Question

在我的应用程序中，我有一个异步任务，它将从远程服务器下载文件。在该课程中，我设置了一个具有取消按钮的ProgressDialog。如果我只使用一次异步任务并创建AsyncTask实例，可能会更容易。我可以像我在一些样本上看到的那样打电话给asyncTask.cancel(true)。

但在我的Activity中，我已多次执行AsyncTask：

new MyAsynTask().execute(url_of_file_1); 
new MyAsynTask().execute(url_of_file_2);
new MyAsynTask().execute(url_of_file_3);

虽然这不完全是结构，但感觉是这样的。

这就是MyAsyncTask的样子：

        private class MyAsyncTask extends AsyncTask<String, Integer, String> {
            ProgressDialog pdialog;

            @Override
            protected void onPreExecute() {
                super.onPreExecute();
                if(!MyActivity.this.isFinishing()){
                    mProgressDialog = new ProgressDialog(MyActivity.this);
                    mProgressDialog.setCancelable(false);
                    mProgressDialog.setButton(DialogInterface.BUTTON_POSITIVE, "Cancel", new CancelOnClickListener());
                 }
            }
            @Override
            protected String doInBackground(String... fileUrl) {

                try {

                    //do connection to url things
                    if(!isCancelled()){
                        // download the file

                    }else{
                        pdialog.dismiss();
                        mProgressDialog.dismiss();
                    }
                }catch(MalformedURLException e){

                }catch(FileNotFoundException e){

                }catch(Exception e){

                }
                return null;

            }


            @Override
            protected void onProgressUpdate(Integer... values) {

                if(!MyActivity.this.isFinishing()){
                    mProgressDialog.setMessage("Downloading..." + values[0]);
                    mProgressDialog.show();
                    super.onProgressUpdate(values);
                }
            }
            @Override
            protected void onPostExecute(String result) {
                if(!MyActivity.this.isFinishing()){
                    super.onPostExecute(result);
                    mProgressDialog.dismiss();

                }
            }

            private final class CancelOnClickListener implements DialogInterface.OnClickListener {

                public void onClick(DialogInterface dialog, int which) {
                    new MyAsyncTask().cancel(true); // is this correct?
                    MyActivity.this.finish();
                    try {
                        MyActivity.this.finalize();
                    } catch (Throwable e) {
                        application.shortToast("Error encountered in closing the page");
                    }
                    // maybe i should call super.onBackPressed();
                    application.shortToast("Download Cancelled");
                }
            }
        }

当我按下取消时发生的事情是它总是有这个例外，但我的应用程序有时不会崩溃...

    08-14 23:07:12.702: E/WindowManager(8623): Activity com.android.app.MyActivityhas leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@43f7c938 that was originally added here
    08-14 23:07:12.702: E/WindowManager(8623): android.view.WindowLeaked: Activity com.android.app.MyActivityhas leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@43f7c938 that was originally added here
    08-14 23:07:12.702: E/WindowManager(8623):  at android.view.ViewRootImpl.<init>(ViewRootImpl.java:384)
    08-14 23:07:12.702: E/WindowManager(8623):  at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:292)
    08-14 23:07:12.702: E/WindowManager(8623):  at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:224)
    08-14 23:07:12.702: E/WindowManager(8623):  at android.view.WindowManagerImpl$CompatModeWrapper.addView(WindowManagerImpl.java:149)
    08-14 23:07:12.702: E/WindowManager(8623):  at android.view.Window$LocalWindowManager.addView(Window.java:547)
    08-14 23:07:12.702: E/WindowManager(8623):  at android.app.Dialog.show(Dialog.java:285)
    08-14 23:07:12.702: E/WindowManager(8623):  at com.android.app.MyActivity$MyAsyncTask.onPreExecute(PartsActivity.java:784)
    08-14 23:07:12.702: E/WindowManager(8623):  at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586)
    08-14 23:07:12.702: E/WindowManager(8623):  at android.os.AsyncTask.execute(AsyncTask.java:534)
    08-14 23:07:12.702: E/WindowManager(8623):  at com.android.app.MyActivity$SecondAsyncTask.onPostExecute(PartsActivity.java:980)
    08-14 23:07:12.702: E/WindowManager(8623):  at com.android.app.MyActivity$SecondAsyncTask.onPostExecute(PartsActivity.java:1)
    08-14 23:07:12.702: E/WindowManager(8623):  at android.os.AsyncTask.finish(AsyncTask.java:631)
    08-14 23:07:12.702: E/WindowManager(8623):  at android.os.AsyncTask.access$600(AsyncTask.java:177)
    08-14 23:07:12.702: E/WindowManager(8623):  at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)

。。。。

那么当我按下ProgressDialog中的取消按钮时，结束那些被执行的AysnTask的正确方法是什么？

Answer 1

保留每项任务的参考： MyAsynTask task1 = new MyAsynTask(); task1.execute(url_of_file_1);

由于您的异常具有其他性质，因此当您单击取消按钮（即事件线程，而不是后台线程）时，需要关闭该对话框。在“取消”按钮回调中： myDialog.dissmiss() task1.cancel(true);

Android-如何结束多个AsyncTask

1 个答案: