Question

我正在尝试从互联网下载.txt文件，然后阅读并执行它。我成功地下载，阅读和执行单行查询文件。但问题是我无法从文件中执行多行查询。我做了一些研究，他们不适合我的需要，所以我提出了一个解决方案，但我无法弄清楚一些错误。我的想法是将.txt文件逐行转换为List，然后为List中的每个String执行sqlite中的查询。这是我的一些代码：

    public void updateDB(View v){

    new DownloadFileFromURL().execute(file_url);

    File file = new File(Environment
            .getExternalStorageDirectory().toString()
            + "/update.txt")

    Log.i("UPDATE", "SQL DOWNLOADED");

    while(start.equals(true)){

        List<String> list = readUpdate2("update.txt");
        for (String string : list) {
            datasource.executeRaw(string);
            Log.i("UPDATE", "EXEC SQL # : " + list.size());
        }

    file.delete();}}

public List<String> readUpdate2(String url){
    File sdcard = Environment.getExternalStorageDirectory();
     //Get the text file
    List<String> list = null;
      File file = new File(sdcard,url);

      try {

        BufferedReader br = new BufferedReader(new FileReader(file));
        String line;

          while((line = br.readLine()) != null) {
                      // this is where the error happens :
              list.add(line);
              Log.i("UPDATE", "LINE : " + line);
          }
      }
      catch (IOException e) {
      }
      return list;
}

问题是我遇到了Nullpointer异常。它说这条线是空的。这是logcat：

03-30 18:01:18.965: E/AndroidRuntime(12474): FATAL EXCEPTION: main
03-30 18:01:18.965: E/AndroidRuntime(12474): java.lang.IllegalStateException: Could not execute method of the activity
03-30 18:01:18.965: E/AndroidRuntime(12474):    at android.view.View$1.onClick(View.java:3838)
03-30 18:01:18.965: E/AndroidRuntime(12474):    at android.view.View.performClick(View.java:4475)
03-30 18:01:18.965: E/AndroidRuntime(12474):    at android.view.View$PerformClick.run(View.java:18786)
03-30 18:01:18.965: E/AndroidRuntime(12474):    at android.os.Handler.handleCallback(Handler.java:730)
03-30 18:01:18.965: E/AndroidRuntime(12474):    at android.os.Handler.dispatchMessage(Handler.java:92)
03-30 18:01:18.965: E/AndroidRuntime(12474):    at android.os.Looper.loop(Looper.java:137)
03-30 18:01:18.965: E/AndroidRuntime(12474):    at android.app.ActivityThread.main(ActivityThread.java:5493)
03-30 18:01:18.965: E/AndroidRuntime(12474):    at java.lang.reflect.Method.invokeNative(Native Method)
03-30 18:01:18.965: E/AndroidRuntime(12474):    at java.lang.reflect.Method.invoke(Method.java:525)
03-30 18:01:18.965: E/AndroidRuntime(12474):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1209)
03-30 18:01:18.965: E/AndroidRuntime(12474):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1025)
03-30 18:01:18.965: E/AndroidRuntime(12474):    at dalvik.system.NativeStart.main(Native Method)
03-30 18:01:18.965: E/AndroidRuntime(12474): Caused by: java.lang.reflect.InvocationTargetException
03-30 18:01:18.965: E/AndroidRuntime(12474):    at java.lang.reflect.Method.invokeNative(Native Method)
03-30 18:01:18.965: E/AndroidRuntime(12474):    at java.lang.reflect.Method.invoke(Method.java:525)
03-30 18:01:18.965: E/AndroidRuntime(12474):    at android.view.View$1.onClick(View.java:3833)
03-30 18:01:18.965: E/AndroidRuntime(12474):    ... 11 more
03-30 18:01:18.965: E/AndroidRuntime(12474): Caused by: java.lang.NullPointerException
03-30 18:01:18.965: E/AndroidRuntime(12474):    at com.meemarbashi.meemardictionary.UpdateActivity.readUpdate2(UpdateActivity.java:292)
03-30 18:01:18.965: E/AndroidRuntime(12474):    at com.meemarbashi.meemardictionary.UpdateActivity.updateDB(UpdateActivity.java:223)
03-30 18:01:18.965: E/AndroidRuntime(12474):    ... 14 more

所以基本上我没有从.txt文件中获取文本然后我无法向我的列表中添加任何内容。我该怎么办？

提前致谢

Answer 1

这可能是空指针异常的原因：

List<String> list = null;

尝试分配新列表而不是null

执行多行SQLite查询

1 个答案: