如果AsyncTask被取消，该怎么办？

您的路线是正确的，但doInBackground()您还需要专门致电isCancelled()以检查是否已取消，然后从返回doInBackground()。然后您的代码将正常工作。

请参阅AsyncTask文档“取消任务”

这是文档中的引用，以方便参考：

可以通过调用随时取消任务cancel(boolean)。调用此方法将导致后续调用isCancelled()返回true。调用此方法后，将在返回后调用onCancelled(Object)，而不是。为了确保尽快取消任务，应始终定期检查的返回值，如果可能的话（例如在循环内）。onPostExecute(Object)doInBackground(Object[])isCancelled()doInBackground(Object[])

编辑：每个请求，一些示例代码：

private class MyAsyncTask extends AsyncTask<Void,Void,Void> {

    private SQLiteDatabase db;

    @Override
    protected void onPreExecute() {
        // any kind of initialization or setup needed before the
        //     background thread kicks off. remember: this is still on
        //     on the main (UI) thread

        // since youre doing DB I/O, Ill make believe Im initializing the DB here
        db = DatabaseHelper.getInstance(MainActvity.this).getWritableDatabase();
    }

    /*
     * The background thread to do your disk and network I/O. If you need
     * to pass in any parameters, this is the first Void in the template
     */
    @Override
    protected Void doInBackground(Void... params) {

        // other stuff you need to do in the background. Since you want an
        //   all-or-nothing type thing, we will use a transaction to manually
        //   control the db
        db.beginTransaction();
        try {
            // do network I/O to retrieve what you need and then write to DB.
            ...
            ... // if theres a loop in here somewhere when reading the data, check !isCancelled() as part of the condition or as one of the first statements and then break
            ...
            db.setTransactionSuccessful(); // assuming everything works, need to set
                                         // this successful here at the end of the try
        } catch (InterruptedException ie) { // or some other exception
            cancel(true); // heres where you can call cancel() if youve been interrupted
        } catch (IOException ioe) { // if your network connection has problems
            cancel(true);
        } finally {
            db.endTransaction();
            // other cleanup, like closing the HTTP connection...
            //   no need to close the DB if you implement it properly
        }
        return null; // if there was some return value, that would go here
    }

    @Override
    protected void onCancelled(Void result) {
        // depending on how you implement doInBackground(), you may not even need this,
        //    unless you have a lot of other "state" you need to reset aside from the DB transaction
    }

    @Override
    protected void onPostExecute(Void result) {
        // any other items to do on main (UI) thread after doInBackground() finishes
        //   remember, this only gets called if cancel() is not called!
    }
}

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