问题
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();
回答1:
You need to call method on correct object.
toastObject.cancel()
回答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
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.
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();
}
}
回答3:
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();
回答4:
Here is the Code.
final Toast toastobject = Toast.makeText(context, "This message will disappear when toast.close(); is called", Toast.LENGTH_SHORT);
Now you can use the Object of toastobject. Its Reference
toastobject.cancel();
You can use it in Thread or whenever you would like to Close the Toast.
回答5:
You can reuse a toast, this will make it display immediately.
myToast.setText(toastMsg);
myToast.show();
回答6:
There are many ways by which we can cancel previous Toast when we want to show another Toast. below I have written a simplest an easy way to implement it. First of all, we have to create a variable which can be accessed in the whole class.
private Toast toast;
After creating the variable which can be accessed by whole class we have to create a method in our class which displays the toast message and checks if the previous toast is displaying then cancel it.
public void showToast(String message) {
if (toast != null) {
toast.cancel();
}
toast = Toast.makeText(getApplicationContext(), message, Toast.LENGTH_SHORT);
toast.show();
}
you can change toast message by runtime calling above method.
showToast("message 1");
//after some time
showToast("message 2");
hope it helps.
回答7:
Toast has a method to hide current toast message
public void cancel() {
mTN.hide();
}
Try calling t.cancel() when it is necessary.
回答8:
You can create static method and use it to show a toast:
public static Toast toast = null;
public static showToast(Context context,String msg){
if(toast!=null) //this will cancel the toast on the screen if one exists
toast.cancel();
toast = Toast.makeText(context,msg);
toast.show();
}
回答9:
Simple. Simply call the method .cancel() on the toast once you want to create another toast.
Start by defining a Toast variable at the top of your class like this
private Toast mToast;
Later, When you want to create a new Toast(and have the old one disappear), do this.
if(mToast != null) {
mToast.cancel(); //if a toast exists it deletes it, allowing you to create a new one
}
mToast = Toast.makeText(this, "This will show up now!", Toast.LENGTH_LONG);
mToast.show(); //creates the new toast.
回答10:
public static Toast sToast=null;
// create Toast object;
public void showToast(String msg)
{
//here is checking whether toast object is null or not;if not null gonna cancel the toast that is showing in phone window and make it null;
if(sToast!=null)
{
sToast.cancel;
sToast=null;
}
//if toast object is null,gonna create new instance and make it shown on phone window.
if(sToast==null)
{
sToast=Toast.makeText(currentActivity.this,msg,Duration);
sToast.setGravity();
sToast.show();
}
}
回答11:
You can use one shoot technique. Oke let's start defining:
private Toast mToast;
private showOnce=false;
Later when you wanna show toast once:
if(showOnce==false){
mToast=Toast.makeText(this, "Once!", Toast.LENGTH_LONG);
mToast.show();
showOnce=true;
}
来源：https://stackoverflow.com/questions/10070108/can-i-cancel-previous-toast-when-i-want-to-show-an-other-toast