[self setNeedsDisplay];
}
@end