我正在使用 arcgis 为 ios 制作一个应用程序，该应用程序允许用户通过拖动手指在地图上自由绘制（红线）。我曾尝试使用 arcgis 提供的草图层示例来实现这一点，但没有运气。我也尝试使用 opengl，但我的绘图并没有停留在它绘制的位置。简而言之，我试图做的是在地图上徒手绘制，当我平移和缩放地图时，绘图会停留在绘制它的地图上的坐标处，并根据缩放进行拉伸和收缩。
使用 opengl 视图，我能够绘制。我的问题是我需要让图纸保持在地质坐标上。这是我的绘图代码。目前我正在获取屏幕上x和y的触摸坐标，需要将其更改为地图上的经度和纬度，然后将其转换为屏幕上的x和y。我不知道该怎么做。
// Drawings a line onscreen based on where the user touches
- (void) renderLineFromPoint:(CGPoint)start toPoint:(CGPoint)end
{
static GLfloat* vertexBuffer = NULL;
static NSUInteger vertexMax = 64;
NSUInteger vertexCount = 0, count, i;
[EAGLContext setCurrentContext:context];
glBindFramebufferOES(GL_FRAMEBUFFER_OES, viewFramebuffer);
// Convert locations from Points to Pixels
CGFloat scale = self.contentScaleFactor;
start.x *= scale;
start.y *= scale;
end.x *= scale;
end.y *= scale;
// Allocate vertex array buffer
if(vertexBuffer == NULL)
vertexBuffer = malloc(vertexMax * 2 * sizeof(GLfloat));
// Add points to the buffer so there are drawing points every X pixels
count = MAX(ceilf(sqrtf((end.x - start.x) * (end.x - start.x) + (end.y -start.y) * (end.y - start.y)) / kBrushPixelStep), 1);
for(i = 0; i < count; ++i)
{
if(vertexCount == vertexMax)
{
vertexMax = 2 * vertexMax;
vertexBuffer = realloc(vertexBuffer, vertexMax * 2 * sizeof GLfloat));
}
vertexBuffer[2 * vertexCount + 0] = start.x + (end.x - start.x) * ((GLfloat)i / (GLfloat)count);
vertexBuffer[2 * vertexCount + 1] = start.y + (end.y - start.y) * ((GLfloat)i / (GLfloat)count);
vertexCount += 1;
}
// Render the vertex array
glVertexPointer(2, GL_FLOAT, 0, vertexBuffer);
glDrawArrays(GL_POINTS, 0, vertexCount);
// Display the buffer
glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer);
[context presentRenderbuffer:GL_RENDERBUFFER_OES];
}
// Reads previously recorded points and draws them onscreen. This is the
Shake Me message that appears when the application launches.
- (void) playback:(NSMutableArray*)recordedPaths
{
NSData* data = [recordedPaths objectAtIndex:0];
CGPoint* point = (CGPoint*)[data bytes];
NSUInteger count = [data length] / sizeof(CGPoint), i;
// Render the current path
for(i = 0; i < count - 1; ++i, ++point)
[self renderLineFromPoint:*point toPoint:*(point + 1)];
// Render the next path after a short delay
[recordedPaths removeObjectAtIndex:0];
if([recordedPaths count])
[self performSelector:@selector(playback:) withObject:recordedPaths
afterDelay:0.01];
}
// Handles the start of a touchPaintingView.m 12-08-07 9:34 AM
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
CGRect bounds = [self bounds];
UITouch* touch = [[event touchesForView:self] anyObject];
firstTouch = YES;
// Convert touch point from UIView referential to OpenGL one (upside-down flip)
location = [touch locationInView:self];
location.y = bounds.size.height - location.y;
}
// Handles the continuation of a touch.
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
CGRect bounds = [self bounds];
UITouch* touch = [[event touchesForView:self] anyObject];
// Convert touch point from UIView referential to OpenGL one (upside-down flip)
if (firstTouch)
{
firstTouch = NO;
previousLocation = [touch previousLocationInView:self];
previousLocation.y = bounds.size.height - previousLocation.y;
}
else
{
location = [touch locationInView:self];
location.y = bounds.size.height - location.y;
previousLocation = [touch previousLocationInView:self];
previousLocation.y = bounds.size.height - previousLocation.y;
}
// Render the stroke
[self renderLineFromPoint:previousLocation toPoint:location];
}
// Handles the end of a touch event when the touch is a tap.
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
CGRect bounds = [self bounds];
UITouch* touch = [[event touchesForView:self] anyObject];
if (firstTouch)
{
firstTouch = NO;
previousLocation = [touch previousLocationInView:self];
previousLocation.y = bounds.size.height - previousLocation.y;
[self renderLineFromPoint:previousLocation toPoint:location];
}
}