问题
I'm using a Snackbar from the com.android.support:design:22.2.0 library. I'm using it to undo deletions. To make my life easier, I'm going to make the UI look like things are actually deleted from the data source, and if the undo button in the snack bar is not pressed, actually perform the deletions from the data source. So, I want to know when the Snackbar is no longer visible, so it's safe to delete the items.
I can call getView() on the Snackbar, but I'm not sure what listener I should be using. I tried setOnSystemUiVisibilityChangeListener() but that didn't work, I believe it is only for the system status bar.
Additionally, Snackbar can not be extended, as it has a private constructor.
回答1:
Google design library supports Snackbar callbacks in version 23. See Snackbar docs and Callback docs. You will then get notified when the Snackbar gets dismissed (and also when shown) and also the type of dismissal if this is useful for you:
snackbar.addCallback(new Snackbar.Callback() {
@Override
public void onDismissed(Snackbar snackbar, int event) {
//see Snackbar.Callback docs for event details
...
}
@Override
public void onShown(Snackbar snackbar) {
...
}
});
回答2:
snackbar.setCallback(new Snackbar.Callback() {
@Override
public void onDismissed(Snackbar snackbar, int event) {
if (event == Snackbar.Callback.DISMISS_EVENT_TIMEOUT) {
// Snackbar closed on its own
}
}
@Override
public void onShown(Snackbar snackbar) {
...
}
});
回答3:
Recently I stumbled upon this matter myself when for scrolling and showing Snackback, too many were shown before the first even disappeared. I had to find a way to know if the app should have laid down the Snackbar.
I personally found this solution.
It is true Snackbar itself does not offer any kind of listener for it's state/visibility, but you can still get the View Object out of Snackbar ( getView(); ). From the View Object you have the chance to use a wide variety of methods to add listeners.
To implement it you have to go out of the common "all-in-one-line" Toast/Snackbar usage, because adding listeners returns void .
I personally found OnAttachStateChangeListener to fulfill my needs.
Dropping a snipper with my code in case it might turn useful for you.
Snackbar snack = Snackbar.make(getView(), "My Placeholder Text", Snackbar.LENGTH_LONG);
snack.getView().addOnAttachStateChangeListener(new View.OnAttachStateChangeListener() {
@Override
public void onViewAttachedToWindow(View v) {
canDisplaySnackbar = false;
}
@Override
public void onViewDetachedFromWindow(View v) {
Handler h = new Handler();
h.postDelayed(new Runnable() {
@Override
public void run() {
canDisplaySnackbar = true;
}
}, 1000);
}
});
snack.show();
Please note that this is just my implementation for my own problem, Handler with a postDelayed Runnable might not even fit your case. It was just to give a general idea of the implementation I suggested using a snippet I already own.
回答4:
To be notified when a snackbar has been shown or dismissed, you can provide a Snackbar.Callback via setCallback(Callback).
回答5:
Snackbar.addCallback in kotlin
val snackBar = Snackbar
.make(view, "Text Snackbar", Snackbar.LENGTH_LONG)
.addCallback(object : BaseTransientBottomBar.BaseCallback<Snackbar>() {
override fun onShown(transientBottomBar: Snackbar?) {
super.onShown(transientBottomBar)
}
override fun onDismissed(transientBottomBar: Snackbar?, event: Int) {
super.onDismissed(transientBottomBar, event)
}
})
val snackBarView = snackBar.view
snackBarView.setBackgroundColor(Color.RED)
snackBar.show()
回答6:
onDismissed is also called when the action Text is clicked for that reason need to put one condition like
event == Snackbar.Callback.DISMISS_EVENT_TIMEOUT
And now new code is look like below.
final Snackbar snackBar = Snackbar.make(findViewById(R.id.root_layout), result, Snackbar.LENGTH_LONG);
snackbar.addCallback(new Snackbar.Callback() {
@Override
public void onDismissed(Snackbar snackbar, int event) {
if (event == Snackbar.Callback.DISMISS_EVENT_TIMEOUT) {
// Snackbar closed on its own
}
}
@Override
public void onShown(Snackbar snackbar) {
...
}
});
snackBar.show();
回答7:
setCallback is now deprecated and addCallback should be used
https://developer.android.com/reference/android/support/design/widget/BaseTransientBottomBar.html#addCallback(android.support.design.widget.BaseTransientBottomBar.BaseCallback)
回答8:
There is currently no way to get notification when the Snackbar has finished displaying.
In this thread a workaround is discussed based on a timer for the duration of the Snackbar display. Snackbar in Support Library doesn't include OnDismissListener()?
One issue to consider with this workaround is it is possible that the Snackbar duration is restarted. The material design specification for Snackbar says this will happen if an unrelated dialog or popup is displayed.
回答9:
Currently you can't achieve it.
There isn't a listener called when the snackbar is dimissed.
The easiest way to do that is to temporarily save the record elsewhere (even a local variable), then re-insert it if they happen to hit the undo button.
回答10:
I have exactly the same problem as yours. My solution is...
final Snackbar povrati_obrisani_unos = Snackbar.make (coordinatorLayout, "Ponisti brisanje", Snackbar.LENGTH_INDEFINITE)
.addCallback (new Snackbar.Callback (){
@Override
public void onDismissed(Snackbar transientBottomBar, int event) {
super.onDismissed (transientBottomBar, event);
if(event==DISMISS_EVENT_SWIPE){//here we detect if snackbar is swipped away and not cliked (which is undo in my case)
Uri uriDelete = Uri.parse (obrisano.getImageuri ());
ContentResolver contentResolver = getContentResolver();
contentResolver.delete (uriDelete, null, null);
Toast.makeText (MainActivity.this,
"Ocitavanje i slika su trajno obrisani", Toast.LENGTH_SHORT).show ();
}
That is all, do not want to copy-paste snackbar.action which is undo. Want to be clear as I possibly can here.
Regards Nenad
回答11:
snackbar.addCallback(new Snackbar.Callback() {
public void onShown(Snackbar snackbar) {
// on show
}
public void onDismissed(Snackbar snackbar, int event) {
// on dismiss
}
});
回答12:
Thanks to @SergeyMilakov in Kotlin it is:
@SuppressLint("WrongConstant") // Suppress an error when set duration.
private fun showSnackbar() {
val DURATION = 5000
Snackbar.make(view!!, "Remove item?"), DURATION).apply {
setAction("Undo") {
// Your action when a button is clicked.
}
addCallback(object : BaseTransientBottomBar.BaseCallback<Snackbar>() {
/* override fun onShown(transientBottomBar: Snackbar?) {
super.onShown(transientBottomBar)
Timber.d("*** onShown")
}*/
override fun onDismissed(transientBottomBar: Snackbar?, event: Int) {
super.onDismissed(transientBottomBar, event)
if (event != Snackbar.Callback.DISMISS_EVENT_ACTION) {
// Your action when the Snackbar is closed and the button was not clicked.
}
}
})
view.setBackgroundColor(ContextCompat.getColor(context, R.color.black))
setActionTextColor(ContextCompat.getColor(context, R.color.yellow))
show()
}
}
Note that Snackbar shows, even if you move to other screens (for instance, back). So, don't forget to check whether you make actions on the right screen.
Also Snackbar doesn't restore after screen rotation.
来源：https://stackoverflow.com/questions/30926380/how-can-i-be-notified-when-a-snackbar-has-dismissed-itself