如何在Xcode中跟踪多个触摸 [英] How to track multiple touches in Xcode
问题描述
最近我正在创建一个可以同时拖动多个对象的应用程序。我曾尝试使用 UIPanGestureRecognizer
来获取手指触摸的坐标,但我不知道哪个触摸属于哪个手指。
Recently I'm making an app that can drag multiple objects at the same time. I had tried to use UIPanGestureRecognizer
to get the coordinates of finger touches, but I couldn't know which touch belongs to which finger.
我需要支持四个手指同时平移而不会使用Objective-C相互干扰。
I need to support four fingers panning simultaneously without interfering with each other using Objective-C.
我有搜索了一段时间的洗液,但他们显示的答案对我不起作用。任何帮助将不胜感激。
I had searched for the soulution for a while, but the answers they show didn't work for me. Any help would be appreciated.
推荐答案
我在相当长的一段时间内遇到了同样的问题并最终解决了它。以下是我的 DrawView.m
中的代码,它是 UIView
的子类,能够支持使用图纸 drawRect:
。
I've struggled with the same problem for quite a long time and finally solved it. The following is the code in my DrawView.m
, which is a subclass of UIView
that is able to support drawings using drawRect:
.
#import "DrawView.h"
#define MAX_TOUCHES 4
@interface DrawView() {
bool touchInRect[MAX_TOUCHES];
CGRect rects[MAX_TOUCHES];
UITouch *savedTouches[MAX_TOUCHES];
}
@end
@implementation DrawView
-(id)initWithCoder:(NSCoder *)aDecoder {
self = [super initWithCoder:aDecoder];
if (self) {
// Initialization code
self.multipleTouchEnabled = YES;
for (int i=0; i<MAX_TOUCHES; i++) {
rects[i] = CGRectMake(200, 200, 50 ,50);
savedTouches[i] = NULL;
touchInRect[i] = false;
}
}
return self;
}
- (void)drawRect:(CGRect)rect {
// Drawing code
[[UIColor blueColor] set];
CGContextRef context = UIGraphicsGetCurrentContext();
for (int i=0; i<MAX_TOUCHES; i++) {
CGContextFillRect(context, rects[i]);
CGContextStrokePath(context);
}
}
#pragma mark - Handle Touches
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
NSArray *allTouches = [touches allObjects];
for (int i=0; i<[allTouches count]; i++) {
UITouch *touch = allTouches[i];
CGPoint newPoint = [touch locationInView:self];
for (int j=0; j<MAX_TOUCHES; j++) {
if (CGRectContainsPoint(rects[j], newPoint) && !touchInRect[j]) {
touchInRect[j] = true;
savedTouches[j] = touch;
break;
}
}
}
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
NSArray *allTouches = [touches allObjects];
for (int i=0; i<[allTouches count]; i++) {
UITouch *touch = allTouches[i];
CGPoint newPoint = [touch locationInView:self];
for (int j=0; j<MAX_TOUCHES; j++) {
if (touch == savedTouches[j]) {
rects[j] = [self rectWithSize:rects[j].size andCenter:newPoint];
[self setNeedsDisplay];
break;
}
}
}
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
NSArray *allTouches = [touches allObjects];
for (int i=0; i<[allTouches count]; i++) {
UITouch *touch = allTouches[i];
for (int j=0; j<MAX_TOUCHES; j++) {
if (touch == savedTouches[j]) {
touchInRect[j] = false;
savedTouches[j] = NULL;
break;
}
}
}
}
- (CGRect)rectWithSize:(CGSize)size andCenter:(CGPoint)point {
return CGRectMake(point.x - size.width/2, point.y - size.height/2, size.width, size.height);
}
@end
我设置 MAX_TOUCHES
为4,因此屏幕上会有四个对象。这个的基本概念是在 touchesBegan时将每个
被调用,稍后当 UITouch
ID存储在 savedTouches
数组中: : touchesMoved ::
调用时,将每个ID与屏幕上的触摸进行比较。
I set the MAX_TOUCHES
as 4, so there will be four objects on the screen. The basic concept of this is to store each UITouch
ID in the savedTouches
array when touchesBegan::
is called, and later compare each ID with the touches on screen when touchesMoved::
called.
只需将代码粘贴到 .m
文件中即可。样本结果如下所示:
Just paste the code into your .m
file and it'll work. The sample result is shown here:
希望这有助于:)
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