Android中贝塞尔曲线的绘制方法示例代码

// 贝赛尔曲线成员变量(起始点，控制（操作点），终止点，3点坐标) 
private int startX, startY, controlX, controlY, endX, endY; 
// Path 
private Path path; 
// 为了不影响主画笔，这里绘制贝赛尔曲线单独用一个新画笔 
private Paint paintQ; 
// 随机库（让贝赛尔曲线更明显） 
private Random random; 

/** 
 * SurfaceView初始化函数 
 */ 
public MySurfaceView(Context context) { 
 super(context); 
 ... 
  //贝赛尔曲线相关初始化 
  path = new Path(); 
  paintQ = new Paint(); 
  paintQ.setAntiAlias(true); 
  paintQ.setStyle(Style.STROKE); 
  paintQ.setStrokeWidth(5); 
  paintQ.setColor(Color.WHITE); 
  random = new Random(); 
 ... 
} 

/** 
 * 绘制贝赛尔曲线 
 * 
 * @param canvas 主画布 
 */ 
public void drawQpath(Canvas canvas) { 
 path.reset();// 重置path 
 // 贝赛尔曲线的起始点 
 path.moveTo(startX, startY); 
 // 设置贝赛尔曲线的操作点以及终止点 
 path.quadTo(controlX, controlY, endX, endY); 
 // 绘制贝赛尔曲线（Path） 
 canvas.drawPath(path, paintQ); 
} 

/** 
 * 触屏事件监听 
 */ 
@Override 
public boolean onTouchEvent(MotionEvent event) { 
 endX = (int) event.getX(); 
 endY = (int) event.getY(); 
 return true; 
} 
/** 
 * 游戏逻辑 
 */ 
private void logic() { 
 if (endX != 0 && endY != 0) { 
  // 设置操作点为线段x/y的一半 
  cOntrolX= random.nextInt((endX - startX) / 2); 
  cOntrolY= random.nextInt((endY - startY) / 2); 
 } 
} 

package com.qpath; 
import java.util.Random; 
import android.content.Context; 
import android.graphics.Canvas; 
import android.graphics.Color; 
import android.graphics.Paint; 
import android.graphics.Paint.Style; 
import android.graphics.Path; 
import android.view.KeyEvent; 
import android.view.MotionEvent; 
import android.view.SurfaceHolder; 
import android.view.SurfaceHolder.Callback; 
import android.view.SurfaceView; 
/** 
 * 赛贝尔曲线 
 * @author Himi 
 * 
 */ 
public class MySurfaceView extends SurfaceView implements Callback, Runnable { 
 private SurfaceHolder sfh; 
 private Paint paint; 
 private Thread th; 
 private boolean flag; 
 private Canvas canvas; 
 public static int screenW, screenH; 
 // -----------以上是SurfaceView游戏框架 
 // 贝赛尔曲线成员变量(起始点，控制（操作点），终止点，3点坐标) 
 private int startX, startY, controlX, controlY, endX, endY; 
 // Path 
 private Path path; 
 // 为了不影响主画笔，这里绘制贝赛尔曲线单独用一个新画笔 
 private Paint paintQ; 
 // 随机库（让贝赛尔曲线更明显） 
 private Random random; 
 /** 
  * SurfaceView初始化函数 
  */ 
 public MySurfaceView(Context context) { 
  super(context); 
  sfh = this.getHolder(); 
  sfh.addCallback(this); 
  paint = new Paint(); 
  paint.setColor(Color.WHITE); 
  paint.setAntiAlias(true); 
  setFocusable(true); 
  // -----------以上是SurfaceView游戏框架 
  //贝赛尔曲线相关初始化 
  path = new Path(); 
  paintQ = new Paint(); 
  paintQ.setAntiAlias(true); 
  paintQ.setStyle(Style.STROKE); 
  paintQ.setStrokeWidth(5); 
  paintQ.setColor(Color.WHITE); 
  random = new Random(); 
 } 
 /** 
  * SurfaceView视图创建，响应此函数 
  */ 
 public void surfaceCreated(SurfaceHolder holder) { 
  screenW = this.getWidth(); 
  screenH = this.getHeight(); 
  flag = true; 
  // 实例线程 
  th = new Thread(this); 
  // 启动线程 
  th.start(); 
  // -----------以上是SurfaceView游戏框架 
 } 
 /** 
  * 游戏绘图 
  */ 
 public void myDraw() { 
  try { 
   canvas = sfh.lockCanvas(); 
   if (canvas != null) { 
    canvas.drawColor(Color.BLACK); 
    // -----------以上是SurfaceView游戏框架 
    drawQpath(canvas); 
   } 
  } catch (Exception e) { 
   // TODO: handle exception 
  } finally { 
   if (canvas != null) 
    sfh.unlockCanvasAndPost(canvas); 
  } 
 } 
 /** 
  * 绘制贝赛尔曲线 
  * 
  * @param canvas 主画布 
  */ 
 public void drawQpath(Canvas canvas) { 
  path.reset();// 重置path 
  // 贝赛尔曲线的起始点 
  path.moveTo(startX, startY); 
  // 设置贝赛尔曲线的操作点以及终止点 
  path.quadTo(controlX, controlY, endX, endY); 
  // 绘制贝赛尔曲线（Path） 
  canvas.drawPath(path, paintQ); 
 } 
 /** 
  * 触屏事件监听 
  */ 
 @Override 
 public boolean onTouchEvent(MotionEvent event) { 
  endX = (int) event.getX(); 
  endY = (int) event.getY(); 
  return true; 
 } 
 /** 
  * 游戏逻辑 
  */ 
 private void logic() { 
  if (endX != 0 && endY != 0) { 
   // 设置操作点为线段x/y的一半 
   cOntrolX= random.nextInt((endX - startX) / 2); 
   cOntrolY= random.nextInt((endY - startY) / 2); 
  } 
 } 
 /** 
  * 按键事件监听 
  */ 
 @Override 
 public boolean onKeyDown(int keyCode, KeyEvent event) { 
  return super.onKeyDown(keyCode, event); 
 } 
 public void run() { 
  while (flag) { 
   long start = System.currentTimeMillis(); 
   myDraw(); 
   logic(); 
   long end = System.currentTimeMillis(); 
   try { 
    if (end - start <50) { 
     Thread.sleep(50 - (end - start)); 
    } 
   } catch (InterruptedException e) { 
    e.printStackTrace(); 
   } 
  } 
 } 
 /** 
  * SurfaceView视图状态发生改变，响应此函数 
  */ 
 public void surfaceChanged(SurfaceHolder holder, int format, int width, 
   int height) { 
 } 
 /** 
  * SurfaceView视图消亡时，响应此函数 
  */ 
 public void surfaceDestroyed(SurfaceHolder holder) { 
  flag = false; 
 } 
}