gamecanvas.html

是MIDP 的API 查詢文件, 大家可以看一下裡面的index.html, 再用Package 或 Class 名字來查.

 (UP, DOWN, FIRE, etc.); key events are always generated for all other 
 keys.  
 <p><DD><DL>
<DT><B>Parameters:</B><DD><CODE>suppressKeyEvents</CODE> - <code>true</code> to suppress the regular
 key event mechanism for game keys, otherwise <code>false</code>.</DL>
</DD>
</DL>

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<A NAME="getGraphics()"><!-- --></A><H3>
getGraphics</H3>
<PRE>
protected <A HREF="../../../../javax/microedition/lcdui/Graphics.html">Graphics</A> <B>getGraphics</B>()</PRE>
<DL>
<DD>Obtains the Graphics object for rendering a GameCanvas.  The returned 
 Graphics object renders to the off-screen buffer belonging to this 
 GameCanvas.
 <p>	 
 Rendering operations do not appear on the display until flushGraphics()
 is called; flushing the buffer does not change its contents (the pixels
 are not cleared as a result of the flushing operation).
 <p>
 A new Graphics object is created and returned each time this method is
 called; therefore, the needed Graphics object(s) should be obtained 
 before the game starts then re-used while the game is running.  
 For each GameCanvas instance, all of the provided graphics objects will
 render to the same off-screen buffer. 
 <P>
 <P>The newly created Graphics object has the following properties:
 </P>
 <ul>
 <LI>the destination is this GameCanvas' buffer;
 <LI>the clip region encompasses the entire buffer;
 <LI>the current color is black;
 <LI>the font is the same as the font returned by
 <A HREF="../../../../javax/microedition/lcdui/Font.html#getDefaultFont()"><CODE>Font.getDefaultFont()</CODE></A>;
 <LI>the stroke style is <A HREF="../../../../javax/microedition/lcdui/Graphics.html#SOLID"><CODE>SOLID</CODE></A>; and
 <LI>the origin of the coordinate system is located at the upper-left
 corner of the buffer.
 </ul>     
 <p><DD><DL>
<DT><B>Returns:</B><DD>the Graphics object that renders to this GameCanvas' 
 off-screen buffer<DT><B>See Also: </B><DD><A HREF="../../../../javax/microedition/lcdui/game/GameCanvas.html#flushGraphics()"><CODE>flushGraphics()</CODE></A>, 
<A HREF="../../../../javax/microedition/lcdui/game/GameCanvas.html#flushGraphics(int, int, int, int)"><CODE>flushGraphics(int, int, int, int)</CODE></A></DL>
</DD>
</DL>
<HR>

<A NAME="getKeyStates()"><!-- --></A><H3>
getKeyStates</H3>
<PRE>
public int <B>getKeyStates</B>()</PRE>
<DL>
<DD>Gets the states of the physical game keys.  Each bit in the returned
 integer represents a specific key on the device.  A key's bit will be
 1 if the key is currently down or has been pressed at least once since
 the last time this method was called.  The bit will be 0 if the key
 is currently up and has not been pressed at all since the last time 
 this method was called.  This latching behavior ensures that a rapid
 key press and release will always be caught by the game loop, 
 regardless of how slowly the loop runs.
 <p>
 For example:<code><pre>
 
      // Get the key state and store it
      int keyState = getKeyStates();
      if ((keyState & LEFT_KEY) != 0) {
          positionX--;
      }
      else if ((keyState & RIGHT_KEY) != 0) {
          positionX++;
      }

 </pre></code>
 <p>
 Calling this method has the side effect of clearing any latched state.
 Another call to getKeyStates immediately after a prior call will 
 therefore report the system's best idea of the current state of the
 keys, the latched bits having been cleared by the first call.
 <p>
 Some devices may not be able to query the keypad hardware directly and
 therefore, this method may be implemented by monitoring key press and
 release events instead.  Thus the state reported by getKeyStates might
 lag the actual state of the physical keys since the timeliness
 of the key information is be subject to the capabilities of each
 device.  Also, some devices may be incapable of detecting simultaneous
 presses of multiple keys.
 <p>
 This method returns 0 unless the GameCanvas is currently visible as
 reported by <A HREF="../../../../javax/microedition/lcdui/Displayable.html#isShown()"><CODE>Displayable.isShown()</CODE></A>.
 Upon becoming visible, a GameCanvas will initially indicate that 
 all keys are unpressed (0); if a key is held down while the GameCanvas
 is being shown, the key must be first released and then pressed in 
 order for the key press to be reported by the GameCanvas.
 <p><DD><DL>
<DT><B>Returns:</B><DD>An integer containing the key state information (one bit per 
 key), or 0 if the GameCanvas is not currently shown.<DT><B>See Also: </B><DD><A HREF="../../../../javax/microedition/lcdui/game/GameCanvas.html#UP_PRESSED"><CODE>UP_PRESSED</CODE></A>, 
<A HREF="../../../../javax/microedition/lcdui/game/GameCanvas.html#DOWN_PRESSED"><CODE>DOWN_PRESSED</CODE></A>, 
<A HREF="../../../../javax/microedition/lcdui/game/GameCanvas.html#LEFT_PRESSED"><CODE>LEFT_PRESSED</CODE></A>, 
<A HREF="../../../../javax/microedition/lcdui/game/GameCanvas.html#RIGHT_PRESSED"><CODE>RIGHT_PRESSED</CODE></A>, 
<A HREF="../../../../javax/microedition/lcdui/game/GameCanvas.html#FIRE_PRESSED"><CODE>FIRE_PRESSED</CODE></A>, 
<A HREF="../../../../javax/microedition/lcdui/game/GameCanvas.html#GAME_A_PRESSED"><CODE>GAME_A_PRESSED</CODE></A>, 
<A HREF="../../../../javax/microedition/lcdui/game/GameCanvas.html#GAME_B_PRESSED"><CODE>GAME_B_PRESSED</CODE></A>, 
<A HREF="../../../../javax/microedition/lcdui/game/GameCanvas.html#GAME_C_PRESSED"><CODE>GAME_C_PRESSED</CODE></A>, 
<A HREF="../../../../javax/microedition/lcdui/game/GameCanvas.html#GAME_D_PRESSED"><CODE>GAME_D_PRESSED</CODE></A></DL>
</DD>
</DL>
<HR>

<A NAME="paint(javax.microedition.lcdui.Graphics)"><!-- --></A><H3>
paint</H3>
<PRE>
public void <B>paint</B>(<A HREF="../../../../javax/microedition/lcdui/Graphics.html">Graphics</A>&nbsp;g)</PRE>
<DL>
<DD>Paints this GameCanvas.  By default, this method renders the 
 the off-screen buffer at (0,0).  Rendering of the buffer is 
 subject to the clip region and origin translation of the Graphics
 object.<DD><DL>
<DT><B>Overrides:</B><DD><CODE><A HREF="../../../../javax/microedition/lcdui/Canvas.html#paint(javax.microedition.lcdui.Graphics)">paint</A></CODE> in class <CODE><A HREF="../../../../javax/microedition/lcdui/Canvas.html">Canvas</A></CODE></DL>
</DD>
<DD><DL>
<DT><B>Parameters:</B><DD><CODE>g</CODE> - the Graphics object with which to render the screen.<DT><B>Throws:</B><DD><CODE><A HREF="../../../../java/lang/NullPointerException.html">NullPointerException</A></CODE> - if <code>g</code> is <code>null</code></DL>
</DD>
</DL>
<HR>

<A NAME="flushGraphics(int, int, int, int)"><!-- --></A><H3>
flushGraphics</H3>
<PRE>
public void <B>flushGraphics</B>(int&nbsp;x,
                          int&nbsp;y,
                          int&nbsp;width,
                          int&nbsp;height)</PRE>
<DL>
<DD>Flushes the specified region of the off-screen buffer to the display. 
 The contents of the off-screen buffer are not changed as a result of 
 the flush operation.  This method does not return until the flush has
 been completed, so the app may immediately begin to render the next 
 frame to the same buffer once this method returns.
 <p>
 If the specified region extends beyond the current bounds of the 
 GameCanvas, only the intersecting region is flushed.  No pixels are
 flushed if the specified width or height is less than 1.
 <p>
 This method does nothing and returns immediately if the GameCanvas is
 not currently shown or the flush request cannot be honored because the
 system is busy.
 <p><DD><DL>
<DT><B>Parameters:</B><DD><CODE>x</CODE> - the left edge of the region to be flushed<DD><CODE>y</CODE> - the top edge of the region to be flushed<DD><CODE>width</CODE> - the width of the region to be flushed<DD><CODE>height</CODE> - the height of the region to be flushed<DT><B>See Also: </B><DD><A HREF="../../../../javax/microedition/lcdui/game/GameCanvas.html#flushGraphics()"><CODE>flushGraphics()</CODE></A></DL>
</DD>
</DL>
<HR>

<A NAME="flushGraphics()"><!-- --></A><H3>
flushGraphics</H3>
<PRE>
public void <B>flushGraphics</B>()</PRE>
<DL>
<DD>Flushes the off-screen buffer to the display.  The size of the flushed 
 area is equal to the size of the GameCanvas.  The contents
 of the  off-screen buffer are not changed as a result of the flush 
 operation.  This method does not return until the flush has been
 completed, so the app may immediately begin to render the next frame
 to the same buffer once this method returns.
 <p>
 This method does nothing and returns immediately if the GameCanvas is
 not currently shown or the flush request cannot be honored because the
 system is busy.
 <p><DD><DL>
<DT><B>See Also: </B><DD><A HREF="../../../../javax/microedition/lcdui/game/GameCanvas.html#flushGraphics(int, int, int, int)"><CODE>flushGraphics(int,int,int,int)</CODE></A></DL>
</DD>
</DL>
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