java - 如何避免捕获 IOException？

Question

我有使用以下doInBackground方法的 AsyncTask 。这应该是读取和写入流。问题是当连接断开时 IOException 在buffer为空之前被调用（它在之前离开while循环len != -1），我想避免这种情况。

protected Boolean doInBackground(String... StringUrls) {

    try {

   // ...

 len = in.read(buffer);

        while (len != -1) {

            bufOutstream.write(buffer, 0, len);
            len = in.read(buffer);

            if (Recorder.this.isCancelled)  {

            Recorder.this.stopSelf();
                break;
            }

        }


        bufOutstream.close();

    } catch (IOException e) {
        System.err.println("Caught IOException: " + e.getMessage());

        // 
    }


   return true;
}

Answer 1

抛出异常时，len 保存上一次读取迭代的值，即最后一次成功。

无论如何，我建议：

    try
    {
        while ( (len = in.read()) > -1 )
        {

            bufOutstream.write(buffer, 0, len);

            if (Recorder.this.isCancelled)  
            {

                Recorder.this.stopSelf();
                break;
            }
        }
    }
    catch ( Exception e )
    {
        System.err.println("Caught IOException: " + e.getMessage());
    }
    finally
    {
        if ( in != null )
        {
            try
            {
                in.close();
            }
            catch ( Exception e )
            {
                // And I don't caaare
            }
        }

        if ( bufOutstream != null )
        {
            try
            {
                bufOutstream.close()
            }
            catch ( Exception e )
            {
                // And I don't caaare
            }
        }
    }

Answer 2

如果不想退出 while 循环，则需要将 try catch 块移到 while 循环内。不过，我建议以异常退出循环。这是我将使用的代码：

protected Boolean doInBackground(String... StringUrls) {
    Boolean success = true;
    len = 0;

    try {
        while (len != -1) {
            bufOutstream.write(buffer, 0, len);
            len = in.read(buffer);

            if (Recorder.this.isCancelled)  {

            Recorder.this.stopSelf();
                break;
            }
        }
    } catch (IOException e) {
            // do something with the exception and if you can't handle it here 
            // rethrow it!
            success = false;
    } finally {
        try {
            bufOutstream.close();
        } catch (Exception e) {
            // do something with the exception and if you can't handle it here 
            // rethrow it!
        }
    }

    return success;
}

Answer 3

在这种情况下，您可以检查您的 while 循环中的条件：
if您发现即使len != -1没有变为 false，也会抛出异常，
然后吞下 IOException，else您可以独占抛出它。

受保护的布尔doInBackground（字符串... StringUrls）{

        尝试 {
            //...
            int len = in.read(buffer);

            而（len！= -1）{
                尝试{
                bufOutstream.write(buffer, 0, len);
                len = in.read(buffer);

                if (Recorder.this.isCancelled) {
                Recorder.this.stopSelf();
                    休息;
                }
                }catch(IOException ioe){
                    如果（len == -1）{
                        抛出新的 IOException(ioe);
                    }
                        /*IOException 在不满足 len != -1 的情况下被吞掉*/
                }
            }
            bufOutstream.close();

        } 捕捉（IOException e）{
            System.err.println("捕获 IOException:" + e.getMessage());
            // ...
        }
    }