我正在尝试通过 android 在 Internet 上下载图像文件，并使用以下代码：
public class AndroidDownloadFileByProgressBarActivity extends Activity {
// button to show progress dialog
Button btnShowProgress;
// Progress Dialog
private ProgressDialog pDialog;
ImageView my_image;
// Progress dialog type (0 - for Horizontal progress bar)
public static final int progress_bar_type = 0;
// File url to download
private static String file_url = "http://api.androidhive.info/progressdialog/hive.jpg";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// show progress bar button
btnShowProgress = (Button) findViewById(R.id.btnProgressBar);
// Image view to show image after downloading
my_image = (ImageView) findViewById(R.id.my_image);
/**
* Show Progress bar click event
* */
btnShowProgress.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// starting new Async Task
new DownloadFileFromURL().execute(file_url);
}
});
}
/**
* Showing Dialog
* */
@Override
protected Dialog onCreateDialog(int id) {
switch (id) {
case progress_bar_type:
pDialog = new ProgressDialog(this);
pDialog.setMessage("Downloading file. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setMax(100);
pDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
pDialog.setCancelable(true);
pDialog.show();
return pDialog;
default:
return null;
}
}
/**
* Background Async Task to download file
* */
class DownloadFileFromURL extends AsyncTask<String, String, String> {
/**
* Before starting background thread
* Show Progress Bar Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
showDialog(progress_bar_type);
}
/**
* Downloading file in background thread
* */
@Override
protected String doInBackground(String... f_url) {
int count;
try {
URL url = new URL(f_url[0]);
URLConnection conection = url.openConnection();
conection.connect();
// getting file length
int lenghtOfFile = conection.getContentLength();
// input stream to read file - with 8k buffer
InputStream input = new BufferedInputStream(url.openStream(), 8192);
// Output stream to write file
OutputStream output = new FileOutputStream("/sdcard/downloadedfile.jpg");
byte data[] = new byte[1024];
long total = 0;
while ((count = input.read(data)) != -1) {
total += count;
// publishing the progress....
// After this onProgressUpdate will be called
publishProgress(""+(int)((total*100)/lenghtOfFile));
// writing data to file
output.write(data, 0, count);
}
// flushing output
output.flush();
// closing streams
output.close();
input.close();
} catch (Exception e) {
Log.e("Error: ", e.getMessage());
}
return null;
}
/**
* Updating progress bar
* */
protected void onProgressUpdate(String... progress) {
// setting progress percentage
pDialog.setProgress(Integer.parseInt(progress[0]));
}
/**
* After completing background task
* Dismiss the progress dialog
* **/
@Override
protected void onPostExecute(String file_url) {
// dismiss the dialog after the file was downloaded
dismissDialog(progress_bar_type);
// Displaying downloaded image into image view
// Reading image path from sdcard
String imagePath = Environment.getExternalStorageDirectory().toString() + "/downloadedfile.jpg";
// setting downloaded into image view
my_image.setImageDrawable(Drawable.createFromPath(imagePath));
}
}
}
但在 LogCat 我有一个错误。它显示：/sdcard/downloadedfile.jpg（权限被拒绝）。我正在使用android 3.1，我不知道如何解决它，请帮助我！
非常感谢。