diff options
Diffstat (limited to 'docs/html/training/tv/optimizing-layouts-tv.jd')
| -rw-r--r-- | docs/html/training/tv/optimizing-layouts-tv.jd | 246 |
1 files changed, 246 insertions, 0 deletions
diff --git a/docs/html/training/tv/optimizing-layouts-tv.jd b/docs/html/training/tv/optimizing-layouts-tv.jd new file mode 100644 index 0000000..6eac6d3 --- /dev/null +++ b/docs/html/training/tv/optimizing-layouts-tv.jd @@ -0,0 +1,246 @@ +page.title=Optimizing Layouts for TV +parent.title=Designing for TV +parent.link=index.html + +trainingnavtop=true +next.title=Optimizing Navigation for TV +next.link=optimizing-navigation-tv.html + +@jd:body + +<div id="tb-wrapper"> +<div id="tb"> + +<h2>This lesson teaches you to</h2> +<ol> + <li><a href="#DesignLandscapeLayouts">Design Landscape Layouts</a></li> + <li><a href="#MakeTextControlsEasyToSee">Make Text and Controls Easy to See</a></li> + <li><a href="#DesignForLargeScreens">Design for High-Density Large Screens</a></li> + <li><a href="#HandleLargeBitmaps">Handle Large Bitmaps in Your Application</a></li> +</ol> + +<h2>You should also read</h2> +<ul> + <li><a href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple Screens</a></li> +</ul> + +</div> +</div> + +<p> +When your application is running on a television set, you should assume that the user is sitting about +ten feet away from the screen. This user environment is referred to as the +<a href="http://en.wikipedia.org/wiki/10-foot_user_interface">10-foot UI</a>. To provide your +users with a usable and enjoyable experience, you should style and lay out your UI accordingly.. +</p> +<p> +This lesson shows you how to optimize layouts for TV by: +</p> +<ul> + <li>Providing appropriate layout resources for landscape mode.</li> + <li>Ensuring that text and controls are large enough to be visible from a distance.</li> + <li>Providing high resolution bitmaps and icons for HD TV screens.</li> +</ul> + +<h2 id="DesignLandscapeLayouts">Design Landscape Layouts</h2> + +<p> +TV screens are always in landscape orientation. Follow these tips to build landscape layouts optimized for TV screens: +</p> +<ul> + <li>Put on-screen navigational controls on the left or right side of the screen and save the + vertical space for content.</li> + <li>Create UIs that are divided into sections, by using <a href="{@docRoot}guide/topics/fundamentals/fragments.html">Fragments</a> + and use view groups like {@link android.widget.GridView} instead + of {@link android.widget.ListView} to make better use of the + horizontal screen space.</li> + <li>Use view groups such as {@link android.widget.RelativeLayout} + or {@link android.widget.LinearLayout} to arrange views. + This allows the Android system to adjust the position of the views to the size, alignment, + aspect ratio, and pixel density of the TV screen.</li> + <li>Add sufficient margins between layout controls to avoid a cluttered UI.</li> +</ul> + +<p> +For example, the following layout is optimized for TV: +</p> + +<img src="{@docRoot}images/training/panoramio-grid.png" /> + +<p> +In this layout, the controls are on the lefthand side. The UI is displayed within a +{@link android.widget.GridView}, which is well-suited to landscape orientation. +In this layout both GridView and Fragment have the width and height set +dynamically, so they can adjust to the screen resolution. Controls are added to the left side Fragment programatically at runtime. +The layout file for this UI is {@code res/layout-land-large/photogrid_tv.xml}. +(This layout file is placed in {@code layout-land-large} because TVs have large screens with landscape orientation. For details refer to +<a href="{@docRoot}guide/practices/screens_support.html">Supporting Multiple Screens</a>.)</p> + +res/layout-land-large/photogrid_tv.xml +<pre> +<RelativeLayout + android:layout_width="fill_parent" + android:layout_height="fill_parent" > + + <fragment + android:id="@+id/leftsidecontrols" + android:layout_width="0dip" + android:layout_marginLeft="5dip" + android:layout_height="match_parent" /> + + <GridView + android:id="@+id/gridview" + android:layout_width="wrap_content" + android:layout_height="wrap_content" /> + +</RelativeLayout> +</pre> + +<p> +To set up action bar items on the left side of the screen, you can also include the <a +href="http://code.google.com/p/googletv-android-samples/source/browse/#git%2FLeftNavBarLibrary"> +Left navigation bar library</a> in your application to set up action items on the left side +of the screen, instead of creating a custom Fragment to add controls: +</p> + +<pre> +LeftNavBar bar = (LeftNavBarService.instance()).getLeftNavBar(this); +</pre> + +<p> +When you have an activity in which the content scrolls vertically, always use a left navigation bar; +otherwise, your users have to scroll to the top of the content to switch between the content view and +the ActionBar. Look at the +<a href="http://code.google.com/p/googletv-android-samples/source/browse/#git%2FLeftNavBarDemo"> +Left navigation bar sample app</a> to see how to simple it is to include the left navigation bar in your app. +</p> + +<h2 id="MakeTextControlsEasyToSee">Make Text and Controls Easy to See</h2> +<p> +The text and controls in a TV application's UI should be easily visible and navigable from a distance. +Follow these tips to make them easier to see from a distance : +</p> + +<ul> + <li>Break text into small chunks that users can quickly scan.</li> + <li>Use light text on a dark background. This style is easier to read on a TV.</li> + <li>Avoid lightweight fonts or fonts that have both very narrow and very broad strokes. Use simple sans-serif + fonts and use anti-aliasing to increase readability.</li> + <li>Use Android's standard font sizes: + <pre> + <TextView + android:id="@+id/atext" + android:layout_width="wrap_content" + android:layout_height="wrap_content" + android:gravity="center_vertical" + android:singleLine="true" + android:textAppearance="?android:attr/textAppearanceMedium"/> + </pre></li> + <li>Ensure that all your view widgets are large enough to be clearly visible to someone sitting 10 feet away + from the screen (this distance is greater for very large screens). The best way to do this is to use + layout-relative sizing rather than absolute sizing, and density-independent pixel units instead of absolute + pixel units. For example, to set the width of a widget, use wrap_content instead of a pixel measurement, + and to set the margin for a widget, use dip instead of px values. + </li> +</ul> +<p> + +</p> + +<h2 id="DesignForLargeScreens">Design for High-Density Large Screens</h2> + +<p> +The common HDTV display resolutions are 720p, 1080i, and 1080p. Design your UI for 1080p, and then +allow the Android system to downscale your UI to 720p if necessary. In general, downscaling (removing pixels) +does not degrade the UI (Notice that the converse is not true; you should avoid upscaling because it degrades +UI quality). +</p> + +<p> +To get the best scaling results for images, provide them as <a href="{@docRoot}guide/developing/tools/draw9patch.html"> +9-patch image</a> elements if possible. +If you provide low quality or small images in your layouts, they will appear pixelated, fuzzy, or grainy. This +is not a good experience for the user. Instead, use high-quality images. +</p> + +<p> +For more information on optimizing apps for large screens see <a href="{@docRoot}training/multiscreen/index.html"> +Designing for multiple screens</a>. +</p> + +<h2 id="HandleLargeBitmaps">Design to Handle Large Bitmaps</h2> + +<p> +The Android system has a limited amount of memory, so downloading and storing high-resolution images can often +cause out-of-memory errors in your app. To avoid this, follow these tips: +</p> + +<ul> + <li>Load images only when they're displayed on the screen. For example, when displaying multiple images in + a {@link android.widget.GridView} or + {@link android.widget.Gallery}, only load an image when + {@link android.widget.Adapter#getView(int, View, ViewGroup) getView()} + is called on the View's {@link android.widget.Adapter}. + </li> + <li>Call {@link android.graphics.Bitmap#recycle()} on + {@link android.graphics.Bitmap} views that are no longer needed. + </li> + <li>Use {@link java.lang.ref.WeakReference} for storing references + to {@link android.graphics.Bitmap} objects in a in-memory + <a href="{@link java.util.Collection}.</li> + <li>If you fetch images from the network, use {@link android.os.AsyncTask} + to fetch them and store them on the SD card for faster access. + Never do network transactions on the application's UI thread. + </li> + <li>Scale down really large images to a more appropriate size as you download them; otherwise, downloading the image + itself may cause an "Out of Memory" exception. Here is sample code that scales down images while downloading: + + <pre> + // Get the source image's dimensions + BitmapFactory.Options options = new BitmapFactory.Options(); + // This does not download the actual image, just downloads headers. + options.inJustDecodeBounds = true; + BitmapFactory.decodeFile(IMAGE_FILE_URL, options); + // The actual width of the image. + int srcWidth = options.outWidth; + // The actual height of the image. + int srcHeight = options.outHeight; + + // Only scale if the source is bigger than the width of the destination view. + if(desiredWidth > srcWidth) + desiredWidth = srcWidth; + + // Calculate the correct inSampleSize/scale value. This helps reduce memory use. It should be a power of 2. + int inSampleSize = 1; + while(srcWidth / 2 > desiredWidth){ + srcWidth /= 2; + srcHeight /= 2; + inSampleSize *= 2; + } + + float desiredScale = (float) desiredWidth / srcWidth; + + // Decode with inSampleSize + options.inJustDecodeBounds = false; + options.inDither = false; + options.inSampleSize = inSampleSize; + options.inScaled = false; + // Ensures the image stays as a 32-bit ARGB_8888 image. + // This preserves image quality. + options.inPreferredConfig = Bitmap.Config.ARGB_8888; + + Bitmap sampledSrcBitmap = BitmapFactory.decodeFile(IMAGE_FILE_URL, options); + + // Resize + Matrix matrix = new Matrix(); + matrix.postScale(desiredScale, desiredScale); + Bitmap scaledBitmap = Bitmap.createBitmap(sampledSrcBitmap, 0, 0, + sampledSrcBitmap.getWidth(), sampledSrcBitmap.getHeight(), matrix, true); + sampledSrcBitmap = null; + + // Save + FileOutputStream out = new FileOutputStream(LOCAL_PATH_TO_STORE_IMAGE); + scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 100, out); + scaledBitmap = null; + </pre> + </li> </ul>
\ No newline at end of file |