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1 <?xml version="1.0" encoding="utf-8"?> |
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2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
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3 <!-- This component and the accompanying materials are made available under the terms of the License |
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4 "Eclipse Public License v1.0" which accompanies this distribution, |
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5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
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6 <!-- Initial Contributors: |
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7 Nokia Corporation - initial contribution. |
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8 Contributors: |
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9 --> |
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10 <!DOCTYPE concept |
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11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
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12 <concept id="GUID-056165A7-E8A1-4868-8051-9EC58C5A3342" xml:lang="en"><title>Usability |
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13 considerations</title><prolog><metadata><keywords/></metadata></prolog><conbody> |
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14 <section id="GUID-E4B60228-49E7-415D-AFF1-9E9B622D2197"> <p>All touch and |
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15 gestural interfaces have to appear competent and safe. The interface needs |
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16 to look as though it is not going to misuse users' personal data or break |
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17 down. Optimizing system performance is critical here. Low screen refresh rate |
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18 and latent images do not give the impression of a trustworthy touch UI. The |
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19 use of touch screen and sensors may also increase battery consumption of mobile |
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20 devices.</p><note><p>Touch screens consume most power during touch operations, |
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21 and reducing unnecessary user interaction can help increase power efficiency. |
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22 Specifically with resistive touch screens, avoiding excessively long touch |
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23 and drag user actions is recommended. The continuous touch event flow keeps |
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24 the CPU busy. The screen lock turns off the touch completely. To learn more |
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25 about both optimizing system performance and battery life in Symbian applications, |
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26 see the <xref href="http://www.forum.nokia.com/main/resources/user_experience/power_management/" scope="external">Power Management</xref> section at Forum Nokia.</p></note><p>The |
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27 best products predict the needs of their users and then fulfill those needs |
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28 in unexpectedly pleasing ways. Adaptive targets are one way to do this. Controls |
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29 that match the users actions well are another way devices can be clever.</p> <p><b>Interaction |
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30 design</b></p><p>Use appropriate and simple interaction logic:</p><ul> |
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31 <li><p>Navigation and controls should be clear and meaningful to prevent mistakes: |
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32 strokes along the touch panel should produce a logical outcome. </p></li> |
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33 <li><p>The coolest interaction in the world is empty unless it has clear meaning |
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34 for the person performing it. When using indirect controls, the UI response |
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35 should relate to the action the user is performing. </p></li> |
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36 <li><p>Meaningful controls are easier to learn and remember. </p></li> |
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37 </ul> <p>Touch UI can employ direct or indirect controls, or a combination |
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38 of both:</p><ul> |
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39 <li><p>Direct controls allow users to simply tap the item they want to manipulate |
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40 right on the screen itself, move it, make it bigger, scroll it, and so on. |
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41 For more information, see <xref href="GUID-CCE6DC36-625C-487C-9AD8-F1BF8E36080A.dita">UI |
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42 components</xref> and <xref href="GUID-BB8B3A11-0BBC-4759-A7F4-A28C9E70573F.dita">Touch |
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43 support for common UI components</xref>. </p></li> |
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44 <li><p>Indirect controls use some other means to manipulate an object, for |
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45 example, shaking, tilting, flipping, waving and so on. For more information, |
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46 see <xref href="GUID-AE979B97-5610-42F3-99A7-5A3D66D3C2E6.dita">Sensor interaction</xref>.</p></li> |
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47 <li><p>While the Symbian style provides for the use of scroll bars, it is |
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48 common to reverse the page scrolling orientation in applications such as browser. |
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49 In absence of scroll bars, users will flick or drag the page upwards rather |
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50 than pull a scroller down to move the page up, that is, to scroll down. In |
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51 this case, scroll bars are used as navigation indicators.</p></li> |
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52 </ul><fig id="GUID-604A80CE-CB23-45A9-BC29-A01395CD6A2F"> |
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53 <image href="GUID-EE5937B6-9103-4711-B13B-06A62D56AF79_d0e47077_href.png" scale="60" placement="inline"/> |
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54 </fig><p>Direct taps and strokes are far easier for the user to understand |
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55 and pick up than abstract, indirect ones. A single view should always employ |
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56 only a few indirect strokes, so that the controls do not confuse the user. </p><p><b>Visual |
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57 design</b></p><p>On touch screens, it is important to make a clear distinction |
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58 between touchable areas, and non-touchable areas, such as text. </p><ul> |
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59 <li><p>Borders, glow effects, or other indicators can be used to highlight |
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60 the interaction. </p></li> |
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61 <li><p>Note that theme design alone is not sufficient for indicating touch |
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62 functionality: where one theme may indicate touch, another may not.</p></li> |
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63 </ul><p>See also:</p><ul> |
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64 <li><p><xref href="GUID-5486EFD3-4660-4C19-A007-286DE48F6EEF.dita">Scale and positioning |
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65 of controls</xref></p></li> |
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66 <li><p><xref href="GUID-3CA039D8-A74D-4C9E-B4F5-6E153C7F65A1.dita">Finger vs. stylus</xref></p></li> |
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67 <li><p><xref href="GUID-7BFEEDF7-3DB8-42FF-9D7A-F98E536F7686.dita">Sensor interaction</xref></p></li> |
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68 </ul> </section> |
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69 </conbody></concept> |