objective-c – 两个NSScrollView实例之间的同步滚动

2023年8月14日 190次阅读

我有两个NSScrollView实例都呈现相同内容的视图.然而,第二滚动视图具有在第一滚动视图中呈现的文档视图的缩小版本.宽度和高度都可以单独缩放,原始宽度 – 高度约束可能会丢失,但这并不重要.

我有同步滚动工作,甚至考虑到第二个滚动视图需要根据缩放对齐其滚动行为.有一点小问题我一直把头发拉过来：

>由于两个视图都快乐地沿着较小的视图滚动,需要慢慢赶上较大的视图,以便它们同时“到达”文档的末尾.现在这没有发生,结果是较小的视图位于较大视图之前的“文档结束”.

同步滚动的代码基于Apple的文档“同步滚动视图”中的示例.我已将synchronizedViewContentBoundsDidChange：改编为以下代码：

- (void) synchronizedViewContentBoundsDidChange: (NSNotification *) notification {

    // get the changed content view from the notification
    NSClipView *changedContentView = [notification object];

    // get the origin of the NSClipView of the scroll view that
    // we're watching
    NSPoint changedBoundsOrigin = [changedContentView documentVisibleRect].origin;;

    // get our current origin
    NSPoint curOffset = [[self contentView] bounds].origin;
    NSPoint newOffset = curOffset;

    // scrolling is synchronized in the horizontal plane
    // so only modify the x component of the offset
    // "scale" variable will correct for difference in size between views
    NSSize ownSize = [[self documentView] frame].size;
    NSSize otherSize = [[[self synchronizedScrollView] documentView] frame].size;
    float scale = otherSize.width / ownSize.width;
    newOffset.x = floor(changedBoundsOrigin.x / scale);

    // if our synced position is different from our current
    // position, reposition our content view
    if (!NSEqualPoints(curOffset, changedBoundsOrigin)) {
        // note that a scroll view watching this one will
        // get notified here
        [[self contentView] scrollToPoint:newOffset];
        // we have to tell the NSScrollView to update its
        // scrollers
        [self reflectScrolledClipView:[self contentView]];
    }

}

我将如何更改该代码以实现所需的效果(两个滚动条到达文档的末尾)？

编辑：一些澄清,因为当我自己回读它时会感到困惑：滚动第一个视图到达结尾时,较小的视图需要减慢速度.这可能意味着重新评估该缩放因子……但是如何？

编辑2：我根据Alex的建议更改了方法：

    NSScroller *myScroll = [self horizontalScroller];
NSScroller *otherScroll = [[self synchronizedScrollView] horizontalScroller];

//[otherScroll setFloatValue: [myScroll floatValue]];

NSLog(@"My scroller value: %f", [myScroll floatValue]);
NSLog(@"Other scroller value: %f", [otherScroll floatValue]);

// Get the changed content view from the notification.
NSClipView *changedContentView = [notification object];

// Get the origin of the NSClipView of the scroll view that we're watching.
NSPoint changedBoundsOrigin = [changedContentView documentVisibleRect].origin;;

// Get our current origin.
NSPoint curOffset = [[self contentView] bounds].origin;
NSPoint newOffset = curOffset;

// Scrolling is synchronized in the horizontal plane so only modify the x component of the offset.
NSSize ownSize = [[self documentView] frame].size;
newOffset.x = floor(ownSize.width * [otherScroll floatValue]);

// If our synced position is different from our current position, reposition our content view.
if (!NSEqualPoints(curOffset, changedBoundsOrigin)) {
    // Note that a scroll view watching this one will get notified here.
    [[self contentView] scrollToPoint: newOffset];
    // We have to tell the NSScrollView to update its scrollers.
    [self reflectScrolledClipView:[self contentView]];
}

使用这种方法,当两个滚动条达到0.7的值时,较小的视图被较大的视图“超越”,这是不好的.较大的视图然后滚动到文档的末尾.

最佳答案 我想你可能会以错误的方式接近这一点.我认为你应该得到每个卷轴相对于自身滚动的距离的百分比,并将其应用于另一个视图.如何使用NSScroller的-floatValue这样做的一个例子：

NSScroller *myScroll = [self verticalScroller];
NSScroller *otherScroll = [otherScrollView verticalScroller];

[myScroll setFloatValue:otherScroll.floatValue];
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