只更新用户控件的一部分

Question

我正在为视频使用开发时间轴用户控件。这是我工作的照片：

这里我有问题。当currentTime改变时，我必须更新UI。但当我使用this.Invalidate（）;它刷新了整个控制。但我想更新指针（灰色背景中的白线）。因为它导致控制在非常微小的时间变化时反复闪烁。 如何更新指针？ 这是我的onPaint方法

 private void OnPaint(object sender, System.Windows.Forms.PaintEventArgs e)
    {
        int width = this.Width;
        int height = this.Height;
        int Floor = height - FloorDistance;
        Pen SecPen = new Pen(SecColor);
        Pen MinPen = new Pen(MinColor);
        SolidBrush TimeLineBrush = new SolidBrush(Color.Gray);
        StringFormat stringFormat = new StringFormat();
        SolidBrush TimesolidBrush = new SolidBrush(TimeColor);
        SolidBrush BackBrush = new SolidBrush(TimlineBackColor);
        SolidBrush PointerBrush = new SolidBrush(PointerColor);
        stringFormat.FormatFlags = StringFormatFlags.DirectionVertical;
        switch (Zoom)
        {
            case ZoomLEvel.Quarter:
                width = (int)Math.Ceiling((TotalDuration / 900)) * ThickDistance;
                break;
            case ZoomLEvel.Minute:
                width = (int)Math.Ceiling((TotalDuration / 60)) * ThickDistance;
                break;
            case ZoomLEvel.Secound:
                width = (int)Math.Ceiling(TotalDuration) * ThickDistance;
                break;
            case ZoomLEvel.MiliSecound:
                width = (int)Math.Ceiling(TotalDuration * 10) * ThickDistance;
                break;
        }
        width += 11;
        this.Width = width;

        e.Graphics.FillRectangle(TimeLineBrush, 0, Floor, width, 3);
        e.Graphics.FillRectangle(BackBrush, 0, 0, width, height - FloorDistance);

        int x = ThickDistance;
        int step = 0;
        while (x <= width - ThickDistance)
        {
            if (step % 5 == 0)
            {
                e.Graphics.DrawLine(MinPen, x, Floor, x, Floor - _MinHeight);
                // print time
                string time = "";
                double totalSecounds = 0;
                PointF pointF = new PointF(x - 8, Floor + 5);


                switch (Zoom)
                {
                    case ZoomLEvel.Quarter:
                        totalSecounds = step * 900;
                        break;
                    case ZoomLEvel.Minute:
                        totalSecounds = step * 60;
                        break;
                    case ZoomLEvel.Secound:
                        totalSecounds = step;
                        break;
                    case ZoomLEvel.MiliSecound:
                        totalSecounds = step / 10d;
                        break;
                }

                time = (new TimeSpan(0, 0, 0, (int)totalSecounds, (int)(step % 10) * 100)).ToString(@"hh\:mm\:ss\:fff");
                e.Graphics.DrawString(time, this.Font, TimesolidBrush, pointF, stringFormat);

            }
            else
                e.Graphics.DrawLine(SecPen, x, Floor, x, Floor - _SecHeight);
            x += ThickDistance;
            step++;
        }
        int PointerTime = 0;//(int)Math.Floor(CurrentTime);
        int pointerX = 0;
        switch (Zoom)
        {
            case ZoomLEvel.Quarter:

                PointerTime = (int)Math.Floor(CurrentTime / 900);
                pointerX = PointerTime * ThickDistance;
                break;
            case ZoomLEvel.Minute:
                PointerTime = (int)Math.Floor(CurrentTime / 60);
                pointerX = PointerTime * ThickDistance;
                break;
            case ZoomLEvel.Secound:
                PointerTime = (int)Math.Floor(CurrentTime);
                pointerX = PointerTime * ThickDistance;
                break;
            case ZoomLEvel.MiliSecound:
                PointerTime = (int)Math.Floor(CurrentTime * 10);
                pointerX = PointerTime * ThickDistance;
                break;
        }
        pointerX += 5;
        e.Graphics.FillRectangle(PointerBrush, pointerX, 0, 2, height - FloorDistance);
    }

Answer 1

Invalidate()方法的重载采用Rectangle类型参数来定义要刷新的区域，称为剪切矩形。你应该传递指针的边界矩形（白线，所有边可能有10个像素的填充）。在OnPaint()方法中，您应该检查e.ClipRectangle属性以查找需要重绘的区域。现在对于所有绘图逻辑（e.Graphics。 DrawX（）调用），您应该首先确认该元素是否与剪切区域相交（可以使用Rectangle.IntersectsWith()轻松完成）。如果是，则应调用 DrawX 方法，否则不应该。

为避免闪烁，您应该将控件的DoubleBuffered属性设置为True。实现真正流畅的渲染还有很长的路要走。

此外，我发现您在OnPaint方法中声明了很多画笔和笔，并且在使用后没有处理它们。我假设其中许多将一次又一次地被要求，所以你可能想要在类级别声明它们，然后将它们放在你控件的Dispose()方法中。考虑到这是一个与视频相关的应用程序，这将为您节省一些处理。

希望有所帮助。