J2ME常用功能代码片断

最新推荐文章于 2023-11-26 22:31:32 发布

原创最新推荐文章于 2023-11-26 22:31:32 发布 · 241 阅读

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CC 4.0 BY-SA版权

文章标签：

#j2me #primitive #null #immutable #image #string

本文介绍了J2ME环境下进行文件IO读写的实现方法，并提供了字符串转换为整数等primitive类型的示例代码。此外，还探讨了ChoiceGroup控件的正确使用方式及其限制。

1：IO读写

因为J2ME只支持有限的几个IO类，要用这几个类满足自己的需求确实不容易。

      try
     {
            InputStream is = new Object().getClass().getResourceAsStream("/52.txt");
            ByteArrayOutputStream baos = new ByteArrayOutputStream(1024);
            byte[] bytes = new byte[128];
            int size;
            while( (size = is.read(bytes)) != -1 ){
                 baos.write(bytes, 0, size);
            }
           data = baos.toByteArray();
           iSize = data.length;
           contentCan = new contentCanvas(new String(data));
           is.close();
           is = null;
           baos.close();
           baos = null;
     }
     catch (Exception e)
     {
          e.printStackTrace();
     }

2：字符串转换成整数或其它primitive类型

image_1_num = Integer.parseInt(str3.substring(0,str3.indexOf("-")));
image_2_num = Integer.parseInt(str3.substring(str3.indexOf("-")+1));

用了无数次了，但每次还是忘记。

3：ChoiceGroup的一个小问题

看API文档

public ChoiceGroup(String label,                   int choiceType,                   String[] stringElements,                   Image[] imageElements)

Creates a new ChoiceGroup, specifying its title, the type of the ChoiceGroup, and an array of Strings and Images to be used as its initial contents.

The type must be one of EXCLUSIVE, MULTIPLE, or POPUP. The IMPLICIT type is not allowed for ChoiceGroup.

The stringElements array must be non-null and every array element must also be non-null. The length of the stringElements array determines the number of elements in the ChoiceGroup. The imageElements array may be null to indicate that the ChoiceGroup elements have no images. If the imageElements array is non-null, it must be the same length as the stringElements array. Individual elements of the imageElements array may be null in order to indicate the absence of an image for the corresponding ChoiceGroup element. Non-null elements of the imageElements array may refer to mutable or immutable images.