小编Sha*_*ank的帖子

我正在尝试开发一个自定义组件,即弧形滑块,我完成了弧和拇指,但无法弄清楚如何绘制圆角边弧以及其中的浮雕效果.此刻滑块看起来像这样

绘制弧的代码是

private void drawSlider(Canvas canvas) {
    float sweepDegrees = (value * arcWidthInAngle)
            / (maximumValue - minimumValue);

    // the grey empty part of the circle
    drawArc(canvas, startAngle, arcWidthInAngle, mTrackColor);
    // the colored "filled" part of the circle
    drawArc(canvas, startAngle, sweepDegrees, mFillColor);

    // the thumb to drag.       
    int radius = ((diameter/2) - (mArcThickness/2));
    Point thumbPoint = calculatePointOnArc(centerX, centerY, radius, startAngle + sweepDegrees);

    thumbPoint.x = thumbPoint.x - (mThumbDiameter/2);
    thumbPoint.y = thumbPoint.y - (mThumbDiameter/2);

    Bitmap thumbBitmap = BitmapFactory.decodeResource(
            mContext.getResources(), R.drawable.circle25);

    thumbBitmap = getResizedBitmap(thumbBitmap, …

我在mainViewControllers视图中添加了UISplitViewController视图,代码如下.

    documentsRootViewController = [[DocumentsRootViewController alloc] initWithStyle:UITableViewStylePlain];
    UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:documentsRootViewController];
    documentsRootViewController.title = @"Document List";

    documentDetailView = [[DocumentsDetailView alloc] initWithNibName:@"DocumentsDetailView" bundle:nil];
    documentsRootViewController.detailViewController = documentDetailView;

    docSplitViewController = [[UISplitViewController alloc] init];
    docSplitViewController.viewControllers = [NSArray arrayWithObjects:navigationController, documentDetailView, nil];
    docSplitViewController.delegate = documentDetailView;

    CGRect splitViewFrame = CGRectMake(0, 0, cetralArea.frame.size.width, cetralArea.frame.size.height);         
    docSplitViewController.view.frame = splitViewFrame;
    [cetralArea addSubview:docSplitViewController.view];

现在我想要的是从UISplitViewController的DetailView呈现一个ViewController我试图在DetailViewControllers下面单击我这样做!按钮单击.

- (IBAction) buttonClicked:(id)sender
{
    NSString *phrase = nil; // Document password (for unlocking most encrypted PDF files)    
    NSArray *pdfs = [[NSBundle mainBundle] pathsForResourcesOfType:@"pdf" inDirectory:nil];    
    NSString *filePath = [pdfs …

我正在尝试实现自定义滑块,如下图所示.

到目前为止我所做的事情看起来像这样

请帮助我画出具有这种效果的弧线.我的代码如下,我正在做的是使用线宽为kLineWidth的CGContextAddArc绘制弧.

- (void)drawThumbAtPoint:(CGPoint)sliderButtonCenterPoint inContext: (CGContextRef)context {
UIGraphicsPushContext(context);
CGContextBeginPath(context);

CGContextMoveToPoint(context, sliderButtonCenterPoint.x, sliderButtonCenterPoint.y);

CGImageRef imageRef = [UIImage imageNamed:@"circle25.png"].CGImage;
CGRect rect = CGRectMake(sliderButtonCenterPoint.x - kThumbRadius, sliderButtonCenterPoint.y - kThumbRadius, kThumbRadius*2, kThumbRadius*2);
CGContextDrawImage(context, rect, imageRef);

//CGContextAddArc(context, sliderButtonCenterPoint.x, sliderButtonCenterPoint.y, kThumbRadius, 0.0, 2*M_PI, NO);

CGContextFillPath(context);
UIGraphicsPopContext();
}

- (CGPoint)drawArcTrack:(float)track atPoint:(CGPoint)center withRadius:(CGFloat)radius inContext:(CGContextRef)context {
UIGraphicsPushContext(context);
CGContextBeginPath(context);

float angleFromTrack = translateValueFromSourceIntervalToDestinationInterval(track, self.minimumValue, self.maximumValue, 0, M_PI/3);// 2*M_PI

CGFloat startAngle = (4*M_PI)/3;
CGFloat endAngle = startAngle + angleFromTrack;

CGContextAddArc(context, center.x, center.y, radius, startAngle, endAngle, NO);

CGPoint arcEndPoint = CGContextGetPathCurrentPoint(context); …

我知道React Native中有一个"View"组件,就像Android VieGroup一样,它更像是LinearLayout - 孩子们按行或列排列.

我想知道如何实现'FrameLayout'行为 - 在布局中堆叠儿童,并且可以为每个孩子分配一个独特的重力位置.

例如:将5个子项放入组件中,4个子项中的每一个都与布局的每个角对齐,最后一个子项与布局的中心对齐.

如何编写React Native"渲染"功能？