项目里需要一个完全可自定义的仪表盘，其中需要分三个警示断来提示，这里以温度为例，0°C以下用蓝色刻度，70°C以下用绿色刻度，70°C以上红色刻度。
由于需要展示十几个这种图标，并且更新频率接近实时，所以对性能要求比较高。
改了几版后达到要求，最终效果图如下：
为了保持移植到其他项目的便利性，未使用xml的属性值来定义。 并且只有一个文件，复制粘贴简单；大部分参数都设有默认值，并且支持所有的参数可以通过配置来修改。
GaugeView gaugeView = findViewById(R.id.gaugu);
GaugeView.Config cfg = new GaugeView.Config();
cfg.labelText = "温度"; // 所有项均可在此配置修改
gaugeView.config(cfg);
// 中间值格式，最大值，最小值，刻度线（dialStep的值，必须被最大值减最小值整除），第一个警戒线，第二个警戒线
gaugeView.init("%.1f°C", 100f, -30f, 10, 10, 70);
gaugeView.updateVal(30f);
package org.tcshare.widgets;
import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.LinearGradient;
import android.graphics.Paint;
import android.graphics.RadialGradient;
import android.graphics.RectF;
import android.graphics.Shader;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.view.View;
import androidx.annotation.Nullable;
import java.text.DecimalFormat;
/**
* @author 爱T鱼
* @date 2021年1月5日
*/
public class GaugeView extends View {
protected int bgRound1 = Color.parseColor("#99122a73");
protected int bgRound2 = Color.parseColor("#66122a73");
protected int bgRound3 = Color.parseColor("#22142f80");
protected int bgRound4 = Color.parseColor("#0e2267");
protected int circle1 = Color.parseColor("#0d1d4c");
protected int bgRadius1;
protected int bgRadius2;
protected int bgRadius3;
protected int bgRadius4;
protected int circleRadius1;
protected int circleRadius2;
// 背景圆画笔
protected Paint roundPaint;
protected int mWidth;
protected int mHeight;
protected int mCx;
protected int mCy;
protected int radius;
// 刻度画笔
protected Paint pointerPaint;
protected float textSizeDial = 14; // 刻度字体大小
protected Paint.FontMetrics pointerFontMetrics;
// 标题画笔
protected Paint labelPaint;
// 长刻度线半径
protected int radiusDial;
protected float maxVal = 150f;
protected float minVal = -50f;
protected int lowDialLimit = 20; // 低段温度警戒线
protected int highDialLimit = 80; // 中段警戒线
protected int colorDialLower = Color.parseColor("#00faff"); // 低中高三个色段表盘刻度
protected int colorDialMiddle = Color.GREEN;
protected int colorDialHigh = Color.RED;
protected int lengthLDial = 16;// 长刻度线的长度
protected int lengthSDial = 8;// 短刻度线的长度
protected float strokeLDial = 3;
protected float strokeSDial = 1;
protected float circleRadius1StrokeWidth = 2f;
protected float circleRadius2StrokeWidth = 4f;
protected float pointerLineDegree = 135; // 多少角度
protected float arcStartDegree = pointerLineDegree; // 弧线起始角度
protected Paint valPaint;
protected Paint.FontMetrics labelFontMetrics;
protected Paint.FontMetrics valFontMetrics;
protected String valText = "";
protected float realVal; // 真实的值
protected float valTextSize = 40f;// 值字体大小
protected int valTextColor = Color.WHITE;// 值字体颜色
protected String labelText = "";
protected float labelTextSize = 20f;// 标签字体
protected int labelTextColor = Color.WHITE;// 标签字体颜色
protected Paint arcPaint;
protected RectF mArcRect = new RectF(), mCircleArcRect1 = new RectF(), mCircleArcRect2 = new RectF(); // 指针（半扇形）及描边线
protected float arcPaintStrokeWidth = 2f; // 描边宽度
protected int arcColor = Color.parseColor("#ff8e00");
protected int[] colors = new int[]{Color.TRANSPARENT, Color.TRANSPARENT, Color.TRANSPARENT, arcColor};
protected int[] colorsArcLine = new int[]{arcColor, arcColor, Color.TRANSPARENT};
protected Shader arcShader;
protected Shader arcLineShader;
protected float sweepAngle = 0;
protected String formatter = "%.0f";
protected int drawDialNum = 100;
protected int dialStep = 10; // 分度
protected float valRange;
protected float stepDegree;
protected float sRoateDegree;
protected DecimalFormat decimalFormat = new DecimalFormat(".0");
private Bitmap pLineCache; // 绘制点线缓存，该步骤耗时长
public GaugeView(Context context) {
super(context);
init();
}
public GaugeView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
init();
}
public GaugeView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
public GaugeView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
init();
}
protected void init() {
// 初始化圆背景画笔
roundPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
// 扫描扇
arcPaint = new Paint();
arcPaint.setAntiAlias(true);
// 刻度
pointerPaint = new Paint();
pointerPaint.setAntiAlias(true);
pointerPaint.setTextSize(textSizeDial);
pointerPaint.setTextAlign(Paint.Align.CENTER);
pointerFontMetrics = pointerPaint.getFontMetrics();
// 标题
labelPaint = new Paint();
labelPaint.setAntiAlias(true);
labelPaint.setTextAlign(Paint.Align.CENTER);
labelPaint.setFakeBoldText(true);
labelPaint.setTextSize(labelTextSize);
labelPaint.setColor(labelTextColor);
labelFontMetrics = labelPaint.getFontMetrics();
// 值
valPaint = new Paint();
valPaint.setAntiAlias(true);
valPaint.setTextAlign(Paint.Align.CENTER);
// valPaint.setFakeBoldText(true);
valPaint.setTextSize(valTextSize);
valPaint.setColor(valTextColor);
valFontMetrics = valPaint.getFontMetrics();
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
drawBG(canvas);
drawArc(canvas);
drawPointerLine(canvas);
drawValText(canvas);
drawLabelText(canvas);
}
private void drawArc(Canvas canvas) {
canvas.save();
arcPaint.setStyle(Paint.Style.FILL);
arcPaint.setShader(arcShader);
canvas.drawArc(mArcRect, arcStartDegree, sweepAngle, true, arcPaint);
arcPaint.setStyle(Paint.Style.STROKE);
arcPaint.setColor(arcColor);
arcPaint.setShader(null);
arcPaint.setStrokeWidth(arcPaintStrokeWidth);
canvas.drawArc(mArcRect, arcStartDegree, sweepAngle, false, arcPaint);
arcPaint.setStrokeWidth(arcPaintStrokeWidth);
canvas.drawArc(mCircleArcRect1, arcStartDegree, sweepAngle, false, arcPaint);
canvas.drawArc(mCircleArcRect2, arcStartDegree, sweepAngle, false, arcPaint);
arcPaint.setStrokeWidth(arcPaintStrokeWidth);
// arcPaint.setShader(arcLineShader);
canvas.translate(mCx, mCy);
canvas.rotate(arcStartDegree + sweepAngle);
canvas.drawLine(radiusDial, 0, circleRadius2, 0, arcPaint);
canvas.restore();
}
private void drawLabelText(Canvas canvas) {
canvas.save();
canvas.translate(mCx, mCy + (bgRadius3 + circleRadius1) / 2f);
int textBaseLine = (int) (0 + (labelFontMetrics.bottom - labelFontMetrics.top) / 2 - labelFontMetrics.bottom);
canvas.drawText(labelText, 0, textBaseLine, labelPaint);
canvas.restore();
}
private void drawValText(Canvas canvas) {
if (valText != null) {
canvas.save();
canvas.translate(mCx, mCy);
int textBaseLine = (int) (0 + (valFontMetrics.bottom - valFontMetrics.top) / 2 - valFontMetrics.bottom);
canvas.drawText(valText, 0, textBaseLine, valPaint);
canvas.restore();
}
}
private void drawPointerLine(Canvas c) {
if(pLineCache == null) {
pLineCache = Bitmap.createBitmap(mWidth, mHeight, Bitmap.Config.ARGB_8888);
Canvas pointerLineCacheCanvas = new Canvas(pLineCache);
// pointerLineCacheCanvas.save();
pointerLineCacheCanvas.translate(mCx, mCy);
pointerLineCacheCanvas.rotate(pointerLineDegree);
for (int i = 0; i <= valRange; i++) {
if (i < lowDialLimit) {
pointerPaint.setColor(colorDialLower);
} else if (i <= highDialLimit) {
pointerPaint.setColor(colorDialMiddle);
} else {
pointerPaint.setColor(colorDialHigh);
}
if (i % dialStep == 0) { //长表针
pointerPaint.setStrokeWidth(strokeLDial);
pointerLineCacheCanvas.drawLine(radiusDial, 0, radiusDial - lengthLDial, 0, pointerPaint);
// String text = String.format("%.0f", minVal + i); // format 性能跟不上
drawPointerText(pointerLineCacheCanvas, decimalFormat.format(minVal + i), i);
} else { //短表针
pointerPaint.setStrokeWidth(strokeSDial);
int offset = (lengthLDial - lengthSDial) / 2;
pointerLineCacheCanvas.drawLine(radiusDial - offset, 0, radiusDial - lengthSDial, 0, pointerPaint);
}
pointerLineCacheCanvas.rotate(sRoateDegree);
}
// pointerLineCacheCanvas.restore();
}
c.drawBitmap(pLineCache,0,0, null);
}
private void drawPointerText(Canvas canvas, String text, int i) {
canvas.save();
int currentCenterX = (int) (radiusDial - lengthLDial - strokeLDial - pointerPaint.measureText(String.valueOf(text)) / 2);
canvas.translate(currentCenterX, 0);
canvas.rotate(360 - pointerLineDegree - i * sRoateDegree);
int textBaseLine = (int) (0 + (pointerFontMetrics.bottom - pointerFontMetrics.top) / 2 - pointerFontMetrics.bottom);
canvas.drawText(text, 0, textBaseLine, pointerPaint);
canvas.restore();
}
private void drawBG(Canvas canvas) {
canvas.save();
roundPaint.setStyle(Paint.Style.FILL);
roundPaint.setColor(bgRound1);
roundPaint.setStrokeWidth(0);
canvas.drawCircle(mCx, mCy, bgRadius1, roundPaint);
roundPaint.setColor(bgRound2);
canvas.drawCircle(mCx, mCy, bgRadius2, roundPaint);
roundPaint.setColor(bgRound3);
canvas.drawCircle(mCx, mCy, bgRadius3, roundPaint);
roundPaint.setColor(bgRound4);
canvas.drawCircle(mCx, mCy, bgRadius4, roundPaint);
roundPaint.setColor(circle1);
roundPaint.setStyle(Paint.Style.STROKE);
roundPaint.setStrokeWidth(circleRadius1StrokeWidth);
canvas.drawCircle(mCx, mCy, circleRadius1, roundPaint);
roundPaint.setStrokeWidth(circleRadius2StrokeWidth);
canvas.drawCircle(mCx, mCy, circleRadius2, roundPaint);
canvas.restore();
}
@SuppressLint("DrawAllocation")
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
// 获取控件区域宽高
int minimumWidth = getSuggestedMinimumWidth();
int minimumHeight = getSuggestedMinimumHeight();
mWidth = resolveMeasured(widthMeasureSpec, minimumWidth);
mHeight = resolveMeasured(heightMeasureSpec, minimumHeight);
// 获取x/y轴中心点
mCx = mWidth / 2;
mCy = mHeight / 2;
radius = Math.min(mWidth, mHeight) / 2;
bgRadius1 = radius;
bgRadius2 = (int) (radius * 0.95f);
bgRadius3 = (int) (radius * 0.88f);
bgRadius4 = (int) (radius * 0.6f);
circleRadius1 = (int) (radius * 0.64f);
circleRadius2 = (int) (radius * 0.62f);
// 长刻度线
radiusDial = bgRadius3;
mArcRect.set(mCx - radiusDial, mCy - radiusDial, mCx + radiusDial, mCy + radiusDial);
mCircleArcRect1.set(mCx - circleRadius1, mCy - circleRadius1, mCx + circleRadius1, mCy + circleRadius1);
mCircleArcRect2.set(mCx - circleRadius2, mCy - circleRadius2, mCx + circleRadius2, mCy + circleRadius2);
arcShader = new RadialGradient(mCx, mCy, bgRadius2, colors, null, Shader.TileMode.REPEAT);
arcLineShader = new LinearGradient(radiusDial, 0, circleRadius2, 0, colorsArcLine, null, Shader.TileMode.REPEAT);
pLineCache = null; // 重建缓存画布， 绘制点线耗时长
}
/**
* @param formatter 中间值格式化
* @param maxVal 最大值
* @param minVal 最小值
* @param dialStep 必须能被最大范围整除 (maxVal - minVal) / dialStep = 0
* @param lowDialLimit 警戒线1
* @param highDialLimit 警戒线2
*/
public void init(String formatter, float maxVal, float minVal, int dialStep, int lowDialLimit, int highDialLimit) {
this.dialStep = dialStep;
float drawDegree = (360 - (180 - pointerLineDegree) * 2);
this.maxVal = maxVal;
this.minVal = minVal;
this.valRange = maxVal - minVal;
this.formatter = formatter;
this.drawDialNum = (int) Math.ceil(valRange / dialStep);
this.stepDegree = drawDegree / drawDialNum;
this.lowDialLimit = (int) (lowDialLimit - minVal);
this.highDialLimit = (int) (highDialLimit - minVal);
this.sRoateDegree = stepDegree / dialStep; // 短刻度旋转角度
invalidate();
}
public void updateVal(float val) {
realVal = Math.max(Math.min(val, maxVal), minVal);
valText = String.format(formatter, realVal);
sweepAngle = (realVal - minVal) / valRange * (360 - (180 - pointerLineDegree) * 2);
invalidate();
}
private int resolveMeasured(int measureSpec, int desired) {
int specSize = MeasureSpec.getSize(measureSpec);
int result;
switch (MeasureSpec.getMode(measureSpec)) {
case MeasureSpec.UNSPECIFIED:
result = desired;
break;
case MeasureSpec.AT_MOST:
result = Math.max(specSize, desired);
break;
case MeasureSpec.EXACTLY:
result = specSize;
break;
default:
result = specSize;
break;
}
return result;
}
private float dp2px(float dp){
return TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp,this.getContext().getResources().getDisplayMetrics());
}
public void config(GaugeView.Config cfg) {
this.bgRound1 = cfg.bgRound1;
this.bgRound2 = cfg.bgRound2;
this.bgRound3 = cfg.bgRound3;
this.bgRound4 = cfg.bgRound4;
this.circle1 = cfg.circle1;
this.textSizeDial = dp2px(cfg.textSizeDial); // 刻度字体大小
this.maxVal = cfg.maxVal;
this.minVal = cfg.minVal;
this.lowDialLimit = cfg.lowDialLimit; // 低段温度警戒线
this.highDialLimit = cfg.highDialLimit; // 中段警戒线
this.colorDialLower = cfg.colorDialLower; // 低中高三个色段表盘刻度
this.colorDialMiddle = cfg.colorDialMiddle;
this.colorDialHigh = cfg.colorDialHigh;
this.lengthLDial = cfg.lengthLDial;// 长刻度线的长度
this.lengthSDial = cfg.lengthSDial;// 短刻度线的长度
this.strokeLDial = cfg.strokeLDial;
this.strokeSDial = cfg.strokeSDial;
this.circleRadius1StrokeWidth = cfg.circleRadius1StrokeWidth;
this.circleRadius2StrokeWidth = cfg.circleRadius2StrokeWidth;
this.pointerLineDegree = cfg.pointerLineDegree; // 多少角度
this.arcStartDegree = pointerLineDegree; // 弧线起始角度
this.valTextSize = dp2px(cfg.valTextSize);// 值字体大小
this.valTextColor = cfg.valTextColor;// 值字体颜色
this.labelText = cfg.labelText;
this.labelTextSize = dp2px(cfg.labelTextSize);// 标签字体
this.labelTextColor = cfg.labelTextColor;// 标签字体颜色
this.arcPaintStrokeWidth = cfg.arcPaintStrokeWidth; // 描边宽度
this.arcColor = cfg.arcColor;
this.colors = cfg.colors != null ? cfg.colors : new int[]{Color.TRANSPARENT, Color.TRANSPARENT, Color.TRANSPARENT, cfg.arcColor};
this.colorsArcLine = cfg.colorsArcLine != null ? cfg.colorsArcLine : new int[]{cfg.arcColor, cfg.arcColor, Color.TRANSPARENT};
;
this.formatter = cfg.formatter;
this.drawDialNum = cfg.drawDialNum;
this.dialStep = cfg.dialStep; // 分度
this.decimalFormat= cfg.decimalFormat;
init();
invalidate();
}
public static class Config {
public int bgRound1 = Color.parseColor("#99122a73");
public int bgRound2 = Color.parseColor("#66122a73");
public int bgRound3 = Color.parseColor("#22142f80");
public int bgRound4 = Color.parseColor("#0e2267");
public int circle1 = Color.parseColor("#0d1d4c");
public float textSizeDial = 12; // 刻度字体大小
public float maxVal = 150f;
public float minVal = -50f;
public int lowDialLimit = 20; // 低段温度警戒线
public int highDialLimit = 80; // 中段警戒线
public int colorDialLower = Color.parseColor("#00faff"); // 低中高三个色段表盘刻度
public int colorDialMiddle = Color.GREEN;
public int colorDialHigh = Color.RED;
public int lengthLDial = 16;// 长刻度线的长度
public int lengthSDial = 8;// 短刻度线的长度
public float strokeLDial = 3;
public float strokeSDial = 1;
public float circleRadius1StrokeWidth = 2f;
public float circleRadius2StrokeWidth = 4f;
public float pointerLineDegree = 135; // 多少角度
public float valTextSize = 30f;// 值字体大小
public int valTextColor = Color.WHITE;// 值字体颜色
public String labelText = "";
public float labelTextSize = 14f;// 标签字体
public int labelTextColor = Color.WHITE;// 标签字体颜色
public float arcPaintStrokeWidth = 2f; // 描边宽度
public int arcColor = Color.parseColor("#f6a800");
public int[] colors;
public int[] colorsArcLine;
public String formatter = "%.0f";
public int drawDialNum = 100;
public int dialStep = 10; // 分度
public DecimalFormat decimalFormat= new DecimalFormat(".0");
}
}