轉載請標明出處：http://blog.csdn.net/zhaoyanjun6/article/details/123524086
本文出自【趙彥軍的博客】

文章目錄

• 畫筆模式
• 畫線條
• 畫圓
• 畫矩形
• 畫弧形
• 其他
• 清空畫筆樣式
• 實戰-繪制圓環
• 實戰-圓環中繪制文字

本文示例代碼詳見：https://gitee.com/zhaoyanjun/text-draw

畫筆模式

mPaint.setStyle(Paint.Style.FILL); //設置畫筆模式為填充

• STROKE //描邊
• FILL //填充
• FILL_AND_STROKE //描邊加填充

實驗代碼

Paint paint = new Paint(); paint.setColor(Color.BLUE); paint.setStrokeWidth(40); //為了實驗效果明顯，特地設置描邊寬度非常大// 描邊 paint.setStyle(Paint.Style.STROKE); canvas.drawCircle(200,200,100,paint);// 填充 paint.setStyle(Paint.Style.FILL); canvas.drawCircle(200,500,100,paint);// 描邊加填充 paint.setStyle(Paint.Style.FILL_AND_STROKE); canvas.drawCircle(200, 800, 100, paint);

畫線條

class MyView(context: Context?, attrs: AttributeSet?) : View(context, attrs) {private val paint = Paint()init {paint.color = resources.getColor(R.color.black, null) //畫筆顏色paint.isAntiAlias = true //抗鋸齒paint.strokeWidth = 30f //畫筆寬度}override fun onDraw(canvas: Canvas) {super.onDraw(canvas)val startX = width / 2fval startY = height / 2f//畫線條canvas.drawLine(startX, startY, startX + 200, startY + 200, paint)} }

效果圖

setStrokeCap(Paint.Cap cap)

設置線冒樣式，取值有

• Cap.ROUND(圓形線冒)
• Cap.SQUARE(方形線冒)
• Paint.Cap.BUTT(無線冒)

注意：冒多出來的那塊區域就是線帽！就相當于給原來的直線加上一個帽子一樣，所以叫線帽

setStrokeJoin(Paint.Join join)

設置線段連接處樣式，取值有：

• Join.MITER（結合處為銳角）、
• Join.Round(結合處為圓弧)、
• Join.BEVEL(結合處為直線)

畫圓

canvas.drawCircle(startX, startY, 100f, paint)

畫矩形

canvas.drawRect(startX, startY, startX + 100, startY + 100, paint)

畫弧形

canvas.drawArc(rectF, 30f, 180f, true, paint)

其他

setStrokeWidth(float width) 設置畫筆寬度 setAntiAlias(boolean aa) //抗鋸齒

清空畫筆樣式

//清空畫筆復位 reset()

源碼如此：

實戰-繪制圓環

效果圖

class MyView(context: Context?, attrs: AttributeSet?) : View(context, attrs) {private val paint = Paint()private val radius = 300finit {paint.color = resources.getColor(R.color.black, null) //畫筆顏色paint.isAntiAlias = true //抗鋸齒}override fun onDraw(canvas: Canvas) {super.onDraw(canvas)val startX = width / 2fval startY = height / 2f//繪制圓環paint.color = Color.parseColor("#dddddd")paint.strokeWidth = 30fpaint.style = Paint.Style.STROKEcanvas.drawCircle(startX, startY, radius, paint)//繪制弧形paint.color = Color.REDpaint.strokeCap = Paint.Cap.ROUNDval rectF = RectF(startX - radius, startY - radius, startX + radius, startY + radius)canvas.drawArc(rectF, -90f, 225f, false, paint)} }

實戰-圓環中繪制文字

重要的是文字居中顯示。

計算文字在圓環中的居中文字，有兩種方式：

• 方式一：paint.getTextBounds(content, 0, content.length, bounds)
• 方式二：val fontMetrics = paint.fontMetrics

具體示例，如下所示：

class MyView(context: Context, attrs: AttributeSet?) : View(context, attrs) {private val paint = Paint()private val radius = 300finit {paint.isAntiAlias = true //抗鋸齒}override fun onDraw(canvas: Canvas) {super.onDraw(canvas)val startX = width / 2fval startY = height / 2f//繪制圓環paint.color = Color.parseColor("#dddddd")paint.strokeWidth = 30fpaint.style = Paint.Style.STROKEcanvas.drawCircle(startX, startY, radius, paint)//繪制弧形paint.color = Color.REDpaint.strokeCap = Paint.Cap.ROUNDval rectF = RectF(startX - radius, startY - radius, startX + radius, startY + radius)canvas.drawArc(rectF, -90f, 225f, false, paint)//繪制文字val content = "ababcfp"paint.textSize = 80fpaint.style = Paint.Style.FILL//居中繪制paint.textAlign = Paint.Align.CENTER//加載字體paint.typeface = ResourcesCompat.getFont(context, R.font.fangzheng)//獲取文字的的邊界，這個邊界基于文字baselineval bounds = Rect()paint.getTextBounds(content, 0, content.length, bounds)//獲取邊界的高度val boundHeight = bounds.bottom - bounds.topcanvas.drawText(content, startX, startY + boundHeight / 2, paint)//方式二val fontMetrics = paint.fontMetricsval boundHeight2 = fontMetrics.descent - fontMetrics.ascentcanvas.drawText(content, startX, startY + boundHeight2 / 2, paint)} }

總結

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