Can I cancel previous Toast when I want to show an other Toast?

Question

In my app, I construct a calendar widget for my activity, when I scroll it to previous or next month, I let it make a toast and show it.

The question is, the toast need time to show, when I scroll it fast enough, for example, I scrolled to "2012/05" and "2012/06" and scroll to "2012/07" without pause, I have to wait the Toast of "2012/05", "2012/06","2012/07" to show one by one slowly.

Seems like Android has an invisible queue to manage toasts

how can I clean it and only show the last toast? Can I show a specific Toast immediately without waiting?

I searched the "android.widget.Toast.java" and find a method cancel(), but unfortunately it does not work as follows.

if (t != null) {     t.cancel(); } t = Toast.makeText(this.mContext, mHelper.getYear() + "年"                 + (mHelper.getMonth() + 1) + "月", Toast.LENGTH_SHORT); t.show(); 

Answer 1

You just need to declare a "Toast" var like this:

Toast toastMessage; 

Then in your function, do it like this:

if (toastMessage!= null) {     toastMessage.cancel(); } toastMessage= Toast.makeText(context, "The message you want to display", duration); toastMessage.show(); 

Answer 2

Here is my answer copied from another similar question here:

• Android cancel Toast when exiting the app and when toast is being shown

The Boast class accomplishes exactly what you need. Most recent code can be found on GitHub here:

• Boast.java

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The trick is to keep track of the last Toast that was shown, and to cancel that one.

What I have done is to create a Toast wrapper, that contains a static reference to the last Toast displayed.

When I need to show a new one, I first cancel the static reference, before showing the new one (and saving it in the static).

Here's full code of the Boast wrapper I made - it mimics enough of the Toast methods for me to use it. By default the Boast will cancel the previous one, so you don't build up a queue of Toasts waiting to be displayed.

If you just want to know how to cancel the notifications when exiting your app, you will find lots of help in there.

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package mobi.glowworm.lib.ui.widget;  import android.annotation.SuppressLint; import android.content.Context; import android.content.res.Resources; import android.support.annotation.Nullable; import android.widget.Toast;  import java.lang.ref.WeakReference;  /**  * {@link Toast} decorator allowing for easy cancellation of notifications. Use this class if you  * want subsequent Toast notifications to overwrite current ones. </p>  * <p/>  * By default, a current {@link Boast} notification will be cancelled by a subsequent notification.  * This default behaviour can be changed by calling certain methods like {@link #show(boolean)}.  */ public class Boast {     /**      * Keeps track of certain Boast notifications that may need to be cancelled. This functionality      * is only offered by some of the methods in this class.      * <p>      * Uses a {@link WeakReference} to avoid leaking the activity context used to show the original {@link Toast}.      */     @Nullable     private volatile static WeakReference<Boast> weakBoast = null;      @Nullable     private static Boast getGlobalBoast() {         if (weakBoast == null) {             return null;         }          return weakBoast.get();     }      private static void setGlobalBoast(@Nullable Boast globalBoast) {         Boast.weakBoast = new WeakReference<>(globalBoast);     }       // ////////////////////////////////////////////////////////////////////////////////////////////////////////      /**      * Internal reference to the {@link Toast} object that will be displayed.      */     private Toast internalToast;      // ////////////////////////////////////////////////////////////////////////////////////////////////////////      /**      * Private constructor creates a new {@link Boast} from a given {@link Toast}.      *      * @throws NullPointerException if the parameter is <code>null</code>.      */     private Boast(Toast toast) {         // null check         if (toast == null) {             throw new NullPointerException("Boast.Boast(Toast) requires a non-null parameter.");         }          internalToast = toast;     }      // ////////////////////////////////////////////////////////////////////////////////////////////////////////      /**      * Make a standard {@link Boast} that just contains a text view.      *      * @param context  The context to use. Usually your {@link android.app.Application} or      *                 {@link android.app.Activity} object.      * @param text     The text to show. Can be formatted text.      * @param duration How long to display the message. Either {@link Toast#LENGTH_SHORT} or      *                 {@link Toast#LENGTH_LONG}      */     @SuppressLint("ShowToast")     public static Boast makeText(Context context, CharSequence text, int duration) {         return new Boast(Toast.makeText(context, text, duration));     }      /**      * Make a standard {@link Boast} that just contains a text view with the text from a resource.      *      * @param context  The context to use. Usually your {@link android.app.Application} or      *                 {@link android.app.Activity} object.      * @param resId    The resource id of the string resource to use. Can be formatted text.      * @param duration How long to display the message. Either {@link Toast#LENGTH_SHORT} or      *                 {@link Toast#LENGTH_LONG}      * @throws Resources.NotFoundException if the resource can't be found.      */     @SuppressLint("ShowToast")     public static Boast makeText(Context context, int resId, int duration)             throws Resources.NotFoundException {         return new Boast(Toast.makeText(context, resId, duration));     }      /**      * Make a standard {@link Boast} that just contains a text view. Duration defaults to      * {@link Toast#LENGTH_SHORT}.      *      * @param context The context to use. Usually your {@link android.app.Application} or      *                {@link android.app.Activity} object.      * @param text    The text to show. Can be formatted text.      */     @SuppressLint("ShowToast")     public static Boast makeText(Context context, CharSequence text) {         return new Boast(Toast.makeText(context, text, Toast.LENGTH_SHORT));     }      /**      * Make a standard {@link Boast} that just contains a text view with the text from a resource.      * Duration defaults to {@link Toast#LENGTH_SHORT}.      *      * @param context The context to use. Usually your {@link android.app.Application} or      *                {@link android.app.Activity} object.      * @param resId   The resource id of the string resource to use. Can be formatted text.      * @throws Resources.NotFoundException if the resource can't be found.      */     @SuppressLint("ShowToast")     public static Boast makeText(Context context, int resId) throws Resources.NotFoundException {         return new Boast(Toast.makeText(context, resId, Toast.LENGTH_SHORT));     }      // ////////////////////////////////////////////////////////////////////////////////////////////////////////      /**      * Show a standard {@link Boast} that just contains a text view.      *      * @param context  The context to use. Usually your {@link android.app.Application} or      *                 {@link android.app.Activity} object.      * @param text     The text to show. Can be formatted text.      * @param duration How long to display the message. Either {@link Toast#LENGTH_SHORT} or      *                 {@link Toast#LENGTH_LONG}      */     public static void showText(Context context, CharSequence text, int duration) {         Boast.makeText(context, text, duration).show();     }      /**      * Show a standard {@link Boast} that just contains a text view with the text from a resource.      *      * @param context  The context to use. Usually your {@link android.app.Application} or      *                 {@link android.app.Activity} object.      * @param resId    The resource id of the string resource to use. Can be formatted text.      * @param duration How long to display the message. Either {@link Toast#LENGTH_SHORT} or      *                 {@link Toast#LENGTH_LONG}      * @throws Resources.NotFoundException if the resource can't be found.      */     public static void showText(Context context, int resId, int duration)             throws Resources.NotFoundException {         Boast.makeText(context, resId, duration).show();     }      /**      * Show a standard {@link Boast} that just contains a text view. Duration defaults to      * {@link Toast#LENGTH_SHORT}.      *      * @param context The context to use. Usually your {@link android.app.Application} or      *                {@link android.app.Activity} object.      * @param text    The text to show. Can be formatted text.      */     public static void showText(Context context, CharSequence text) {         Boast.makeText(context, text, Toast.LENGTH_SHORT).show();     }      /**      * Show a standard {@link Boast} that just contains a text view with the text from a resource.      * Duration defaults to {@link Toast#LENGTH_SHORT}.      *      * @param context The context to use. Usually your {@link android.app.Application} or      *                {@link android.app.Activity} object.      * @param resId   The resource id of the string resource to use. Can be formatted text.      * @throws Resources.NotFoundException if the resource can't be found.      */     public static void showText(Context context, int resId) throws Resources.NotFoundException {         Boast.makeText(context, resId, Toast.LENGTH_SHORT).show();     }      // ////////////////////////////////////////////////////////////////////////////////////////////////////////      /**      * Close the view if it's showing, or don't show it if it isn't showing yet. You do not normally      * have to call this. Normally view will disappear on its own after the appropriate duration.      */     public void cancel() {         internalToast.cancel();     }      /**      * Show the view for the specified duration. By default, this method cancels any current      * notification to immediately display the new one. For conventional {@link Toast#show()}      * queueing behaviour, use method {@link #show(boolean)}.      *      * @see #show(boolean)      */     public void show() {         show(true);     }      /**      * Show the view for the specified duration. This method can be used to cancel the current      * notification, or to queue up notifications.      *      * @param cancelCurrent <code>true</code> to cancel any current notification and replace it with this new      *                      one      * @see #show()      */     public void show(boolean cancelCurrent) {         // cancel current         if (cancelCurrent) {             final Boast cachedGlobalBoast = getGlobalBoast();             if ((cachedGlobalBoast != null)) {                 cachedGlobalBoast.cancel();             }         }          // save an instance of this current notification         setGlobalBoast(this);          internalToast.show();     }  }