Dubsar is an open-source dictionary app by the same author that supports different themes (fonts, color schemes). A knob is used to select themes within the app. The theme changes as the knob rotates, including the theming of the generated discrete knob itself.
Dubsar is available for free on the App Store.
cpyn is an audio-player app by the same author inspired by the Spin tab in the demo apps here. Unlike the demo here, cpyn provides an array of audio features like equalization, reverb and cross fading. It also allows you to play in reverse and scratch records as they play.
Quite a few generated continuous knobs appear to adjust various audio settings. Unlike the demos here, the knob control is not used for the turntable, which is entirely built on OpenGL, not UIKit. Note that some settings support fine tuning via the vertical pan gesture vs. one-finger rotation.
Have an app in the App Store using this knob control? Get in touch, and I'll post your screenshot here.
This is a generic, reusable knob control you can insert into any application. You may provide custom knob images or use the customizable default images. The control animates rotation of the image in response to one of several configurable gestures from the user. The knob has a number of configurable modes:
- Linear return mode: Like a circular generalization of the UIPickerView control. Only certain discrete positions are allowed. The knob rotates to follow the user's gesture, but on release returns to an allowed position. The time scale for the return animation may be configured as a property of the control.
- Wheel of Fortune mode: Like linear return, except for the animation after the user releases the knob. Only a narrow strip between each pair of segments is excluded, like the pegs on the rim of a carnival wheel. If the knob was released in one of those small excluded strips, it rotates just far enough to exit the excluded strip. Otherwise, the knob stays where the user leaves it. This mode is like continuous mode except for the behavior in the excluded strips and the availability of the positionIndex property.
- Continuous mode: Like a circular generalization of the UISlider control or a potentiometer/volume knob. Often used with min. and max. angles, but can also be circular. Knob remains wherever the user leaves it and can attain any value between the min. and max. equally.
- Rotary dial mode: Like an old rotary telephone dial.
It responds to four different gestures, depending on the value of a property:
- One-finger rotation: Custom gesture recognition. The spot under your finger tracks your touch as you rotate the knob.
- Two-finger rotation: The standard iOS two-finger rotation gesture.
- Vertical pan: Drag your finger up or down to increase or decrease the value of the position property, respectively.
- Tap: Select a position for the knob or dial a number in rotary dial mode by tapping.
The knob control can be circular, permitting the user to rotate it all the way around, or it can have a min. and max. angle in continuous and discrete modes.
The control is distributed as a single pair of files (IOSKnobControl.h and IOSKnobControl.m in this directory), which you can simply drop into your project. Without any externally supplied image, the control generates appropriate, customizable images in all modes. It can also accept externally supplied images. You can use any of the images in the demo project here or supply your own.
The knob control and all images must be square. Images will usually be circles or regular polygons, with a transparent background or a solid one that matches the view behind it. However, the aspect ratio must be 1:1. The effect of the animation is circular rotation. This only works if the control is square. You can produce other effects, for example, by partially clipping a square control or using an oblong background. But the control itself always has to be square.
The control honors the enabled property. That is, if you set enabled to NO, it enters the UIControlStateDisabled and stops responding to user input. If specified, a disabled image is displayed instead of the normal image. Even when disabled, the control's position may always be specified at any time programmatically, with or without animation. With appropriate images, a disabled knob control may be used as a dial view to display a numeric value.
There are two demo apps, one in Objective-C, in the KnobControlDemo-ObjC subdirectory, and one in Swift, in the KnobControlDemo-Swift subdirectory. Both exercise the same functionality using the same Objective-C knob control. Both demos contain projects that can be used to build a simple demo app to exercise the different modes of the control and provide examples of use. Both use storyboards and autolayout and so require iOS 6.0 or greater. The control works on 64-bit devices. (Swift requires both iOS 7.0 or greater on the device or simulator and Xcode6-Beta4 or later to compile Swift.)
The control itself, the IOSKnobControl class, may be compiled down to iOS 5.0, but the demo projects will not build if the iOS Deployment Target is set below 6.0 for reasons that have nothing to do with the control. The control uses ARC, so it cannot be used below iOS 5.0 without modification. It has not been tested below iOS 6.1, however, and there may be problems there that have not yet been discovered.
See iOS Knob Control and Violation.
All API documentation can be found in IOSKnobControl.h. Browsable HTML documentation generated from this source is checked into this repository in the doc/html subdirectory. See doc/html/index.html.
The HTML documentation here is built with Appledoc. If you install Appledoc (from a distro like Homebrew or MacPorts or from source; see https://github.com/tomaz/appledoc#quick-install) you can use the build-appledoc script in this directory to update the HTML if it is out of date and install the documentation as a docset that you can view with XCode.
Stable releases are indicated by tags in the repo (e.g., 1.1.0.2) and notes in the ChangeLog. When in doubt, use the last stable release tag as opposed to the HEAD revision. If no development has been done since the last release, those may be the same revision.
Known bugs, planned enhancements and other issues are tracked on Github.
Some images (the nice ones) courtesy of Mike Calvert (@bloodymonster).
The software and media here are available under The BSD 3-Clause License:
Copyright (c) 2013-14, Jimmy Dee
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