Most mobile devices do not have a keyboard or a pointing device. They use touchscreens to allow users to physically interact with what is shown on the screen and type on a virtual keyboard. Fingers or a stylus are used in place of a mouse pointer. Icons, like those found on desktops and laptops, are clicked with a touch rather than a mouse button. Mobile device manufacturers use the word tap or touch when describing operations and steps when using a mobile device. You will see both of these terms in instruction manuals, and they mean the same thing. This course uses the term touch.
There are two types of touchscreens:
- Capacitive - Consists of a glass screen coated with a conductor. Because the human body is also a conductor, touching the screen interrupts the electrical field of the screen. This change is measured by the touch processor to determine the vertical and horizontal location of the touch on the screen.
- Resistive - Consists of transparent layers of material capable of conducting electricity. These layers have a small air gap between them. One layer conducts electricity from top to bottom, while the other conducts electricity from left to right. When pressure is exerted on the screen, the two layers touch. When the layers touch, the vertical and horizontal locations are calculated by the touch processor from where the electricity is interrupted.
In addition to a single touch, mobile devices have the ability to recognize when two or more points of contact are made on the screen. This is called multi-touch. These are some common gestures used to perform functions:
- Slide or swipe - Move between screens horizontally or vertically. Touch the screen, slide your finger quickly in the direction you want to move the screen and let go.
- Double touch - Zoom items such as photographs, maps, and text. Touch the screen twice quickly to zoom in. Touch the screen twice quickly again to zoom out.
- Long touch - Select items, such as text, icons, or photos. Touch and hold the screen until options become available for the item you are touching.
- Scroll - Scroll items that are too large for the screen, such as photos or web pages. Touch and hold the screen, moving your finger in the direction you want to move the item. Lift your finger when you reach the area of the screen you want to see.
- Pinch - Zoom out from objects, such as photographs, maps, and text. Touch the screen with two fingers and pinch them together to zoom out from the object.
- Spread - Zoom in on objects, such as photographs, maps, and text. Touch the screen with two fingers and spread them apart to zoom in on the object.
These gestures may be different between devices. Many other gestures can also be used, depending on the device and operating system version. Check the device documentation for additional information.
Some smartphones have a proximity sensor that turns off the touchscreen when the phone is up to your ear and turns it on when you pull the device away from your ear. This prevents icons or numbers from being activated by contact with your face or ear, and also saves power.