qml 自定义滑动条（官方example）

  Rectangle {      id: frame      clip: true      width: 160      height: 160      border.color: "black"      anchors.centerIn: parent      Text {          id: content          text: "ABC"          font.pixelSize: 169          MouseArea {              id: mouseArea              drag.target: content              drag.minimumX: frame.width - width              drag.minimumY: frame.height - height              drag.maximumX: 0              drag.maximumY: 0              anchors.fill: content          }      }      ScrollIndicator {          id: verticalIndicator          active: mouseArea.pressed          orientation: Qt.Vertical          size: frame.height / content.height          position: -content.y / content.height          anchors { top: parent.top; right: parent.right; bottom: parent.bottom }      }      ScrollIndicator {          id: horizontalIndicator          active: mouseArea.pressed          orientation: Qt.Horizontal          size: frame.width / content.width          position: -content.x / content.width          anchors { left: parent.left; right: parent.right; bottom: parent.bottom }      }  }