android path基本使用以及贝塞尔曲线入门
今天周一,产品要求版本迭代到1.5.3,发现需求没啥东西,后台暂时也给不了数据,于是又有时间写博客了,这是我很喜欢的模式,今天讲下path的基本使用以及贝塞尔曲线入门,后期会讲些贝塞尔曲线结合动画的效果,瞬间让你装逼找不到自己,当然这中间需要时间去研究,这是一个快乐的过程,毕竟这是一个自己感兴趣的事,年龄大了,发现能干自己感兴趣的事还能赚钱养活自己都不容易,切入正题
Path是一个神奇的东西,能把它搞懂,可以实现网上看到的很多效果,现在开始讲下Path的基本使用
我们知道在canvas中有个方法canvas.drawPath(path,paint);这就是绘制path,path就是一条路径可以简单的理解为,google官方SDK解释:
/** * The Path class encapsulates compound (multiple contour) geometric paths * consisting of straight line segments, quadratic curves, and cubic curves. * It can be drawn with canvas.drawPath(path, paint), either filled or stroked * (based on the paint's Style), or it can be used for clipping or to draw * text on a path. */
看不懂怎么办,没关系,我也看不懂,但是不影响你实现你想实现的效果,如果你那天成功了,谁还在意你的过去,只要你不和方舟子合不来一般是没问题的,我们学这些无非是看它的api提供了什么方法,然后每个方法有啥用,应用层就是这么玩的,
path方法如下:
path构造函数就2个,一个是无参的,一个是带参的
public Path(Path src) 这是通过传递一个path构建一个新的path路径,现在讲讲常用的方法
1:reset() 意思是重置,其实是把你绘制在path上的图形全部清除,比如你在这path绘制了线或者点什么的,调用了reset()方法后,path上什么都没了
2:set(Path path)用传递过来的path代替之前path上的绘制的内容,这个进入源码有注释的,
3:moveTo(float startX,float endY);绘制线的起点坐标,如果不指定的话,系统默认是在原点(0,0)开始,这个写个demo就能测试出来
4:lineTo(float x,float y)这是配合moveTo()使用的,表示二个点连接成一条线,lineTo(x,y)在有moveTo()时候相当于终点,在多次调用的时候相当于起点,写个demo,说明下
package smart.com.pathview; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Path; import android.util.AttributeSet; import android.view.View; /** * Created by admin on 2016/12/7. */ public class PathDemo extends View {private Paint paint; private Path path; public PathDemo(Context context, AttributeSet attrs) {super(context, attrs); paint = new Paint(); paint.setColor(Color.DKGRAY); paint.setStrokeWidth(2); paint.setStyle(Paint.Style.STROKE); path = new Path(); }@Override protected void onDraw(Canvas canvas) {super.onDraw(canvas); canvas.drawPath(path,paint); path.moveTo(10,10);//起点 path.lineTo(100,100);//终点 path.lineTo(200,200);//这个起点是相当于 100,100 canvas.drawPath(path,paint); } }
效果:
5:rMoveTo(),rLineTo(),path类还有其他方法带r的都是相对于某一个点,rLineTo()是相当于rMoveTo()点坐标的,比如rMoveTo(10,10) 而rLine(100,100)相当于rMoveTo()起点而言,最终的绘制一条线的起点为(10,10),终点为(100+10,100+10),这个很好测试,其实你绘制线后再绘制二个终点的坐标,一看就知道了
package smart.com.pathview; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Path; import android.util.AttributeSet; import android.view.View; /** * Created by admin on 2016/12/7. */ public class PathDemo extends View {private Paint paint; private Path path,path1; public PathDemo(Context context, AttributeSet attrs) {super(context, attrs); paint = new Paint(); paint.setColor(Color.RED); paint.setStrokeWidth(2); paint.setStyle(Paint.Style.STROKE); paint.setAntiAlias(true); path = new Path(); path1 = new Path(); }@Override protected void onDraw(Canvas canvas) {super.onDraw(canvas); path.moveTo(10,10); path.lineTo(200,200); canvas.drawPath(path,paint); paint.setColor(Color.BLUE); path1.rMoveTo(100,10); path1.rLineTo(300,10); canvas.drawPath(path1,paint); paint.setColor(Color.BLACK); paint.setStrokeWidth(8); //绘制2个点测试 canvas.drawPoint(200,200,paint); canvas.drawPoint(400,20,paint); } }
效果:
看图说话,
6:add...(),path中很多add()方法我截图看下:
什么添加椭圆 添加弧度,矩形,圆角矩形,圆形等,现在就写个添加圆形玩玩
@Override protected void onDraw(Canvas canvas) {super.onDraw(canvas); path.addCircle(200,200,150, Path.Direction.CCW); canvas.drawPath(path,paint); }
效果图:
你会发现path.addCircle()有一个参数Path.Direction.CCW,啥意,点击进去看源码,发现一个单词clockwise,意思是顺时针方向,那么Path.Direction.CW就是反方向了,这个你画圆时看不出来的,画什么矩形也是看不出来的,那么canvas还有一个方法,用这个方法来测试上面的2个参数什么顺时针和逆时针一眼就看的出来
@Override protected void onDraw(Canvas canvas) {super.onDraw(canvas); RectF rectF = new RectF(60,60,400,400); path.addRect(rectF, Path.Direction.CCW); canvas.drawPath(path,paint); paint.setColor(Color.MAGENTA); paint.setTextSize(24); paint.setStrokeWidth(2); canvas.drawTextOnPath("杭州今天天气不错",path,0,0,paint); }
效果:
Direction.CW 逆时针:
ok,这样直观一眼就看的出来,
7:close()闭合,就是当path绘制线大于或者等于3条的时候,使用close会构成一个封闭的图形,比如绘制三角形或者矩形
8:isEmpty()是否是空
9:isRect()是否是矩形
10:setFillType(FillType ft)填充模式:进入源码发现有如下几种:
public enum FillType {// these must match the values in SkPath.h /** * Specifies that "inside" is computed by a non-zero sum of signed * edge crossings. */ WINDING (0), /** * Specifies that "inside" is computed by an odd number of edge * crossings. */ EVEN_ODD (1), /** * Same as {@link #WINDING}, but draws outside of the path, rather than inside. */ INVERSE_WINDING (2), /** * Same as {@link #EVEN_ODD}, but draws outside of the path, rather than inside. */ INVERSE_EVEN_ODD(3); FillType(int ni) {nativeInt = ni; }final int nativeInt; }
发现有四种填充模式:前提是path添加的图形要相交
WINDING:
@Override protected void onDraw(Canvas canvas) {super.onDraw(canvas); mEndPath = new Path(); mEndPath.offset(100,100); mEndPath.addCircle(200, 200, 100, Path.Direction.CW); mEndPath.addCircle(300, 300, 100, Path.Direction.CW); mEndPath.setFillType(Path.FillType.WINDING); paint.setColor(Color.RED); canvas.drawPath(mEndPath,paint); }
效果:
EVEN_ODD:
@Override protected void onDraw(Canvas canvas) {super.onDraw(canvas); mEndPath = new Path(); mEndPath.offset(100,100); mEndPath.addCircle(200, 200, 100, Path.Direction.CW); mEndPath.addCircle(300, 300, 100, Path.Direction.CW); mEndPath.setFillType(Path.FillType.EVEN_ODD); paint.setColor(Color.RED); canvas.drawPath(mEndPath,paint); }
效果:
INVERSE_WINDING:
INVERSE_EVEN_ODD:
没有不设置填充模式:
@Override protected void onDraw(Canvas canvas) {super.onDraw(canvas); mEndPath = new Path(); mEndPath.offset(100,100); mEndPath.addCircle(200, 200, 100, Path.Direction.CW); mEndPath.addCircle(300, 300, 100, Path.Direction.CW); // mEndPath.setFillType(Path.FillType.INVERSE_EVEN_ODD); paint.setColor(Color.RED); canvas.drawPath(mEndPath,paint); }
效果:
你会发现什么都没设置和WINDING模式是一样的,也就是说默认就是WINDING模式,
可能有些人会问,怎么背景会变啊,说明不是只局限我们使用path绘制的内容,而是作用于canvas上
对上面的四个模式总结:
FillType.WINDING:取path所有所在区域;
FillType.EVEN_ODD:取path所在并不相交区域;
FillType.INVERSE_WINDING:取path所有未占区域;
FillType.INVERSE_EVEN_ODD:取path未占或相交区域;
是不是可以使用这些知识把奥迪的标志绘制出来玩玩,好,动手
package smart.com.pathview; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Path; import android.graphics.RectF; import android.util.AttributeSet; import android.view.View; /** * Created by admin on 2016/12/7. */ public class PathDemo extends View {private Paint paint; private Path path; private int raduis; private float y; public PathDemo(Context context, AttributeSet attrs) {super(context, attrs); paint = new Paint(); paint.setColor(Color.DKGRAY); paint.setStrokeWidth(6); paint.setStyle(Paint.Style.STROKE); paint.setAntiAlias(true); path = new Path(); raduis = 40; y = 60; }@Override protected void onDraw(Canvas canvas) {super.onDraw(canvas); for(int i=1;i<5;i++){path.addCircle(60*i, y, raduis, Path.Direction.CW); }path.setFillType(Path.FillType.EVEN_ODD); canvas.drawPath(path,paint); } }
效果:
是不是还可以画一个奥运的五环标志
package smart.com.pathview; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Path; import android.graphics.RectF; import android.util.AttributeSet; import android.view.View; /** * Created by admin on 2016/12/7. */ public class PathDemo extends View {private Paint paint; private Path path; private int raduis; private float y; public PathDemo(Context context, AttributeSet attrs) {super(context, attrs); paint = new Paint(); paint.setColor(Color.DKGRAY); paint.setStrokeWidth(6); paint.setStyle(Paint.Style.STROKE); paint.setAntiAlias(true); path = new Path(); raduis = 60; y = 160; }@Override protected void onDraw(Canvas canvas) {super.onDraw(canvas); path.addCircle(100, y, raduis, Path.Direction.CW); path.addCircle(230, y, raduis, Path.Direction.CW); path.addCircle(360, y, raduis, Path.Direction.CW); path.addCircle(165, 230, raduis, Path.Direction.CW);// (230-110)/2+100 这些y轴数据不是精确计算的,是估值 path.addCircle(295, 230, raduis, Path.Direction.CW);//同理上面 path.setFillType(Path.FillType.EVEN_ODD); canvas.drawPath(path,paint); } }
效果:
11: public void computeBounds(RectF bounds, boolean exact)计算path绘制的内容所占的区域
package smart.com.pathview; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Path; import android.graphics.RectF; import android.util.AttributeSet; import android.util.Log; import android.view.View; /** * Created by admin on 2016/12/7. */ public class PathDemo extends View {private Paint paint; private Path path; public PathDemo(Context context, AttributeSet attrs) {super(context, attrs); paint = new Paint(); paint.setColor(Color.DKGRAY); paint.setStrokeWidth(6); paint.setStyle(Paint.Style.STROKE); paint.setAntiAlias(true); path = new Path(); }@Override protected void onDraw(Canvas canvas) {super.onDraw(canvas); path = new Path(); path.offset(100,100); path.addCircle(200, 200, 100, Path.Direction.CW); path.addCircle(300, 300, 100, Path.Direction.CW); path.setFillType(Path.FillType.EVEN_ODD); RectF rectF = new RectF(); path.computeBounds(rectF,false); canvas.drawPath(path,paint); paint.setColor(Color.RED); canvas.drawRect(rectF,paint);//绘制矩形 path所占的区域 } }
效果:
12:op(Path path, Op op)与传递进来的path与当前调用此op()方法的path通过参数op合并出一些效果,
public enum Op {/** * Subtract the second path from the first path. */ DIFFERENCE, /** * Intersect the two paths. */ INTERSECT, /** * Union (inclusive-or) the two paths. */ UNION, /** * Exclusive-or the two paths. */ XOR, /** * Subtract the first path from the second path. */ REVERSE_DIFFERENCE }
发现也有5中模式等着我去做测试了,头晕
DIFFERENCE:
package smart.com.pathview; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Path; import android.graphics.RectF; import android.util.AttributeSet; import android.util.Log; import android.view.View; /** * Created by admin on 2016/12/7. */ public class PathDemo extends View {private Paint paint; public PathDemo(Context context, AttributeSet attrs) {super(context, attrs); paint = new Paint(); paint.setColor(Color.RED); paint.setStrokeWidth(8); paint.setStyle(Paint.Style.STROKE); paint.setAntiAlias(true); }@Override protected void onDraw(Canvas canvas) {super.onDraw(canvas); Path path1 = new Path(); path1.addCircle(150, 150, 100, Path.Direction.CW); Path path2 = new Path(); path2.addCircle(200, 200, 100, Path.Direction.CW); path1.op(path2, Path.Op.DIFFERENCE); canvas.drawPath(path1, paint); paint.setColor(Color.DKGRAY); paint.setStrokeWidth(2); canvas.drawCircle(150, 150, 100,paint); canvas.drawCircle(200, 200, 100,paint); } }
效果:
注:红色表示效果,绘制2个圆是做对比看的
INTERSECT:
效果:
UNION:
效果
XOR:
效果:
REVERSE_DIFFERENCE:
效果:
根据上面的效果总结:
Path.Op.DIFFERENCE:减去Path2后Path1剩下的部分
Path.Op.INTERSECT:保留Path1与Path2共同的部分
Path.Op.REVERSE_DIFFERENCE:减去Path1后Path2剩下的部分
Path.Op.UNION:保留全部Path1和Path2
Path.Op.XOR:包含Path1与Path2但不包括两者相交的部分
昨天龙体欠佳,晚上回去也没把博客写完,今天把余下的博客写完,ok,走入正题,开始学习贝塞尔曲线
在这就不讲什么那个牛逼的人发明了贝塞尔曲线了,要了解的话去百度百科吧,了解他,他也不会教你啥,还是要看博客自己学习,只能心里对那些牛逼的人默默的尊重和敬仰,没学贝塞尔曲线之前,我们所有的轨迹都是线性的,贝塞尔曲线分为一阶,二阶,三阶...n阶等,在sdk中只提供了二和三阶曲线的函数,哪一阶呢,其实它就是个一条直线,这会涉及到高等数学中的知识,臣妾不才,只读了个大专,大学也没上过什么高等数学的知识,全凭小学数学功底,我们学习贝塞尔曲线只要根据给的api和数学公式,学会套用就行,至于那些很复杂的,可以划分成多个二或者三阶曲线去实现,基本上需求很到,现在就开始从一阶曲线学习
一阶曲线的公式:
说明p0是起点,p1是终点,现在就套用这公式玩,
package smart.com.pathview; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.util.AttributeSet; import android.view.View; /** * Created by admin on 2016/12/13. */ public class LineView extends View {private float startX,startY; private float endX,endY ; private Paint paint; private float t; public LineView(Context context, AttributeSet attrs) {super(context, attrs); paint = new Paint(); paint.setAntiAlias(true); paint.setStrokeWidth(3); paint.setStyle(Paint.Style.STROKE); startX = 100; startY = 100; endX = 300; endY = 300; }@Override protected void onDraw(Canvas canvas) {super.onDraw(canvas); paint.setColor(Color.parseColor("#e5e5e5")); paint.setStrokeWidth(3); canvas.drawLine(startX,startY,endX,endY,paint); if(t>=1.0){t = 1.0f; }float pointX = (1-t)*startX+t*endX; float pointY =(1-t)*startY+t*endY; paint.setColor(Color.RED); paint.setStrokeWidth(5); canvas.drawPoint(pointX,pointY,paint); postDelayed(new Runnable() {@Override public void run() {t+=0.01; invalidate(); }},50); } }
效果:
可能有些人会说网上运动的是直线啊 ,没事,一样搞,
package smart.com.pathview; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.util.AttributeSet; import android.view.View; /** * Created by admin on 2016/12/13. */ public class LineView extends View {private float startX,startY; private float endX,endY ; private Paint paint; private float t; public LineView(Context context, AttributeSet attrs) {super(context, attrs); paint = new Paint(); paint.setAntiAlias(true); paint.setStrokeWidth(3); paint.setStyle(Paint.Style.STROKE); startX = 100; startY = 100; endX = 300; endY = 300; }@Override protected void onDraw(Canvas canvas) {super.onDraw(canvas); paint.setColor(Color.parseColor("#e5e5e5")); canvas.drawLine(startX,startY,endX,endY,paint); if(t>=1.0){t = 1.0f; }float pointX = (1-t)*startX+t*endX; float pointY =(1-t)*startY+t*endY; paint.setColor(Color.RED); canvas.drawLine(startX,startY,pointX,pointY,paint);//绘制t在0~1时间内的运动轨迹 postDelayed(new Runnable() {@Override public void run() {t+=0.01; invalidate(); }},50); } }
效果:
一阶曲线是没有控制点的,就只有起点和终点,
二阶曲线:
二阶曲线需要三个元素,一个是起点,二是终点,三是控制点,控制点决定了这条曲线的弯曲程度,
电脑上的画图软件相信都会知道,我们看看这个画图软件中的曲线就是一个二阶曲线,
看看二阶曲线SDK中给我们提供的api调用,封装在Path类中
public void quadTo(float x1, float y1, float x2, float y2)
参数说明:
x1,y1是控制点,x2,y2是终点
还有一个函数:
public void rQuadTo(float dx1, float dy1, float dx2, float dy2)
参数说明:
(dx1,dy1)是相当于moveTo()的,不是坐标中的绝对值,而是相对于moveTo()坐标中的值,
二阶曲线的公式:
说明:
p0是起点,p1是控制点,p2是终点
现在根据这个公式,我们做一个简单的实验效果,就是控制点是我手在屏幕上移动的点,当然起点和终点肯定是已知的,不然上面那个方程怎么求,
package smart.com.pathview; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Path; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.View; /** * Created by admin on 2016/12/13. */ public class TwoCurveView extends View {private float startX,startY; private float endX,endY ; private float contorlX = 200,contorlY = 60;//默认值 private Paint paint; private float t; private Path path; public TwoCurveView(Context context, AttributeSet attrs) {super(context, attrs); paint = new Paint(); paint.setAntiAlias(true); paint.setStrokeWidth(4); paint.setStyle(Paint.Style.STROKE); paint.setColor(Color.BLACK); startX = 60; startY = 350; endX = 450; endY = 350; path = new Path(); }@Override protected void onDraw(Canvas canvas) {super.onDraw(canvas); path.reset(); path.moveTo(startX,startY); path.quadTo(contorlX,contorlY,endX,endY); canvas.drawPath(path,paint); }@Override public boolean onTouchEvent(MotionEvent event) {if(event.getAction()==MotionEvent.ACTION_MOVE){contorlX = event.getX(); contorlY = event.getY(); invalidate(); }return true; } }
效果:
可能在看别的博客会发现别人有演示的动画,这样看起来更直观点,比如这种图:
这个我当时想自己通过绘制出来的,但是有些地方没想明白,后来请教了石宗银大神,在这感谢石神的教导,在我心中他是一位智者,一位受人尊敬的leader,好了不吹了,再吹他衣服都要吹没了
首先p0p1,p1p2这二条直线绘制出来没问题的,红色的轨迹也好绘制,根据二阶曲线的公式,你可以把这些轨迹看成无数个点构成,所以你只要绘制无数个点就行了,当时想不明白的是哪绿色的辅助线不怎么绘制出来,根据这个思路把代码实现下:
package smart.com.pathview; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Path; import android.graphics.PointF; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.View; import java.util.ArrayList; import java.util.List; /** * Created by admin on 2016/12/13. */ public class TwoCurveView extends View {private float startX,startY; private float endX,endY ; private float contorlX = 200,contorlY = 60;//默认值 private Paint paint; private float t; private Path path; private List<PointF> points;//存储曲线上运动的点 public TwoCurveView(Context context, AttributeSet attrs) {super(context, attrs); paint = new Paint(); paint.setAntiAlias(true); paint.setStrokeWidth(4); paint.setStyle(Paint.Style.STROKE); paint.setColor(Color.BLACK); startX = 60; startY = 350; endX = 450; endY = 350; path = new Path(); points = new ArrayList<>(); }@Override protected void onDraw(Canvas canvas) {super.onDraw(canvas); if(t>=1.0f){t=1.0f; }//绘制2根线 起点-控制点 控制点-终点 paint.setColor(Color.parseColor("#e5e5e5")); canvas.drawLine(startX,startY,contorlX,contorlY,paint); canvas.drawLine(contorlX,contorlY,endX,endY,paint); // float p3x = (1 - t) * startX+ t* contorlX; float p3y = (1 - t) *startY + t * contorlY; float p4x = (1 - t) * contorlX + t * endX; float p4y = (1 - t) * contorlY + t * endY; paint.setColor(Color.GREEN); //这是绘制辅助线说明轨迹的运动情况 轨迹的运动情况 canvas.drawLine(p3x, p3y, p4x, p4y, paint); //绘制曲线轨迹 float p5x = (1 - t) * p3x + t * p4x; float p5y = (1 - t) * p3y + t * p4y; points.add(new PointF(p5x, p5y)); paint.setColor(Color.RED); PointF ps, pe; for (int i = 1; i < points.size(); i++) {//其实这个二阶曲线就是由无数个点构成,然后把前后2个点构成一条直线 ps = points.get(i - 1); pe = points.get(i); canvas.drawLine(ps.x, ps.y, pe.x, pe.y, paint);//绘制贝塞尔在时间0到1内运动轨迹 }postDelayed(new Runnable() {@Override public void run() {t+=0.01; invalidate(); }},50); if(t==1.0f){//绘制曲线轨迹曲线 path.reset();//记得一定要重置path path.moveTo(startX,startY); path.quadTo(contorlX,contorlY,endX,endY); canvas.drawPath(path,paint); }}@Override public boolean onTouchEvent(MotionEvent event) {switch (event.getAction()){case MotionEvent.ACTION_DOWN:case MotionEvent.ACTION_MOVE:contorlX = event.getX(); contorlY = event.getY(); t = 0; points.clear(); invalidate(); break; }return true; } }
效果:
下面画图分析这个运动轨迹
现在讲下三阶曲线,它是由2个控制点,一个起点,一个终点构成的,api:
public void cubicTo(float x1, float y1, float x2, float y2,float x3, float y3)
参数说明:
(x,y1)是控制点1
(x2,y2)是控制点2
(x3,y3)是终点
现在和上面一样,绘制一个动态的三阶曲线运动轨迹:
package smart.com.pathview; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Path; import android.graphics.PointF; import android.util.AttributeSet; import android.view.View; import java.util.ArrayList; import java.util.List; /** * Created by admin on 2016/12/13. */ public class ThreeCurveView extends View {private float startX,startY; private float endX,endY ; private float contorlX1 = 90,contorlY1 = 60;//默认值 private float contorlX2 = 400,contorlY2 = 60;//默认值 private Paint paint; private float t; private Path path; private List<PointF> points;//存储曲线上运动的点 public ThreeCurveView(Context context, AttributeSet attrs) {super(context, attrs); paint = new Paint(); paint.setAntiAlias(true); paint.setStrokeWidth(4); paint.setStyle(Paint.Style.STROKE); paint.setColor(Color.BLACK); startX = 60; startY = 350; endX = 450; endY = 350; path = new Path(); points = new ArrayList<>(); }@Override protected void onDraw(Canvas canvas) {super.onDraw(canvas); if(t>=1.0f){t=1.0f; }//绘制线 起点-控制点1 控制点1-控制点2 控制点2-终点 paint.setStrokeWidth(4); paint.setColor(Color.parseColor("#e5e5e5")); canvas.drawLine(startX,startY,contorlX1,contorlY1,paint); canvas.drawLine(contorlX1,contorlY1,contorlX2,contorlY2,paint); canvas.drawLine(contorlX2,contorlY2,endX,endY,paint); //绘制轨迹直线 float p3x = (1 - t) * startX+ t* contorlX1; float p3y = (1 - t) *startY + t * contorlY1; float p4x = (1 - t) * contorlX1 + t * contorlX2; float p4y = (1 - t) * contorlY1 + t * contorlY2; float p5x = (1 - t) * contorlX1+ t* contorlX2; float p5y = (1 - t) *contorlY1 + t * contorlY2; float p6x = (1 - t) * contorlX2 + t * endX; float p6y = (1 - t) * contorlY2 + t * endY; float pc7x = (1 - t) * p3x + t * p4x; float pc7y = (1 - t) * p3y + t * p4y; float pc8x = (1 - t) * p5x + t * p6x; float pc8y = (1 - t) * p5y + t * p6y; paint.setColor(Color.GREEN); //绘制曲线运动轨迹 canvas.drawLine(p3x, p3y, p4x, p4y, paint); canvas.drawLine(p5x, p5y, p6x, p6y, paint); paint.setColor(Color.BLUE); //绘制辅助线 canvas.drawLine(pc7x, pc7y, pc8x, pc8y, paint); float p9x = (1 - t) * pc7x + t * pc8x; float p9y = (1 - t) * pc7y + t * pc8y; points.add(new PointF(p9x, p9y)); paint.setColor(Color.RED); PointF ps, pe; for (int i = 1; i < points.size(); i++) {//其实这个二阶曲线就是由无数个点构成,然后把前后2个点构成一条直线 ps = points.get(i - 1); pe = points.get(i); canvas.drawLine(ps.x, ps.y, pe.x, pe.y, paint);//绘制贝塞尔在时间0到1内曲线运动轨迹 }paint.setColor(Color.parseColor("#e5e5e5")); paint.setStrokeWidth(6); paint.setColor(Color.BLUE); canvas.drawPoint(contorlX1,contorlY1,paint); canvas.drawPoint(contorlX2,contorlY2,paint); path.reset(); if(t==1.0f){path.moveTo(startX,startY); path.cubicTo(contorlX1,contorlY1,contorlX2,contorlY2,endX,endY); canvas.drawPath(path,paint); }postDelayed(new Runnable() {@Override public void run() {t+=0.01; invalidate(); }},50); } }
效果:
ok,大于3阶曲线,水平有限,写不出来,实际也很少用到,写的吐血!
现在写个demo玩下:
第一个例子就是在画笔上写文字了,不是通过drawText...()去绘制的,很简单
package smart.com.pathview; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Path; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.View; /** * Created by admin on 2016/12/13. */ public class DemoCurveView extends View {private Path path; private Paint paint; public DemoCurveView(Context context, AttributeSet attrs) {super(context, attrs); initPaint(); }private void initPaint() {paint = new Paint(); paint.setAntiAlias(true); paint.setStrokeWidth(4); paint.setStyle(Paint.Style.STROKE); paint.setColor(Color.GRAY); path = new Path(); }@Override public boolean onTouchEvent(MotionEvent event) {switch (event.getAction()){case MotionEvent.ACTION_DOWN:path.moveTo(event.getX(),event.getY()); break; case MotionEvent.ACTION_MOVE:path.lineTo(event.getX(),event.getY()); invalidate(); break; }return true; }@Override protected void onDraw(Canvas canvas) {super.onDraw(canvas); canvas.drawPath(path,paint); } }
效果:
另外一种实现方式:就是通过我们所学的二阶曲线,这个关键一点就是控制点是不断变化的,是以你上一个点为控制点,所以只要记录上一个点为控制点就ok
package smart.com.pathview; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Path; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.View; /** * Created by admin on 2016/12/13. */ public class DemoCurveView extends View {private Path path; private Paint paint; private float contorlx1,contorly1;//控制点 public DemoCurveView(Context context, AttributeSet attrs) {super(context, attrs); initPaint(); }private void initPaint() {paint = new Paint(); paint.setAntiAlias(true); paint.setStrokeWidth(4); paint.setStyle(Paint.Style.STROKE); paint.setColor(Color.GRAY); path = new Path(); }@Override public boolean onTouchEvent(MotionEvent event) {switch (event.getAction()){case MotionEvent.ACTION_DOWN:path.moveTo(event.getX(),event.getY()); contorlx1 = event.getX(); contorly1 = event.getY(); break; case MotionEvent.ACTION_MOVE:float endX = event.getX(); float endY = event.getY(); path.quadTo(contorlx1,contorly1,endX,endY); contorlx1 = endX; contorly1 = endY; invalidate(); break; }return true; }@Override protected void onDraw(Canvas canvas) {super.onDraw(canvas); canvas.drawPath(path,paint); } }
效果:
就写到这里把,太累,龙体欠佳啊!
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