android：ExecutorService：-ExecutorService不等待executorService完成

Question

I have an executorService that does not wait for the executorService part to complete and it directly returns the return value without waiting below is my code: Please see if I am implementing the executorService properly and help me correct it if required

 public boolean validateForm() {
        flag=true;
        executorService = Executors.newSingleThreadExecutor();
            Future f = executorService.submit(new Runnable() {
                public void run() {
                    Log.e("FLAGssssss", "" + flag);
                    checkSourceCode(new BooleanCallBack() {
                        @Override
                        public void onSuccess(boolean result) {
                            Log.e("RESULT  ISSSSS", "" + result);
                            validateCode = result;
                            Log.e("validateSourceCode  ISSSSS", "" + validateSourceCode(result));
                            if (validateSourceCode(result) == false) {
                                flag = false;
                            }
                            Log.e("FLAG ISSSSS", "" + flag);
                        }
                    });
                }
            });
            try {
                if (f.get() != null) {
                    flag = true;
                }
                Log.e("FUTURE IS", "" + f.get());

            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (ExecutionException e) {
                e.printStackTrace();
            }
        if (!accept_checkbox.isChecked()) {
            Toast.makeText(getActivity().getBaseContext(), "Accept The Terms & Conditions To Proceed", Toast.LENGTH_LONG).show();
            //        accept_checkbox.requestFocus();
            flag = false;
        }
        if (!validateAddress()) {
            flag = false;
        }
        if (!validatelandmark()) {
            flag = false;
        }
        if (!validateDistrict()) {
            flag = false;
        }
        if (!validatePincode()) {
            flag = false;
        }
        if (!validateFullfillment()) {
            flag = false;
        }
        if (flag) {
            saveData();
        }

        executorService.shutdown();
        return flag; //flag is returned even before the executorService above is executed first
    }

Answer 1

It looks like there is some confusion on what constitutes a callback from being constructed vs. a callback executing.

The following code is creating and submitting a new Runnable task, but the Runnable is only printing a message and then constructing a BooleanCallBack . I'm not sure exactly what BooleanCallBack does, but assuming it really is a callback, the code in the callback will not execute right away.

For simplicity, lets think of the Runnable like this:

Future future = executorService.submit(new Runnable() {
    public void run() {
        sysou("runnable is running");
        checkSourceCode(new BooleanCallBack() {
            @Override
            public void onSuccess(boolean result) {
                sysou("callback from the runnable is running");
            }
        });
    }
});

When you invoke future.get() , it waits for the run() method to complete execution, which involves constructing the BooleanCallBack but not actually running it. Similar to how constructing a new Runnable object does not mean the code in the run() method is executed.

So if your code calls future.get() , the only thing you can be sure of is that the run() method has completed (ie you have gotten the "runnable is running" message). NOT that BooleanCallBack.onSuccess() has executed.

If you actually want to wait for the "callback from the runnable is running" bit, then you need to establish a reference to the BooleanCallBack so you can check its status.