自定义绘制View

scale(floatsx,floatsy)//对canvas执行缩放

skew(floatsx,floatsy)//对canvas执行倾斜变换

translate(floatdx,floatdy)//移动canvas，向右dx,向下dy

//Path

moveTo(floatx,floaty)//Setthebeginningofthenextcontourtothepoint(x,y).

lineTo(floatx,floaty)//Addalinefromthelastpointtothespecifiedpoint(x,y).

//canvas

drawTextOnPath(Stringtext,Pathpath,floathOffset,floatvOffset,Paintpaint)//

paint.setPathEffect(PathEffecteffect);

publicclassDrawViewextendsView

{

//定义记录前一个拖动事件发生点的坐标

floatpreX;

floatpreY;

privatePathpath;

publicPaintpaint=null;

//定义一个内存中的图片，该图片将作为缓冲区

BitmapcacheBitmap=null;

//定义cacheBitmap上的Canvas对象

CanvascacheCanvas=null;

publicDrawView(Contextcontext,intwidth,intheight)

{

super(context);

//创建一个与该View相同大小的缓存区

cacheBitmap=Bitmap.createBitmap(width,height,

Bitmap.Config.ARGB_8888);

cacheCanvas=newCanvas();

path=newPath();

//设置cacheCanvas将会绘制到内存中的cacheBitmap上

cacheCanvas.setBitmap(cacheBitmap);

//设置画笔的颜色

paint=newPaint(Paint.DITHER_FLAG);

paint.setColor(Color.RED);

//设置画笔风格

paint.setStyle(Paint.Style.STROKE);

paint.setStrokeWidth(1);

//反锯齿

paint.setAntiAlias(true);

paint.setDither(true);

}

@Override

publicbooleanonTouchEvent(MotionEventevent)

{

//获取拖动事件的发生位置

floatx=event.getX();

floaty=event.getY();

switch(event.getAction())

{

caseMotionEvent.ACTION_DOWN:

//从前一个点绘制到当前点之后，把当前点定义成下次绘制的前一个点

path.moveTo(x,y);

preX=x;

preY=y;

break;

caseMotionEvent.ACTION_MOVE:

//从前一个点绘制到当前点之后，把当前点定义成下次绘制的前一个点

path.quadTo(preX,preY,x,y);

preX=x;

preY=y;

break;

caseMotionEvent.ACTION_UP:

cacheCanvas.drawPath(path,paint);//①

path.reset();

break;

}

invalidate();

//返回true表明处理方法已经处理该事件

returntrue;

}

@Override

publicvoidonDraw(Canvascanvas)

{

PaintbmpPaint=newPaint();

//将cacheBitmap绘制到该View组件上

canvas.drawBitmap(cacheBitmap,0,0,bmpPaint);//②

//沿着path绘制

canvas.drawPath(path,paint);

}

}