Adobe 38039481 User Guide - Page 500

FLASH CS3 494 User Guide Flash Lite developers face additional challenges because performance on mobile devices varies greatly. If content must be published to many different devices, developers sometimes have to author for the lowest common denominator. Optimizing mobile content requires making trade-offs. For example, one technique may make the content look better, while another results in better performance. As you evaluate these trade-offs, you will be going back and forth repeatedly between testing in the emulator and testing on the target device. You must see your content on the actual device to evaluate the trueness of colors, text readability, physical interactions, UI responsiveness, and other aspects of the real mobile experience. Flash Lite guidelines for animation in mobile devices When creating animated content for a mobile devices, keep device CPU limitations in mind. Following these guidelines can help prevent Flash Lite content from running slowly: • When creating a new Flash Lite file, check that the document is set up correctly. Although Flash files scale smoothly, performance can suffer if the file is not running at its native Stage size and has to scale in the player. Try to set the document Stage size to match the resolution of the target device. Also set the Flash Player to the correct version of Flash Lite and select an appropriate device profile in Device Central. • Flash Lite can render vector graphics at low, medium, and high quality. The higher the rendering quality, the more smoothly and accurately Flash Lite renders vector graphics and the greater the demand on the device's CPU. To provide complex animation, experiment with changing the player's quality setting and then thoroughly test the SWF file. To control the rendering quality of a SWF file, use the _quality property or the SetQuality command. Valid values for the _quality property are LOW, MEDIUM, and HIGH. • Limit the number of simultaneous tweens. Reduce the number of tweens, or sequence the animation so that one begins when another ends. • Use transparency (alpha) effects on symbols sparingly because they are CPU intensive. In particular, avoid tweening symbols with alpha levels that are not fully opaque (less than 100%). • Avoid CPU-intensive visual effects, such as large masks, extensive motion, alpha blending, extensive gradients, and complex vectors. • Experiment with combinations of tweens, keyframe animations, and ActionScript-driven movement to produce the most efficient results. • Rendering vector ovals and circles is much more memory intensive than rendering quadrangles. Using round and oval strokes also greatly increases CPU use. • Test animations frequently on actual target devices. • When Flash draws an animated region, it defines a rectangular bounding box around the area. Optimize the drawing by making that rectangle as small as possible. Avoid overlapping tweens, because Flash interprets the merged area as a single rectangle, resulting in a larger total region. Use Flash's Show Redraw Region feature to optimize the animation. • Avoid using _alpha = 0 and _visible = false to hide on-screen movie clips. If you simply turn a movie clip's visibility off or change its alpha to zero, it is still included in line-rendering calculations, which can affect performance. • Similarly, do not try to hide a movie clip by obscuring it behind another piece of artwork. It will still be included in the player's calculations. Instead, move movie clips completely off the Stage or remove them by calling removeMovieClip.