1、设置内容组件

void PropertyPanel::init(){    messageWhenEmpty = TRANS("(nothing selected)");     addAndMakeVisible (viewport);    viewport.setViewedComponent (propertyHolderComponent = new PropertyHolderComponent());    viewport.setFocusContainer (true);}

2、设置大小

void PropertyPanel::resized(){    viewport.setBounds (getLocalBounds());    updatePropHolderLayout();}

3、布局内容。

void PropertyPanel::updatePropHolderLayout() const{    const int maxWidth = viewport.getMaximumVisibleWidth();    propertyHolderComponent->updateLayout (maxWidth);     const int newMaxWidth = viewport.getMaximumVisibleWidth();    if (maxWidth != newMaxWidth)    {        // need to do this twice because of scrollbars changing the size, etc.        propertyHolderComponent->updateLayout (newMaxWidth);    }}

 

 

具体原理还是没如何弄明白，应当是监听了子控件的大小变化。