Question

我一直收到此错误

NullPointer

08-16 22:55:46.360: ERROR/AndroidRuntime(11047): Caused by: java.lang.NullPointerException
  08-16 22:55:46.360: ERROR/AndroidRuntime(11047):     at com.fttech.htmlParser.releaseInfo.onCreate(releaseInfo.java:62)
08-16 22:55:46.360: ERROR/AndroidRuntime(11047):     at  android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1048)
08-16 22:55:46.360: ERROR/AndroidRuntime(11047):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1712)

它指向我的元素

    Element paragraph = overview.select("p").last();

我正在使用它来检索文章

    try {
        doc = Jsoup.connect(url).get();
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } 
    if(doc == null){
        Toast.makeText(this, "Couldnt retrieve game info", Toast.LENGTH_SHORT);
    }
    else{

    // Get the overview div
    Element overview = doc.select("div#object-overview").last();

Answer 1

每当你在一个链中找到一个带select（“”）的元素你的调用last（），假设它总是找到至少1个元素，在没有说“p”的情况下“在文件中，就是当你遇到崩溃时。

这只是简单的NullPointerExceptions，你需要学习防御性编码：

// If you believe overview could be null
if(overview != null){
    ArrayList<Element> paragraphs = overview.select("p"); // Whatever type select(String) returns
    Element lastParagraph = null;
    if(paragraphs != null){
         lastParagraph = paragraphs.last();
    } else {
     // Deal with not finding "p" (lastParagraph is null in this situation)
    }

   // Continue with lastParagraph 

} else {
  // Deal with overview being null
}

Number 1 Java Error（向下滚动）

此外，您不应该使用catch all Exception包装代码，尝试捕获每个异常并单独处理它们。

查找get（）方法Jsoup get()的API（无论如何eclipse告诉你）它会抛出IOException，所以你应该只是抓住它。

  try {
        doc = Jsoup.connect(url).get();
    } catch (IOException e) {
        Log.e("Tag", "Jsoup get didn't get a document", e);
    }

Number 5 Java Error（向下滚动）

DOM seletor方法中的NullPointerException

1 个答案: