如何从一个字节数组下载EPUB文件

本文介绍了如何从一个字节数组下载EPUB文件的处理方法，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

我试图做这样的事情：

公共无效的onClick（视图v）{            WebServiceC web服务= WebServiceC（）;            epubDownloaded = webService.downloadEpub（publi.getId（））;             文件fil​​eEpub =新的文件（Environment.getExternalStorageDirectory（），test.epub）;             如果（fileEpub.exists（））{                fileEpub.delete（）;              }             尝试{                    FOS的FileOutputStream =新的FileOutputStream（arquivoEpub.getPath（））;                    fos.write（epubDownloaded）;                    fos.close（）;                  }赶上（IOException异常五）{                        e.printStackTrace（）;                    }        }    }）;

不过，这是行不通的。

  

致命异常：在主显示java.lang.NullPointerException  java.io.OutputStream.write（OutputStream.java:82）

------------------------------------编辑---------- --------------------------------谢谢..我解决我的问题这种方式 - >

诠释计数;                    WebServiceC web服务=新WebServiceC（）;                    epubDownloaded = webService.downloadEpub（publi.getId（））;                    输入的InputStream =新ByteArrayInputStream进行（epubDownloaded）;                    OutputStream的输出= NULL;                    尝试{                        输出=新的FileOutputStream（Environment.getExternalStorageDirectory（）+/ test.epub）;                    }赶上（FileNotFoundException异常五）{                        e.printStackTrace（）;                    }                    字节的数据[] =新的字节[1024];                    尝试{                        而（（计数= input.read（数据））！= - 1）{                            output.write（数据0，计）;                        }                    }赶上（IOException异常五）{                        // TODO自动生成catch块                        e.printStackTrace（）;                    }

解决方案

在code中的唯一的地方，我可以看到一个 NullPointerException异常一个可以引发在该行的FileOutputStream FOS =新的FileOutputStream（arquivoEpub.getPath（））;

只有时间的FileOutputStream 的构造函数可以抛出一个 NullPointerException异常是当它传递一个空值，其构造的FileOutputStream（的FileDescriptor fdObj）。我不知道有什么功能 arquivoEpub.getPath（）的回报，所以我不能做任何其他的猜测。

另外，如果可能的话，后期到底是哪行相当于82号线，因为这是该异常被抛出就行了。

I'm trying to do something like:

public void onClick(View v) { WebServiceC webService = WebServiceC(); epubDownloaded = webService.downloadEpub(publi.getId()); File fileEpub=new File(Environment.getExternalStorageDirectory(), "test.epub"); if (fileEpub.exists()) { fileEpub.delete(); } try { FileOutputStream fos=new FileOutputStream(arquivoEpub.getPath()); fos.write(epubDownloaded); fos.close(); }catch (IOException e) { e.printStackTrace(); } } });

But it doesn't work.

FATAL EXCEPTION: main java.lang.NullPointerException at java.io.OutputStream.write(OutputStream.java:82)

------------------------------------EDIT------------------------------------------ Thanks .. I solved my problem this way ->

int count; WebServiceC webService = new WebServiceC(); epubDownloaded = webService.downloadEpub(publi.getId()); InputStream input = new ByteArrayInputStream(epubDownloaded); OutputStream output = null; try { output = new FileOutputStream(Environment.getExternalStorageDirectory()+"/test.epub"); } catch (FileNotFoundException e) { e.printStackTrace(); } byte data[] = new byte[1024]; try { while ((count = input.read(data)) != -1) { output.write(data, 0, count); } } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); }

解决方案

The only place in your code that I can see that a NullPointerException that can be thrown is in the line FileOutputStream fos=new FileOutputStream(arquivoEpub.getPath());.

The only time the constructor of FileOutputStream can throw a NullPointerException is when it is passed a null value with its constructor FileOutputStream(FileDescriptor fdObj). I don't know what the function arquivoEpub.getPath() returns, so I cannot make any other guesses.

Also, if possible, post exactly which line corresponded to line 82, as that is the line that the exception is thrown on.