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Android Reference

SurfaceHolder


android.view

Interface SurfaceHolder



  • public interface SurfaceHolder
    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 other than the one running its SurfaceView, you will want to carefully read the methods lockCanvas() and Callback.surfaceCreated().

    • Field Detail

      • SURFACE_TYPE_NORMAL

        @Deprecated
        static final int SURFACE_TYPE_NORMAL
        Deprecated. this is ignored, this value is set automatically when needed.
        See Also:
        Constant Field Values
      • SURFACE_TYPE_HARDWARE

        @Deprecated
        static final int SURFACE_TYPE_HARDWARE
        Deprecated. this is ignored, this value is set automatically when needed.
        See Also:
        Constant Field Values
      • SURFACE_TYPE_GPU

        @Deprecated
        static final int SURFACE_TYPE_GPU
        Deprecated. this is ignored, this value is set automatically when needed.
        See Also:
        Constant Field Values
      • SURFACE_TYPE_PUSH_BUFFERS

        @Deprecated
        static final int SURFACE_TYPE_PUSH_BUFFERS
        Deprecated. this is ignored, this value is set automatically when needed.
        See Also:
        Constant Field Values
    • Method Detail

      • addCallback

        void addCallback(SurfaceHolder.Callback callback)
        Add a Callback interface for this holder. There can several Callback interfaces associated with a holder.
        Parameters:
        callback - The new Callback interface.
      • removeCallback

        void removeCallback(SurfaceHolder.Callback callback)
        Removes a previously added Callback interface from this holder.
        Parameters:
        callback - The Callback interface to remove.
      • setType

        @Deprecated
        void setType(int type)
        Deprecated. this is ignored, this value is set automatically when needed.
        Sets the surface's type.
      • setFixedSize

        void setFixedSize(int width,
                        int height)
        Make the surface a fixed size. It will never change from this size. When working with a 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.
      • setFormat

        void setFormat(int format)
        Set the desired PixelFormat of the surface. The default is OPAQUE. When working with a SurfaceView, this must be called from the same thread running the SurfaceView's window.
        Parameters:
        format - A constant from PixelFormat.
        See Also:
        PixelFormat
      • setKeepScreenOn

        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. This is safe to call from any thread.
        Parameters:
        screenOn - Set to true to force the screen to stay on, false to allow it to turn off.
      • lockCanvas

        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 cannot 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(android.graphics.Canvas) call, preventing SurfaceView from creating, destroying, or modifying the surface while it is being drawn. This can be more convenient 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.
      • lockCanvas

        Canvas lockCanvas(Rect dirty)
        Just like lockCanvas() but allows specification of 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:
        lockCanvas()
      • unlockCanvasAndPost

        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:
        lockCanvas()
      • getSurfaceFrame

        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.
      • getSurface

        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.


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