4-lists.pdf

ListView (link) An ordered collection of selectable choices key attributes in XML: android:clickable="bool" set to false to disable the list android:id="@+id/theID" unique ID for use in Java code android:entries="@array/array" set of opti...

ListView (link) An ordered collection of selectable choices key attributes in XML: android:clickable="bool" set to false to disable the list android:id="@+id/theID" unique ID for use in Java code android:entries="@array/array" set of options to appear in the list (must match an array in strings.xml)  Static lists static list: Content is fixed and known before the app runs. – Declare the list elements in the strings.xml resource file. Android iPhone... Max OS X  Dynamic lists dynamic list: Content is read or generated as the program runs. – Comes from a data file, or from the internet, etc. – Must be set in the Java code. – Suppose we have the following file and want to make a list from it: // res/raw/oses.txt Android iPhone... Max OS X  List adapters adapter: Helps turn list data into list view items. – common adapters: ArrayAdapter, CursorAdapter Syntax for creating an adapter: ArrayAdapter name = new ArrayAdapter(activity, layout, array); the activity is usually this the default layout for lists is android.R.layout.simple_list_item_1 get the array by reading your file or data source of choice (it can be an array like String[], or a list like ArrayList) – Once you have an adapter, you can attach it to your list by calling the setAdapter method of the ListView object in the Java code.  List adapter example ArrayList myArray =...; // load data from file ArrayAdapter adapter = new ArrayAdapter( this, android.R.layout.simple_list_item_1, myArray); ListView list = (ListView) findViewById(R.id.mylist); list.setAdapter(myAdapter);  Handling list events Unfortunately lists don't use a simple onClick event. – Several fancier GUI widgets use other kinds of events. – The event listeners must be attached in the Java code, not in the XML. – Understanding how to attach these event listeners requires the use of Java anonymous inner classes. anonymous inner class: A shorthand syntax for declaring a small class without giving it an explicit name. – The class can be made to extend a given super class or implement a given interface. – Typically the class is declared and a single object of it is constructed and used all at once.  Attaching event listener in Java // MainActivity.java public void mybuttonOnClick() {... } Button button = (Button) findViewById(R.id.mybutton); button.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { // code to run when the button gets clicked } }); // this was the required style for event listeners // in older versions of Android :-/  List events List views respond to the following events: – setOnItemClickListener(AdapterView.OnItemClickListener) Listener for when an item in the list has been clicked. – setOnItemLongClickListener(AdapterView.OnItemLongClickListener) Listener for when an item in the list has been clicked and held. – setOnItemSelectedListener(AdapterView.OnItemSelectedListener) Listener for when an item in the list has been selected. Others: – onDrag, onFocusChanged, onHover, onKey, onScroll, onTouch,...  List event listener example ListView list = (ListView) findViewById(R.id.id); list.setOnItemClickListener( new AdapterView.OnItemClickListener() { @Override public void onItemClick(AdapterView list, View row, int index, long rowID) { // code to run when user clicks that item... } } );