Presenting Lists of Data

1. Presenting Lists of Data

2. Lists of Data • Issues involved • unknown number of elements • allowing the user to scroll • Data sources • most common • ArrayList(can also use arrays) • database (Cursor) • other possible sources • user input • files

3. Approaches • TextView • myTextView.setMovementMethod(new ScrollingMovementMethod()); • limited functionality • ScrollView widget within an Activity • used to allow scrolling • most widgets do not scroll by default • multiple uses, including lists • ListView widget within an Activity • most flexibility • greatest code complexity • ListActivity • direct subclass of Activity • most common approach in mobile programming • simple way to provide a list

4. ScrollView widget within Activity

5. ScrollView • Automatically allows scrolling • Two options • ScrollView • vertical scrolling • HorizontalScrollView • horizontal scrolling • Defined within associated .xml file • Contains a single child • Child can be a Layout

6. Sample .xml code - ScrollView <ScrollView android:layout_width="match_parent" android:layout_height="match_parent" > <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/tvList" /> </ScrollView>

7. Sample .xml code - ScrollView <ScrollView android:layout_width=“match_parent" android:layout_height="wrap_content" android:text="Scrolling" > <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="vertical" > <TextView android:layout_width="match_parent" android:layout_height="wrap_content" android:id="@+id/tvInScroll" android:text="Texting 1" /> <Button android:layout_width="match_parent" android:layout_height="wrap_content" android:text="Buttonning 1" /> </LinearLayout> </ScrollView>

8. ListView widget within an Activity

9. ListView widget within an Activity • Allows for greatest functionality • additional widgets can be associated with Activity • greater code complexity • More than one column requires a Map object • expensive – generally a table layout or database should be used instead • Bound to an Adapter data source • Bound via setAdapter() method • ArrayAdapter • CursorAdapter • Adapter is associated with a widget • widget is within an additional.xml file

10. Sample .xml code - ListView <ListView android:layout_width="match_parent" android:layout_height="wrap_content" android:id="@+id/lvList" />

11. Sample .xml code – Additional .xml file Filename: listrow.xml <TextViewxmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/tvText" android:layout_width="wrap_content" android:layout_height="wrap_content" > </TextView>

12. Sample .java code – ListView ListViewlv = (ListView)findViewById(R.id.lvList); … ArrayAdapter<String> myAdapter = new ArrayAdapter<String> (this, R.layout.listrow, R.id.tvText, myStringArray); lv.setAdapter(myAdapter);

13. Sample .java code – ListView Retrieving selected element from ListView lv.setOnItemClickListener(new OnItemClickListener() { @Override public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) { //arg0 is the ListView //arg1 is the TextView within the View //arg2 is the position of the current TextView (same as arg3 for now) //arg3 is the selected row System.out.println(“Selected row: “ + arg3)); TextView current= (TextView)arg0.getChildAt((int) arg3); System.out.println(“Selected value: “ + current.getText()); } });

14. ListActivity

15. ListActivity • Class extends ListActivity • ListActivity is a direct subclass of Activity • No associated .xml file • provides for simple coding • limits functionality as no additional widgets can be used • still most common approach • setContentView() method is not used • ListActivity automatically hosts a ListView • if needed, ListView can be obtained via the getListView() method

16. ListActivity • ListView associated with ListActivity works similar to a ListView defined within an .xml file • Bound to an Adapter data source • bound via setListAdapter() method • ArrayAdapter • CursorAdapter • Adapter is associated with a prebuilt (Android defined) layout • android.R.layout.simple_X • X represents a valid layout • see R.layout class for exhaustive list of layouts

17. Sample .java code – ListActivity public class MyListActivity extends ListActivity { public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); //Note the absence of setContentView() call … setListAdapter(new ArrayAdapter<String> (this, android.R.layout.simple_list_item_1, myStringArray)); } }

18. Sample .java code – ListView Retrieving selected element from a ListActivity’sListView getListView().setOnItemClickListener(new OnItemClickListener() { @Override public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) { //arg0 is the ListView //arg1 is the TextView within the View //arg2 is the position of the current TextView (same as arg3 for now) //arg3 is the selected row System.out.println(“Selected row: “ + arg3)); System.out.println(“Selected value: “ + myArrayList.get((int)arg3)); } });