我目前正在智能设备项目中处理弯曲的进度条。我重写了OnPaint函数。
在Override OnPaint()函数中,我以深灰色绘制弯曲的进度条,并以黄色绘制进度条的一部分以反映进度条的变化值(例如30%)。但是,当值连续变化时,我可以看到进度条颜色的一部分变为黄色。但是,弯曲的进度条本身也会重新绘制。有没有人知道如何在值变化时避免重绘原始曲线进度条的方法?因此,当值发生变化时,它只会用黄色重绘进度条的一部分,而不是带灰色的原始进度条。这是我在OnPaint函数中使用的代码。
protected override void OnPaint(PaintEventArgs e)
{
gx = e.Graphics;
// Draw the original curved progress bar
int intPosition1 = m_NumberOfSpoke;
for (int intCounter1 = 0; intCounter1 < m_NumberOfSpoke; intCounter1++)
{
intPosition1 = intPosition1 % m_NumberOfSpoke;
DrawLine(e.Graphics,
GetCoordinate(m_CenterPoint, m_InnerCircleRadius, m_Angles[intPosition1]),
GetCoordinate(m_CenterPoint, m_OuterCircleRadius, m_Angles[intPosition1]),
Color.DarkGray, m_SpokeThickness);
intPosition1++;
}
// Draw a part of the progress bar to reflect the changing current value(such as 30%)
int intPosition = CurrentValue;
for (int intCounter1 = 0; intCounter1 < CurrentValue; intCounter1++)
{
intPosition = intPosition % CurrentValue;
DrawLine(gx,
GetCoordinate(m_CenterPoint, m_InnerCircleRadius, m_Angles[intPosition]),
GetCoordinate(m_CenterPoint, m_OuterCircleRadius, m_Angles[intPosition]),
Color.Yellow, m_SpokeThickness);
intPosition++;
}
base.OnPaint(e);
}
我尝试使用Override OnBackgroundPaint绘制原始曲线进度条作为背景,以避免在OnPaint中再次重绘它,但它不起作用。加载表单时我看不到任何内容。有什么想法吗?
感谢您提前提供任何帮助。
问候
答案 0 :(得分:3)
这是对实际屏幕的DrawLine调用的负载,并且很可能会导致闪烁。您应该通过创建一个后台缓冲区来双倍缓冲,完成所有绘制,然后通过一行调用DrawBitmap
将这些缓冲到屏幕上:
protected override void OnPaint(PaintEventArgs e)
{
using(var buffer = new Bitmap(this.Width, this.Height))
using(var gx = Graphics.FromImage(buffer))
{
// for loops to draw to gx
....
e.Graphics.DrawBitmap(buffer, ...);
}
}
我也非常倾向于不做上面的事情,但是缓存该缓冲区以防止在每次调用时生成Bitmap的垃圾。
Bitmap m_buffer;
Gramphic m_gx;
protected override void OnPaint(PaintEventArgs e)
{
if(m_buffer == null)
{
m_buffer = new Bitmap(this.Width, this.Height))
m_gx = Graphics.FromImage(buffer))
}
// clear the backbuffer with a FillRect
// for loops to draw to m_gx
....
e.Graphics.DrawBitmap(m_buffer, ...);
}
我甚至可能更进一步,如果控件的灰色部分始终相同并执行“三重缓冲”,保留图像的缓存版本并绘制灰色,然后在OnPaint中,blit到图形,绘制黄色,然后blit到屏幕。
Bitmap m_buffer;
Bitmap m_backimage;
Gramphic m_gx;
protected override void OnPaint(PaintEventArgs e)
{
if(m_buffer == null)
{
m_backimage = new Bitmap(this.Width, this.Height);
var g = Graphics.FromImage(m_backImage);
// for loop to draw the grey stuff to g
....
m_buffer = new Bitmap(this.Width, this.Height))
m_gx = Graphics.FromImage(buffer))
}
m_gx.DrawImage(m_backImage);
// for loop to draw *just the yellow* to m_gx
....
e.Graphics.DrawBitmap(m_buffer, ...);
}
你可能不得不重写OnResize和其他一些东西,加上Dispose来清理这些成员级的GDI对象,但是perf会更好,而且不会闪烁。