UIImage 检测触摸和拖动 [英] UIImage detecting touch and dragging

问题描述

这是一个相当常见的问题，我有几个答案，而且我快到了.我有一个按钮，按下时会创建一个图像(代码如下)

Fairly common question this, to which I have a few answers and I'm nearly there. I have a button which when pressed, will create an image (code as follows)

(numImages 在加载时设置为零，并用作创建的所有图像的标签号的计数)

(numImages is set on load to ZERO and is used as a count up for the tag numbers of all images created)

UIImage *tmpImage = [[UIImage imageNamed:[NSString stringWithFormat:@"%i.png", sender.tag]] retain];
UIImageView *myImage = [[UIImageView alloc] initWithImage:tmpImage];

numImages += 1;

myImage.userInteractionEnabled = YES;
myImage.tag = numImages;
myImage.opaque = YES;
[self.view addSubview:myImage];
[myImage release];

然后我有一个 touchesBegan 方法，它会检测触摸的内容.我需要它做的是允许用户拖动新创建的图像.它几乎可以工作，但是当您拖动它时，图像会在整个地方闪烁.我可以访问您单击的图像，因为我可以得到它的标签，但我不能很好地拖动它.

I then have a touchesBegan method which will detect what's touched. What I need it to do is to allow the user to drag the newly created image. It's nearly working, but the image flickers all over the place when you drag it. I can access the image which you click on as I can get it's TAG, but I just cannot drag it nicely.

- (void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {

    UITouch *touch = [[event allTouches] anyObject];
    CGPoint location = [touch locationInView:touch.view];

    if (touch.view.tag > 0) {
        touch.view.center = location;
    }

    NSLog(@"tag=%@", [NSString stringWithFormat:@"%i", touch.view.tag]);

}

- (void) touchesMoved:(NSSet *)touches withEvent: (UIEvent *)event {
    [self touchesBegan:touches withEvent:event];
}

它的工作原理是，当我单击它们时，我会为每个图像获得标签的输出.但是当我拖动时，它会闪烁……有什么想法吗?

It works, in that I get an output of the tag for each image as I click on them. But when I drag, it flashes... any ideas?

推荐答案

回答我自己的问题 - 我决定创建一个类来处理我放置在视图上的图像.

In answer to my own question - I decided to create a class for handling the images I place on the view.

如果有人感兴趣，请编码....

Code if anyone's interested....

可拖动的.h

#import <Foundation/Foundation.h>
@interface Draggable : UIImageView {
    CGPoint startLocation;
}
@end

可拖动的.m

#import "Draggable.h"
@implementation Draggable

- (void) touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event {
    // Retrieve the touch point
    CGPoint pt = [[touches anyObject] locationInView:self];
    startLocation = pt;
    [[self superview] bringSubviewToFront:self];
}
- (void) touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event {
    // Move relative to the original touch point
    CGPoint pt = [[touches anyObject] locationInView:self];
    CGRect frame = [self frame];
    frame.origin.x += pt.x - startLocation.x;
    frame.origin.y += pt.y - startLocation.y;
    [self setFrame:frame];
}
@end

然后叫它

UIImage *tmpImage = [[UIImage imageNamed:"test.png"] retain];
UIImageView *imageView = [[UIImageView alloc] initWithImage:tmpImage];

CGRect cellRectangle;
cellRectangle = CGRectMake(0,0,tmpImage.size.width ,tmpImage.size.height );
UIImageView *dragger = [[Draggable alloc] initWithFrame:cellRectangle];
[dragger setImage:tmpImage];
[dragger setUserInteractionEnabled:YES];

[self.view addSubview:dragger];
[imageView release];
[tmpImage release];

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