java Batik画布的getUpdateManager返回null

Question

当使用蜡染从JSVGCanvas获取UpdateManager时，它返回null

public void init() {
    canvas = new JSVGCanvas(null, true, false);
    canvas.setDocumentState(JSVGCanvas.ALWAYS_DYNAMIC);
}

public void paint(final DomainObject domainObject) {
    UpdateManager updateManager = canvas.getUpdateManager();
    RunnableQueue runnableQueue = updateManager.getUpdateRunnableQueue();
    runnableQueue.invokeLater(new Runnable() {
        public void run() {
            // Document operations here
        }
    });
}

如何管理此错误

Answer 1

绘画方法必须分成两部分，一部分是将GVTTreeRendererListener注册到JSVGCanvas对象。渲染完成后，此侦听器将调用执行实际绘制工作的方法，此时UpdateManager对象将出现在画布中

public void init() {
    canvas = new JSVGCanvas(null, true, false);
    canvas.setDocumentState(JSVGCanvas.ALWAYS_DYNAMIC);
}

public void paint(final DomainObject domainObject) {
    canvas.addGVTTreeRendererListener(new GVTTreeRendererAdapter() {
        public void gvtRenderingCompleted(GVTTreeRendererEvent e) {
            renderComplete(domainObject);
        }
    });
}

public void renderComplete(DomainObject domainObject) {
    UpdateManager updateManager = canvas.getUpdateManager();
    RunnableQueue runnableQueue = updateManager.getUpdateRunnableQueue();
    runnableQueue.invokeLater(new Runnable() {
        public void run() {
            // Document operations here
        }
    });
}

免责声明： 答案是在这个蜡染论坛上找到的，我决定把它记录在这里，作为一个更有用的资源http://batik.2283329.n4.nabble.com/UpdateManager-is-Null-td2974717.html