Android change what buttons do

Buttons

A button consists of text or an icon (or both text and an icon) that communicates what action occurs when the user touches it.

Depending on whether you want a button with text, an icon, or both, you can create the button in your layout in three ways:

• With text, using the Button class:
• With an icon, using the ImageButton class:
• With text and an icon, using the Button class with the android:drawableLeft attribute:

Key classes are the following:

Responding to Click Events

When the user clicks a button, the Button object receives an on-click event.

To define the click event handler for a button, add the android:onClick attribute to the 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’s a layout with a button using android:onClick :

Within the Activity that hosts this layout, the following method handles the click event:

Kotlin

The method you declare in the android:onClick attribute must have a signature exactly as shown above. Specifically, the method must:

• Be public
• Return void
• Define a View as its only parameter (this will be the View that was clicked)

Using an OnClickListener

You can also declare the click event handler programmatically rather than in an XML layout. This might be necessary if you instantiate the Button at runtime or you need to declare the click behavior in a Fragment subclass.

To declare the event handler programmatically, create an View.OnClickListener object and assign it to the button by calling setOnClickListener(View.OnClickListener) . For example:

Kotlin

Styling Your Button

The appearance of your button (background image and font) may vary from one device to another, because devices by different manufacturers often have different default styles for input controls.

You can control exactly how your controls are styled using a theme that you apply to your entire application. For instance, to ensure that all devices running Android 4.0 and higher use the Holo theme in your app, declare android:theme=»@android:style/Theme.Holo» in your manifest’s element. Also read the blog post, Holo Everywhere for information about using the Holo theme while supporting older devices.

To customize individual buttons with a different background, specify the android:background attribute with a drawable or color resource. Alternatively, you can apply a style for the button, which works in a manner similar to HTML styles to define multiple style properties such as the background, font, size, and others. For more information about applying styles, see Styles and Themes.

Borderless button

One design that can be useful is a «borderless» button. Borderless buttons resemble basic buttons except that they have no borders or background but still change appearance during different states, such as when clicked.

To create a borderless button, apply the borderlessButtonStyle style to the button. For example:

Custom background

If you want to truly redefine the appearance of your button, you can specify a custom background. Instead of supplying a simple bitmap or color, however, your background should be a state list resource that changes appearance depending on the button’s current state.

You can define the state list in an XML file that defines three different images or colors to use for the different button states.

To create a state list drawable for your button background:

Create three bitmaps for the button background that represent the default, pressed, and focused button states.

To ensure that your images fit buttons of various sizes, create the bitmaps as Nine-patch bitmaps.

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Hands-on with Material Components for Android: Buttons

Part 4 of a series covering practical usage of Material Components for Android

This post will be covering the features and API of Button components. To find out how to handle initial setup of Material Components for Android (including the Gradle dependency and creating an app theme), please see my original post:

Setting up a Material Components theme for Android

Attribute by attribute

Buttons are arguably the most widely-used components in any app. This is largely due to their versatility, allowing users to perform actions and make choices that ultimately guide the flow of an experience. A single line of contained text and/or an icon indicate the action a button can perform.

Material Buttons are slightly different to traditional Android buttons in that they do not include additional insets (4dp on the left/right) and have more letter-spacing, different default colors and other attributes that improve legibility and affordance amongst other components.

From a design perspective, there are three main types of buttons which are intended to offer hierarchical levels of emphasis:

• Text button (low emphasis): No container. Best used for less important actions, especially when other main content needs to be emphasised.

In addition to this, buttons can be grouped together into a fourth type: Toggle button. This allows related button actions to be horizontally arranged in a common container. The buttons themselves can be selected/deselected to indicate an active/inactive choice.

Basic usage 🏁

A MaterialButton can be included in your layout like so:

Choosing a style 🤔

As discussed in the intro section above, a variety of button types exist. These types map to styles that you can apply to a MaterialButton . There also exists a variety of sub-styles for specific use cases, such as to adjust padding for an icon. The full list of styles and their attributes can be found on GitHub. These style variants inherit from Widget.MaterialComponents.Button , each with an optional style suffix:

• Text button: *.TextButton (main), *.TextButton.Icon , *.TextButton.Snackbar , *.TextButton.Dialog , *.TextButton.Dialog.Icon , *.TextButton.Dialog.Flush
• Outlined button: *.OutlinedButton (main), *.OutlinedButton.Icon
• Contained button (unelevated): *.UnelevatedButton (main), *.UnelevatedButton.Icon
• Contained button (raised): No suffix (default, main), *.Icon

Adding an icon 🔷

An icon can be added to a button. It is displayed at the start, before the text label. In order to get the correct icon padding, it is recommended that you use a *.Icon style variant (shown above in the “Choosing a style” section).

The icon can be added in XML:

Alternatively, it can be done programmatically:

A few additional attributes exist for adjusting the icon size and position:

• iconSize : The width/height of the icon. The default value is the supplied Drawable ’s intrinsic width.

• iconGravity : The gravity of the icon. This can be set to start ( ICON_GRAVITY_START , default, at start of button), end ( ICON_GRAVITY_END , at end of button), textStart ( ICON_GRAVITY_TEXT_START , at start of centered text label) or textEnd ( ICON_GRAVITY_TEXT_END , at end of centered text label).

• iconPadding : The spacing between the icon and the text label. Typically you would not want to change this. The default value is 4dp for text buttons and 8dp for all other types.

Attributes related to icon tinting are discussed in the “Theming” section below.

Grouping Buttons to create a Toggle Button 👨‍👩‍👧‍👦

In order to create a toggle button, we need to add MaterialButton s as child View s to a MaterialButtonToggleGroup (a custom ViewGroup ).

Note: MaterialButtonToggleGroup was added in the 1.1.0-alpha05 release of Material Components for Android.

Grouping

This can be done in XML:

Alternatively, it can be done programmatically:

The MaterialButtonToggleGroup handles layout and adjusting of only the relevant shape corners in the row of MaterialButton s. The appearance of the MaterialButton s is determined by whichever style they each use. It is advised to use a consistent style for all children and also recommended to use the outlined button type.

Adjusting selected behavior

When added to a MaterialButtonToggleGroup , child MaterialButton s automatically become “selectable” (i.e. The android:checkable attribute is set to true).

Thus, there exists a couple of attributes for adjusting how MaterialButtonToggleGroup manages this:

• singleSelection : Determines whether or not only a single button in the group can be checked at a time. The default value is false, meaning multiple buttons can be checked/unchecked independently.

Listening for selection state

We are able to query for and adjust the current checked button(s) in a variety of ways:

We are also able to listen for checked changes by adding an OnButtonCheckedListener to a MaterialButtonToggleGroup :

Listeners can also be removed with the MaterialButtonToggleGroup#removeListener and MaterialButtonToggleGroup#clearListeners functions.

Orientation

The default arrangement of buttons within a toggle group is horizontal. However, seeing as MaterialButtonToggleGroup extends LinearLayout , it also supports vertical arrangement. This can be set programmatically or in XML:

The interesting thing to note here is the extra attributes on the child MaterialButton (s). It is recommended to set the width to match_parent and to remove the top/bottom insets from the child buttons so as to have them sit flush against each other vertically. This also, however, requires adjusting the minHeight to make up for the lack of insets.

Theming 🎨

Buttons can be themed in terms of the three Material Theming subsystems: color, typography and shape. We have already shown which styles to use in the “Choosing a style” section above. When implementing a global custom MaterialButton and MaterialButtonToggleGroup styles, reference them in your app theme with the materialButtonStyle / materialButtonOutlinedStyle and materialButtonToggleGroupStyle attributes respectively.

Color

The color of the MaterialButton background can be customized with the backgroundTint attribute. This requires a ColorStateList , meaning a for checked/enabled/disabled states is required. It defaults to colorPrimary (enabled)/ colorOnSurface (disabled) for contained buttons and transparent(unchecked)/ colorPrimary (checked) for all other types, with different opacities per state. There is also a backgroundTintMode attribute to change the tint PorterDuff.Mode , although typically you would want to keep this the same.

The color of the text label can be customized with the android:textColor attribute. This too requires a ColorStateList . It defaults to colorOnPrimary (enabled)/ colorOnSurface (disabled) for contained buttons and colorPrimary (enabled or checked)/ colorOnSurface (disabled or unchecked) for all other types, with different opacities per state.

The color of the optional icon can be customized with the iconTint attribute. This too requires a ColorStateList and the defaults are the same as those of android:textColor . As before, there is also an iconTintMode attribute.

Lastly, the color of the button touch ripple can be customized with the rippleColor attribute. It too accepts a ColorStateList and defaults to colorOnPrimary for contained buttons and colorPrimary for all other types, with different opacities per state.

Typography

The button text label will adopt the fontFamily attribute defined in your app theme.

While you would typically want to keep most aspects of the button text appearance as is, the Material Guidelines suggest we can use sentence case over the standard all caps for the text label, if desired. To achieve this, we would create a new style:

We could apply this directly to a button or in an individual button style by referencing it with the android:textAppearance attribute. Alternatively, it can be applied globally by referencing it in your app theme with the textAppearanceButton attribute.

Shape

The shape of a button background can be customized with the shapeAppearance attribute. This defaults to shapeAppearanceSmallComponent .

While not strictly shape theming, it is worth mentioning that the width of an outlined button stroke can be adjusted with the strokeWidth attribute. This defaults to 1dp.

More resources 📚

• The source code for the Playground app used in this article can be found on GitHub.
• Buttons Design Documentation
• Buttons API Documentation
• Toggle Buttons API Documentation

I hope this post has provided some insight into Material Buttons and how they can be used in your Android app(s). If you have any questions, thoughts or suggestions then I’d love to hear from you!

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How to customize your Android home button shortcut

The best thing about Android is how customizable it is. Not everyone likes the default actions assigned to certain buttons or button combinations, and one of the most common complaints is with the home button on the older Samsung Galaxy devices. It is possible to make the home button do what you want, rather than what the manufacturer decided, using the following workaround.

Samsung, along with many other manufacturers, is leaving the home button by the wayside as the ever-increasing displays gobble up more and more of the smartphone’s front panel. The stylish Samsung Galaxy S8 was the first flagship from the Korean company to ditch it, and now even lower-range devices in the A-series follow suit. Nonetheless, the physical home button still has its fans, and we’ll show you how to get the most out of it.

For demonstration purposes, we’re using a Samsung Galaxy S7 on Android Nougat, although it should work on most phones that have a physical home button. By default, a double-tap of the S7 home button takes you to the camera shortcut but, for the purposes of this tutorial, we want to make it launch the Play Store instead. On older Galaxy devices, a single tap of the physical home button will bring you to your home screen, a double-tap launches S Voice, and long-press launch Google Now with a long press.

First, you’ll need a specialized app from the Google Play Store, so download and install it on your device. There are several apps that provide the same functionality, but for this example, we’re using Button Mapper: Remap your keys.

How to change the home button action

1. When you fire up Button Mapper, it will first advise you to authorize the app in your Settings. Button Mapper will be able to see which app is currently on your screen. While this isn’t unusual for an app with these capabilities, just be warned. We recommend you look up the developer of these apps to check for legitimacy.
2. After authorization, we’ll be able to reprogram the physical Home and Volume buttons for different actions (additional options require a paid version). In this example, we’ll customize what happens with a double-tap.
3. Remapping a button is a four-step process. First, select the Home Button to see a menu of customization options. Select Double Tap.

Even with the free version can be a life-changer. / © NextPit

1. Next, choose whether you want to map the double tap to an action, application or shortcut. We chose Applications in this example.
2. Then we’re presented with a list of applications. Select Play Store and voila! Double tapping the Home Button now opens leads to Google’s market of apps and games.
3. If you ever want to go back to how it was before, you can clear your app defaults in Settings.
4. We actually think that the way the S7 launches the camera from a double-tap of the home button is a really useful feature, so If you have an older Galaxy device, you can use Button Mapper to make the double-press a camera shortcut rather than an S Voice shortcut.

• Best custom ROMs for Android
• Best root apps for Android

Happy customizing! What other cool modifications have you made to your Galaxy? Tell us about them in the comments.

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