java.lang.Objectjava.awt.image.BufferStrategy
public abstract class BufferStrategy
The BufferStrategy class represents the mechanism with which to organize complex memory on a particular Canvas or Window. Hardware and software limitations determine whether and how a particular buffer strategy can be implemented. These limitations are detectible through the capabilities of the GraphicsConfiguration used when creating the Canvas or Window.
It is worth noting that the terms buffer and surface are meant to be synonymous: an area of contiguous memory, either in video device memory or in system memory.
There are several types of complex buffer strategies, including sequential ring buffering and blit buffering. Sequential ring buffering (i.e., double or triple buffering) is the most common; an application draws to a single back buffer and then moves the contents to the front (display) in a single step, either by copying the data or moving the video pointer. Moving the video pointer exchanges the buffers so that the first buffer drawn becomes the front buffer , or what is currently displayed on the device; this is called page flipping .
Alternatively, the contents of the back buffer can be copied, or blitted forward in a chain instead of moving the video pointer.
Double buffering: *********** *********** * * ------> * * [To display] <---- * Front B * Show * Back B. * <---- Rendering * * <------ * * *********** *********** Triple buffering: [To *********** *********** *********** display] * * --------+---------+------> * * <---- * Front B * Show * Mid. B. * * Back B. * <---- Rendering * * <------ * * <----- * * *********** *********** ***********
Here is an example of how buffer strategies can be created and used:
// Check the capabilities of the GraphicsConfiguration ... // Create our component Window w = new Window(gc); // Show our window w.setVisible(true); // Create a general double-buffering strategy w.createBufferStrategy(2); BufferStrategy strategy = w.getBufferStrategy(); // Main loop while (!done) { // Prepare for rendering the next frame // ... // Render single frame do { // The following loop ensures that the contents of the drawing buffer // are consistent in case the underlying surface was recreated do { // Get a new graphics context every time through the loop // to make sure the strategy is validated Graphics graphics = strategy.getDrawGraphics(); // Render to graphics // ... // Dispose the graphics graphics.dispose(); // Repeat the rendering if the drawing buffer contents // were restored } while (strategy.contentsRestored()); // Display the buffer strategy.show(); // Repeat the rendering if the drawing buffer was lost } while (strategy.contentsLost()); } // Dispose the window w.setVisible(false); w.dispose();
// Check the capabilities of the GraphicsConfiguration ... // Create our component Window w = new Window(gc); // Show our window w.setVisible(true); // Create a general double-buffering strategy w.createBufferStrategy(2); BufferStrategy strategy = w.getBufferStrategy(); // Render loop while (!done) { Graphics g = strategy.getDrawGraphics(); // Call this each time through to see if the underlying surface // was recreated. If it was you may need to redraw. if (strategy.contentsRestored()) { // Surface was recreated and reset, may require redrawing. } // Draw to graphics ... strategy.show(); if (strategy.contentsLost()) { // The surface was lost since last call to getDrawGraphics, you // may need to redraw. } } // Dispose the window w.setVisible(false); w.dispose();
Constructor Summary | |
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BufferStrategy
() |
Method Summary | |
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abstract boolean |
contentsLost
() Returns whether the drawing buffer was lost since the last call to getDrawGraphics. |
abstract boolean |
contentsRestored
() Returns whether the drawing buffer was recently restored from a lost state and reinitialized to the default background color (white). |
void |
dispose
() Releases system resources currently consumed by this BufferStrategy and removes it from the associated Component. |
abstract BufferCapabilities |
getCapabilities
() Returns the BufferCapabilities for this BufferStrategy. |
abstract Graphics |
getDrawGraphics
() Creates a graphics context for the drawing buffer. |
abstract void |
show
() Makes the next available buffer visible by either copying the memory (blitting) or changing the display pointer (flipping). |
Methods inherited from class java.lang. Object |
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clone , equals , finalize , getClass , hashCode , notify , notifyAll , toString , wait , wait , wait |
Constructor Detail |
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public BufferStrategy()
Method Detail |
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public abstract BufferCapabilities getCapabilities()
public abstract Graphics getDrawGraphics()
public abstract boolean contentsLost()
public abstract boolean contentsRestored()
public abstract void show()
public void dispose()