使用扫描仪读取文件时获取空指针感知

Question

I want to read a text file and parse the string until eof..here is a code snippet.. programs.txt is under assets directory

    public void insert_programs() throws FileNotFoundException {
    BufferedReader bfr = null;
    try {
        bfr = new BufferedReader(new 
                InputStreamReader(getAssets().open("programs.txt"))); // <-- NPE occurs on that line 

    } catch (IOException e) {
        e.printStackTrace();
    }
    Scanner pgm = new Scanner(bfr);
    pgm.useDelimiter("*{3}");
    while (pgm.hasNext()) {
        String str = pgm.next();
            process(str);
        }
    }

Logs

03-14 18:05:34.936: E/AndroidRuntime(467):  at dalvik.system.NativeStart.main(Native Method)
03-14 18:05:34.936: E/AndroidRuntime(467): Caused by: java.lang.NullPointerException
03-14 18:05:34.936: E/AndroidRuntime(467):  at android.content.ContextWrapper.getAssets(ContextWrapper.java:74)
03-14 18:05:34.936: E/AndroidRuntime(467):  at c.theworld.com.nikhil.Database.insert_programs(Database.java:40)

Answer 1

add this into your code:

bfr = new BufferedReader(new 
            InputStreamReader(this.getAssets().open("programs.txt")));

Answer 2

looks like your BufferedReader is going to null. have you tried putting the scanner code inside try catch block. if your program gets IOException then bfr will be null and you'll get NPE.

public void insert_programs() throws FileNotFoundException { 
    BufferedReader bfr = null; 
    try { 
        bfr = new BufferedReader(new  
                InputStreamReader(getAssets().open("programs.txt"))); 

Scanner pgm = new Scanner(bfr); 
    pgm.useDelimiter("*{3}"); 
    while (pgm.hasNext()) { 
        String str = pgm.next(); 
            process(str); 
        }
    } catch (IOException e) { 
        e.printStackTrace(); 
    } 

    } 

Answer 3

The method ContextWrapper.getAssets() is throwing the NullPointerException . You are extending ContextWrapper (or another class that extends it) and it looks like that has not been initialized properly. The base Context within the ContextWrapper is null.