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

问题描述

相当常见的问题，我有几个答案，我几乎就在那里。我有一个按钮，当按下时，将创建一个图像（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设置加载到ZERO并用作标记的计数创建的所有图像的数量）

(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，可以检测触摸的内容。我需要它做的是允许用户拖动新创建的图像。它几乎正常工作，但拖动它时图像会闪烁不已。我可以访问你点击的图像，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];
}

它有效，因为我得到每个图像的标记输出为我点击它们。但是当我拖动时，它闪烁......任何想法？

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

在回答我自己的问题时 - 我决定创建一个用于处理我放在视图上的图像的类。

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

代码如果有人感兴趣....

Code if anyone's interested....

可拖动.h

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

Draggable.m

Draggable.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

并称之为

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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