When QML uses layout layout, a large number of ＜ unknown file ＞: QML qquicklayoutattached: binding loop detected for property circular binding warnings appear

         First QML There are three tools to implement layout ：

        （1） anchor ：anchors

        （2） Layout manager ：RowLayout、ColumnLayout、GridLayout

        （3） positioner ：Row、Column、Grid、Flow、Position、Repeater

         When implementing the child control to follow the change with the window size , Often use layout manager RowLayout、ColumnLayout、GridLayout, These three layout managers and those three locators Row、Column、Grid There is a difference , When the size of the layout manager changes, the child controls can also follow the change , You can limit the minimum size 、 Maximum size 、 Best size 、 Adaptive width and height , But although the locator can also follow the change through the relationship between the width and height and the parent control , But we cannot limit the minimum 、 Maximum 、 Best size 、 Nor can it adapt to width and height , To achieve the same effect, it is certainly not as convenient as using the layout manager directly .

        This article mainly explains the use of layout manager in nesting , Often appear wide 、 High circular binding warning prompt , It takes a long time for the program to enter the screen ：

 

The following error is reported in the above code ：

  reason ：

        The above code shows ,ColumnLayout The size of fill for the father's all ,ColumnLayout It's nested RowLayout, And to RowLayout Adaptive width and 32 Height , However, the actual width and height of the layout manager in the layout manager is determined by the width and height of its child controls , So for RowLayout Set the adaptive width and 32 The height of is actually invalid ,RowLayout The actual width and height of is determined by the width and height of its child controls , But its child controls in the code Rectangle The minimum width of is set to the width of the father 30%, This creates an interdependent dead cycle ：

        RowLayout The width and height of is controlled by its two child controls Rectangle The total width and height of , And two child controls Rectangle The width is determined by the father RowLayout The width of the determines .

resolvent ：

（1） The best solution ：

When using layout manager nested , A control with settable width and height should be used （Item or Rectangle） As a barrier ：

 （2） Other solutions ： Avoid setting the width and height of its child controls in the directly nested layout manager to be affected by the father , You can set follow grandpa level or above , But often we just need to follow the effect of our father , So this method is not very good .