Checkboxes allow the user to select one or more options from a set. Typically, you should present each checkbox option in a vertical list.
To create each checkbox option, create a CheckBox
in your layout. Because
a set of checkbox options allows the user to select multiple items, each checkbox is managed
separately and you must register a click listener for each one.
Responding to Click Events
When the user selects a checkbox, the CheckBox
object receives an
on-click event.
To define the click event handler for a checkbox, add the android:onClick
attribute to the
<CheckBox>
element in your XML
layout. The value for this attribute must be the name of the method you want to call in response
to a click event. The Activity
hosting the layout must then implement the
corresponding method.
For example, here are a couple CheckBox
objects in a list:
<?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"> <CheckBox android:id="@+id/checkbox_meat" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/meat" android:onClick="onCheckboxClicked"/> <CheckBox android:id="@+id/checkbox_cheese" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/cheese" android:onClick="onCheckboxClicked"/> </LinearLayout>
Within the Activity
that hosts this layout, the following method handles the
click event for both checkboxes:
public void onCheckboxClicked(View view) { // Is the view now checked? boolean checked = ((CheckBox) view).isChecked(); // Check which checkbox was clicked switch(view.getId()) { case R.id.checkbox_meat: if (checked) // Put some meat on the sandwich else // Remove the meat break; case R.id.checkbox_cheese: if (checked) // Cheese me else // I'm lactose intolerant break; // TODO: Veggie sandwich } }
The method you declare in the android:onClick
attribute
must have a signature exactly as shown above. Specifically, the method must:
Tip: If you need to change the checkbox state
yourself (such as when loading a saved CheckBoxPreference
),
use the setChecked(boolean)
or toggle()
method.