昨天，在有关适用于iPad 2的新Garageband的演示中，Apple演示了一个有趣的功能:使用加速度计检测抽头压力。 (请参阅Garageband page上的鼓部分。)
我想知道如果iPad平放在桌子上怎么办？没有运动，没有可测量的加速度，不是吗？
最佳答案
一些好的答案。这是一些工作代码。我将其实现为UIGestureRecognizer的子类，以便您可以将其放入并将其附加到UIView或UIButton。一旦触发，它将“压力”设置为介于0.0f和2.0f之间的 float 。您可以选择设置识别所需的最小和最大压力。享受。
//
// CPBPressureTouchGestureRecognizer.h
// PressureSensitiveButton
//
// Created by Anthony Picciano on 3/21/11.
// Copyright 2011 Anthony Picciano. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
// OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
// IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
// NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
// THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
#import <UIKit/UIKit.h>
#define CPBPressureNone 0.0f
#define CPBPressureLight 0.1f
#define CPBPressureMedium 0.3f
#define CPBPressureHard 0.8f
#define CPBPressureInfinite 2.0f
@interface CPBPressureTouchGestureRecognizer : UIGestureRecognizer <UIAccelerometerDelegate> {
@public
float pressure;
float minimumPressureRequired;
float maximumPressureRequired;
@private
float pressureValues[30];
uint currentPressureValueIndex;
uint setNextPressureValue;
}
@property (readonly, assign) float pressure;
@property (readwrite, assign) float minimumPressureRequired;
@property (readwrite, assign) float maximumPressureRequired;
@end
//
// CPBPressureTouchGestureRecognizer.h
// PressureSensitiveButton
//
// Created by Anthony Picciano on 3/21/11.
// Copyright 2011 Anthony Picciano. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
// OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
// IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
// NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
// THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
#import <UIKit/UIGestureRecognizerSubclass.h>
#import "CPBPressureTouchGestureRecognizer.h"
#define kUpdateFrequency 60.0f
#define KNumberOfPressureSamples 3
@interface CPBPressureTouchGestureRecognizer (private)
- (void)setup;
@end
@implementation CPBPressureTouchGestureRecognizer
@synthesize pressure, minimumPressureRequired, maximumPressureRequired;
- (id)initWithTarget:(id)target action:(SEL)action {
self = [super initWithTarget:target action:action];
if (self != nil) {
[self setup];
}
return self;
}
- (id)init {
self = [super init];
if (self != nil) {
[self setup];
}
return self;
}
- (void)setup {
minimumPressureRequired = CPBPressureNone;
maximumPressureRequired = CPBPressureInfinite;
pressure = CPBPressureNone;
[[UIAccelerometer sharedAccelerometer] setUpdateInterval:1.0f / kUpdateFrequency];
[[UIAccelerometer sharedAccelerometer] setDelegate:self];
}
#pragma -
#pragma UIAccelerometerDelegate methods
-(void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration {
int sz = (sizeof pressureValues) / (sizeof pressureValues[0]);
// set current pressure value
pressureValues[currentPressureValueIndex%sz] = acceleration.z;
if (setNextPressureValue > 0) {
// calculate average pressure
float total = 0.0f;
for (int loop=0; loop<sz; loop++) total += pressureValues[loop];
float average = total / sz;
// start with most recent past pressure sample
if (setNextPressureValue == KNumberOfPressureSamples) {
float mostRecent = pressureValues[(currentPressureValueIndex-1)%sz];
pressure = fabsf(average - mostRecent);
}
// caluculate pressure as difference between average and current acceleration
float diff = fabsf(average - acceleration.z);
if (pressure < diff) pressure = diff;
setNextPressureValue--;
if (setNextPressureValue == 0) {
if (pressure >= minimumPressureRequired && pressure <= maximumPressureRequired)
self.state = UIGestureRecognizerStateRecognized;
else
self.state = UIGestureRecognizerStateFailed;
}
}
currentPressureValueIndex++;
}
#pragma -
#pragma UIGestureRecognizer subclass methods
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
setNextPressureValue = KNumberOfPressureSamples;
self.state = UIGestureRecognizerStatePossible;
}
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
self.state = UIGestureRecognizerStateFailed;
}
- (void)reset {
pressure = CPBPressureNone;
setNextPressureValue = 0;
currentPressureValueIndex = 0;
}
@end
关于ios - 使用加速度计检测水龙头压力强度，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/5179426/