Android Selection Controls

Android offers selection Controls like


1. List View.

2. Spinner

3. Check box

4. Radio Button

The List View:


ListView represents a list of items that can be selected. It is similar to the ListBox in C#.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView  
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:id="@+id/txt"
    />
    <ListView
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content"
    android:id="@+id/List"
    />
</LinearLayout>

To populate the list and handle the ItemClick event we can do it like this :

final String [] items=new String[]{"Item1","Item2","Item3","Item4"};
        ArrayAdapter ad=new ArrayAdapter(this,android.R.layout.simple_list_item_1,items);
        list=(ListView)findViewById(R.id.List);
        list.setAdapter(ad);
list.setOnItemClickListener(new OnItemClickListener()
        {

   public void onItemClick(AdapterView arg0, View arg1, int arg2,
     long arg3) {
    // TODO Auto-generated method stub
    TextView txt=(TextView)findViewById(R.id.txt);
    txt.setText(list.getItemAtPosition(arg2).toString());
    
    
   }
         
        }
        );

The above code displays the selected item text in the textview:
The parameters of the OnItemClick method are:


• Arg0:the listview, notice that it is of type AdapterView.

• Arg1: the view that represents the selected item, in this example it will be a TextView

• Arg2: the position of the selected item.

• Arg3: the id of the selected item.

When creating the adapter you can specify the layout of the list by using simple_list_item_1 to display a simple list or by using


simple_list_item_single_choice to display radio buttons for single selection

Or by using simple_list_item_multiple_choice to display check boxes for multiple selection

You can set the choice mode of the list by using setchoicemode() method:

public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.main);
        final String [] items=new String[]{"Item1","Item2","Item3","Item4"};
        ArrayAdapter ad=new ArrayAdapter(this,android.R.layout.simple_list_item_multiple_choice,items);
        setListAdapter(ad);
      ListView list=getListView();
        list.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
        
    }

Now suppose you want to change the text of the an item when it is clicked, you can do it like this:

list.setOnItemClickListener(new OnItemClickListener()
        {

   public void onItemClick(AdapterView arg0, View arg1, int arg2,
     long arg3) {
    // TODO Auto-generated method stub
    TextView txt=(TextView)findViewById(R.id.txt);
    items[arg2]="changed";
    list.setAdapter(new ArrayAdapter(ListControls.this,android.R.layout.simple_list_item_1,items));
    
   }
         
        }
        );

Or a more neat way:

list.setOnItemClickListener(new OnItemClickListener()
        {

   public void onItemClick(AdapterView arg0, View arg1, int arg2,
     long arg3) {
    // TODO Auto-generated method stub
    TextView temp=(TextView)arg1;
    temp.setText("changed 2");
   }
         
        }
        );

See that you actually change the value of the string array item at the selected position then bind the listview with the adapter again. Or you capture the View object and do what you want.



If the activity will contain just one listview you can create an activity that extends list view. In this case you don’t have to specify a layout as a listview will fill the screen.

public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
                final String [] items=new String[]{"Item1","Item2","Item3","Item4"};
        ArrayAdapter ad=new ArrayAdapter(this,android.R.layout.simple_list_item_1,items);
        setListAdapter(ad);

If you want to reference or customize this listview then you can define it in the layouts xml fine by assigning it the id “android:id/list” so that the activity knows which listView is the main list for the activity .

This example shows a listview and a textview

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView  
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:id="@+id/txt"
    android:text="List View Demo"
    />
    
    <ListView
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"
    android:id="@android:id/list"
    />
</LinearLayout>

Now if you want to customize the ui of each row of the listview you define two layouts files: the first has the layout of the activity and the other has layout of each row in the listview