ScrollPicker: A better Android NumberPicker

This is a demo project to showcase and test ScrollPicker, a customizable and data-bindable UI element for android that picks an item from a collection. It can work with an arbitrary Collection of items. It does not have the bugs of NumberPicker and it's much more convenient to use.
If you'd like to clone only the ScrollPicker and not all this demo project to change it for your needs, here is the droid you're looking for.

Functionality

Extras not available in NumberPicker

Fixes NumberPicker bugs

• When NumberPicker's height is too short, it renders the separator lines on top of the first and third items.
  Whereas ScrollPicker's separators always stay where they should be. They know their place. Good doggies.
• There's also a couple of other bugs I saw in stackoverflow questions. ScrollPicker does not have them.

ScrollPicker is customizable

You can set

• How many items should it display at a time, it's not always only 3 like in the case of NumberPicker.
• Text size and color for the items, with a possibility to set different values of these for the selected item.
• Selector style: classic 2 lines, rectangular or filled rectangle.
• Selector line width. If you set a 0 width, the selector won't be displayed.
• Bold text.

Ease of use

• You can set an arbitrary JVM Collection (List, Set, etc) with setItems(..). In case of Ints the value you'll get back will be the selected int item itself, in the other cases it will be the item's index and the items will be displayed with toString().
  So for example all of these work when you give them to setItems(..):

    val numbers: List< Int > = listOf(-5, 3, -15, 7, 4, -50, 2, 70)
    val dates: ArrayList< Date > = arrayListOf(Date(), Date(), Date())
    val colors: Set< String > = setOf("red", "green", "blue")

You can data-bind on these collections too if you wrap them into ObservableField thanks to

    public void setItems( final ObservableField< ? extends Collection > items )

Or you can use setItemsIntRange( int fromInclusive, int toInclusive ) to set int ranges more easily.

• A Collection of integers can have arbitrary values and it's not limited to only a range of positives as with NumberPicker. No more conversion to strings and giving up of easy handling of int values is necessary.
• No setMinValue and setMaxValue call is necessary. Just set your Collection.
• Uses AutoResizeTextView so texts that would otherwise be too long are also displayed in a decent way.
• Scrolls much more conveniently than NumberPicker. You can scroll 300 items in one big velocity motion.
• Using the one-item-up or one-item-down functionality - by tapping above or below the area with the selector - is more comfy: when you do it multiple times without waiting until the selection animation is finished all taps are accounted for and it will go down or up in the list as many times as you tapped (instead of just acting weird in case of NumberPicker), and you can use it while scrolling too.

Data binding! - get automatic syncronization with your ViewModel data

• Value is two-way data-bindable.
• isEnabled is data-bindable.
• The Collection of items is data-bindable, but you can only set it from code, not from xml due to lack of possible xml attribute types.
  In your viewmodel you could have

    var shownList: ObservableField< Collection< Any > > = ObservableField()
    val numbers: ArrayList< Int > // here's your data from the model
    shownList.set(numbers)

then in your view layer (fragment, activity, etc):

    scrollPicker.setItems(viewModel.shownList)

Stuff that NumberPicker can do but ScrollPicker can't

• You can't have the items displayed in a loop (like as with wrapSelectorWheel in NumberPicker).
• The user can't edit the items from the UI.

Error handling

ScrollPicker throws a RuntimeException on setting an invalid value that isn't in the collection.

JavaDoc page

Usage

In module build.gradle:

repositories {
    mavenCentral()
    ...
}
...

dependencies {
    implementation "com.github.tomeees:scrollpicker:1.7.5"
    ...
}

Donation

If you found it useful, please consider donating. Thank you!

Cloning and trying out this project

This repository has a subrepo in the form of ScrollPicker, which is a module of the Android project and resides in the 'scroll_picker' folder. Follow these steps to clone this project:

1. git clone https://github.com/tomeeeS/ScrollPickerDemo
2. change directory to ...ScrollPickerDemo/scroll_picker
3. execute the following command and notice the dot (.) at the end, which means to not make a top level folder with the project name ScrollPicker, but copy the code directly under the scroll_picker folder: git clone https://github.com/tomeeeS/ScrollPicker .

Dependencies

ScrollPicker (scroll_picker library module)

• Purely written in Java 7.
• Minsdk is 11.

The demo part (app module, it will Not be a dependency for you if you use ScrollPicker in your project)

• Written in kotlin
• Minsdk is 16.

Tests

• We set an int list to the picker, then perform scrolls on it. Between these scrolls, when it becomes stationary after it does the correction scroll to be in a perfect position selecting an item, we perform the checks on it. We check if the vertical scroll position is perfect (is divisible by the height of one item), if the value of the picker is correct and if the content description is correct (it's the selected item's displayed String 'value') for accessibility.
  Then we repeat this test after setting a string list to the picker.

Licence:

Apache-2.0 (do with it whatever you please)