我试图从服务器下载文件。代码如下：
class download_file extends AsyncTask<Void, Void, Void>
{
@Override
protected void onPreExecute()
{
super.onPreExecute();
showProgressdialog(""+selected_file_url);
}
@Override
protected Void doInBackground(Void... params)
{
String fullPath = Environment.getExternalStorageDirectory().getAbsolutePath() + "/MYFOLDER/";
try
{
URL url = new URL(selected_file_url);
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.setDoOutput(true);
//connect
urlConnection.connect();
//set the path where we want to save the file
File SDCardRoot = Environment.getExternalStorageDirectory();
File dirr = new File(fullPath);
if (!dirr.exists()) {dirr.mkdirs();}
File file = new File(fullPath, selected_file_name +".xls");
if(file.exists())
file.delete();
file.createNewFile();
FileOutputStream fileOutput = new FileOutputStream(file);
InputStream inputStream = urlConnection.getInputStream();
totalSize = urlConnection.getContentLength();
showProgressdialog(selected_file_url);
getActivity().runOnUiThread(new Runnable()
{
public void run()
{
pb.setMax(totalSize);
}
});
//create a buffer...
byte[] buffer = new byte[2048];
int bufferLength = 0;
while ( (bufferLength = inputStream.read(buffer)) > 0 )
{
fileOutput.write(buffer, 0, bufferLength);
downloadedSize += bufferLength;
// update the progressbar //
getActivity().runOnUiThread(new Runnable()
{
public void run()
{
pb.setProgress(downloadedSize);
float per = ((float)downloadedSize/totalSize) * 100;
tv_download_message.setText("Downloaded " + downloadedSize + "KB / " + totalSize + "KB (" + (int)per + "%)" );
}
});
}
fileOutput.close();
getActivity().runOnUiThread(new Runnable()
{
public void run()
{
// pb.dismiss(); // if you want close it..
}
});
} catch (final MalformedURLException e) {
showError("Error : MalformedURLException " + e);
e.printStackTrace();
} catch (final IOException e) {
showError("Error : IOException " + e);
e.printStackTrace();
}
catch (final Exception e) {
showError("Error : Please check your internet connection " + e);
}
return null;
}
@Override
protected void onPostExecute(Void result)
{
dialog.dismiss();
}
}
并通过
调用上面的下载 selected_file_url = file_url_list[position];
selected_file_name = temp[2];
new download_file().execute();
弹出
的错误消息`ERROR: IOException java.io.FileNotFoundException" + <link>
但是，我已经测试了网络浏览器中的链接，该文件可以成功下载到我的桌面。
上述代码出了什么问题？
答案 0 :(得分：0)
试试这个简单的例子：
import java.io.BufferedInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.net.URLConnection;
import android.app.Activity;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class download extends Activity {
public static final int DIALOG_DOWNLOAD_PROGRESS = 0;
private Button startBtn;
private ProgressDialog mProgressDialog;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
startBtn = (Button)findViewById(R.id.startBtn);
startBtn.setOnClickListener(new OnClickListener(){
public void onClick(View v) {
startDownload();
}
});
}
private void startDownload() {
String url = "http://yoursite"; //your download url
new DownloadFileAsync().execute(url);
}
@Override
protected Dialog onCreateDialog(int id) {
switch (id) {
case DIALOG_DOWNLOAD_PROGRESS:
mProgressDialog = new ProgressDialog(this);
mProgressDialog.setMessage("Downloading file..");
mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
mProgressDialog.setCancelable(false);
mProgressDialog.show();
return mProgressDialog;
default:
return null;
}
}
class DownloadFileAsync extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
showDialog(DIALOG_DOWNLOAD_PROGRESS);
}
@Override
protected String doInBackground(String... aurl) {
int count;
try {
URL url = new URL(aurl[0]);
URLConnection conexion = url.openConnection();
conexion.connect();
int lenghtOfFile = conexion.getContentLength();
Log.d("ANDRO_ASYNC", "Lenght of file: " + lenghtOfFile);
InputStream input = new BufferedInputStream(url.openStream());
OutputStream output = new FileOutputStream("/sdcard/YOURFLIENAME.XLS"); //save file in SD Card
byte data[] = new byte[1024];
long total = 0;
while ((count = input.read(data)) != -1) {
total += count;
publishProgress(""+(int)((total*100)/lenghtOfFile));
output.write(data, 0, count);
}
output.flush();
output.close();
input.close();
} catch (Exception e) {}
return null;
}
protected void onProgressUpdate(String... progress) {
Log.d("ANDRO_ASYNC",progress[0]);
mProgressDialog.setProgress(Integer.parseInt(progress[0]));
}
@Override
protected void onPostExecute(String unused) {
dismissDialog(DIALOG_DOWNLOAD_PROGRESS);
}
}
}
AndroidManifest.xml - 为应用提供必要的权限
由于我们要从互联网上下载文件并将其存储在SD卡上，我们需要为我们的应用程序提供两项特定权限。确保 AndroidManifest.xml 文件中包含以下行：
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
如需进一步参考，您可以查看this示例。