Spinners are basically drop down menu which provides an easy way to select an item from a set of items. Spinner is used in Open Event Android to allow user select quantity of tickets as shown in the image above. This blog post will guide you on how its implemented in Open Event Android.
Add Spinner to the XML file
| <Spinner android:id=“@+id/orderRange” android:layout_width=“30dp” android:layout_height=“30dp” android:spinnerMode=“dialog” android:textSize=“@dimen/text_size_small” /> |
The above code spinnet will create a spinner type view with 30dp height and width, spinnerMode can be dialog or dropDown following are example spinner for both of the modes left being dialog type and right dropDown type.
(Image Source: Stack Overflow)
Set Up Adapter and Populate Data on Spinner
To show the list of acceptable Quantities for a Ticket, create an ArrayList of String and add all values from ticket.minOrder to ticket.maxOrder along with a zero option. Since ArrayList is of String and the values are integer they need to be converted to String using Integer.toString(i) method. Following code snippet will give you more understanding about it.
| val spinnerList = ArrayList<String>() spinnerList.add(“0”) for (i in ticket.minOrder..ticket.maxOrder) { spinnerList.add(Integer.toString(i)) } |
We will also need to set up an onItemSelectedListener to listen for Item Selections and override onItemSelected and onNothingSelected functions in it. Whenever an item is selected onItemSelected is called with arguments such as view, position of the selected item, id etc, these can be used to find the selected Quantity from the ArrayList of acceptable Quantities.
| itemView.orderRange.onItemSelectedListener = object : AdapterView.OnItemSelectedListener { override fun onItemSelected(parent: AdapterView<*>, view: View, pos: Int, id: Long) { itemView.order.text = spinnerList[pos] selectedListener?.onSelected(ticket.id, spinnerList[pos].toInt()) } override fun onNothingSelected(parent: AdapterView<*>) { } } |
Since Spinner is an Adapter Based view we need to create a SpinnerAdapter and attach it with the Spinner. If you want to create custom Spinners you would have to create a custom adapter for it along with a layout for its row elements or else one can use library-provided layout. Given below is the implementation for library-provided spinner row type. There are different options available for row type we are using R.layout.select_dialog_singlechoice because we need single selectable Quantity spinner along with Radio button for every ticket.
itemView.orderRange.adapter = ArrayAdapter(itemView.context, R.layout.select_dialog_singlechoice, spinnerList)
Resources
- Android Developers Documentation : https://developer.android.com/guide/topics/ui/controls/spinner
- Stack OverFlow: https://www.javatpoint.com/android-spinner-example