I want to find the pressure of the touch. I just don't know how to accomplish that result with out jailbreaking it and getting the raw touch data. Does anyone know How I would do this?
You cannot get the pressure from the SDK nor undocumented methods. However you can detect the size of touch with undocumented methods.
In the GSEvent, which is a lower-level representation of UIEvent, there is a structure known as GSPathInfo with members:
typedef struct GSPathInfo {
unsigned char pathIndex; // 0x0 = 0x5C
unsigned char pathIdentity; // 0x1 = 0x5D
unsigned char pathProximity; // 0x2 = 0x5E
CGFloat pathPressure; // 0x4 = 0x60
CGFloat pathMajorRadius; // 0x8 = 0x64
CGPoint pathLocation; // 0xC = 0x68
GSWindowRef pathWindow; // 0x14 = 0x70
} GSPathInfo;
We notice that there is a pathPressure
and pathMajorRadius
. I can assure you the pressure member is useless – it always gives 0. However pathMajorRadius
does contain meaningful information – it gives the major radius of the touch in millimeters. You can therefore give an extremely rough estimation if it's a heavy touch or light touch from the radius.
-(void)touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event {
GSEventRef gsevent = [event _gsEvent];
GSPathInfo first_touch = GSEventGetPathInfoAtIndex(gsevent, 0);
if (first_touch.pathMajorRadius >= 9)
NSLog(@"huge (heavy) touch");
else
NSLog(@"little (light) touch");
}
Let me warn you again this is undocumented and you should not use it in AppStore apps.
Edit: On 3.2 and above the pathMajorRadius
of a GSPathInfo is also available as an undocumented property in UITouch:
@property(assign, nonatomic, setter=_setPathMajorRadius:) CGFloat _pathMajorRadius;
so the code above could be rewritten using pure Objective-C:
-(void)touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event {
UITouch* any_touch = [touches anyObject];
if (any_touch._pathMajorRadius >= 9)
NSLog(@"huge (heavy) touch");
else
NSLog(@"little (light) touch");
}