Android用Canvas画一个折线图，并加以简单封装，2021吊打面试官系列
}
下面来简单封装一下
1.首先提供给外界输入数据的方法：
public void setChartdate(String[] xdate, int[] ydate, float[] linedate) {
this.xdate = xdate; //x轴坐标
this.ydate = ydate; //y轴坐标
this.linedate = linedate; //坐标点的y轴上的位置
}
2.进行数据为空判断和越界判断
if (xdate.length!=0&&ydate.length!=0&&linedate.length!=0&&xdate.length>=linedate.length){
if (yMaxdata()>=lineMaxdata()){
drawAxis(canvas);
}
}
其中yMaxdata(),lineMaxdata()方法作用为取ydate与linedate中的最大值
3.将所有写死的数据与传进来的数据产生联系。
private void drawDaxes(Canvas canvas, Paint p) {
//开始y绘制坐标系
canvas.drawLine(widthCriterion, hightCriterion, widthCriterion, hightCriterion * (yCopies - 1), p);
//绘制y角
canvas.drawLine(widthCriterion - minCriterion, hightCriterion + minCriterion, widthCriterion + 2, hightCriterion, p);
canvas.drawLine(widthCriterion, hightCriterion, widthCriterion + minCriterion - 2, hightCriterion + minCriterion, p);
//开始x绘制坐标系
canvas.drawLine(widthCriterion - 4, hightCriterion * (yCopies - 1), widthCriterion * (xCopies - 1), hightCriterion * (yCopies - 1), p);
//绘制x角
canvas.drawLine(widthCriterion * (xCopies - 1) - minCriterion, hightCriterion * (yCopies - 1) - minCriterion, widthCriterion * (xCopies - 1), hightCriterion * (yCopies - 1) + 2, p);
canvas.drawLine(widthCriterion * (xCopies - 1) - minCriterion, hightCriterion * (yCopies - 1) + minCriterion, widthCriterion * (xCopies - 1), hightCriterion * (yCopies - 1) - 2, p);
}
private void drawAxispoint(Canvas canvas, Paint p) {
textFont = widthCriterion / 5 * 2;
Typeface font = Typeface.create(Typeface.SANS_SERIF, Typeface.BOLD);
p.setTypeface(font);
p.setTextSize(textFont);
//画x轴数据
for (int i = 0; i < xdate.length; i++) {
String text = xdate[i];
int stringWidth = (int) p.measureText(text); //文本长度
canvas.drawText(text, (i + 1) * widthCriterion - stringWidth / 2, hightCriterion * (yCopies - 1) + textFont, p);// 画文本
}
for (int i = 0; i < ydate.length; i++) {
String text = String.valueOf(ydate[i]);
int stringWidth = (int) p.measureText(text);
//文本长度
if (i == 0) {
} else {
canvas.drawText(text, widthCriterion - textFont-stringWidth, hightCriterion * (yCopies - 1) - i * hightCriterion + stringWidth / 2, p);// 画文本
}
}
}
private void drawbrokenLine(Canvas canvas, Paint p) {
float line=(hightCriterion * (yCopies - 1)-hightCriterion*2)/ydate[ydate.length-1];
for (int i = 0; i float height=hightCriterion * (yCopies-1)-line*linedate[i]; if (i!=linedate.length-1){ float elseheight=hightCriterion * (yCopies-1)-line*linedate[i+1]; canvas.drawLine(widthCriterion*(i+1),height , widthCriterion * (i+2), elseheight, p); canvas.drawCircle(widthCriterion*(i+1), height, 10, p); }else{ float endheight=hightCriterion * (yCopies-1)-line*linedate[linedate.length-1]; canvas.drawCircle(widthCriterion*(i+1), endheight, 10, p); } } } 现在就可以根据给到的数据动态绘制简单折线图 接下来看效果 在Activity中找到控件后，调用控件的setChartdate()方法; 数据如下： private String[] xdata={“0”,“1”,“2”,“3”,“4”,“5”,“6”,“7”,“8”}; private int[] yfata={0,10,20,30,40,50,60,70}; private float[] linedata={5,10,6,30,5,62.5f,6,2,}; 传入数据： linechartview.setChartdate(xdata,yfata,linedata); 效果图如下： 封装后java代码如下 public class LineChartView extends View { private int minCriterion; private int hightCriterion; private int widthCriterion; private int canvasHeight; private int canvasWidth; private int textFont; private String[] xdate; private int[] ydate; private float[] linedate; private int xCopies; private float yCopies; public void setChartdate(String[] xdate, int[] ydate, float[] linedate) { this.xdate = xdate; this.ydate = ydate; this.linedate = linedate; } public LineChartView(Context context) { super(context); } public LineChartView(Context context, @Nullable AttributeSet attrs) { super(context, attrs); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); if (xdate.length!=0&&ydate.length!=0&&linedate.length!=0&&xdate.length>=linedate.length){ if (yMaxdata()>=lineMaxdata()){ drawAxis(canvas); } } } //绘制 private void drawAxis(Canvas canvas) { xCopies = xdate.length + 2; yCopies = ydate.length + 2; Paint daxesPaint, axispointPaint, brokenLinePaint; //画布宽度 canvasWidth = canvas.getWidth(); //画布高度 canvasHeight = canvas.getHeight(); widthCriterion = canvasWidth / xCopies; hightCriterion = (int) (canvasHeight / yCopies); minCriterion = widthCriterion > hightCriterion ? hightCriterion / 2 : widthCriterion / 2; //开始绘制底层背景 daxesPaint = new Paint(); daxesPaint.setColor(Color.BLACK); daxesPaint.setAntiAlias(true); //去掉锯齿效果 daxesPaint.setStrokeWidth(7.0f); drawDaxes(canvas, daxesPaint); //开始绘制坐标点 axispointPaint = daxesPaint; drawAxispoint(canvas, axispointPaint); //开始绘制折线和线上的点 brokenLinePaint=axispointPaint; brokenLinePaint.setStrokeWidth(5.0f); drawbrokenLine(canvas,brokenLinePaint); } private void drawDaxes(Canvas canvas, Paint p) { //开始y绘制坐标系 canvas.drawLine(widthCriterion, hightCriterion, widthCriterion, hightCriterion * (yCopies - 1), p); //绘制y角 canvas.drawLine(widthCriterion - minCriterion, hightCriterion + minCriterion, widthCriterion + 2, hightCriterion, p); canvas.drawLine(widthCriterion, hightCriterion, widthCriterion + minCriterion - 2, hightCriterion + minCriterion, p); //开始x绘制坐标系 canvas.drawLine(widthCriterion - 4, hightCriterion * (yCopies - 1), widthCriterion * (xCopies - 1), hightCriterion * (yCopies - 1), p); //绘制x角 canvas.drawLine(widthCriterion * (xCopies - 1) - minCriterion, hightCriterion * (yCopies - 1) - minCriterion, widthCriterion * (xCopies - 1), hightCriterion * (yCopies - 1) + 2, p); canvas.drawLine(widthCriterion * (xCopies - 1) - minCriterion, hightCriterion * (yCopies - 1) + minCriterion, widthCriterion * (xCopies - 1), hightCriterion * (yCopies - 1) - 2, p); } private void drawAxispoint(Canvas canvas, Paint p) { textFont = widthCriterion / 5 * 2; Typeface font = Typeface.create(Typeface.SANS_SERIF, Typeface.BOLD); p.setTypeface(font); p.setTextSize(textFont); //画x轴数据 for (int i = 0; i < xdate.length; i++) { String text = xdate[i]; int stringWidth = (int) p.measureText(text); //文本长度 canvas.drawText(text, (i + 1) * widthCriterion - stringWidth / 2, hightCriterion * (yCopies - 1) + textFont, p);// 画文本 } for (int i = 0; i < ydate.length; i++) { String text = String.valueOf(ydate[i]); int stringWidth = (int) p.measureText(text); //文本长度 if (i == 0) { } else { canvas.drawText(text, widthCriterion - textFont-stringWidth, hightCriterion * (yCopies - 1) - i * hightCriterion + stringWidth / 2, p);// 画文本 } } } private void drawbrokenLine(Canvas canvas, Paint p) { float line=(hightCriterion * (yCopies - 1)-hightCriterion*2)/ydate[ydate.length-1]; for (int i = 0; i float height=hightCriterion * (yCopies-1)-line*linedate[i]; if (i!=linedate.length-1){ float elseheight=hightCriterion * (yCopies-1)-line*linedate[i+1]; canvas.drawLine(widthCriterion*(i+1),height , widthCriterion * (i+2), elseheight, p); canvas.drawCircle(widthCriterion*(i+1), height, 10, p); }else{ float endheight=hightCriterion * (yCopies-1)-line*linedate[linedate.length-1]; canvas.drawCircle(widthCriterion*(i+1), endheight, 10, p); } } } private float yMaxdata(){ float max = 0; for (int i = 0; i < ydate.length; i++) { if (ydate[i] > max) { max = ydate[i]; } } return max; } 在此为大家准备了四节优质的Android高级进阶视频： 架构师项目实战——全球首批Android开发者对Android架构的见解 链接:GitHub 免费获取！ max = 0; for (int i = 0; i < ydate.length; i++) { if (ydate[i] > max) { max = ydate[i]; } } return max; } 在此为大家准备了四节优质的Android高级进阶视频： 架构师项目实战——全球首批Android开发者对Android架构的见解 链接:GitHub 免费获取！ [外链图片转存中…(img-7bZc5KGi-1643783639591)] 领取获取往期Android高级架构资料、源码、笔记、视频。高级UI、性能优化、架构师课程、NDK、混合式开发（ReactNative+Weex）微信小程序、Flutter全方面的Android进阶实践技术，群内还有技术大牛一起讨论交流解决问题。
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