返回的InputStream NullPointerException异常（JAVA） [英] InputStream returning NullPointerException (Java)

问题描述

下面是code，它是获得NullPointerException异常错误：

 的InputStream是= getAssets（）开（twentyone.txt）。
InputStreamReader的IZ =新InputStreamReader的（是）;
的BufferedReader BR =新的BufferedReader（IZ）;
 

可能是什么问题呢？

*编辑：在的printStackTrace

  03-19 18：20：18.662：E / AndroidRuntime（929）：由：显示java.lang.NullPointerException
 

编辑2：code，直到异常：

 公共类ListViewAa3扩展ListViewA {



公众的String []的过程（字符串CTI）抛出IOException异常{
    字符串CTID = CTI;
    Log.d（外尝试调用，标签1）;
    尝试{
        Log.d（开始尝试引用，标签2）;
        尝试{
    InputStream的是= getAssets（）开（USCOUNTIES.txt）。
    InputStreamReader的IZ =新InputStreamReader的（是）;
    的BufferedReader BR =新的BufferedReader（IZ）;}赶上（例外五）{e.printStackTrace（）;}
 

解决方案

OK，我知道了。我不得不主要活动的范围内传递给这个类，然后用 context.getAssets.open（twentyone.txt）;

要谁的人有同样的问题，这样做： 将这个在类活动的onCreate功能：  上下文语境= getApplicationContext（）;

传递上下文到新类的函数（在我的情况的过程（一个字符串，上下文的背景下）） 然后输入此过程中的功能：

 的InputStream是= context.getAssets（）开（twentyone.txt）。
 

我花了4小时图这样的傻事了。

Here is the code that is getting the NullPointerException error:

InputStream is = getAssets().open("twentyone.txt");
InputStreamReader iz=new InputStreamReader(is);
BufferedReader br = new BufferedReader(iz);

What could be going wrong?

*Edit: the printStackTrace

03-19 18:20:18.662: E/AndroidRuntime(929): Caused by: java.lang.NullPointerException

Edit 2: Code till the exception:

public class ListViewAa3 extends ListViewA{



public String[] process(String cti)throws IOException{
    String ctid=cti;
    Log.d("Outside try invoked","tag1");
    try{
        Log.d("beginning of try invoked","tag2");
        try{
    InputStream is = getAssets().open("USCOUNTIES.txt");
    InputStreamReader iz=new InputStreamReader(is);
    BufferedReader br = new BufferedReader(iz);}catch(Exception e){e.printStackTrace();}

解决方案

OK, I got it. I had to pass the context of the main activity to this class, then use context.getAssets.open("twentyone.txt");

To anyone who has the same problem, do this: Put this in the onCreate function of the class with activity: Context context=getApplicationContext();

Pass context to the new class's function(in my case "process(String a,Context context)") Then type this in the process function:

InputStream is = context.getAssets().open("twentyone.txt");

Took me 4 hours to figure such a silly thing out.

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