Question

可能重复：
Drawing on the iPhone in objective c

我写过这个......

在.h文件中：

#import <UIKit/UIKit.h>

@interface DrawView : UIView {
    CGPoint gestureStartPoint,currentPosition;
    CGContextRef c;
    UIBezierPath *currentPath;
}

@property(nonatomic,retain)UIBezierPath *currentPath;

@end

在.m文件中：

#import "DrawView.h"

@implementation DrawView

@synthesize currentPath;

- (id)initWithFrame:(CGRect)frame {
    [self drawRect:CGRectMake(0, 0, 320, 480)];
    self = [super initWithFrame:frame];
    if (self) {
        currentPath = [[UIBezierPath alloc]init];
        currentPath.lineWidth=3;
    }
    return self;
}




- (void)drawRect:(CGRect)rect {
    [[UIColor redColor] set];
    [currentPath strokeWithBlendMode:kCGBlendModeNormal alpha:1.0];
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [touches anyObject];
    currentPosition = [touch locationInView:self]; 
    [currentPath addLineToPoint:(currentPosition)];
    [self setNeedsDisplay];
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [touches anyObject];
    gestureStartPoint = [touch locationInView:self];
    [currentPath moveToPoint:(gestureStartPoint)];
}

- (void)dealloc {
    [super dealloc];
}


@end

我想让用户在iPhone屏幕上绘制图像，然后将该图像用于游戏......但这并没有画任何东西......

Answer 1

这是因为您的currentPath未分配。如果您实例化资源[UIView initWithFrame：]中的视图将永远不会被调用。实现[UIView initWithCoder：]并在那里分配它。

- (void)commonInit
{
    currentPath = [[UIBezierPath alloc] init];
    currentPath.lineWidth=3;
}

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self)
    {
        [self commonInit];
    }
    return self;
}

- (id)initWithCoder:(NSCoder*)aDecoder
{
    self = [super initWithCoder:aDecoder];
    if (self)
    {
        [self commonInit];
    }
    return self;
}

或者，如果它是零，你可以在touchesBegan中创建路径。

- (UIBezierPath*)currentPath
{
    if (currentPath = nil)
    {
        currentPath = [[UIBezierPath alloc] init];
        currentPath.lineWidth=3;
    }
    return currentPath;
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];
    gestureStartPoint = [touch locationInView:self];

    [[self currentPath] moveToPoint:(gestureStartPoint)];
}

但是，代码中存在一些问题。

在self = [super initWithFrame：frame]之前调用[self drawRect：CGRectMake（0,0,320,480）]。你不能在那里调用任何方法。您只能在
中编写代码
if（self！= nil） { //你的代码 }
currentPath泄漏。以dealloc发布。
永远不要直接调用drawRect。改为调用[UIView setNeedsDisplay]。

在目标c中绘制iPhone

1 个答案: