Component.BltBufferStrategy
, Component.FlipBufferStrategy
public abstract class BufferStrategy extends Object
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 detectable 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();
Modifier | Constructor | Description |
---|---|---|
protected |
Constructor for subclasses to call. |
Modifier and Type | Method | Description |
---|---|---|
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). |
protected BufferStrategy()
public abstract BufferCapabilities getCapabilities()
BufferCapabilities
for this BufferStrategy
.public abstract Graphics getDrawGraphics()
public abstract boolean contentsLost()
getDrawGraphics
. Since the buffers in a buffer strategy are usually type VolatileImage
, they may become lost. For a discussion on lost buffers, see VolatileImage
.getDrawGraphics
.public abstract boolean contentsRestored()
VolatileImage
, they may become lost. If a surface has been recently restored from a lost state since the last call to getDrawGraphics
, it may require repainting. For a discussion on lost buffers, see VolatileImage
.getDrawGraphics
.public abstract void show()
public void dispose()
BufferStrategy
and removes it from the associated Component. After invoking this method, getBufferStrategy
will return null. Trying to use a BufferStrategy
after it has been disposed will result in undefined behavior.
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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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https://docs.oracle.com/en/java/javase/21/docs/api/java.desktop/java/awt/image/BufferStrategy.html