[Concepts and Jetpack Compose implementation](https://developer.android.com/topic/performance/hardware-accel) Beginning in Android 3.0 (API level 11), the Android 2D rendering pipeline supports hardware acceleration, meaning that all drawing operations that are performed on a [`View`](https://developer.android.com/reference/android/view/View)'s canvas use the GPU. Because of the increased resources required to enable hardware acceleration, your app will consume more RAM. Hardware acceleration is enabled by default if your Target API level is \>=14, but can also be explicitly enabled. If your application uses only standard views and [`Drawable`](https://developer.android.com/reference/android/graphics/drawable/Drawable)s, turning it on globally shouldn't cause any adverse drawing effects. However, because hardware acceleration isn't supported for all of the 2D drawing operations, turning it on might affect some of your custom views or drawing calls. Problems usually manifest themselves as invisible elements, exceptions, or wrongly rendered pixels. To remedy this, Android gives you the option to enable or disable hardware acceleration at multiple levels. See [Control hardware acceleration](https://developer.android.com/topic/performance/views/hardware-accel-views#controlling). If your application performs custom drawing, test your application on actual hardware devices with hardware acceleration turned on to find any problems. The [Support for drawing operations](https://developer.android.com/topic/performance/views/hardware-accel-views#drawing-support) section describes known issues with hardware acceleration and how to work around them. Also see [OpenGL with the Framework APIs](https://developer.android.com/develop/ui/views/graphics/opengl/about-opengl) and [Renderscript](https://developer.android.com/guide/topics/renderscript). ## Control hardware acceleration You can control hardware acceleration at the following levels: - Application - Activity - Window - View #### Application level In your Android manifest file, add the following attribute to the [``](https://developer.android.com/guide/topics/manifest/application-element) tag to enable hardware acceleration for your entire application: #### Activity level If your application does not behave properly with hardware acceleration turned on globally, you can control it for individual activities as well. To enable or disable hardware acceleration at the activity level, you can use the `android:hardwareAccelerated` attribute for the [``](https://developer.android.com/guide/topics/manifest/activity-element) element. The following example enables hardware acceleration for the entire application but disables it for one activity: #### Window level If you need even more fine-grained control, you can enable hardware acceleration for a given window with the following code: ### Kotlin ```kotlin window.setFlags( WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED, WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED ) ``` ### Java ```java getWindow().setFlags( WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED, WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED); ``` > [!NOTE] > **Note:** You currently cannot disable hardware acceleration at the window level. #### View level You can disable hardware acceleration for an individual view at runtime with the following code: ### Kotlin ```kotlin myView.setLayerType(View.LAYER_TYPE_SOFTWARE, null) ``` ### Java ```java myView.setLayerType(View.LAYER_TYPE_SOFTWARE, null); ``` > [!NOTE] > **Note:** You currently cannot enable hardware acceleration at the view level. View layers have other functions besides disabling hardware acceleration. See [View layers](https://developer.android.com/topic/performance/views/hardware-accel-views#layers) for more information about their uses. ## Determine if a view is hardware accelerated It is sometimes useful for an application to know whether it is currently hardware accelerated, especially for things such as custom views. This is particularly useful if your application does a lot of custom drawing and not all operations are properly supported by the new rendering pipeline. There are two different ways to check whether the application is hardware accelerated: - [`View.isHardwareAccelerated`](https://developer.android.com/reference/android/view/View#isHardwareAccelerated()) returns `true` if the [`View`](https://developer.android.com/reference/android/view/View) is attached to a hardware accelerated window. - [`Canvas.isHardwareAccelerated`](https://developer.android.com/reference/android/graphics/Canvas#isHardwareAccelerated) returns `true` if the [`Canvas`](https://developer.android.com/reference/android/graphics/Canvas) is hardware accelerated. If you must do this check in your drawing code, use [`Canvas.isHardwareAccelerated`](https://developer.android.com/reference/android/graphics/Canvas#isHardwareAccelerated()) instead of [`View.isHardwareAccelerated`](https://developer.android.com/reference/android/view/View#isHardwareAccelerated()) when possible. When a view is attached to a hardware accelerated window, it can still be drawn using a non-hardware accelerated Canvas. This happens, for example, when drawing a view into a bitmap for caching purposes. ## Android drawing models When hardware acceleration is enabled, the Android framework utilizes a new drawing model that utilizes *display lists* to render your application to the screen. To fully understand display lists and how they might affect your application, it is useful to understand how Android draws views without hardware acceleration as well. The following sections describe the software-based and hardware-accelerated drawing models. ### Software-based drawing model In the software drawing model, views are drawn with the following two steps: 1. Invalidate the hierarchy 2. Draw the hierarchy Whenever an application needs to update a part of its UI, it invokes [`invalidate()`](https://developer.android.com/reference/android/view/View#invalidate()) (or one of its variants) on any view that has changed content. The invalidation messages are propagated all the way up the view hierarchy to compute the regions of the screen that need to be redrawn (the dirty region). The Android system then draws any view in the hierarchy that intersects with the dirty region. Unfortunately, there are two drawbacks to this drawing model: - First, this model requires execution of a lot of code on every draw pass. For example, if your application calls [`invalidate`](https://developer.android.com/reference/android/view/View#invalidate()) on a button and that button sits on top of another view, the Android system redraws the view even though it hasn't changed. - The second issue is that the drawing model can hide bugs in your application. Since the Android system redraws views when they intersect the dirty region, a view whose content you changed might be redrawn even though [`invalidate`](https://developer.android.com/reference/android/view/View#invalidate()) was not called on it. When this happens, you are relying on another view being invalidated to obtain the proper behavior. This behavior can change every time you modify your application. Because of this, you should always call [`invalidate`](https://developer.android.com/reference/android/view/View#invalidate()) on your custom views whenever you modify data or state that affects the view's drawing code. > [!NOTE] > **Note:** Android views automatically call [`invalidate`](https://developer.android.com/reference/android/view/View#invalidate()) when their properties change, such as the background color or the text in a [`TextView`](https://developer.android.com/reference/android/widget/TextView). ### Hardware accelerated drawing model The Android system still uses [`invalidate`](https://developer.android.com/reference/android/view/View#invalidate()) and [`draw`](https://developer.android.com/reference/android/view/View#draw(android.graphics.Canvas)) to request screen updates and to render views, but handles the actual drawing differently. Instead of executing the drawing commands immediately, the Android system records them inside display lists, which contain the output of the view hierarchy's drawing code. Another optimization is that the Android system only needs to record and update display lists for views marked dirty by an [`invalidate`](https://developer.android.com/reference/android/view/View#invalidate()) call. Views that have not been invalidated can be redrawn by re-issuing the previously recorded display list. The new drawing model contains three stages: 1. Invalidate the hierarchy 2. Record and update display lists 3. Draw the display lists With this model, you cannot rely on a view intersecting the dirty region to have its [`draw`](https://developer.android.com/reference/android/view/View#draw(android.graphics.Canvas)) method executed. To ensure that the Android system records a view's display list, you must call [`invalidate`](https://developer.android.com/reference/android/view/View#invalidate()). Forgetting to do so causes a view to look the same even after it has been changed. Using display lists also benefits animation performance because setting specific properties, such as alpha or rotation, does not require invalidating the targeted view (it is done automatically). This optimization also applies to views with display lists (any view when your application is hardware accelerated.) For example, assume there is a [`LinearLayout`](https://developer.android.com/reference/android/widget/LinearLayout) that contains a [`ListView`](https://developer.android.com/reference/android/widget/ListView) above a [`Button`](https://developer.android.com/reference/android/widget/Button). The display list for the [`LinearLayout`](https://developer.android.com/reference/android/widget/LinearLayout) looks like this: - `DrawDisplayList(ListView)` - `DrawDisplayList(Button)` Assume now that you want to change the [`ListView`](https://developer.android.com/reference/android/widget/ListView)'s opacity. After invoking `setAlpha(0.5f)` on the [`ListView`](https://developer.android.com/reference/android/widget/ListView), the display list now contains this: - `SaveLayerAlpha(0.5)` - `DrawDisplayList(ListView)` - `Restore` - `DrawDisplayList(Button)` The complex drawing code of [`ListView`](https://developer.android.com/reference/android/widget/ListView) was not executed. Instead, the system only updated the display list of the much simpler [`LinearLayout`](https://developer.android.com/reference/android/widget/LinearLayout). In an application without hardware acceleration enabled, the drawing code of both the list and its parent are executed again. ## Support for drawing operations When hardware accelerated, the 2D rendering pipeline supports the most commonly used [`Canvas`](https://developer.android.com/reference/android/graphics/Canvas) drawing operations as well as many less-used operations. All of the drawing operations that are used to render applications that ship with Android, default widgets and layouts, and common advanced visual effects such as reflections and tiled textures are supported. The following table describes the support level of various operations across API levels: |---|---|---|---|---| | | | | | First supported API level | | Canvas ||||| | drawBitmapMesh() (colors array) | 18 | | drawPicture() | 23 | | drawPosText() | 16 | | drawTextOnPath() | 16 | | drawVertices() | 29 | | setDrawFilter() | 16 | | clipPath() | 18 | | clipRegion() | 18 | | clipRect(Region.Op.XOR) | 18 | | clipRect(Region.Op.Difference) | 18 | | clipRect(Region.Op.ReverseDifference) | 18 | | clipRect() with rotation/perspective | 18 | | Paint ||||| | setAntiAlias() (for text) | 18 | | setAntiAlias() (for lines) | 16 | | setFilterBitmap() | 17 | | setLinearText() | ✗ | | setMaskFilter() | ✗ | | setPathEffect() (for lines) | 28 | | setShadowLayer() (other than text) | 28 | | setStrokeCap() (for lines) | 18 | | setStrokeCap() (for points) | 19 | | setSubpixelText() | 28 | | Xfermode ||||| | PorterDuff.Mode.DARKEN (framebuffer) | 28 | | PorterDuff.Mode.LIGHTEN (framebuffer) | 28 | | PorterDuff.Mode.OVERLAY (framebuffer) | 28 | | Shader ||||| | ComposeShader inside ComposeShader | 28 | | Same type shaders inside ComposeShader | 28 | | Local matrix on ComposeShader | 18 |
### Canvas scaling The hardware accelerated 2D rendering pipeline was built first to support unscaled drawing, with some drawing operations degrading quality significantly at higher scale values. These operations are implemented as textures drawn at scale 1.0, transformed by the GPU. Starting in API level 28, all drawing operations can scale without issue. The following table shows when implementation was changed to correctly handle large scales:
|---|---| | | | | Drawing operation to be scaled | First supported API level | | drawText() | 18 | | drawPosText() | 28 | | drawTextOnPath() | 28 | | Simple Shapes | 17 | | Complex Shapes | 28 | | drawPath() | 28 | | Shadow layer | 28 |
> [!NOTE] > **Note:** 'Simple' shapes are `drawRect()`, `drawCircle()`, `drawOval()`, `drawRoundRect()`, and `drawArc()` (with `useCenter=false`) commands issued with a `Paint` that doesn't have a `PathEffect`, and doesn't contain non-default joins (using `setStrokeJoin()` or `setStrokeMiter()`). Other instances of those draw commands fall under 'Complex' in the preceding chart. If your application is affected by any of these missing features or limitations, you can turn off hardware acceleration for just the affected portion of your application by calling [`setLayerType(View.LAYER_TYPE_SOFTWARE, null)`](https://developer.android.com/reference/android/view/View#setLayerType(int,%20android.graphics.Paint)). This way, you can still take advantage of hardware acceleration everywhere else. See [Control hardware acceleration](https://developer.android.com/topic/performance/views/hardware-accel-views#controlling) for more information on how to enable and disable hardware acceleration at different levels in your application. ## View layers In all versions of Android, views have had the ability to render into off-screen buffers, either by using a view's drawing cache, or by using [`Canvas.saveLayer`](https://developer.android.com/reference/android/graphics/Canvas#saveLayer(android.graphics.RectF,%20android.graphics.Paint)). Off-screen buffers, or layers, have several uses. You can use them to get better performance when animating complex views or to apply composition effects. For example, you can implement fade effects using `Canvas.saveLayer` to temporarily render a view into a layer and then composite it back on screen with an opacity factor. Beginning in Android 3.0 (API level 11), you have more control on how and when to use layers with the [`View.setLayerType`](https://developer.android.com/reference/android/view/View#setLayerType(int,%20android.graphics.Paint)) method. This API takes two parameters: the type of layer you want to use and an optional [`Paint`](https://developer.android.com/reference/android/graphics/Paint) object that describes how the layer should be composited. You can use the [`Paint`](https://developer.android.com/reference/android/graphics/Paint) parameter to apply color filters, special blending modes, or opacity to a layer. A view can use one of three layer types: - [`LAYER_TYPE_NONE`](https://developer.android.com/reference/android/view/View#LAYER_TYPE_NONE): The view is rendered normally and is not backed by an off-screen buffer. This is the default behavior. - [`LAYER_TYPE_HARDWARE`](https://developer.android.com/reference/android/view/View#LAYER_TYPE_HARDWARE): The view is rendered in hardware into a hardware texture if the application is hardware accelerated. If the application is not hardware accelerated, this layer type behaves the same as [`LAYER_TYPE_SOFTWARE`](https://developer.android.com/reference/android/view/View#LAYER_TYPE_SOFTWARE). - [`LAYER_TYPE_SOFTWARE`](https://developer.android.com/reference/android/view/View#LAYER_TYPE_SOFTWARE): The view is rendered in software into a bitmap. The type of layer you use depends on your goal: - **Performance** : Use a hardware layer type to render a view into a hardware texture. Once a view is rendered into a layer, its drawing code doesn't have to be executed until the view calls [`invalidate`](https://developer.android.com/reference/android/view/View#invalidate()). Some animations, such as alpha animations, can then be applied directly onto the layer, which is very efficient for the GPU to do. - **Visual effects** : Use a hardware or software layer type and a [`Paint`](https://developer.android.com/reference/android/graphics/Paint) to apply special visual treatments to a view. For example, you can draw a view in black and white using a [`ColorMatrixColorFilter`](https://developer.android.com/reference/android/graphics/ColorMatrixColorFilter). - **Compatibility**: Use a software layer type to force a view to be rendered in software. If a view that is hardware accelerated (for instance, if your whole application is hardware accelerated), is having rendering problems, this is an easy way to work around limitations of the hardware rendering pipeline. ### View layers and animations Hardware layers can deliver faster and smoother animations when your application is hardware accelerated. Running an animation at 60 frames per second isn't always possible when animating complex views that issue a lot of drawing operations. This can be alleviated by using hardware layers to render the view to a hardware texture. The hardware texture can then be used to animate the view, eliminating the need for the view to constantly redraw itself when it's being animated. The view is not redrawn unless you change the view's properties, which calls [`invalidate`](https://developer.android.com/reference/android/view/View#invalidate()), or if you call [`invalidate`](https://developer.android.com/reference/android/view/View#invalidate()) manually. If you are running an animation in your application and don't obtain the smooth results you want, consider enabling hardware layers on your animated views. When a view is backed by a hardware layer, some of its properties are handled by the way the layer is composited on screen. Setting these properties will be efficient because they don't require the view to be invalidated and redrawn. The following is a list of properties that affect the way the layer is composited. Calling the setter for any of these properties results in optimal invalidation and no redrawing of the targeted view: - `alpha`: Changes the layer's opacity - `x`, `y`, `translationX`, `translationY`: Changes the layer's position - `scaleX`, `scaleY`: Changes the layer's size - `rotation`, `rotationX`, `rotationY`: Changes the layer's orientation in 3D space - `pivotX`, `pivotY`: Changes the layer's transformations origin These properties are the names used when animating a view with an [`ObjectAnimator`](https://developer.android.com/reference/android/animation/ObjectAnimator). If you want to access these properties, call the appropriate setter or getter. For example, to modify the alpha property, call [`setAlpha`](https://developer.android.com/reference/android/view/View#setAlpha(float)). The following code snippet shows the most efficient way to rotate a view in 3D around the Y-axis: ### Kotlin ```kotlin view.setLayerType(View.LAYER_TYPE_HARDWARE, null) ObjectAnimator.ofFloat(view, "rotationY", 180f).start() ``` ### Java ```java view.setLayerType(View.LAYER_TYPE_HARDWARE, null); ObjectAnimator.ofFloat(view, "rotationY", 180).start(); ``` Because hardware layers consume video memory, it is highly recommended that you enable them only for the duration of the animation and then disable them after the animation is done. You can accomplish this using animation listeners: ### Kotlin ```kotlin view.setLayerType(View.LAYER_TYPE_HARDWARE, null) ObjectAnimator.ofFloat(view, "rotationY", 180f).apply { addListener(object : AnimatorListenerAdapter() { override fun onAnimationEnd(animation: Animator) { view.setLayerType(View.LAYER_TYPE_NONE, null) } }) start() } ``` ### Java ```java view.setLayerType(View.LAYER_TYPE_HARDWARE, null); ObjectAnimator animator = ObjectAnimator.ofFloat(view, "rotationY", 180); animator.addListener(new AnimatorListenerAdapter() { @Override public void onAnimationEnd(Animator animation) { view.setLayerType(View.LAYER_TYPE_NONE, null); } }); animator.start(); ``` For more information on property animation, see [Property animation](https://developer.android.com/guide/topics/graphics/prop-animation). ## Tips and tricks Switching to hardware accelerated 2D graphics can instantly increase performance, but you should still design your application to use the GPU effectively by following these recommendations: **Reduce the number of views in your application** : The more views the system has to draw, the slower it will be. This applies to the software rendering pipeline as well. Reducing views is one of the easiest ways to optimize your UI. **Avoid overdraw** : Don't draw too many layers on top of each other. Remove any views that are completely obscured by other opaque views on top of it. If you need to draw several layers blended on top of each other, consider merging them into a single layer. A good rule of thumb with current hardware is to not draw more than 2.5 times the number of pixels on screen per frame (transparent pixels in a bitmap count!). **Don't create render objects in draw methods** : A common mistake is to create a new `https://developer.android.com/reference/android/graphics/Paint` or a new `https://developer.android.com/reference/android/graphics/Path` every time a rendering method is invoked. This forces the garbage collector to run more often and also bypasses caches and optimizations in the hardware pipeline. **Don't modify shapes too often** : Complex shapes, paths, and circles for example, are rendered using texture masks. Every time you create or modify a path, the hardware pipeline creates a new mask, which can be expensive. **Don't modify bitmaps too often** : Every time you change the content of a bitmap, it is uploaded again as a GPU texture the next time you draw it. **Use alpha with care** : When you make a view translucent using `https://developer.android.com/reference/android/view/View#setAlpha(float)`, `https://developer.android.com/reference/android/view/animation/AlphaAnimation`, or `https://developer.android.com/reference/android/animation/ObjectAnimator`, it is rendered in an off-screen buffer which doubles the required fill-rate. When applying alpha on very large views, consider setting the view's layer type to `LAYER_TYPE_HARDWARE`.