ViewPortHandler class is responsible for handling the view-port of the chart. This means it’s responsible for what is visible in the chart-view, it’s current state in terms of translation and zoom / scale level, the size of the chart and it’s drawing area and current offsets. The
ViewPortHandler allows to directly access all the above mentioned properties and modify them.
Unlike modifying the view-port via the
Chart class, as described here, modifying the
ViewPortHandler directly is not always a completely safe way of changing what is visible and should be performed with care by a person familiar with the API. Incorrect use can lead to unexpected behaviour. However, the
ViewPortHandler offers more advanced methods of view-port modification.
Getting an instance
An instance of the
ViewPortHandler can be acquired the following way only:
ViewPortHandler handler = chart.getViewPortHandler();
Scale & Translation
getScaleX(): Returns the current scale / zoom level on the x-axis.
getScaleY(): Returns the current scale / zoom level on the y-axis.
getTransX(): Returns the current translation (movement) on the x-axis.
getTransY(): Returns the current translation (movement) on the y-axis.
Chart dimensions & content
getChartWidth(): Returns the width of the chart.
getChartHeight(): Returns the height of the chart.
getContentRect(): Returns the current content area as a
More methods can be found in the JavaDocs or via studying the API.