如何从一个字节数组下载EPUB文件 [英] How can I download epub file from a byte array

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.

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