如何防止双击刷新按钮

Question

I'm developing an android app where i've a refresh button in my action bar. This button call a function that re-open the same activity. This activity contains an asyncTask to load the content.

At the moment i'm encountering this problem. When i click on the refresh button it works fine, but if i click on the refresh button when the AsyncTask is still working (i've a progress bar to check the status) the app crashes.

The error that i receive is: NullPointerException

Is it possible to disable that button until the activity (and its AsyncTask) are completely loaded?

Answer 1

In your button's OnClickListener , from where you execute the AsyncTask , add this code:

button.setEnabled(false);

In onPostExecute() method of your AsyncTask , place this:

button.setEnabled(true);

If you also give the 'cancel' option to the user(ie if you have overridden the onCancelled() method in your AsyncTask ), enable the button in onCancelled() .

Edit 1 :

Declare a boolean flag in your activity:

boolean menuButtonIsEnabled = true;

In your OnClickListener , set this flag to false:

menuButtonIsEnabled = false;

In onPostExecute() method of your AsyncTask :

menuButtonIsEnabled = true;

Override the onPrepareOptionsMenu(Menu) method in your activity:

@Override
public boolean onPrepareOptionsMenu (Menu menu){
    super.onPrepareOptionsMenu(menu);

    MenuItem button = menu.findItem(R.id.whatever_menu_button);

    if(menuButtonIsEnabled){
        button.setEnabled(true);
    } else {
        button.setEnabled(false);
    } 
    return true; 
}

Answer 2

In your onClickListener, the first thing you do is deactivate the button. This way it cannot be clicked again until you reactivate it :

button.setOnClickListener(new OnClickListener() {

    @Override
    public void onClick(View target) {
        target.setClickable(false);
        target.setEnbled(false);
        // Start your asynctask
    }
}

in your AsyncTask.onPostResult(), you can reactivate the click on the button.

Nota: setClickable(false) prevents the button from reacting to clicks events, but setEnabled(false) also usually changes the appearance of the button.

Answer 3

您可以尝试从AsyncTask onPreExecute 禁用按钮，并从AsyncTask onPostExecute 启用按钮

Answer 4

You can check the status of your task.... On click of refresh button...

if(yourAsyncTaskObject != null && yourAsyncTaskObject.getStatus() != AsyncTask.Status.RUNNING){
         then start your activity again here
    }