如何在android acharteninge線圖中添加虛線？

我已嘗試在acharteninge圖形主體中添加虛線。但我沒有成功。請幫幫我。如何在android acharteninge線圖中添加虛線？

這裏是我的代碼：

XYMultipleSeriesRenderer multiRenderer = new XYMultipleSeriesRenderer(); 

    multiRenderer.setShowLegend(false); 
    multiRenderer.setAxesColor(Color.WHITE); 
    multiRenderer.setXLabelsColor(Color.rgb(0,0,0)); 
    multiRenderer.setYLabelsColor(0, Color.rgb(0,0,0)); 
    multiRenderer.setLabelsColor(Color.BLACK); 
    multiRenderer.setAxisTitleTextSize(22.2f); 
    multiRenderer.setLabelsTextSize(22.2f); 
    multiRenderer.setChartTitle(""); 
    multiRenderer.setXTitle("\n Weak Graph"); 
    multiRenderer.setYTitle("Result in"+"Units"); 
    multiRenderer.setZoomButtonsVisible(true); 
    multiRenderer.setYLabelsAlign(Align.RIGHT); 
    multiRenderer.setMarginsColor(Color.argb(0x00, 0xff, 0x00, 0x00)); 
    multiRenderer.setApplyBackgroundColor(true); 
    multiRenderer.setYAxisMin(2); 
    multiRenderer.setMargins(new int[] {30, 80, 10, 10});

我想虛線這樣的形象。

https://drive.google.com/file/d/0B2NGqFM-F0bNZDVCbkRkRUkxdTg/edit?usp=sharing

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