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我尝试通过使用asynkTask来在后台创建进度条。我是来自服务器的downlroading文件，并通过使用进度条显示文件下载的进度，这工作正常。如何在后台运行进度条？
为了创建这个进度条，我提到了这个link。
我的代码：
package com.example.androidhive;
import java.io.BufferedInputStream;
import java.io.File;
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.graphics.drawable.Drawable;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.ProgressBar;
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;
String file = Environment.getExternalStorageDirectory()+"/MyAudio";
ProgressBar progressBar;
// File url to download
private static String file_url = "my url";
@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);
File f = new File(file);
if (!f.exists()) {
f.mkdirs();
} else {
// f.delete();
}
progressBar = (ProgressBar) findViewById(R.id.progressBar1);
/**
* Show Progress bar click event
* */
btnShowProgress.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// starting new Async Task
if (progressBar.getVisibility() != View.VISIBLE) {
progressBar.setVisibility(View.VISIBLE);
}
new DownloadFileFromURL().execute(file_url);
}
});
}
@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
}
/**
* 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/Audio/downloadedfile.jpg");
OutputStream output = new FileOutputStream(file+
"audio.zip");
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]));
progressBar.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);
if (progressBar.getVisibility() != View.VISIBLE) {
progressBar.setVisibility(View.VISIBLE);
}
// 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));
}
}
}
但我的问题是，当我靠近我的应用程序，然后重新打开我的进度条没有显示。 但我的文件在background.I下载我想显示下载文件的进度，如果应用程序将关闭并再次打开它，我想显示下载的进度。
如何我创建这个任何一个请帮我...