[英]Async Task not getting canceled
我正在嘗試使用AsyncTask下載文件,並且還想實現進度對話框中的“取消”按鈕以取消下載。
我認為問題出在“ doInBackground”方法中。 這是我的asynctask:
public class Download_result extends AsyncTask<String,Integer,Void>{
ProgressDialog progressDialog;
Context context;
String pdfFile;
Download_result(Context context, String pdfFile){
this.context=context;
this.pdfFile=pdfFile;
}
@Override
protected void onPreExecute() {
progressDialog = new ProgressDialog(context);
progressDialog.setTitle("Downloading...");
progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressDialog.setMax(200);
progressDialog.setCancelable(false);
progressDialog.setProgress(0);
progressDialog.setButton(DialogInterface.BUTTON_NEGATIVE, "Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
Download_result.this.cancel(true); //cancel asynctask here
dialog.dismiss();
}
});
progressDialog.show();
}
@Override
protected Void doInBackground(String... params) {
//given below
}
@Override
protected void onProgressUpdate(Integer... values) {
progressDialog.setProgress(values[0]);
}
@Override
protected void onPostExecute(Void result) {
progressDialog.cancel();
}
}
“ doInBackground”方法:
@Override
protected Void doInBackground(String... params) {
String url_1=params[0];
int file_length=0;
try {
URL url = new URL(url_1);
URLConnection urlConnection = url.openConnection();
urlConnection.connect();
file_length=urlConnection.getContentLength();
filesize=file_length;
File sdCard = Environment.getExternalStorageDirectory();
File new_folder = new File (sdCard.getAbsolutePath() + "/xxx");
File input_file = new File(new_folder,pdfFile);
InputStream inputStream = new BufferedInputStream(url.openStream(),8192);
byte[] data=new byte[1024];
int total=0,count=0;
OutputStream outputStream = new FileOutputStream(input_file);
while ((count=inputStream.read(data))!=-1){
total+=count;
outputStream.write(data,0,count);
int progress= (total*200)/file_length;
downloadedsize=total;
publishProgress(progress);
if(isCancelled()){
break; or return null; // same result
}
}
inputStream.close();
outputStream.close();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
嘗試這個:
boolean downloadstatus = true;
@Override
protected void onPreExecute() {
progressDialog = new ProgressDialog(context);
progressDialog.setTitle("Downloading...");
progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressDialog.setMax(200);
progressDialog.setCancelable(false);
progressDialog.setProgress(0);
progressDialog.setButton(DialogInterface.BUTTON_NEGATIVE, "Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
download.cancel(true);
downloadstatus=false; //add boolean check
dialog.dismiss();
}
});
progressDialog.show();
}
現在在您的doInbackGround()
while ((count=inputStream.read(data))!=-1){
if(!your_AsyncTask.isCancelled() || downloadstatus !=false){
total+=count;
outputStream.write(data,0,count);
int progress= (total*200)/file_length;
downloadedsize=total;
publishProgress(progress);
}else{
break;
}
}
這是對我自己的帖子的回復(將來可能有人需要它):
實際上,我的asynctask會被取消,但我不知道,因為我認為當我們取消asynctask時,該文件不應存在。 但是實際上,當我們取消異步任務時,文件將被存儲,但是文件的大小較小。
例如。 假設文件為1mb,並且我已取消asynctask,而進度對話框顯示50%,則僅存儲500kb的文件,我認為這是實際文件。 對不起,我錯了。 因此,邏輯是當有人按“取消”時,您也需要刪除一半的下載文件。 對不起我的英語,我知道這太糟糕了。
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