在 Android 中实现文件下载的进度条 [英] Implement Progress Bar for File Download in Android
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问题描述
我是 Android 开发的新手.
I am new to Android Development.
我编写了以下代码来从互联网.它工作正常.现在我想在此期间附加一个进度条下载过程.我尝试将 AsyncTask 子类化并在 doInBackground() 方法中编写下载代码.但是,不知怎么的,我想不通.
I've written the following code to download a video file from the internet. It works fine. Now I want to attach a progress bar during the download process.I tried to subclass AsyncTask and write the download code inside doInBackground() method. But, somehow I can't figure it out.
有人可以帮我修改这段代码来实现吗?
Can somebody please help me modify this code to accomplish that?
package sample.android.download;
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import org.apache.http.util.ByteArrayBuffer;
import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.widget.TextView;
public class DownloadDemo extends Activity {
private TextView tv;
private String videoURL = "http://mysite-name.com/videos/videofile_name.mp4";
private String fileName = "my_video.mp4";
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
tv = (TextView) findViewById(R.id.TextView01);
if(checkExternalMedia()==true) {
DownloadFromUrl(videoURL,fileName);
tv.append("
Download Complete!");
}
else {
tv.append("
External Media is NOT readable/writable");
}
}
/** Method to check whether external media available and writable. */
private boolean checkExternalMedia(){
boolean mExternalStorageAvailable = false;
boolean mExternalStorageWriteable = false;
boolean stat;
String state = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED.equals(state)) {
// Can read and write the media
mExternalStorageAvailable = mExternalStorageWriteable = true;
stat = true;
}
else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
// Can only read the media
mExternalStorageAvailable = true;
mExternalStorageWriteable = false;
stat = false;
} else {
// Can't read or write
mExternalStorageAvailable = mExternalStorageWriteable = false;
stat = false;
}
tv.append("
External Media: readable="+mExternalStorageAvailable+ "writable="+mExternalStorageWriteable);
return stat;
}
/** Method to download an external file from the network to the SD card. */
public void DownloadFromUrl(String videoURL, String fileName) {
try {
File root = android.os.Environment.getExternalStorageDirectory();
tv.append("
External file system root: "+root);
File dir = new File (root.getAbsolutePath() + "/video");
//dir.mkdirs();
URL url = new URL(videoURL); //you can write here any link
File file = new File(dir, fileName);
long startTime = System.currentTimeMillis();
Log.d("ImageManager", "download begining");
Log.d("ImageManager", "download url:" + url);
Log.d("ImageManager", "downloaded file name:" + fileName);
/* Open a connection to that URL. */
URLConnection ucon = url.openConnection();
/*
* Define InputStreams to read from the URLConnection.
*/
InputStream is = ucon.getInputStream();
BufferedInputStream bis = new BufferedInputStream(is);
/*
* Read bytes to the Buffer until there is nothing more to read(-1).
*/
ByteArrayBuffer baf = new ByteArrayBuffer(5000);
int current = 0;
while ((current = bis.read()) != -1) {
baf.append((byte) current);
}
/* Convert the Bytes read to a String. */
FileOutputStream fos = new FileOutputStream(file);
fos.write(baf.toByteArray());
fos.flush();
fos.close();
Log.d("ImageManager", "download ready in" + ((System.currentTimeMillis() - startTime) / 1000) + " sec");
} catch (IOException e) {
Log.d("ImageManager", "Error: " + e);
}
sendBroadcast(new Intent(Intent.ACTION_MEDIA_MOUNTED, Uri.parse("file://"+ Environment.getExternalStorageDirectory())));
}
}
推荐答案
检查:
http://developer.android.com/guide/topics/ui/对话框.html
请参阅在第二个线程中创建进度条的示例.
See the example on creating a progress bar within a second thread.
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