ext 对齐

layout : {
    type : 'hbox',
    pack : 'end'
}

buttonAlign:'center', //按钮居中

pack : String

Controls how the child items of the container are packed together. Acceptable configuration values for this property are:

• start - child items are packed together at left (HBox) or top (VBox) side of container (*default**)
• center - child items are packed together at mid-width (HBox) or mid-height (VBox) of container
• end - child items are packed together at right (HBox) or bottom (VBox) side of container

Defaults to: 'start'