空指针异常ContextWrapper

本文介绍了空指针异常ContextWrapper的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 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）