1.Bresenham 直线画法 改进版：
/** *//**
* Bresenham Line Algorithm
* @param dashedMask 设置线型的虚线的间隔，为0则画实线。
* @param lineWidth 设置线宽。
* @param x1
* @param y1
* @param x2
* @param y2
*/
public static void bresenhamLine(Graphics g, int dashedMask, int lineWidth, int x1, int y1, int x2, int y2)
...{
g.setColor( 0xFFFFFF );
int x, y;
int dx, dy;
int incx, incy;
int balance;
int i = 0;
if (x2 >= x1)
...{
dx = x2 - x1;
incx = 1;
} else
dx = x1 - x2;
incx = -1;
}
if (y2 >= y1)
dy = y2 - y1;
incy = 1;
dy = y1 - y2;
incy = -1;
x = x1;
y = y1;
if (dx >= dy)
dy <<= 1;
balance = dy - dx;
dx <<= 1;
while (x != x2)
...{
if ((i & dashedMask) == 0)
g.fillRect(x, y, lineWidth, lineWidth);
if (balance >= 0)
...{
y += incy;
balance -= dx;
}
balance += dy;
x += incx;
i++;
}
if ((i & dashedMask) == 0)
g.fillRect(x, y, lineWidth, lineWidth);
}
else
balance = dx - dy;
while (y != y2)
x += incx;
balance -= dy;
balance += dx;
y += incy;
}
2.绘制精灵飞行轨迹方法
使用示例
isFlyEnd=paintPicFly( g, sprite[y][x], sprite[y][x].getX(), sprite[y][x].getY(), x*RECT_W, y*RECT_H, 4 );
* 绘制精灵飞行轨迹
* @param g
* @param sprite
* @param x1 起点
* @param x2 终点
* @param speed 速度
* @return 是否飞行结束
*/
public final boolean paintPicFly( Graphics g, Sprite sprite, int x1, int y1, int x2, int y2, int speed )
if( x1==x2 && y1==y2 )
sprite.paint(g);
return true;
for( ; x!=x2; ) //while (x != x2)
if ((i & speed) == 0 || i == speed )
paintPic( g, sprite, x, y );
return false;
if ((i & speed) == 0 || i == speed )
paintPic( g, sprite, x, y );
for( ; y!=y2; ) //while (y != y2)
return false;
}
void paintPic( Graphics g, Sprite sprite, int x, int y )
sprite.setPosition(x,y);
sprite.paint(g);
// g.setColor( 0xFF0000 );
// g.fillRect(x, y, 1, 1);
3.矩形碰撞检测
/** *//**
* 矩形碰撞检测
* @param x1 矩形1左上角X坐标
* @param y1 矩形1左上角y坐标
* @param w1 矩形1宽
* @param h1 矩形1高
* @param x2 矩形2左上角y坐标
* @param y2 矩形2左上角y坐标
* @param w2 矩形2宽
* @param h2 矩形2高
* @return 是否碰撞
boolean isIntersect(int x1,int y1, int w1, int h1, int x2, int y2, int w2, int h2)
...{
if( Math.abs(x2-x1) < (w1+w2)/2 && Math.abs(y2-y1) < (h1+h2)/2 )
...{
return true;
}
else
return false;
}
/以上方法是有问题的！请参看以下方法
/**
* @param x2 矩形2左上角x坐标
* @return 是否碰撞
public static boolean isIntersect(int x1,int y1, int w1, int h1, int x2, int y2, int w2, int h2)
{
if( isIntersect(x1,y1,w1,h1,x2 ,y2) )
if( isIntersect(x1,y1,w1,h1,x2+w2,y2) )
if( isIntersect(x1,y1,w1,h1,x2+w2,y2+h2) )
if( isIntersect(x1,y1,w1,h1,x2 ,y2+h2) )
return false;
//判断一个点是否在一个矩形内部或者在这个矩形的边上
private static boolean isIntersect(int x,int y, int w, int h, int px, int py)
{
if( px>=x&&px<=x+w && py>=y&&py<=y+h )
return true;
else
return false;
}
4.单Player播放MIDI
static boolean m_isSoundOn;
static boolean m_isMusicOn;
static int m_currentSound;
static int m_currentMIDIID;
static javax.microedition.media.Player m_sound;
static byte[][] s_soundData;
static boolean s_isPlayMid = false;
void LoadSound()
try
SetCurrentInputStream( new DataInputStream("".getClass().getResourceAsStream("/sou") ) );
ReadOffsetTable();
s_soundData = new byte[m_nDataBlocksCount][];
byte[] buffer = new byte[ m_dataBlocksOffset[ m_nDataBlocksCount ] ];
int[] header = m_dataBlocksOffset;
ReadBytes(buffer);
SetCurrentInputStream( null );
System.gc();
for (int i=0; i<m_nDataBlocksCount; i++)
int length = header[ i + 1 ] - header[ i ];
if ( length > 0 )
s_soundData[i] = new byte[length];
System.arraycopy( buffer, header[i], s_soundData[i], 0, length );
header = null;
buffer = null;
System.gc();
m_currentSound = -1;
m_currentMIDIID = -1;
catch ( Exception e ) ...{ }
static void PlaySound(int id)
PlaySoundLoop(id,1);
static void PlaySoundLoop( int id, int loop )
if (id <= dSoundID.Sound_ID_TITLE) // midi
if (!m_isMusicOn)
return;
else // wav
if (!m_isSoundOn && id != dSoundID.Sound_ID_MENUCONFIRM)
if (id == m_currentSound && m_sound!=null&& (m_sound.getState() == javax.microedition.media.Player.STARTED))
return;
else
StopSound(id);
try
InputStream is = new ByteArrayInputStream( s_soundData[id] );
m_sound = javax.microedition.media.Manager.createPlayer(is, "audio/midi");
m_sound.realize();
m_sound.setLoopCount( loop );
m_sound.start();
m_currentSound = id;
s_isPlayMid = false;
catch (Exception e) ...{ e.printStackTrace(); }
static void StopSound(int id)
if( m_sound == null )
else
m_sound.deallocate();
m_sound.close();
m_sound = null;
catch ( Exception e ) ...{ e.printStackTrace(); }
static void ResumeSound()
PlaySound( m_currentSound );
5.从一张大图分割成小图
try
...{
img = Image.createImage("/pics/"+imgNum+".png");//将大图创建到临时Image对象中
Graphics gn; //创建临时绘图设备
for( int i=0; i<y_tile_sum; i++ )
...{
for( int j=0; j<x_tile_sum; j++ )
...{
img_tile[i][j] = Image.createImage(RECT_W, RECT_H); //创建小图的大小
gn = img_tile[i][j].getGraphics(); //创建小图的大小的临时绘图设备
//在该设备上绘制大图temp,但 绘图设备比较小,只有小图那么大,大图多余部分不会被绘制出来
gn.drawImage(img, -j*RECT_W, -i*RECT_H, gn.LEFT|gn.TOP); //绘制大图时候的起点位置
}
}
gn = null;
System.gc(); //通知垃圾回收机制,在需要时候会进行垃圾回收
}
catch(Exception e)...{ e.printStackTrace(); }
6.j2me 保存记录
final static String RECORD_FILENAME = "/assassin.sav";
final static int RECORD_SIZE = 160;
static byte s_recordData[] = new byte[RECORD_SIZE];
public static void RecordStore(boolean save)
RecordStore rs = RecordStore.openRecordStore(RECORD_FILENAME, true);
if (rs.getNumRecords() <= 0)
if (save)
rs.addRecord(s_recordData, 0, RECORD_SIZE);
else
rs.closeRecordStore();
return;
else if (save)
rs.setRecord(1, s_recordData, 0, RECORD_SIZE);
rs.getRecord(1, s_recordData, 0);
rs.closeRecordStore();
rs = null;
catch (Exception e)
本文转自 kome2000 51CTO博客，原文链接:http://blog.51cto.com/kome2000/578525
![add to -append Backend implementation[图]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)