自定义View合辑（9）-计划表

为了加强对自定义 View 的认知以及开发能力，我计划这段时间陆续来完成几个难度从易到难的自定义 View，并简单的写几篇博客来进行介绍，所有的代码也都会开源，也希望读者能给个 star 哈
GitHub 地址：https://github.com/leavesC/CustomView
也可以下载 Apk 来体验下：https://www.pgyer.com/CustomView

先看下效果图：

一、思路解析

这是一个类似于课程表的自定义 View，横向和纵向均是以时间作为计量单位，通过设置当前计划处于哪个星期数下以及跨度时间，在该范围内绘制出相应的背景以及文本

PlanBean 中有两个比较重要字段，一个是该计划的绘制范围，即坐标系 rectF，另一个字段 isEllipsis 是用于标记当前计划的文本是否以省略的形式出现

public class PlanBean {

    private String planId;
    private String planName;
    private String planStartTime;
    private String planEndTime;
    private String color;
    private int dayIndex;
    
    //计划的坐标
    private RectF rectF;
    //文本是否被省略
    private boolean isEllipsis;

}

边框以及时间文本的绘制比较简单，只需要计算出各个起始点和终点的坐标系即可

@Override
    protected void onDraw(Canvas canvas) {
        //先画背景
        bgPaint.setStyle(Paint.Style.FILL);
        bgPaint.setColor(Color.WHITE);
        canvas.drawRect(0, 0, width, realHeight, bgPaint);

        //画左边和上边的边框
        bgPaint.setColor(rectColor);
        bgPaint.setStyle(Paint.Style.FILL);
        canvas.drawRect(0, 0, leftTimeWidth, height, bgPaint);
        canvas.drawRect(leftTimeWidth, 0, width, headerHeight, bgPaint);

        //画线
        canvas.save();
        canvas.translate(leftTimeWidth, 0);
        bgPaint.setColor(lineColor);
        bgPaint.setStrokeWidth(getResources().getDisplayMetrics().density);
        for (int i = 0; i < 7; i++) {
            canvas.drawLine(itemWidth * i, 0, itemWidth * i, height, bgPaint);
        }
        canvas.translate(0, headerHeight);
        for (int i = 0; i < 20; i++) {
            canvas.drawLine(0, i * itemHeight, width - leftTimeWidth + 2, i * itemHeight, bgPaint);
        }
        canvas.restore();

        //画星期数
        canvas.save();
        canvas.translate(leftTimeWidth, 0);
        bgPaint.setTextSize(sp2px(DAY_TEXT_SIZE));
        bgPaint.setColor(Color.BLACK);
        bgPaint.setTextAlign(Paint.Align.CENTER);
        for (String day : DAYS) {
            bgPaint.getTextBounds(day, 0, day.length(), textBounds);
            float offSet = (textBounds.top + textBounds.bottom) >> 1;
            canvas.drawText(day, itemWidth / 2, headerHeight / 2 - offSet, bgPaint);
            canvas.translate(itemWidth, 0);
        }
        canvas.restore();

        //画时间
        for (int i = 0; i < TIMES.length; i++) {
            String time = TIMES[i];
            bgPaint.getTextBounds(time, 0, time.length(), textBounds);
            float offSet = (textBounds.top + textBounds.bottom) >> 1;
            canvas.drawText(time, leftTimeWidth / 2, headerHeight + itemHeight * i - offSet, bgPaint);
        }

       ···
    }

难点在于需要判断计划名的文本高度是否超出了其本身的高度，如果超出了则截断文本，并用省略号结尾
。可以 canvas.drawText() 方法本身是无法获取到文本高度以及自动换行的，此时就需要用到 StaticLayout 了，可以设置最大文本宽度，其内部实现了文本自动换行的功能，并且可以获取到文本换行后的整体高度，通过基本就可以完成想要的效果

    if (planListBeanList != null && planListBeanList.size() > 0) {
            for (PlanBean bean : planListBeanList) {
                bgPaint.setColor(Color.parseColor(bean.getColor()));
                measurePlanBound(bean, planRectF);
                canvas.drawRect(planRectF, bgPaint);
                String planName = bean.getPlanName();
                if (TextUtils.isEmpty(planName)) {
                    continue;
                }
                float planItemHeight = planRectF.bottom - planRectF.top;
                StaticLayout staticLayout = null;
                for (int length = planName.length(); length > 0; length--) {
                    staticLayout = new StaticLayout(planName, planTextPaint, (int) (itemWidth - 4 * getResources().getDisplayMetrics().density),
                            Layout.Alignment.ALIGN_CENTER, 1.1f, 1.1f, true);
                    if (staticLayout.getHeight() > planItemHeight) {
                        planName = planName.substring(0, length) + "...";
                        bean.setEllipsis(true);
                    }
                }

                if (staticLayout == null) {
                    staticLayout = new StaticLayout(planName, planTextPaint, (int) (itemWidth - 4 * getResources().getDisplayMetrics().density),
                            Layout.Alignment.ALIGN_CENTER, 1.1f, 1.1f, true);
                }

                if (staticLayout.getHeight() > planItemHeight) {
                    continue;
                }

                canvas.save();

                canvas.translate(planRectF.left + (itemWidth - staticLayout.getWidth()) / 2, planRectF.top + (planItemHeight - staticLayout.getHeight()) / 2);

                staticLayout.draw(canvas);
                canvas.restore();
            }
        }

由于 StaticLayout 并没有向外提供设置整体最大高度的 API ，所以需要自己来循环判断文本的整体高度是否已经超出最大高度，是的话则对文本进行截取。如果最大高度太小，无法容纳一行文本，则直接不绘制文本

               for (int length = planName.length(); length > 0; length--) {
                    staticLayout = new StaticLayout(planName, planTextPaint, (int) (itemWidth - 4 * getResources().getDisplayMetrics().density),
                            Layout.Alignment.ALIGN_CENTER, 1.1f, 1.1f, true);
                    if (staticLayout.getHeight() > planItemHeight) {
                        planName = planName.substring(0, length) + "...";
                        bean.setEllipsis(true);
                    }
                }

                if (staticLayout == null) {
                    staticLayout = new StaticLayout(planName, planTextPaint, (int) (itemWidth - 4 * getResources().getDisplayMetrics().density),
                            Layout.Alignment.ALIGN_CENTER, 1.1f, 1.1f, true);
                }

                if (staticLayout.getHeight() > planItemHeight) {
                    continue;
                }

另外一个比较重要的点是需要通过计划的时间跨度来计算其坐标系，并将坐标系存储下来，方便判断点击事件

    private void measurePlanBound(PlanBean bean, RectF rect) {
        measurePlanBound(bean.getDayIndex(), bean.getPlanStartTime(), bean.getPlanEndTime(), rect);
        RectF rectF = new RectF(rect);
        bean.setRectF(rectF);
    }

    private void measurePlanBound(int day, String startTime, String endTime, RectF rect) {
        try {
            float left = leftTimeWidth + itemWidth * (day - 1);
            float right = left + itemWidth;
            String[] split = startTime.split(":");
            int startHour = Integer.parseInt(split[0]);
            int startMinute = Integer.parseInt(split[1]);
            float top = ((startHour - START_TIME) * 60 + startMinute) * singleMinuteHeight + headerHeight;
            split = endTime.split(":");
            int endHour = Integer.parseInt(split[0]);
            int endMinute = Integer.parseInt(split[1]);
            float bottom = ((endHour - START_TIME) * 60 + endMinute) * singleMinuteHeight + headerHeight;

            float offset = 1;

            rect.set(left + offset, top + offset, right - offset, bottom - offset);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }