Move the finger trigger size of the touch screen

design guidelines from all mobile platforms

Apple iphone HMI Guide recommended minimum target size is 44px wide, 44px high. Microsoft's Windows Mobile user interface design and interactive design Guide recommends a minimum target size of 26px times 34px. Nokia's developer's Guide suggests that the target size should be no less than 1cmx1cm squared or 28x28 pixels.

Although these guidelines give recommendations for general measurements of touch targets, they differ from each other and are inconsistent with the actual size of the human finger. In fact, they suggest a much smaller size than the average user's finger size, which causes the user to touch the mobile device with a less accurate target location.

　　Too small to touch the target can cause big problems

Small touch targets can make users very difficult to use because they need more accurate positioning. Users need to adjust their fingers, from the point pad to the fingertips, so that they can clearly hit the target. When users use their finger pads, they cover the entire target, so that they do not see the interactive feedback at all, and they can see some of the interactive feedback when they operate with their fingertips. Then, when users use equipment, switch fingertips and finger pads, no doubt reduce their operational efficiency.

Not only that, small touch targets can cause operational errors. When several small touch targets are closer to each other, the user accidentally touches a neighboring target and throws an unexpected action. The error that is caused by the thumb touch screen is more pronounced because it is the largest size. So sometimes the user will tilt the thumb, so that it sideways to touch the screen target, this is a very unnecessary operation.

With the thumb interaction, in the mobile device is actually very common, because most users are not in the hands of the leisure state, many users will feel with one hand plus a thumb, this operation is the most convenient. Users do not want to hit a target, and so that the original use of a hand into the use of two hands, or the original likes to use the thumb of the situation into using other fingers, can be seen, the target is too small, to the user's operation brought to the trouble will be how big.

　　Average index finger pixel width

The MIT Touch Lab, which studies human fingertips, finds that most adults have an average width of 1.6 to 2 centimeters (16–20 millimeters) and convert to 45–57 pixels, which is larger than the recommended size for mobile devices.

Touch the target 45–57 pixels, allowing the user's fingers to close to the target and allow users to see the edge of the target, which provides them with clear interactive feedback to help users determine the accuracy of hit targets, but also to improve the efficiency of the user hit the target. This is consistent with the Fitzpatrick law, where the time to hit a target is inversely proportional to the size of the target, i.e. the smaller the target, the longer the hit time, because it consumes the user's extra attention. The target of a finger size gives the user enough room to hit it without having to worry about accuracy.

　　Average thumb pixel width

Many users will use their index finger to activate the target, but there are many users who like to use thumbs. The big difference with the thumb is that it is wider than the index finger. An adult thumb has an average width of 1 inches (2.5 centimeters) and is converted to 72 pixels.

So the user is very happy to hit a 72px wide target with his thumb, both for quick and accurate positioning, for interactive feedback, and for not having to tilt the thumb in order to hit the target, so that one hand and one thumb are sufficient to complete the operation.

A study of "thumb-touch device interaction" shows that the error rate of user action decreases as the target size becomes larger. The user does not need to switch the role of the finger for hitting the target.

　　Simply speaking the size of the finger is more idealistic, in practical use is sometimes not feasible

The use of many scenes is not feasible if we are to design the finger size exactly as described above. As with mobile devices, your work range is actually very small and limited. This means that the screen size is not enough to support the target when you have a few finger size targets squeezed into the mobile device screen. However, when you reduce the size of the appropriate, combined into the screen, it will appear more reasonable. You need to measure the physical size of your screen and touch the target size to explore exactly how large the target user can touch.

The use of finger-size touch targets on tablets is much easier than mobile devices because of the larger screen space available to the tablet. You are free to use these dimensions without fear of whether they occupy too much space. However, the limitations of the mobile device screen, the finger size can be touched by the target target is the most need to consider. The challenge for designers is to define the most common touch area sizes available for mobile devices. Perhaps fewer touch targets are a reasonable solution, but the premise of this scenario is that designers need to streamline their navigation content.