Question

我有一个字符串对象。我使用bufferedReader.readline()写信给它。我已经注销了s的内容，在logcat中我可以看到它们，所以我知道它不是空的。我后来使用s并在其上调用String.split，但是我得到了一个NPE，为什么，当它已经填充所以不是null？

感谢。

String cachePath = getCacheDir().getAbsolutePath();
        FileReader fr = null;
        try {
            fr = new FileReader(cachePath + "/dbcache/" + "cacheTextFile.txt");
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        BufferedReader br = new BufferedReader(fr);
        String s = null;
        try {
            while((s = br.readLine()) != null) {
            Log.e(TAG, "s = " + s);
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        try {

            fr.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } 



        HashMap<String, String> hash = new HashMap<String, String>();
        Log.e(TAG, "about to call on s"+s.length());
        String[] arr = s.split(",");

        for(int i = 0; i < arr.length; i=i+2){
            String key = arr[i].toString();
            hash.put(key, "-1");
            Log.e(TAG, "hash key = " + hash.get(key));
        }

Answer 1

在while中，您始终会覆盖s字符串..所以当您到达终点时，它将是null

 while((s = br.readLine()) != null) {
    Log.e(TAG, "s = " + s);
 }

这样做..

 StringBuilder stringBuilder = new StringBuilder();
 String currentLine = null;
  while((currentLine = br.readLine()) != null)
        stringBuilder.append(currentLine + "\n");

读取文件后，字符串仍为null

1 个答案: