从 Android Sample ApiDemos 中学习 android.animation API 的用法

关于Android SDK Sample: ApiDemos

背景： HONEYCOMB 3.0 （about versions android-3.0 highlights） 发布于 2011.02，引入了New animation framework；3.1 发布于 2011.05.

在 Android 开发者网站 搜索『animation』，通过『blog』过滤搜索结果，其中一篇文章 2011-02-24 Animation in Honeycomb 排在搜索结果第2位，可见其重要程度，作者是 Chet Haase，一个致力于图形和动画研究的 Android 开发者，可以从他的 个人博客graphics-geek.blogspot.com 阅读更多相关主题的博文。

『Animation in Honeycomb』讨论了一个问题，已经有了能实现 move, scale, rotate, and fade 这些视图动画的 android.view.animation ，为什么还要在 3.0 引入新 APIs android.animation？ 新 APIs 带来了哪些新特性？ 然后进一步展示了这些新特性的强大便利之处。

其中有一段话是这样的：

But for a more detailed view of how things work, check out the API Demos in the SDK for the new animations. There are many small applications written for the new Animations category (at the top of the list of demos in the application, right before the word App. I like working on animation because it usually comes first in the alphabet).

SDK samples 包含了一个例子 ApiDemos，这个例子详尽地展示了如何使用 3.0 SDK API。其中一部分 demos 正是关于新的动画机制（android.animation）。而和 animation 相关的 demos 排在整个列表的最前面，比 App demos 还靠前，这就是我为什么喜欢研究 animation 的原因。

（这个点可真奇特（简（可）单（爱）），不知道这些牛人在想什么，哈哈）

从SDK sample 中获取 ApiDemos

虽然是11年2月发布的，而现在已经是2016年的1月底了，虽然步子慢了五年，但3.x的动画依然没有过时，所以官方提供的 Sample 有什么理由不去学习呢？（除此之外，你认为有什么捷径吗？） （感觉像是发现了一直忽视的宝藏 ╰(￣▽￣)╮）

那么接下来，就把它导入 studio，需要特别说明的是 ApiDemos 位于新的 SDK sample 的 legacy 目录中，位于旧的sdk sample 根目录中：

$HOME/Library/Android/sdk/samples/android-21/legacy/ApiDemos
$HOME/Library/Android/sdk/samples/android-15/ApiDemos

ApiDemos 和动画有关的是（ApiDemos 全部列表见文章最后）：

$ tree -L 2
.
├── animation
│   ├── ActivityTransition.java
│   ├── ActivityTransitionDetails.java
│   ├── AnimationCloning.java
│   ├── AnimationLoading.java
│   ├── AnimationSeeking.java
│   ├── AnimatorEvents.java
│   ├── BouncingBalls.javppa
│   ├── CustomEvaluator.pjava
│   ├── FixedGridLayout.java
│   ├── LayoutAnimations.java
│   ├── LayoutAnimationsByDefault.java
│   ├── LayoutAnimationsHideShow.java
│   ├── ListFlipper.java
│   ├── MultiPropertyAnimation.java
│   ├── PathAnimations.java
│   ├── ReversingAnimation.java
│   ├── Rotate3dAnimation.java
│   ├── ShapeHolder.java
│   ├── Transition3d.java
│   └── Transitions.java
├── app // 这就是 Chet 说的，animation 在 app 上....上...上..上.面  ╮(╯▽╰)╭
├── graphics
│   ├── AnimateDrawable.java
│   ├── AnimateDrawables.java
│   ├── Arcs.java
│   ├── ShadowCardDrag.java
│   ├── ShadowCardStack.java
│   ├── Sweep.java
└── view // 3D transition, Interpolators, Push, Shake
    ├── Animation1.java
    ├── Animation2.java
    ├── Animation3.java
    ├── LayoutAnimation1.java
    ├── LayoutAnimation2.java
    ├── LayoutAnimation3.java
    ├── LayoutAnimation4.java
    ├── LayoutAnimation5.java
    ├── LayoutAnimation6.java
    ├── LayoutAnimation7.java

导入 ApiDemos 到 Android Studio

通过 Android Studio 导入 ApiDemos 时遇到了如下几个问题：

Plugin is too old, please update to a more recent version, or set ANDROID_DAILY_OVERRIDE environment variable to ...

做了如下修改（参照可以正常运行的 Android Studio 项目）：
(1) 修改文件 gradle-wrapper.properties 中的 distributionUrl=https\://services.gradle.org/distributions/gradle-2.4-all.zip;（之前是2.8）
(2) 修改文件 build.gradle (Project: your_app_name) 中的 dependencies: classpath 'com.android.tools.build:gradle:1.3.0；（之前是2.0.0-alpha3）
点击这里查看详细的解释

Error:Execution failed for task ':app:mergeDebugResources'.
ApiDemos/app/src/main/res/xml/preference_switch: Error: The file name must end with .xml

看来官方 sample 也会出现一些低级错误，重命名这个文件加上后缀，可以解决问题。

ApiDemos/app/src/main/java/com/example/android/apis/os/MmsMessagingDemo.java
Error:(19, 30) error: package com.google.android.mms does not exist

我的解决办法很粗暴，直接删掉 os 目录，同时要删掉在 manifest 中声明的对应组件。

ApiDemos/app/src/main/java/com/example/android/apis/app/PrintBitmap.java
Error:(23, 32) error: package android.support.v4.print does not exist

需要导入 support-v4。针对 Studio 2.0 preview4 的导入方法：
File >> Project Structure... >> Modules >> Dependencies >> +1 Library dependency

Error:Execution failed for task ':app:processDebugManifest'.
Manifest merger failed : uses-sdk:minSdkVersion 1 cannot be smaller than version 4 declared in library [com.android.support:support-v4:23.1.1] /Users/weiyi/Develop/AndroidApp/OpenSourceDemo/ApiDemos/app/build/intermediates/exploded-aar/com.android.support/support-v4/23.1.1/AndroidManifest.xml

  Suggestion: use tools:overrideLibrary="android.support.v4" to force usage

解决办法是在 build.gradle (Module) 中增加 mindSdkVersion：

    defaultConfig {
        minSdkVersion 21
    }

因为我是从android-21中导入的ApiDemos，所以项目中有些地方使用了5.0的API，所以把min设置为21。

Error:(65, 40) error: cannot find symbol method sqrt(float)

FloatMath.sqrt(0.125f) 等方法已经从 6.0 SDK 中移除了：All methods were removed from the public API in version 23.
修改 compileSdkVersion 为22（原来是23），同时修改 support-v4 的版本号为 22.2.1

---

经过这几步修改后，终于可以在 Android Strudio 上编译然后运行在 5.1 的系统上。
浪费了一天的时间 :(
写这篇文档又花了大半天 :)

所以，你如果想学习 ApiDemos，可以按照上述步骤自己从 SDK sample 中导入。如果想避免这些修改过程，可以clone我已经改好的：
Learning_Android_Open_Source/ApiDemos

附录：ApiDemos 部分动画截图

附录：ApiDemos 包含的全部示例

$ tree -L 2
.
├── ApiDemos.java
├── ApiDemosApplication.java
├── Shakespeare.java
├── accessibility
│   ├── ClockBackActivity.java
│   ├── ClockBackService.java
│   ├── CustomViewAccessibilityActivity.java
│   ├── TaskBackService.java
│   ├── TaskListActivity.java
│   └── TaskListView.java
├── animation
│   ├── ActivityTransition.java
│   ├── ActivityTransitionDetails.java
│   ├── AnimationCloning.java
│   ├── AnimationLoading.java
│   ├── AnimationSeeking.java
│   ├── AnimatorEvents.java
│   ├── BouncingBalls.java
│   ├── CustomEvaluator.java
│   ├── FixedGridLayout.java
│   ├── LayoutAnimations.java
│   ├── LayoutAnimationsByDefault.java
│   ├── LayoutAnimationsHideShow.java
│   ├── ListFlipper.java
│   ├── MultiPropertyAnimation.java
│   ├── PathAnimations.java
│   ├── ReversingAnimation.java
│   ├── Rotate3dAnimation.java
│   ├── ShapeHolder.java
│   ├── Transition3d.java
│   └── Transitions.java
├── app
│   ├── ActionBarDisplayOptions.java
│   ├── ActionBarMechanics.java
│   ├── ActionBarNavigation.java
│   ├── ActionBarNavigationTarget.java
│   ├── ActionBarSettingsActionProviderActivity.java
│   ├── ActionBarShareActionProviderActivity.java
│   ├── ActionBarTabs.java
│   ├── ActionBarUsage.java
│   ├── ActivityRecreate.java
│   ├── AlarmController.java
│   ├── AlarmService.java
│   ├── AlarmService_Service.java
│   ├── AlertDialogSamples.java
│   ├── Animation.java
│   ├── AppUpdateReceiver.java
│   ├── AppUpdateSspReceiver.java
│   ├── ContactsFilter.java
│   ├── ContactsFilterInstrumentation.java
│   ├── ContactsSelectInstrumentation.java
│   ├── CustomDialogActivity.java
│   ├── CustomTitle.java
│   ├── DeviceAdminSample.java
│   ├── DialogActivity.java
│   ├── DoNothing.java
│   ├── FinishAffinity.java
│   ├── ForegroundService.java
│   ├── ForwardTarget.java
│   ├── Forwarding.java
│   ├── FragmentAlertDialog.java
│   ├── FragmentArguments.java
│   ├── FragmentArgumentsFragment.java
│   ├── FragmentContextMenu.java
│   ├── FragmentCustomAnimations.java
│   ├── FragmentDialog.java
│   ├── FragmentDialogOrActivity.java
│   ├── FragmentHideShow.java
│   ├── FragmentLayout.java
│   ├── FragmentListArray.java
│   ├── FragmentMenu.java
│   ├── FragmentMenuFragment.java
│   ├── FragmentNestingTabs.java
│   ├── FragmentReceiveResult.java
│   ├── FragmentRetainInstance.java
│   ├── FragmentStack.java
│   ├── FragmentStackFragment.java
│   ├── FragmentTabs.java
│   ├── FragmentTabsFragment.java
│   ├── HelloWorld.java
│   ├── IncomingMessage.java
│   ├── IncomingMessageInterstitial.java
│   ├── IncomingMessageView.java
│   ├── IntentActivityFlags.java
│   ├── Intents.java
│   ├── IsolatedService.java
│   ├── IsolatedService2.java
│   ├── LauncherShortcuts.java
│   ├── LoaderCursor.java
│   ├── LoaderCustom.java
│   ├── LoaderRetained.java
│   ├── LoaderThrottle.java
│   ├── LocalSample.java
│   ├── LocalSampleInstrumentation.java
│   ├── LocalService.java
│   ├── LocalServiceActivities.java
│   ├── MenuInflateFromXml.java
│   ├── MessengerService.java
│   ├── MessengerServiceActivities.java
│   ├── NotificationDisplay.java
│   ├── NotifyWithText.java
│   ├── NotifyingController.java
│   ├── NotifyingService.java
│   ├── OneShotAlarm.java
│   ├── OverscanActivity.java
│   ├── PersistentState.java
│   ├── PresentationActivity.java
│   ├── PresentationWithMediaRouterActivity.java
│   ├── PrintBitmap.java
│   ├── PrintCustomContent.java
│   ├── PrintHtmlFromScreen.java
│   ├── PrintHtmlOffScreen.java
│   ├── QuickContactsDemo.java
│   ├── ReceiveResult.java
│   ├── RedirectEnter.java
│   ├── RedirectGetter.java
│   ├── RedirectMain.java
│   ├── RemoteService.java
│   ├── ReorderFour.java
│   ├── ReorderOnLaunch.java
│   ├── ReorderThree.java
│   ├── ReorderTwo.java
│   ├── RepeatingAlarm.java
│   ├── RotationAnimation.java
│   ├── SaveRestoreState.java
│   ├── ScreenOrientation.java
│   ├── SearchInvoke.java
│   ├── SearchQueryResults.java
│   ├── SearchSuggestionSampleProvider.java
│   ├── SecureDialogActivity.java
│   ├── SecureSurfaceViewActivity.java
│   ├── SecureWindowActivity.java
│   ├── SendResult.java
│   ├── ServiceStartArguments.java
│   ├── SetWallpaperActivity.java
│   ├── SoftInputModes.java
│   ├── StatusBarNotifications.java
│   ├── TextToSpeechActivity.java
│   ├── TranslucentActivity.java
│   ├── TranslucentBlurActivity.java
│   ├── VoiceRecognition.java
│   └── WallpaperActivity.java
├── appwidget
│   ├── ExampleAppWidgetConfigure.java
│   ├── ExampleAppWidgetProvider.java
│   └── ExampleBroadcastReceiver.java
├── content
│   ├── ChangedContacts.java
│   ├── ClipboardSample.java
│   ├── DocumentsSample.java
│   ├── ExternalStorage.java
│   ├── FileProvider.java
│   ├── InstallApk.java
│   ├── PickContact.java
│   ├── ReadAsset.java
│   ├── ResourcesLayoutReference.java
│   ├── ResourcesSample.java
│   ├── ResourcesSmallestWidth.java
│   ├── ResourcesWidthAndHeight.java
│   ├── StyledText.java
│   └── TextUndoActivity.java
├── graphics
│   ├── AlphaBitmap.java
│   ├── AnimateDrawable.java
│   ├── AnimateDrawables.java
│   ├── Arcs.java
│   ├── BitmapDecode.java
│   ├── BitmapMesh.java
│   ├── BitmapPixels.java
│   ├── CameraPreview.java
│   ├── Clipping.java
│   ├── ColorFilters.java
│   ├── ColorMatrixSample.java
│   ├── ColorPickerDialog.java
│   ├── Compass.java
│   ├── CompressedTextureActivity.java
│   ├── CreateBitmap.java
│   ├── Cube.java
│   ├── CubeMapActivity.java
│   ├── CubeRenderer.java
│   ├── DensityActivity.java
│   ├── DrawPoints.java
│   ├── FingerPaint.java
│   ├── FrameBufferObjectActivity.java
│   ├── GLES20Activity.java
│   ├── GLES20TriangleRenderer.java
│   ├── GLSurfaceViewActivity.java
│   ├── GradientDrawable1.java
│   ├── GraphicsActivity.java
│   ├── Layers.java
│   ├── MatrixPaletteActivity.java
│   ├── MatrixPaletteRenderer.java
│   ├── MeasureText.java
│   ├── PathEffects.java
│   ├── PathFillTypes.java
│   ├── Patterns.java
│   ├── PictureLayout.java
│   ├── Pictures.java
│   ├── PolyToPoly.java
│   ├── ProxyDrawable.java
│   ├── PurgeableBitmap.java
│   ├── PurgeableBitmapView.java
│   ├── Regions.java
│   ├── RoundRects.java
│   ├── ScaleToFit.java
│   ├── SensorTest.java
│   ├── ShadowCardDrag.java
│   ├── ShadowCardStack.java
│   ├── ShapeDrawable1.java
│   ├── StaticTriangleRenderer.java
│   ├── SurfaceViewOverlay.java
│   ├── Sweep.java
│   ├── TextAlign.java
│   ├── TouchPaint.java
│   ├── TouchRotateActivity.java
│   ├── TranslucentGLSurfaceViewActivity.java
│   ├── TriangleActivity.java
│   ├── TriangleRenderer.java
│   ├── Typefaces.java
│   ├── UnicodeChart.java
│   ├── Vertices.java
│   ├── WindowSurface.java
│   ├── Xfermodes.java
│   ├── kube
│   └── spritetext
├── hardware
│   └── ConsumerIr.java
├── media
│   ├── AudioFxDemo.java
│   ├── MediaPlayerDemo.java
│   ├── MediaPlayerDemo_Audio.java
│   ├── MediaPlayerDemo_Video.java
│   ├── VideoViewDemo.java
│   └── projection
├── nfc
│   ├── ForegroundDispatch.java
│   ├── ForegroundNdefPush.java
│   └── TechFilter.java
├── preference
│   ├── AdvancedPreferences.java
│   ├── DefaultValues.java
│   ├── FragmentPreferences.java
│   ├── LaunchingPreferences.java
│   ├── MyPreference.java
│   ├── PreferenceDependencies.java
│   ├── PreferenceWithHeaders.java
│   ├── PreferencesFromCode.java
│   ├── PreferencesFromXml.java
│   └── SwitchPreference.java
├── security
│   └── KeyStoreUsage.java
├── text
│   ├── Link.java
│   ├── LogTextBox.java
│   ├── LogTextBox1.java
│   └── Marquee.java
└── view
    ├── Animation1.java
    ├── Animation2.java
    ├── Animation3.java
    ├── AutoComplete1.java
    ├── AutoComplete2.java
    ├── AutoComplete3.java
    ├── AutoComplete4.java
    ├── AutoComplete5.java
    ├── AutoComplete6.java
    ├── Baseline1.java
    ├── Baseline2.java
    ├── Baseline3.java
    ├── Baseline4.java
    ├── Baseline6.java
    ├── Baseline7.java
    ├── BaselineNested1.java
    ├── BaselineNested2.java
    ├── BaselineNested3.java
    ├── Buttons1.java
    ├── CheckableFrameLayout.java
    ├── Cheeses.java
    ├── ChronometerDemo.java
    ├── ContentBrowserActivity.java
    ├── ContentBrowserNavActivity.java
    ├── Controls1.java
    ├── Controls2.java
    ├── Controls3.java
    ├── Controls4.java
    ├── Controls5.java
    ├── Controls6.java
    ├── Controls7.java
    ├── Controls8.java
    ├── Controls9.java
    ├── CustomLayout.java
    ├── CustomLayoutActivity.java
    ├── CustomView1.java
    ├── DateWidgets1.java
    ├── DateWidgets2.java
    ├── DragAndDropDemo.java
    ├── DraggableDot.java
    ├── ExpandableList1.java
    ├── ExpandableList2.java
    ├── ExpandableList3.java
    ├── Focus1.java
    ├── Focus2.java
    ├── Focus3.java
    ├── Focus5.java
    ├── GameActivity.java
    ├── GameControllerInput.java
    ├── GameView.java
    ├── Grid1.java
    ├── Grid2.java
    ├── Grid3.java
    ├── GridLayout1.java
    ├── GridLayout2.java
    ├── GridLayout3.java
    ├── HorizontalScrollView1.java
    ├── Hover.java
    ├── HoverInterceptorView.java
    ├── ImageButton1.java
    ├── ImageView1.java
    ├── InternalSelectionFocus.java
    ├── InternalSelectionScroll.java
    ├── InternalSelectionView.java
    ├── LabelView.java
    ├── LayoutAnimation1.java
    ├── LayoutAnimation2.java
    ├── LayoutAnimation3.java
    ├── LayoutAnimation4.java
    ├── LayoutAnimation5.java
    ├── LayoutAnimation6.java
    ├── LayoutAnimation7.java
    ├── LinearLayout1.java
    ├── LinearLayout10.java
    ├── LinearLayout2.java
    ├── LinearLayout3.java
    ├── LinearLayout4.java
    ├── LinearLayout5.java
    ├── LinearLayout6.java
    ├── LinearLayout7.java
    ├── LinearLayout8.java
    ├── LinearLayout9.java
    ├── List1.java
    ├── List10.java
    ├── List11.java
    ├── List12.java
    ├── List13.java
    ├── List14.java
    ├── List15.java
    ├── List16.java
    ├── List17.java
    ├── List2.java
    ├── List3.java
    ├── List4.java
    ├── List5.java
    ├── List6.java
    ├── List7.java
    ├── List8.java
    ├── List9.java
    ├── PopupMenu1.java
    ├── ProgressBar1.java
    ├── ProgressBar2.java
    ├── ProgressBar3.java
    ├── ProgressBar4.java
    ├── RadioGroup1.java
    ├── RatingBar1.java
    ├── RelativeLayout1.java
    ├── RelativeLayout2.java
    ├── RotatingButton.java
    ├── ScrollBar1.java
    ├── ScrollBar2.java
    ├── ScrollBar3.java
    ├── ScrollView1.java
    ├── ScrollView2.java
    ├── SearchViewActionBar.java
    ├── SearchViewAlwaysVisible.java
    ├── SearchViewFilterMode.java
    ├── SecureView.java
    ├── SecureViewOverlay.java
    ├── SeekBar1.java
    ├── Spinner1.java
    ├── SplitTouchView.java
    ├── Switches.java
    ├── SystemUIModes.java
    ├── SystemUIModesOverlay.java
    ├── TableLayout1.java
    ├── TableLayout10.java
    ├── TableLayout11.java
    ├── TableLayout12.java
    ├── TableLayout2.java
    ├── TableLayout3.java
    ├── TableLayout4.java
    ├── TableLayout5.java
    ├── TableLayout6.java
    ├── TableLayout7.java
    ├── TableLayout8.java
    ├── TableLayout9.java
    ├── Tabs1.java
    ├── Tabs2.java
    ├── Tabs3.java
    ├── Tabs4.java
    ├── Tabs5.java
    ├── Tabs6.java
    ├── TextClockDemo.java
    ├── TextSwitcher1.java
    ├── TranslucentBarsActivity.java
    ├── VideoPlayerActivity.java
    ├── Visibility1.java
    ├── WebView1.java
    └── WindowFocusObserver.java

16 directories, 391 files

---

版权声明：《从 Android Sample ApiDemos 中学习 android.animation API 的用法》由 WeiYi.Li 在 2016年01月27日写作。著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。
文章链接：http://li2.me/2016/01/android-sdk-sample...