简单Escp Java:PrintPreviewPane在JDK7中不起作用

Question

我用这个库做点阵印刷

https://blog.jocki.me/simple-escp/

Runnable runner = new Runnable() {
    @Override
    public void run() {
    
    Gson gsonTemplate = new Gson();
        String jsonStringTemplate = gsonTemplate.toJson(result.get("documentTemplate"));
        Template template = new JsonTemplate(jsonStringTemplate);

    
        Gson gson = new Gson();
    String jsonString = new Gson().toJson(result.get("documentValue"));
        java.lang.reflect.Type type1 = new TypeToken<HashMap<String, Object>>() {
        }.getType();

        Map<String, Object> map = gson.fromJson(jsonString, type1);
        MapDataSource dataSource = new MapDataSource(map);

        PrintPreviewPane printPreviewPane = new PrintPreviewPane();
        printPreviewPane.display(template, dataSource);

        jInternalFrameResult.getContentPane().removeAll();
        jInternalFrameResult.repaint();
        jInternalFrameResult.setLayout(new BorderLayout());
        jInternalFrameResult.add(printPreviewPane, BorderLayout.CENTER);
        jInternalFrameResult.setAutoscrolls(true);
        jInternalFrameResult.setFocusable(true);        
    }
};


Thread t = new Thread(runner, "Code Executer");
t.start();

在Java8（OpenJD、OracleJDK）中，它的作用是charm=>；（在Win7-32和64位、1064位、Ubuntu18.04中测试）

但是在java中使用JDK 7（OpenJD、OracleJDK）（在win xp中测试） 我在PrintPreviewPane中发现了NullPointerException：

Exception in thread "Code Executor" java.lang.NullPointerException at
simple.escp.swint.PrintePreviewPane.<init> (PrintPreviewPane.java:81)