public interface

SurfaceHolder

android.view.SurfaceHolder

Class Overview

Abstract interface to someone holding a display surface. Allows you to control the surface size and format, edit the pixels in the surface, and monitor changes to the surface. This interface is typically available through the SurfaceView class.

When using this interface from a thread different than the one running its SurfaceView, you will want to carefully read the lockCanvas() and Callback.surfaceCreated.

Summary

Nested Classes
public interface SurfaceHolder.BadSurfaceTypeException Exception that is thrown from lockCanvas() when called on a Surface whose is SURFACE_TYPE_PUSH_BUFFERS. 
public interface SurfaceHolder.Callback A client may implement this interface to receive information about changes to the surface. 
Constants
int SURFACE_TYPE_GPU Surface type: creates a surface suited to be used with the GPU
int SURFACE_TYPE_HARDWARE Surface type: creates a suited to be used with DMA engines and hardware accelerators.
int SURFACE_TYPE_NORMAL Surface type: creates a regular surface, usually in main, non contiguous, cached/buffered RAM.
int SURFACE_TYPE_PUSH_BUFFERS Surface type: creates a "push" surface, that is a surface that doesn't owns its buffers.
Public Methods
abstract void addCallback(SurfaceHolder.Callback callback)
Add a Callback interface for this holder.
abstract Surface getSurface()
Direct access to the surface object.
abstract Rect getSurfaceFrame()
Retrieve the current size of the surface.
abstract boolean isCreating()
Use this method to find out if the surface is in the process of being created from Callback methods.
abstract Canvas lockCanvas()
Start editing the pixels in the surface.
abstract Canvas lockCanvas(Rect dirty)
Just like lockCanvas() but allows to specify a dirty rectangle.
abstract void removeCallback(SurfaceHolder.Callback callback)
Removes a previously added Callback interface from this holder.
abstract void setFixedSize(int width, int height)
Make the surface a fixed size.
abstract void setFormat(int format)
Set the desired PixelFormat of the surface.
abstract void setKeepScreenOn(boolean screenOn)
Enable or disable option to keep the screen turned on while this surface is displayed.
abstract void setSizeFromLayout()
Allow the surface to resized based on layout of its container (this is the default).
abstract void setType(int type)
Sets the surface's type.
abstract void unlockCanvasAndPost(Canvas canvas)
Finish editing pixels in the surface.

Constants

public static final int SURFACE_TYPE_GPU

Surface type: creates a surface suited to be used with the GPU

Constant Value: 2 (0x00000002)

public static final int SURFACE_TYPE_HARDWARE

Surface type: creates a suited to be used with DMA engines and hardware accelerators.

Constant Value: 1 (0x00000001)

public static final int SURFACE_TYPE_NORMAL

Surface type: creates a regular surface, usually in main, non contiguous, cached/buffered RAM.

Constant Value: 0 (0x00000000)

public static final int SURFACE_TYPE_PUSH_BUFFERS

Surface type: creates a "push" surface, that is a surface that doesn't owns its buffers. With such a surface lockCanvas will fail.

Constant Value: 3 (0x00000003)

Public Methods

public abstract void addCallback (SurfaceHolder.Callback callback)

Add a Callback interface for this holder. There can several Callback interfaces associated to a holder.

Parameters
callback The new Callback interface.

public abstract Surface getSurface ()

Direct access to the surface object. The Surface may not always be available -- for example when using a SurfaceView the holder's Surface is not created until the view has been attached to the window manager and performed a layout in order to determine the dimensions and screen position of the Surface. You will thus usually need to implement Callback.surfaceCreated to find out when the Surface is available for use.

Note that if you directly access the Surface from another thread, it is critical that you correctly implement Callback.surfaceCreated and Callback.surfaceDestroyed to ensure that thread only accesses the Surface while it is valid, and that the Surface does not get destroyed while the thread is using it.

This method is intended to be used by frameworks which often need direct access to the Surface object (usually to pass it to native code). When designing APIs always use SurfaceHolder to pass surfaces around as opposed to the Surface object itself. A rule of thumb is that application code should never have to call this method.

Returns
  • Surface The surface.

public abstract Rect getSurfaceFrame ()

Retrieve the current size of the surface. Note: do not modify the returned Rect. This is only safe to call from the thread of SurfaceView's window, or while inside of lockCanvas().

Returns
  • Rect The surface's dimensions. The left and top are always 0.

public abstract boolean isCreating ()

Use this method to find out if the surface is in the process of being created from Callback methods. This is intended to be used with surfaceChanged(SurfaceHolder, int, int, int).

Returns
  • true if the surface is in the process of being created.

public abstract Canvas lockCanvas ()

Start editing the pixels in the surface. The returned Canvas can be used to draw into the surface's bitmap. A null is returned if the surface has not been created or otherwise can not be edited. You will usually need to implement Callback.surfaceCreated to find out when the Surface is available for use.

The content of the Surface is never preserved between unlockCanvas() and lockCanvas(), for this reason, every pixel within the Surface area must be written. The only exception to this rule is when a dirty rectangle is specified, in which case, non dirty pixels will be preserved.

If you call this repeatedly when the Surface is not ready (before Callback.surfaceCreated or after Callback.surfaceDestroyed), your calls will be throttled to a slow rate in order to avoid consuming CPU.

If null is not returned, this function internally holds a lock until the corresponding unlockCanvasAndPost(Canvas) call, preventing SurfaceView from creating, destroying, or modifying the surface while it is being drawn. This can be more convenience than accessing the Surface directly, as you do not need to do special synchronization with a drawing thread in Callback.surfaceDestroyed.

Returns
  • Canvas Use to draw into the surface.

public abstract Canvas lockCanvas (Rect dirty)

Just like lockCanvas() but allows to specify a dirty rectangle. Every pixel within that rectangle must be written; however pixels outside the dirty rectangle will be preserved by the next call to lockCanvas().

Parameters
dirty Area of the Surface that will be modified.
Returns
  • Canvas Use to draw into the surface.
See Also

public abstract void removeCallback (SurfaceHolder.Callback callback)

Removes a previously added Callback interface from this holder.

Parameters
callback The Callback interface to remove.

public abstract void setFixedSize (int width, int height)

Make the surface a fixed size. It will never change from this size. When working with a {link SurfaceView}, this must be called from the same thread running the SurfaceView's window.

Parameters
width The surface's width.
height The surface's height.

public abstract void setFormat (int format)

Set the desired PixelFormat of the surface. The default is OPAQUE. When working with a {link SurfaceView}, this must be called from the same thread running the SurfaceView's window.

Parameters
format A constant from PixelFormat.
See Also

public abstract void setKeepScreenOn (boolean screenOn)

Enable or disable option to keep the screen turned on while this surface is displayed. The default is false, allowing it to turn off. Enabling the option effectivelty. This is safe to call from any thread.

Parameters
screenOn Supply to true to force the screen to stay on, false to allow it to turn off.

public abstract void setSizeFromLayout ()

Allow the surface to resized based on layout of its container (this is the default). When this is enabled, you should monitor surfaceChanged(SurfaceHolder, int, int, int) for changes to the size of the surface. When working with a {link SurfaceView}, this must be called from the same thread running the SurfaceView's window.

public abstract void setType (int type)

Sets the surface's type. Surfaces intended to be used with OpenGL ES should be of SURFACE_TYPE_GPU, surfaces accessed by DMA engines and hardware accelerators should be of type SURFACE_TYPE_HARDWARE. Failing to set the surface's type appropriately could result in degraded performance or failure.

Parameters
type The surface's memory type.

public abstract void unlockCanvasAndPost (Canvas canvas)

Finish editing pixels in the surface. After this call, the surface's current pixels will be shown on the screen, but its content is lost, in particular there is no guarantee that the content of the Surface will remain unchanged when lockCanvas() is called again.

Parameters
canvas The Canvas previously returned by lockCanvas().
See Also