样式表会传播到所有的子控件，所以你必须使用右选择器来限制它们的范围。因为上下文菜单是QLineEdit的子菜单，所以它也会受到影响。

// What you have probably done:
myLineEdit->setStyleSheet("background-color: gray");

// What you should have done:
myLineEdit->setStyleSheet("QLineEdit { background-color: gray }");      

// What you should do if there might be child widgets of the same type 
// but for which you don't want the style to apply:
myLineEdit->setObjectName("myLineEdit");
myLineEdit->setStyleSheet("QLineEdit#myLineEdit { background-color: gray }");

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有关详细信息，请参见样式表样式表类型。