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SurfaceView

public class SurfaceView
extends View

java.lang.Object
   ↳ android.view.View
     ↳ android.view.SurfaceView


Provides a dedicated drawing surface embedded inside of a view hierarchy. You can control the format of this surface and, if you like, its size; the SurfaceView takes care of placing the surface at the correct location on the screen

The surface is Z ordered so that it is behind the window holding its SurfaceView; the SurfaceView punches a hole in its window to allow its surface to be displayed. The view hierarchy will take care of correctly compositing with the Surface any siblings of the SurfaceView that would normally appear on top of it. This can be used to place overlays such as buttons on top of the Surface, though note however that it can have an impact on performance since a full alpha-blended composite will be performed each time the Surface changes.

The transparent region that makes the surface visible is based on the layout positions in the view hierarchy. If the post-layout transform properties are used to draw a sibling view on top of the SurfaceView, the view may not be properly composited with the surface.

Access to the underlying surface is provided via the SurfaceHolder interface, which can be retrieved by calling getHolder().

The Surface will be created for you while the SurfaceView's window is visible; you should implement SurfaceHolder.Callback#surfaceCreated and SurfaceHolder.Callback#surfaceDestroyed to discover when the Surface is created and destroyed as the window is shown and hidden.

One of the purposes of this class is to provide a surface in which a secondary thread can render into the screen. If you are going to use it this way, you need to be aware of some threading semantics:

Note: Starting in platform version Build.VERSION_CODES.N, SurfaceView's window position is updated synchronously with other View rendering. This means that translating and scaling a SurfaceView on screen will not cause rendering artifacts. Such artifacts may occur on previous versions of the platform when its window is positioned asynchronously.

Summary

Inherited XML attributes

Inherited constants

Inherited fields

Public constructors

SurfaceView(Context context)
SurfaceView(Context context, AttributeSet attrs)
SurfaceView(Context context, AttributeSet attrs, int defStyleAttr)
SurfaceView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes)

Public methods

void draw(Canvas canvas)

Manually render this view (and all of its children) to the given Canvas.

boolean gatherTransparentRegion(Region region)
SurfaceHolder getHolder()

Return the SurfaceHolder providing access and control over this SurfaceView's underlying surface.

IBinder getHostToken()

A token used for constructing SurfaceControlViewHost.

int getImportantForAccessibility()

Gets the mode for determining whether this View is important for accessibility.

SurfaceControl getSurfaceControl()

Return a SurfaceControl which can be used for parenting Surfaces to this SurfaceView.

void setAlpha(float alpha)

Sets the opacity of the view to a value from 0 to 1, where 0 means the view is completely transparent and 1 means the view is completely opaque.

void setChildSurfacePackage(SurfaceControlViewHost.SurfacePackage p)

Display the view-hierarchy embedded within a SurfaceControlViewHost.SurfacePackage within this SurfaceView.

void setClipBounds(Rect clipBounds)

Sets a rectangular area on this view to which the view will be clipped when it is drawn.

void setSecure(boolean isSecure)

Control whether the surface view's content should be treated as secure, preventing it from appearing in screenshots or from being viewed on non-secure displays.

void setVisibility(int visibility)

Set the visibility state of this view.

void setZOrderMediaOverlay(boolean isMediaOverlay)

Control whether the surface view's surface is placed on top of another regular surface view in the window (but still behind the window itself).

void setZOrderOnTop(boolean onTop)

Control whether the surface view's surface is placed on top of its window.

Protected methods

void dispatchDraw(Canvas canvas)

Called by draw to draw the child views.

void onAttachedToWindow()

This is called when the view is attached to a window.

void onDetachedFromWindow()

This is called when the view is detached from a window.

void onMeasure(int widthMeasureSpec, int heightMeasureSpec)

Measure the view and its content to determine the measured width and the measured height.

void onWindowVisibilityChanged(int visibility)

Called when the window containing has change its visibility (between GONE, INVISIBLE, and VISIBLE).

Inherited methods

Public constructors

SurfaceView

public SurfaceView (Context context)

Parameters
context Context

SurfaceView

public SurfaceView (Context context, 
                AttributeSet attrs)

Parameters
context Context

attrs AttributeSet

SurfaceView

public SurfaceView (Context context, 
                AttributeSet attrs, 
                int defStyleAttr)

Parameters
context Context

attrs AttributeSet

defStyleAttr int

SurfaceView

public SurfaceView (Context context, 
                AttributeSet attrs, 
                int defStyleAttr, 
                int defStyleRes)

Parameters
context Context

attrs AttributeSet

defStyleAttr int

defStyleRes int

Public methods

draw

public void draw (Canvas canvas)

Manually render this view (and all of its children) to the given Canvas. The view must have already done a full layout before this function is called. When implementing a view, implement onDraw(android.graphics.Canvas) instead of overriding this method. If you do need to override this method, call the superclass version.
If you override this method you must call through to the superclass implementation.

Parameters
canvas Canvas: The Canvas to which the View is rendered.

gatherTransparentRegion

public boolean gatherTransparentRegion (Region region)

Parameters
region Region

Returns
boolean

getHolder

public SurfaceHolder getHolder ()

Return the SurfaceHolder providing access and control over this SurfaceView's underlying surface.

Returns
SurfaceHolder SurfaceHolder The holder of the surface.

getHostToken

public IBinder getHostToken ()

A token used for constructing SurfaceControlViewHost. This token should be passed from the host process to the client process.

Returns
IBinder The token This value may be null.

getImportantForAccessibility

public int getImportantForAccessibility ()

Gets the mode for determining whether this View is important for accessibility. A view is important for accessibility if it fires accessibility events and if it is reported to accessibility services that query the screen.

Returns
int The mode for determining whether a view is important for accessibility, one of IMPORTANT_FOR_ACCESSIBILITY_AUTO, IMPORTANT_FOR_ACCESSIBILITY_YES, IMPORTANT_FOR_ACCESSIBILITY_NO, or IMPORTANT_FOR_ACCESSIBILITY_NO_HIDE_DESCENDANTS.

getSurfaceControl

public SurfaceControl getSurfaceControl ()

Return a SurfaceControl which can be used for parenting Surfaces to this SurfaceView.

Returns
SurfaceControl The SurfaceControl for this SurfaceView.

setAlpha

public void setAlpha (float alpha)

Sets the opacity of the view to a value from 0 to 1, where 0 means the view is completely transparent and 1 means the view is completely opaque.

Note: setting alpha to a translucent value (0 < alpha < 1) can have significant performance implications, especially for large views. It is best to use the alpha property sparingly and transiently, as in the case of fading animations.

For a view with a frequently changing alpha, such as during a fading animation, it is strongly recommended for performance reasons to either override hasOverlappingRendering() to return false if appropriate, or setting a layer type on the view for the duration of the animation. On versions Build.VERSION_CODES.M and below, the default path for rendering an unlayered View with alpha could add multiple milliseconds of rendering cost, even for simple or small views. Starting with Build.VERSION_CODES.M, LAYER_TYPE_HARDWARE is automatically applied to the view at the rendering level.

If this view overrides onSetAlpha(int) to return true, then this view is responsible for applying the opacity itself.

On versions Build.VERSION_CODES.LOLLIPOP_MR1 and below, note that if the view is backed by a layer and is associated with a layer paint, setting an alpha value less than 1.0 will supersede the alpha of the layer paint.

Starting with Build.VERSION_CODES.M, setting a translucent alpha value will clip a View to its bounds, unless the View returns false from hasOverlappingRendering().

Parameters
alpha float: The opacity of the view. Value is between 0.0 and 1.0 inclusive

setChildSurfacePackage

public void setChildSurfacePackage (SurfaceControlViewHost.SurfacePackage p)

Display the view-hierarchy embedded within a SurfaceControlViewHost.SurfacePackage within this SurfaceView. This can be called independently of the SurfaceView lifetime callbacks. SurfaceView will internally manage reparenting the package to our Surface as it is created and destroyed. If this SurfaceView is above its host Surface (see setZOrderOnTop(boolean) then the embedded Surface hierarchy will be able to receive input. This will take ownership of the SurfaceControl contained inside the SurfacePackage and free the caller of the obligation to call SurfaceControlViewHost.SurfacePackage#release. However, note that SurfaceControlViewHost.SurfacePackage#release and SurfaceControlViewHost#release are not the same. While the ownership of this particular SurfaceControlViewHost.SurfacePackage will be taken by the SurfaceView the underlying SurfaceControlViewHost remains managed by it's original remote-owner.

Parameters
p SurfaceControlViewHost.SurfacePackage: The SurfacePackage to embed. This value cannot be null.

setClipBounds

public void setClipBounds (Rect clipBounds)

Sets a rectangular area on this view to which the view will be clipped when it is drawn. Setting the value to null will remove the clip bounds and the view will draw normally, using its full bounds.

Parameters
clipBounds Rect: The rectangular area, in the local coordinates of this view, to which future drawing operations will be clipped.

setSecure

public void setSecure (boolean isSecure)

Control whether the surface view's content should be treated as secure, preventing it from appearing in screenshots or from being viewed on non-secure displays.

Note that this must be set before the surface view's containing window is attached to the window manager.

See Display.FLAG_SECURE for details.

Parameters
isSecure boolean: True if the surface view is secure.

setVisibility

public void setVisibility (int visibility)

Set the visibility state of this view.

Parameters
visibility int: One of View.VISIBLE, View.INVISIBLE, or View.GONE. Value is View.VISIBLE, View.INVISIBLE, or View.GONE

setZOrderMediaOverlay

public void setZOrderMediaOverlay (boolean isMediaOverlay)

Control whether the surface view's surface is placed on top of another regular surface view in the window (but still behind the window itself). This is typically used to place overlays on top of an underlying media surface view.

Note that this must be set before the surface view's containing window is attached to the window manager.

Calling this overrides any previous call to setZOrderOnTop(boolean).

Parameters
isMediaOverlay boolean

setZOrderOnTop

public void setZOrderOnTop (boolean onTop)

Control whether the surface view's surface is placed on top of its window. Normally it is placed behind the window, to allow it to (for the most part) appear to composite with the views in the hierarchy. By setting this, you cause it to be placed above the window. This means that none of the contents of the window this SurfaceView is in will be visible on top of its surface.

Note that this must be set before the surface view's containing window is attached to the window manager. If you target Build.VERSION_CODES#R the Z ordering can be changed dynamically if the backing surface is created, otherwise it would be applied at surface construction time.

Calling this overrides any previous call to setZOrderMediaOverlay(boolean).

Parameters
onTop boolean: Whether to show the surface on top of this view's window.

Protected methods

dispatchDraw

protected void dispatchDraw (Canvas canvas)

Called by draw to draw the child views. This may be overridden by derived classes to gain control just before its children are drawn (but after its own view has been drawn).

Parameters
canvas Canvas: the canvas on which to draw the view

onAttachedToWindow

protected void onAttachedToWindow ()

This is called when the view is attached to a window. At this point it has a Surface and will start drawing. Note that this function is guaranteed to be called before onDraw(android.graphics.Canvas), however it may be called any time before the first onDraw -- including before or after onMeasure(int, int).
If you override this method you must call through to the superclass implementation.

onDetachedFromWindow

protected void onDetachedFromWindow ()

This is called when the view is detached from a window. At this point it no longer has a surface for drawing.
If you override this method you must call through to the superclass implementation.

onMeasure

protected void onMeasure (int widthMeasureSpec, 
                int heightMeasureSpec)

Measure the view and its content to determine the measured width and the measured height. This method is invoked by measure(int, int) and should be overridden by subclasses to provide accurate and efficient measurement of their contents.

CONTRACT: When overriding this method, you must call setMeasuredDimension(int, int) to store the measured width and height of this view. Failure to do so will trigger an IllegalStateException, thrown by measure(int, int). Calling the superclass' onMeasure(int, int) is a valid use.

The base class implementation of measure defaults to the background size, unless a larger size is allowed by the MeasureSpec. Subclasses should override onMeasure(int, int) to provide better measurements of their content.

If this method is overridden, it is the subclass's responsibility to make sure the measured height and width are at least the view's minimum height and width (getSuggestedMinimumHeight() and getSuggestedMinimumWidth()).

Parameters
widthMeasureSpec int: horizontal space requirements as imposed by the parent. The requirements are encoded with View.MeasureSpec.

heightMeasureSpec int: vertical space requirements as imposed by the parent. The requirements are encoded with View.MeasureSpec.

onWindowVisibilityChanged

protected void onWindowVisibilityChanged (int visibility)

Called when the window containing has change its visibility (between GONE, INVISIBLE, and VISIBLE). Note that this tells you whether or not your window is being made visible to the window manager; this does not tell you whether or not your window is obscured by other windows on the screen, even if it is itself visible.

Parameters
visibility int: The new visibility of the window. Value is View.VISIBLE, View.INVISIBLE, or View.GONE