空指针异常ContextWrapper [英] NullPointer exception in ContextWrapper

问题描述

我有一类称为FileGeneration扩展活动
在FileGeneration我有一个名为方法

I have a class called FileGeneration that extends Activity
In FileGeneration I have a method called

protected OutputStream openAndWriteFile() {

   // Set the Context-mode
   int cxt = Context.MODE_PRIVATE;

   // Check if we are not going to clear the file and the file exists
   if (!clearFile && (new File(this.fileName)).exists()) {

      // Append to the file
      cxt = Context.MODE_APPEND;
   }

   // Try to open the file to write to
   try {

      // Open the File using the Context
      this.os = openFileOutput(this.fileName, cxt);

   } catch (FileNotFoundException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
   }

   // Return the OutputStream
   return this.os;
}

和我得到的logcat这个输出

And I get this output in Logcat

06-08 15:31:43.733: ERROR/AndroidRuntime(2850): java.lang.NullPointerException
06-08 15:31:43.733: ERROR/AndroidRuntime(2850):    at android.content.ContextWrapper.openFileOutput(ContextWrapper.java:158)
06-08 15:31:43.733: ERROR/AndroidRuntime(2850):    at android.content.ContextWrapper.openFileOutput(ContextWrapper.java:158)
06-08 15:31:43.733: ERROR/AndroidRuntime(2850):    at dataconnection.FileGeneration.openAndWriteFile(FileGeneration.java:278)

278线的类

Line 278 in the class is

this.os = openFileOutput(this.fileName, cxt);

但是，当我刚刚与paramters打印方法在logcat中，它说

But when I just print the method with the paramters out in Logcat it says

openFileOutput(Preferences.xml, 1);

该文件不存在，但openFileOutput表示，将创建它，如果它不存在

The file does not exist, but openFileOutput says it will create it, if it does not exist

什么是错的？

推荐答案

我解决了这个问题，（新ContextWrapper（CTX））。openFileOutput（this.fileName，CXT）

这篇关于空指针异常ContextWrapper的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！