出现异常

    java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference
        at android.graphics.BaseRecordingCanvas.drawText(BaseRecordingCanvas.java:446)
        at com.zyl.triangleview.widget.TriangleView.drawLeftTop(TriangleView.java:233)
        at com.zyl.triangleview.widget.TriangleView.onDraw(TriangleView.java:105)