Question

我通过服务下载了许多png文件，现在我正在尝试使用它们。它们会进入用户的SD卡。我已经确认每个文件都在卡上。但是当我尝试将它们中的任何一个设置为ImageView时，我得到了空白区域。

所以，然后我通过手动尝试使用手机的图片浏览器在手机上显示文件，看到文件完好无损。这些文件都不会打开。我想知道的是，在下载需要发生的文件之后我是否缺少任何步骤，以使它们可以作为png文件（或位图文件）查看。以下是我用于下载文件的服务中的代码：

public class DownloadPicture extends IntentService {

    private int result = Activity.RESULT_CANCELED;
    public static final String FILENAME = "filename";
    public static final String FILEPATH = "filepath";
    public static final String RESULT = "result";
    public static final String NOTIFICATION "com.mydomain.myapp.MyBroadcastReceiver";

    public DownloadPicture() {
        super("DownloadPicture");
    }

    public DownloadPicture(String name) {
        super(name);
    }

    @Override
    protected void onHandleIntent(Intent intent) {

        String fileName = intent.getStringExtra(FILENAME);
        String urlPath = this.getResources().getString(R.string.imagesURL) + fileName;
        System.err.println("starting download of: " + fileName);
        System.err.println(urlPath);
        File output = new File(Environment.getExternalStorageDirectory(), fileName);
        if (output.exists()) {output.delete();}

        InputStream stream = null;
        FileOutputStream fos = null;
        try {
          URL url = new URL(urlPath);
          stream = url.openConnection().getInputStream();
          InputStreamReader reader = new InputStreamReader(stream);
          fos = new FileOutputStream(output.getPath());
          int next = -1;
          while ((next = reader.read()) != -1) {
            fos.write(next);
          }

          //Maybe I need to do something else here????

          // Successful finished
          result = Activity.RESULT_OK;

        } catch (Exception e) {
          e.printStackTrace();
        } finally {
          if (stream != null) {
            try {
              stream.close();
            } catch (IOException e) {
              e.printStackTrace();
            }
          }
          if (fos != null) {
            try {
              fos.close();
            } catch (IOException e) {
              e.printStackTrace();
            }
          }
        }

        publishResults(output.getName(), output.getAbsolutePath(), result);
    }
}

Answer 1

不要使用InputStreamReader它会将字节流转换为字符流。 http://docs.oracle.com/javase/6/docs/api/java/io/InputStreamReader.html

在你的情况下，图像必须保留字节流，这样你就可以使用InputStream对象返回的URL：

while ((next = stream.read()) != -1) {
    fos.write(next);
}

下载的png文件不可读

1 个答案: