本文通过示例代码介绍如何自定义简单的直方图表，此图表并非常见的直方图表，而是可以分组的。此文不会过多涉及原理，比较简单，示例图片如下(gif图片没有制作好，有闪烁，请见谅)：
对于该示例的代码实现，其实重点在于坐标轴、文字、直方图的位置控制，需要随滑动距离而动态更新。注意事项会在示例代码中标注。下面贴出示例代码
public class MultiGroupHistogramView extends View {
private int width;
private int height;
// 坐标轴线宽度
private int coordinateAxisWidth;
// 组名称字体大小
private int groupNameTextSize;
// 小组之间间距
private int groupInterval;
// 组内子直方图间距
private int histogramInterval;
private int histogramValueTextSize;
// 图表数值小数点位数
private int histogramValueDecimalCount;
private int histogramHistogramWidth;
private int chartPaddingTop;
private int histogramPaddingStart;
private int histogramPaddingEnd;
// 各组名称到X轴的距离
private int distanceFormGroupNameToAxis;
// 直方图上方数值到直方图的距离
private int distanceFromValueToHistogram;
// 直方图最大高度
private int maxHistogramHeight;
// 轴线画笔
private Paint coordinateAxisPaint;
// 组名画笔
private Paint groupNamePaint;
private Paint.FontMetrics groupNameFontMetrics;
private Paint.FontMetrics histogramValueFontMetrics;
// 直方图数值画笔
private Paint histogramValuePaint;
// 直方图画笔
private Paint histogramPaint;
// 直方图绘制区域
private Rect histogramPaintRect;
// 直方图表视图总宽度
private int histogramContentWidth;
// 存储组内直方图shader color，例如，每组有3个直方图，该SparseArray就存储3个相对应的shader color
private SparseArray<int[]> histogramShaderColorArray;
private List<MultiGroupHistogramGroupData> dataList;
private SparseArray<Float> childMaxValueArray;
private Scroller scroller;
private int minimumVelocity;
private int maximumVelocity;
private VelocityTracker velocityTracker;
public MultiGroupHistogramView(Context context) {
this(context, null);
}
public MultiGroupHistogramView(Context context, @Nullable AttributeSet attrs) {
this(context, attrs, 0);
}
public MultiGroupHistogramView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init(attrs);
}
private void init(AttributeSet attrs) {
setLayerType(View.LAYER_TYPE_HARDWARE, null);
TypedArray typedArray = getContext().obtainStyledAttributes(attrs, R.styleable.MultiGroupHistogramView);
coordinateAxisWidth = typedArray.getDimensionPixelSize(R.styleable.MultiGroupHistogramView_coordinateAxisWidth, DisplayUtil.dp2px(2));
// 坐标轴线颜色
int coordinateAxisColor = typedArray.getColor(R.styleable.MultiGroupHistogramView_coordinateAxisColor, Color.parseColor("#434343"));
// 底部小组名称字体颜色
int groupNameTextColor = typedArray.getColor(R.styleable.MultiGroupHistogramView_groupNameTextColor, Color.parseColor("#CC202332"));
groupNameTextSize = typedArray.getDimensionPixelSize(R.styleable.MultiGroupHistogramView_groupNameTextSize, DisplayUtil.dp2px(15));
groupInterval = typedArray.getDimensionPixelSize(R.styleable.MultiGroupHistogramView_groupInterval, DisplayUtil.dp2px(30));
histogramInterval = typedArray.getDimensionPixelSize(R.styleable.MultiGroupHistogramView_histogramInterval, DisplayUtil.dp2px(10));
// 直方图数值文本颜色
int histogramValueTextColor = typedArray.getColor(R.styleable.MultiGroupHistogramView_histogramValueTextColor, Color.parseColor("#CC202332"));
histogramValueTextSize = typedArray.getDimensionPixelSize(R.styleable.MultiGroupHistogramView_histogramValueTextSize, DisplayUtil.dp2px(12));
histogramValueDecimalCount = typedArray.getInt(R.styleable.MultiGroupHistogramView_histogramValueDecimalCount, 0);
histogramHistogramWidth = typedArray.getDimensionPixelSize(R.styleable.MultiGroupHistogramView_histogramHistogramWidth, DisplayUtil.dp2px(20));
chartPaddingTop = typedArray.getDimensionPixelSize(R.styleable.MultiGroupHistogramView_chartPaddingTop, DisplayUtil.dp2px(10));
histogramPaddingStart = typedArray.getDimensionPixelSize(R.styleable.MultiGroupHistogramView_histogramPaddingStart, DisplayUtil.dp2px(15));
histogramPaddingEnd = typedArray.getDimensionPixelSize(R.styleable.MultiGroupHistogramView_histogramPaddingEnd, DisplayUtil.dp2px(15));
distanceFormGroupNameToAxis = typedArray.getDimensionPixelSize(R.styleable.MultiGroupHistogramView_distanceFormGroupNameToAxis, DisplayUtil.dp2px(15));
distanceFromValueToHistogram = typedArray.getDimensionPixelSize(R.styleable.MultiGroupHistogramView_distanceFromValueToHistogram, DisplayUtil.dp2px(10));
typedArray.recycle();
coordinateAxisPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
coordinateAxisPaint.setStyle(Paint.Style.FILL);
coordinateAxisPaint.setStrokeWidth(coordinateAxisWidth);
coordinateAxisPaint.setColor(coordinateAxisColor);
groupNamePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
groupNamePaint.setTextSize(groupNameTextSize);
groupNamePaint.setColor(groupNameTextColor);
groupNameFontMetrics = groupNamePaint.getFontMetrics();
histogramValuePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
histogramValuePaint.setTextSize(histogramValueTextSize);
histogramValuePaint.setColor(histogramValueTextColor);
histogramValueFontMetrics = histogramValuePaint.getFontMetrics();
histogramPaintRect = new Rect();
histogramPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
scroller = new Scroller(getContext(), new LinearInterpolator());
ViewConfiguration configuration = ViewConfiguration.get(getContext());
minimumVelocity = configuration.getScaledMinimumFlingVelocity();
maximumVelocity = configuration.getScaledMaximumFlingVelocity();
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
width = getMeasuredWidth();
height = getMeasuredHeight();
maxHistogramHeight = height - groupNameTextSize - coordinateAxisWidth - distanceFormGroupNameToAxis - distanceFromValueToHistogram - histogramValueTextSize - chartPaddingTop;
}
/**
* 判断是否可以水平滑动
* @param direction 标识滑动方向 正数：右滑(手指从右至左移动)；负数：左滑(手指由左向右移动)
* 您可参考ScaollView或HorizontalScrollView理解滑动方向
*/
@Override
public boolean canScrollHorizontally(int direction) {
if (direction > 0) {
return histogramContentWidth - getScrollX() - width + histogramPaddingStart + histogramPaddingEnd > 0;
} else {
return getScrollX() > 0;
}
}
/**
* 根据滑动方向获取最大可滑动距离
* @param direction 标识滑动方向 正数：右滑(手指从右至左移动)；负数：左滑(手指由左向右移动)
* 您可参考ScaollView或HorizontalScrollView理解滑动方向
*/
private int getMaxCanScrollX(int direction) {
if (direction > 0) {
return histogramContentWidth - getScrollX() - width + histogramPaddingStart + histogramPaddingEnd > 0 ?
histogramContentWidth - getScrollX() - width + histogramPaddingStart + histogramPaddingEnd : 0;
} else if (direction < 0) {
return getScrollX();
}
return 0;
}
private float lastX;
@Override
public boolean onTouchEvent(MotionEvent event) {
initVelocityTrackerIfNotExists();
velocityTracker.addMovement(event);
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN: {
if (!scroller.isFinished()) {
scroller.abortAnimation();
}
lastX = event.getX();
return true;
}
case MotionEvent.ACTION_MOVE: {
int deltaX = (int) (event.getX() - lastX);
lastX = event.getX();
// 滑动处理
if (deltaX > 0 && canScrollHorizontally(-1)) {
scrollBy(-Math.min(getMaxCanScrollX(-1), deltaX), 0);
} else if (deltaX < 0 && canScrollHorizontally(1)) {
scrollBy(Math.min(getMaxCanScrollX(1), -deltaX), 0);
}
break;
}
case MotionEvent.ACTION_UP: {
velocityTracker.computeCurrentVelocity(1000, maximumVelocity);
int velocityX = (int) velocityTracker.getXVelocity();
fling(velocityX);
recycleVelocityTracker();
break;
}
case MotionEvent.ACTION_CANCEL: {
recycleVelocityTracker();
break;
}
}
return super.onTouchEvent(event);
}
private void initVelocityTrackerIfNotExists() {
if (velocityTracker == null) {
velocityTracker = VelocityTracker.obtain();
}
}
private void recycleVelocityTracker() {
if (velocityTracker != null) {
velocityTracker.recycle();
velocityTracker = null;
}
}
// ACTION_UP事件触发
private void fling(int velocityX) {
if (Math.abs(velocityX) > minimumVelocity) {
if (Math.abs(velocityX) > maximumVelocity) {
velocityX = maximumVelocity * velocityX / Math.abs(velocityX);
}
scroller.fling(getScrollX(), getScrollY(), -velocityX, 0, 0, histogramContentWidth + histogramPaddingStart - width, 0, 0);
}
}
@Override
public void computeScroll() {
if (scroller.computeScrollOffset()) {
scrollTo(scroller.getCurrX(), 0);
}
}
public void setDataList(@NonNull List<MultiGroupHistogramGroupData> dataList) {
this.dataList = dataList;
if (childMaxValueArray == null) {
childMaxValueArray = new SparseArray<>();
} else {
childMaxValueArray.clear();
}
histogramContentWidth = 0;
for (MultiGroupHistogramGroupData groupData : dataList) {
List<MultiGroupHistogramChildData> childDataList = groupData.getChildDataList();
if (childDataList != null && childDataList.size() > 0) {
for (int i = 0; i < childDataList.size(); i++) {
histogramContentWidth += histogramHistogramWidth + histogramInterval;
MultiGroupHistogramChildData childData = childDataList.get(i);
Float childMaxValue = childMaxValueArray.get(i);
if (childMaxValue == null || childMaxValue < childData.getValue()) {
childMaxValueArray.put(i, childData.getValue());
}
}
histogramContentWidth += groupInterval - histogramInterval;
}
}
histogramContentWidth += -groupInterval;
postInvalidate();
}
/**
* 设置组内直方图颜色(并不是设置所有直方图颜色，而是根据每组数据内直方图数量设置)
*/
public void setHistogramColor(int[]... colors) {
if (colors != null && colors.length > 0) {
if (histogramShaderColorArray == null) {
histogramShaderColorArray = new SparseArray<>();
} else {
histogramShaderColorArray.clear();
}
for (int i = 0; i < colors.length; i++) {
histogramShaderColorArray.put(i, colors[i]);
}
}
}
@Override
protected void onDraw(Canvas canvas) {
if (width == 0 || height == 0) {
return;
}
int scrollX = getScrollX();
int axisBottom = height - groupNameTextSize - distanceFormGroupNameToAxis - coordinateAxisWidth / 2;
canvas.drawLine(coordinateAxisWidth / 2 + scrollX, 0, coordinateAxisWidth / 2 + scrollX, axisBottom, coordinateAxisPaint);
canvas.drawLine(scrollX, axisBottom, width + scrollX, axisBottom, coordinateAxisPaint);
if (dataList != null && dataList.size() > 0) {
int xAxisOffset = histogramPaddingStart; // 每个直方图在x轴的偏移量
for (MultiGroupHistogramGroupData groupData : dataList) {
List<MultiGroupHistogramChildData> childDataList = groupData.getChildDataList();
if (childDataList != null && childDataList.size() > 0) {
int groupWidth = 0;
for (int i = 0; i < childDataList.size(); i++) {
MultiGroupHistogramChildData childData = childDataList.get(i);
histogramPaintRect.left = xAxisOffset;
histogramPaintRect.right = histogramPaintRect.left + histogramHistogramWidth;
int childHistogramHeight;
if (childData.getValue() <= 0 || childMaxValueArray.get(i) <= 0) {
childHistogramHeight = 0;
} else {
childHistogramHeight = (int) (childData.getValue() / childMaxValueArray.get(i) * maxHistogramHeight);
}
histogramPaintRect.top = height - childHistogramHeight - coordinateAxisWidth - distanceFormGroupNameToAxis - groupNameTextSize;
histogramPaintRect.bottom = histogramPaintRect.top + childHistogramHeight;
int[] histogramShaderColor = histogramShaderColorArray.get(i);
LinearGradient shader = null;
if (histogramShaderColor != null && histogramShaderColor.length > 0) {
shader = getHistogramShader(histogramPaintRect.left, chartPaddingTop + distanceFromValueToHistogram + histogramValueTextSize,
histogramPaintRect.right, histogramPaintRect.bottom, histogramShaderColor);
}
histogramPaint.setShader(shader);
canvas.drawRect(histogramPaintRect, histogramPaint);
String childHistogramHeightValue = StringUtil.NumericScaleByFloor(String.valueOf(childData.getValue()), histogramValueDecimalCount) + childData.getSuffix();
float valueTextX = xAxisOffset + (histogramHistogramWidth - histogramValuePaint.measureText(childHistogramHeightValue)) / 2;
// 数值绘制Y轴位置特别处理
float valueTextY = histogramPaintRect.top - distanceFormGroupNameToAxis + (histogramValueFontMetrics.bottom) / 2;
canvas.drawText(childHistogramHeightValue, valueTextX, valueTextY, histogramValuePaint);
int deltaX = i < childDataList.size() - 1 ? histogramHistogramWidth + histogramInterval : histogramHistogramWidth;
groupWidth += deltaX;
// 注意此处偏移量累加
xAxisOffset += i == childDataList.size() - 1 ? deltaX + groupInterval : deltaX;
}
String groupName = groupData.getGroupName();
float groupNameTextWidth = groupNamePaint.measureText(groupName);
float groupNameTextX = xAxisOffset - groupWidth - groupInterval + (groupWidth - groupNameTextWidth) / 2;
// 组名绘制Y轴位置特别处理
float groupNameTextY = (height - groupNameFontMetrics.bottom / 2);
canvas.drawText(groupName, groupNameTextX, groupNameTextY, groupNamePaint);
}
}
}
}
private LinearGradient getHistogramShader(float x0, float y0, float x1, float y1, int[] colors) {
return new LinearGradient(x0, y0, x1, y1, colors, null, Shader.TileMode.CLAMP);
}
}代码就这一点，阅读起来应该不难，如有疑问欢迎留言
自定义属性如下：
<declare-styleable name="MultiGroupHistogramView">
<attr name="coordinateAxisWidth" format="dimension" />
<attr name="coordinateAxisColor" format="color" />
<attr name="groupNameTextColor" format="color" />
<attr name="groupNameTextSize" format="dimension" />
<attr name="groupInterval" format="dimension" />
<attr name="histogramInterval" format="dimension" />
<attr name="histogramValueTextColor" format="color" />
<attr name="histogramValueTextSize" format="dimension" />
<attr name="histogramHistogramWidth" format="dimension" />
<attr name="histogramPaddingStart" format="dimension" />
<attr name="histogramPaddingEnd" format="dimension" />
<attr name="chartPaddingTop" format="dimension" />
<attr name="distanceFormGroupNameToAxis" format="dimension" />
<attr name="distanceFromValueToHistogram" format="dimension" />
<!--图表数值小数点位数-->
<attr name="histogramValueDecimalCount">
<enum name="ZERO" value="0" />
<enum name="ONE" value="1" />
<enum name="TWO" value="2" />
</attr>
</declare-styleable>下面贴出使用方法：
private void initMultiGroupHistogramView() {
Random random = new Random();
int groupSize = random.nextInt(5) + 10;
List<MultiGroupHistogramGroupData> groupDataList = new ArrayList<>();
// 生成测试数据
for (int i = 0; i < groupSize; i++) {
List<MultiGroupHistogramChildData> childDataList = new ArrayList<>();
MultiGroupHistogramGroupData groupData = new MultiGroupHistogramGroupData();
groupData.setGroupName("第" + (i + 1) + "组");
MultiGroupHistogramChildData childData1 = new MultiGroupHistogramChildData();
childData1.setSuffix("分");
childData1.setValue(random.nextInt(50) + 51);
childDataList.add(childData1);
MultiGroupHistogramChildData childData2 = new MultiGroupHistogramChildData();
childData2.setSuffix("%");
childData2.setValue(random.nextInt(50) + 51);
childDataList.add(childData2);
groupData.setChildDataList(childDataList);
groupDataList.add(groupData);
}
multiGroupHistogramView.setDataList(groupDataList);
int[] color1 = new int[]{getResources().getColor(R.color.color_orange), getResources().getColor(R.color.colorPrimary)};
int[] color2 = new int[]{getResources().getColor(R.color.color_supper_tip_normal), getResources().getColor(R.color.bg_supper_selected)};
// 设置直方图颜色
multiGroupHistogramView.setHistogramColor(color1, color2);
}
完整示例：https://github.com/670832188/TestApp
原文发布时间为：2019-1-3
本文作者：乱世白衣
本文来自云栖社区合作伙伴“ 安卓巴士Android开发者门户”，了解相关信息可以关注“anzhuobashi”微信公众号