我正在處理我的第一個Android應用程序,但似乎無法使其正常工作。這個應用程序應該從網站(在這種情況下,我的個人網站)下載一個文件(一個pdf,具體),並將其保存在SD卡上。 我看了看這裏四周,發現我應該使用的AsyncTask用於此目的,這是我想出了代碼:AsyncTask無法從外部網站下載文件
package it.uniroma3.tirocinioandroid;
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.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class MainActivity extends Activity implements OnClickListener {
private Button dlbutton;
private ProgressDialog mProgressDialog;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dlbutton = (Button) findViewById(R.id.dlbutton);
dlbutton.setOnClickListener(this);
mProgressDialog = new ProgressDialog(MainActivity.this);
mProgressDialog.setMessage("Currently downloading...");
mProgressDialog.setIndeterminate(false);
mProgressDialog.setMax(100);
mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
Log.i("Main", "finito onCreate");
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
//TODO sistemare il menù
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public void onClick(View v) {
switch (v.getId())
{
case R.id.dlbutton:
DownloadFile downloadFile = new DownloadFile();
downloadFile.execute("http://dragon-nest.net/catalogo.pdf");
Log.i("Main", "finito onClik");
break;
}
}
private class DownloadFile extends AsyncTask<String, Integer, String> {
@Override
protected String doInBackground(String... sUrl) {
try {
URL url = new URL(sUrl[0]);
URLConnection connection = url.openConnection();
connection.connect();
Log.i("Main", "connected");
// this will be useful so that you can show a typical 0-100% progress bar
int fileLength = connection.getContentLength();
// download the file
InputStream input = new BufferedInputStream(url.openStream());
Log.i("Main", "input set");
OutputStream output = new FileOutputStream(Environment.getDataDirectory().getAbsolutePath().concat("download/catalogo.pdf"));
Log.i("Main", "output set");
byte data[] = new byte[1024];
long total = 0;
int count;
while ((count = input.read(data)) != -1) {
total += count;
// publishing the progress....
publishProgress((int) (total * 100/fileLength));
output.write(data, 0, count);
}
output.flush();
output.close();
input.close();
}catch(Exception e){
Log.e("ERROR_TAG", e.getMessage());
return "fine";
}
String s ="fine";
Log.i("Main", "end download");
return s;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
mProgressDialog.show();
Log.i("Main", "end preExecute");
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
mProgressDialog.dismiss();
Log.i("Main", "end postExecute");
}
@Override
protected void onProgressUpdate(Integer... progress) {
super.onProgressUpdate(progress);
mProgressDialog.setProgress(progress[0]);
Log.i("Main", "update...");
}
}
}
然而,這似乎是無法連接到該網站開始下載。從Logcat中可以看出,它在嘗試連接時會產生一個異常,在下載真正開始之前會被捕獲並阻塞所有內容。
這裏也是清單的應用:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="it.uniroma3.tirocinioandroid"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="17" />
<user-permission android:name="android.permission.INTERNET" />
<user-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="it.uniroma3.tirocinioandroid.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="it.uniroma3.tirocinioandroid.FileDownloader"
android:label="@string/title_activity_file_downloader" >
</activity>
</application>
</manifest>
順便說一句,我想看看,也許這是我的地盤行事古怪,但我可以從瀏覽器就好了下載文件。我也嘗試從另一個網站的另一個文件,但我得到同樣的問題。 AVD和我的平板電腦都出現這種情況,所以我不認爲這是AVD相關的問題。
你做了什麼異常?請把這個堆棧跟蹤。而且,如果您下載的網站位於https://請讓我知道。 – Darpan 2013-04-08 09:41:25