Part 2 - Populating a List. View With Data. Contents. Overview. To add rows to a List. View you need to add it to your layout and. IList. Adapter with methods that the List. View calls to. populate itself. Android includes built- in List. Xamarin.Forms are an essential tool for building a mobile app if you want it to be truly useful (and successful). Walt makes cross-platform development. Activity and. Array. Adapter classes that you can use without defining any custom. XML or code. The List. Activity class automatically creates a. List. View and exposes a List. Adapter property to supply the row views. ![]() The built- in adapters take a view resource ID as a parameter that gets. You can use built- in resources such as those in. Android. Resource. Layout so you don't need to write your own. Using List. Activity and Array. Adapter< String> The example Basic. Table/Home. Screen. List. View in only a few lines of code: [Activity(Label = "Basic. Table", Main. Launcher = true, Icon = "@drawable/icon")]. Home. Screen : List. Windows applications in Visual Basic 5 Introduction Best Practices. Forms should contain UI-related only; Any logic should live in modules or (even better) class modules. Activity {. string[] items. On. Create(Bundle bundle).
On. Create(bundle). Vegetables","Fruits","Flower Buds","Legumes","Bulbs","Tubers" }. List. Adapter = new Array. Adapter< String> (this, Android. Resource. Layout. Simple. List. Item. On. List. Item. Click(List. View l, View v, int position, long id). Handling Row Clicks. Usually a List. View will also allow the user to touch a row to perform. To respond to user touches there needs to be one more. List. Activity – On. List. Item. Click. On. List. Item. Click(List. View l, View v, int position, long id). Android. Widget. Toast. Make. Text(this, t, Android. Widget. Toast. Length. Short). Show(). }Now the user can touch a row and a Toast alert will appear: Implementing a List. Adapter. Array. Adapter< string> is great because of its. However, often times you have a. For example, if your data consists of a collection of Employee classes, then you. To customize the. List. View to control what data is displayed. Base. Adapter overriding. Count – To tell the control how many rows are in the data. Get. View – To return a View for each row, populated with data. This method has a parameter for the List. View to pass in an. Get. Item. Id – Return a row identifier (typically the row. To return the data associated with a. The example code in Basic. Table. Adapter/Home. Screen. Adapter. cs. Base. Adapter: public class Home. Screen. Adapter : Base. Adapter< string> {. Activity context. Home. Screen. Adapter(Activity context, string[] items) : base() {. Get. Item. Id(int position). Count {. get { return items. Length; }. public override View Get. View(int position, View convert. View, View. Group parent). View view = convert. View; // re- use an existing view, if one is available. Layout. Inflater. Inflate(Android. Resource. Layout. Simple. List. Item. 1, null). view. Find. View. By. Id< Text. View> (Android. Resource. Id. Text. Text = items[position]. Using a Custom Adapter. Using the custom adapter is similar to the built- in Array. Adapter. passing in a context and the string[] of values to display: List. Adapter = new Home. Screen. Adapter(this, items); Because this example uses the same row layout (Simple. List. Item. 1) the. Row View Re- Use. In this example there are only six items. Since the screen can fit. When displaying hundreds or thousands of. View objects when only eight fit on the screen at a. To avoid this situation, when a row disappears from the screen. As the user scrolls, the. List. View calls Get. View to request new views to display – if. View parameter. If. The Get. View method should follow this pattern to. View Get. View(int position, View convert. View, View. Group parent). View view = convert. View; // re- use an existing view, if one is supplied. Layout. Inflater. Inflate(Android. Resource. Layout. Simple. List. Item. 1, null). // set view properties to reflect data for the given row. Find. View. By. Id< Text. View> (Android. Resource. Id. Text. Text = items[position]. Custom adapter implementations should always re- use the convert. View. object before creating new views to ensure they do not run out of. Some adapter implementations (such as the Cursor. Adapter) don't have a. Get. View method, rather they require two different methods New. View. and Bind. View which enforce row re- use by separating the. Get. View into two methods. There is a. Cursor. Adapter example later in the document. Enabling Fast Scrolling. Fast Scrolling helps the user to scroll through long lists by providing. This screenshot shows the fast scroll handle: Causing the fast scrolling handle to appear is as simple as setting the. Fast. Scroll. Enabled property to true: List. View. Fast. Scroll. Enabled = true; Adding a Section Index. A section index provides additional feedback for users when they are. To cause the section index to appear the Adapter. ISection. Indexer interface to supply the. To implement ISection. Indexer you need to add three methods to an. Get. Sections – Provides the complete list of section index. This method requires an array of. Java Objects so the code needs to create a Java. Lang. Object[]. from a . NET collection. In our example it returns a list of the. Java. Lang. String . Get. Position. For. Section – Returns the first row position for a. Get. Section. For. Position – Returns the section index to be. The example Section. Index/Home. Screen. Adapter. cs file implements those. The constructor. builds the section index by looping through every row and extracting. Index = new Dictionary< string, int> (). Length; i++) { // loop through items. To. String(). if (! Index. Contains. Key(key)). Index. Add(key, i); // add each 'new' letter to the index. Index. Keys. Count]. Index. Keys. Copy. To(sections, 0); // convert letters list to string[]. Interface requires a Java. Lang. Object[], so we create one here. Objects = new Java. Lang. Object[sections. Length]. for (int i = 0; i < sections. Length; i++) {. sections. Objects[i] = new Java. Lang. String(sections[i]). With the data structures created, the ISection. Indexer methods are. Java. Lang. Object[] Get. Sections(). return sections. Objects. public int Get. Position. For. Section(int section). Indexer[sections[section]]. Get. Section. For. Position(int position). Section = 0. for (int i = 0; i < sections. Length; i++). if (Get. Position. For. Section(i) > position). Section = i. return prev. Section. }Your section index titles don't need to map 1: 1 to your actual. This is why the Get. Position. For. Section method exists. Get. Position. For. Section gives you an opportunity to map whatever. For example, you may have a "z" in your index, but you may. C# / CSharp Tutorialjava. Email: info at java. Demo Source and Support. All rights reserved.
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