我正在尝试从我的Android应用内部下载文件。当代码到达
行时connection.connect();
Logcat显示此异常：
09-23 21:41:21.853: W/System.err(6084): android.os.NetworkOnMainThreadException
09-23 21:41:21.863: W/System.err(6084): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1133)
09-23 21:41:21.863: W/System.err(6084): at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:84)
09-23 21:41:21.863: W/System.err(6084): at libcore.io.IoBridge.connectErrno(IoBridge.java:127)
09-23 21:41:21.863: W/System.err(6084): at libcore.io.IoBridge.connect(IoBridge.java:112)
09-23 21:41:21.863: W/System.err(6084): at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192)
09-23 21:41:21.863: W/System.err(6084): at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:459)
09-23 21:41:21.863: W/System.err(6084): at java.net.Socket.connect(Socket.java:842)
09-23 21:41:21.863: W/System.err(6084): at libcore.net.http.HttpConnection.<init>(HttpConnection.java:76)
09-23 21:41:21.873: W/System.err(6084): at libcore.net.http.HttpConnection.<init>(HttpConnection.java:50)
09-23 21:41:21.873: W/System.err(6084): at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:340)
09-23 21:41:21.873: W/System.err(6084): at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:87)
09-23 21:41:21.873: W/System.err(6084): at libcore.net.http.HttpConnection.connect(HttpConnection.java:128)
09-23 21:41:21.873: W/System.err(6084): at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:316)
09-23 21:41:21.873: W/System.err(6084): at libcore.net.http.HttpEngine.connect(HttpEngine.java:311)
09-23 21:41:21.873: W/System.err(6084): at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:290)
09-23 21:41:21.873: W/System.err(6084): at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:240)
09-23 21:41:21.873: W/System.err(6084): at libcore.net.http.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:81)
09-23 21:41:21.873: W/System.err(6084): at com.asde.ipac.AsyncUpdater$1.onClick(AsyncUpdater.java:107)
09-23 21:41:21.883: W/System.err(6084): at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:166)
09-23 21:41:21.883: W/System.err(6084): at android.os.Handler.dispatchMessage(Handler.java:99)
09-23 21:41:21.883: W/System.err(6084): at android.os.Looper.loop(Looper.java:137)
09-23 21:41:21.883: W/System.err(6084): at android.app.ActivityThread.main(ActivityThread.java:5103)
09-23 21:41:21.883: W/System.err(6084): at java.lang.reflect.Method.invokeNative(Native Method)
09-23 21:41:21.883: W/System.err(6084): at java.lang.reflect.Method.invoke(Method.java:525)
09-23 21:41:21.893: W/System.err(6084): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
09-23 21:41:21.893: W/System.err(6084): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-23 21:41:21.893: W/System.err(6084): at dalvik.system.NativeStart.main(Native Method)
这行logcat是connection.connect（）;
09-23 21:41:21.873: W/System.err(6084): at com.asde.ipac.AsyncUpdater$1.onClick(AsyncUpdater.java:107)
这是文件的网址：
private String urlDownload = "http://192.168.0.107/ipac/ipac.apk/";
这是方法的代码：
protected void onPostExecute(String lastVer) {
PackageInfo packageInfo;
try {
packageInfo = ((Activity) ctx).getPackageManager().getPackageInfo(ctx.getPackageName(), 0);
String currentVer = packageInfo.versionName;
System.out.println("Server: "+ lastVer);
System.out.println("Installed: "+ currentVer);
if(!lastVer.equals(currentVer))
{
new AlertDialog.Builder(ctx)
.setTitle("UPDATE AVAILABLE")
.setMessage("New Test available")
.setCancelable(false)
.setPositiveButton("DOWNLOAD", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
try {
System.out.println("0!!!!");
URL url = new URL(urlDownload);
System.out.println("0.2!!!!");
URLConnection connection = url.openConnection();
System.out.println("0.3!!!!" + url.toString());
connection.connect();
System.out.println("1!!!!");
// int fileLength = connection.getContentLength();
// download the file
InputStream input = new BufferedInputStream(url.openStream());
OutputStream output = new FileOutputStream(path);
System.out.println("2!!!!");
byte data[] = new byte[1024];
// long total = 0;
int count;
while ((count = input.read(data)) != -1) {
// total += count;
// publishProgress((int) (total * 100 / fileLength));
output.write(data, 0, count);
}
System.out.println("3!!!!");
output.flush();
output.close();
input.close();
//INSTALL
} catch (Exception e) {
e.printStackTrace();
}
}
})
.setNegativeButton("LATER", null)
.show();
}
} catch (NameNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
可能会发生什么？
答案 0 :(得分：0)
您必须在主线程上使用AsyncTasks或线程，否则Android会像崩溃一样崩溃。
将其放在onCreate（全局变量）之外：
ProgressDialog mProgressDialog;
然后将其放入您的活动内部（在oncreate之外）：
mProgressDialog = new ProgressDialog(About.this);
mProgressDialog.setMessage("Downloading file....");
mProgressDialog.setIndeterminate(false);
mProgressDialog.setMax(100);
mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
Then make that class:
private class DownloadFile extends AsyncTask<String, Integer, String> {
@Override
protected String doInBackground(String... sUrl) {
File folders = new File(Environment.getExternalStorageDirectory()
+ "/pathofthefile/");
folders.mkdirs();
File file;
file = new File(Environment.getExternalStorageDirectory()
+ "/pathofthefile/nameofthefile.extensionofthefile");
if (!file.exists()) {
try {
file.createNewFile();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} else {
file.delete();
try {
file.createNewFile();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
try {
URL url = new URL(sUrl[0]);
URLConnection connection = url.openConnection();
connection.connect();
// 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());
OutputStream output = new FileOutputStream(file);
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();
return "Downloaded";
} catch (Exception e) {
return null;
}
}
@Override
protected void onPreExecute() {
super.onPreExecute();
mProgressDialog.show();
}
@Override
protected void onProgressUpdate(Integer... progress) {
super.onProgressUpdate(progress);
mProgressDialog.setProgress(progress[0]);
}
@Override
protected void onPostExecute(String result) {
mProgressDialog.dismiss();
if (result.equals("Downloaded")) {
//do something here with the downloaded file
}
}
}
最后把它放在onCreate上（或当你想调用下载时）调用AsyncTask类发送要下载的文件的URL：
DownloadFile downloadFile = new DownloadFile();
downloadFile.execute("http://www.page.com/file.mp3");
希望有所帮助！