To display a button in an activity, add a button to the activity's layout XML file:
* ** <Button * android:id="@+id/button_id" * android:layout_height="wrap_content" * android:layout_width="wrap_content" * android:text="@string/self_destruct" />* *
To specify an action when the button is pressed, set a click * listener on the button object in the corresponding activity code:
* *
* public class MyActivity extends Activity {
* protected void onCreate(Bundle savedInstanceState) {
* super.onCreate(savedInstanceState);
*
* setContentView(R.layout.content_layout_id);
*
* final Button button = findViewById(R.id.button_id);
* button.setOnClickListener(new View.OnClickListener() {
* public void onClick(View v) {
* // Code here executes on main thread after user presses button
* }
* });
* }
* }
*
* The above snippet creates an instance of {@link android.view.View.OnClickListener} and wires * the listener to the button using * {@link #setOnClickListener setOnClickListener(View.OnClickListener)}. * As a result, the system executes the code you write in {@code onClick(View)} after the * user presses the button.
* *The system executes the code in {@code onClick} on the * main thread. * This means your onClick code must execute quickly to avoid delaying your app's response * to further user actions. See * Keeping Your App Responsive * for more details.
* *Every button is styled using the system's default button background, which is often * different from one version of the platform to another. If you are not satisfied with the * default button style, you can customize it. For more details and code samples, see the * Styling Your Button * guide.
* *For all XML style attributes available on Button see * {@link android.R.styleable#Button Button Attributes}, * {@link android.R.styleable#TextView TextView Attributes}, * {@link android.R.styleable#View View Attributes}. See the * Styles and Themes * guide to learn how to implement and organize overrides to style-related attributes.
*/ @RemoteView public class Button extends TextView { @ChangeId @EnabledSince(targetSdkVersion = 36) private static final long WEAR_MATERIAL3_BUTTON = 376561342L; private static Boolean sUseWearMaterial3Style; /** * Simple constructor to use when creating a button from code. * * @param context The Context the Button is running in, through which it can * access the current theme, resources, etc. * * @see #Button(Context, AttributeSet) */ public Button(Context context) { this(context, null); } /** * {@link LayoutInflater} calls this constructor when inflating a Button from XML. * The attributes defined by the current theme's * {@link android.R.attr#buttonStyle android:buttonStyle} * override base view attributes. * * You typically do not call this constructor to create your own button instance in code. * However, you must override this constructor when * creating custom views. * * @param context The Context the view is running in, through which it can * access the current theme, resources, etc. * @param attrs The attributes of the XML Button tag being used to inflate the view. * * @see #Button(Context, AttributeSet, int) * @see android.view.View#View(Context, AttributeSet) */ public Button(Context context, AttributeSet attrs) { // Starting sdk 36+, wear devices will use a specific material3 // design. The new design will be applied when all of following conditions are met: // 1. app target sdk is 36 or above. // 2. feature flag rolled-out. // 3. device is a watch. // 4. button uses Theme.DeviceDefault. // getButtonDefaultStyleAttr and getButtonDefaultStyleRes works together to alter the UI // while considering the conditions above. // Their results are mutual exclusive. i.e. when conditions above are all true, // getButtonDefaultStyleRes returns non-zero value(new wear material3), abd // getButtonDefaultStyleAttr returns 0. Otherwise, getButtonDefaultStyleAttr returns system // attr com.android.internal.R.attr.buttonStyle and getButtonDefaultStyleRes returns 0. this(context, attrs, getButtonDefaultStyleAttr(context), getButtonDefaultStyleRes()); } /** * This constructor allows a Button subclass to use its own class-specific base style from a * theme attribute when inflating. The attributes defined by the current theme's * {@code defStyleAttr} override base view attributes. * *For Button's base view attributes see * {@link android.R.styleable#Button Button Attributes}, * {@link android.R.styleable#TextView TextView Attributes}, * {@link android.R.styleable#View View Attributes}. * * @param context The Context the Button is running in, through which it can * access the current theme, resources, etc. * @param attrs The attributes of the XML Button tag that is inflating the view. * @param defStyleAttr The resource identifier of an attribute in the current theme * whose value is the the resource id of a style. The specified style’s * attribute values serve as default values for the button. Set this parameter * to 0 to avoid use of default values. * @see #Button(Context, AttributeSet, int, int) * @see android.view.View#View(Context, AttributeSet, int) */ public Button(Context context, AttributeSet attrs, int defStyleAttr) { this(context, attrs, defStyleAttr, 0); } /** * This constructor allows a Button subclass to use its own class-specific base style from * either a theme attribute or style resource when inflating. To see how the final value of a * particular attribute is resolved based on your inputs to this constructor, see * {@link android.view.View#View(Context, AttributeSet, int, int)}. * * @param context The Context the Button is running in, through which it can * access the current theme, resources, etc. * @param attrs The attributes of the XML Button tag that is inflating the view. * @param defStyleAttr The resource identifier of an attribute in the current theme * whose value is the the resource id of a style. The specified style’s * attribute values serve as default values for the button. Set this parameter * to 0 to avoid use of default values. * @param defStyleRes The identifier of a style resource that * supplies default values for the button, used only if * defStyleAttr is 0 or cannot be found in the theme. * Set this parameter to 0 to avoid use of default values. * * @see #Button(Context, AttributeSet, int) * @see android.view.View#View(Context, AttributeSet, int, int) */ public Button(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) { super(context, attrs, defStyleAttr, defStyleRes); } @Override public CharSequence getAccessibilityClassName() { return Button.class.getName(); } @FlaggedApi(FLAG_ENABLE_ARROW_ICON_ON_HOVER_WHEN_CLICKABLE) @Override public PointerIcon onResolvePointerIcon(MotionEvent event, int pointerIndex) { // By default the pointer icon is an arrow. More specifically, when the pointer icon is set // to null, it will be an arrow. Therefore, we don't need to change the icon when // enableArrowIconOnHoverWhenClickable() and the pointer icon is a null. We only need to do // that when we want the hand icon for hover. if (!enableArrowIconOnHoverWhenClickable() && getPointerIcon() == null && isClickable() && isEnabled() && event.isFromSource(InputDevice.SOURCE_MOUSE) ) { return PointerIcon.getSystemIcon(getContext(), PointerIcon.TYPE_HAND); } return super.onResolvePointerIcon(event, pointerIndex); } private static int getButtonDefaultStyleAttr(Context context) { sUseWearMaterial3Style = useWearMaterial3Style(context); if (sUseWearMaterial3Style) { return 0; } return com.android.internal.R.attr.buttonStyle; } private static int getButtonDefaultStyleRes() { if (sUseWearMaterial3Style != null && sUseWearMaterial3Style) { return com.android.internal.R.style.Widget_Material3_Button; } return 0; } private static boolean useWearMaterial3Style(Context context) { return Flags.useWearMaterial3Ui() && CompatChanges.isChangeEnabled(WEAR_MATERIAL3_BUTTON) && context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_WATCH) && context.getThemeResId() == com.android.internal.R.style.Theme_DeviceDefault; } }