What is toast in android programming?
What is Toasts?
Toast is a notification message that pop up, display a certain amount of time, and automatically fades in and out, most people just use it for debugging purpose.It only fills the amount of space required for the message and the current activity remains visible and interactive.Toast is used to display information for short period of time.
Toast class is used to display the short duration message without creating the hindrance for the user interaction.It doesn't block the running activities.
Toast class extend java.lang.Object class i.e. android.widget.Toast class is the subclass of java.lang.Object class.
Types of Toast
1. Default Toast(comes with predefined parameters )
2.Custom Toast(Developer customize the Toast )
Toast constants
- LENGTH_LONG - show the notification for long period of time(3.5sec).
- LENGTH_SHORT - show the notification for short period of time(2.0sec).
Toast's Methods
- makeText(Context context, int resId, int duration)
Make a standard toast that just contains a text view with the text from a resource.
Parameters
| context | The context to use. Usually your Application or Activity object. |
|---|---|
| resId | The resource id of the string resource to use. Can be formatted text. |
| duration | How long to display the message. Either LENGTH_SHORT or LENGTH_LONG |
- makeText(Context context, CharSequence text, int duration)
Make a standard toast that just contains a text view.
Parameters
| context | The context to use. Usually your Application or Activity object. |
|---|---|
| text | The text to show. Can be formatted text. |
| duration | How long to display the message. Either LENGTH_SHORT or LENGTH_LONG |
Code to Implement Toast in Button
package com.example.buttondemo;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button button;
button=(Button) findViewById(R.id.button1);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Toast.makeText(MainActivity.this,"I am Clicked", Toast.LENGTH_LONG).show();
}
});
}
}
ButtonDemo with Toast : Download ButtonDemo.zip
In Android, a toast message is
a simple visual
message that appears on the screen momentarily. Toast
messages are managed by the application framework, but
they are triggered by you, the developer. You
can use toast messages as an actual part of a
live app, but you can also use them for debugging. To
show something that's happening at run time. I'm
working in a project called ToastMessages. And
in this first demonstration I'll show a ToastMessage on
the screen as the app comes to the screen.
The first step is to declare an instance of
the Toast class. I'll
type the name of the class. And
I'll press Ctrl+Space to be sure I've imported
it, and I'll name the object simply message. Now
to create a toast message object, use a method of the toast class called make
text. There
are two versions of the method, one that
accepts a character sequence or a string. And
one that receives a resource ID for string resources. I'll
use a literal string.
The first argument is the context. And I'll
use this. Meaning
that this toast message object is being created
in the scope of the current activity. Then
I'll pass in a literal string of
activity created. Finally, pass in the duration. Most
commonly, developers use a constant of the Toast class. There
are two available called LENGTH_LONG and LENGTH_SHORT. I'll
use LENGTH_LONG. When
a Toast message appears, it'll show up for
a certain duration, and then go away automatically.
Now that I've created the message object, I
can show it
by calling a method of the object called show. I'll
save my changes and run the app in the emulator. When
the app appears, the toast message appears automatically. And
then it goes away after a moment. To
see that message again, I'll touch the back
button, that unloads the application, then I'll go
to my app list, and I'll locate my app, which is now named Toast, and I'll
run it again.
And I see that the activity is being created
anew. Toast
messages can be used for this sort of debugging at app start-up. But
they can also be used to track user events, events that
are dispatched to tell you that the user has done something. One
of the most common events happens when the
user selects an item from the Options menu. For
example, I'll go to my Options menu and choose Settings. Right
now in this app, that doesn't do anything. But
I'd like to find out when the user does it
and if my code is correct for handling the event.
In Android when the user selects an option
from the menu, you get an event. And
this will be the first demonstration of creating an event handler. In
the activity class I'll place the cursor below the existing methods. I'll
type onopt, and then
I'll press Ctrl+Space. And
I'll choose an override of a method called onOptionsItemSelected. I'll
press Enter, and Eclipse adds an override of that method. I'm
now overriding a method of the Activity class.
And whatever code I add where the to do
comment appears will
be executed when the user chooses something from that menu. I'll
get rid of that comment and then for the
return statement I'll create a Toast message and display it. This
time I'll use a slightly abbreviated syntax. I'll
create the message and immediately show it. So
I'm doing it all in a single statement instead of two statements. The
code will be toast.maketext. Once
again, I'll pass in this for the context,
and the literal string will look like this.
You select it, and then I'll append a property
of this item argument. This
is an instance of the class MenuItem, and I'll call
a method named getTitle, which returns a character sequence.Once again, I'll
use a duration of LENGTH_LONG,
and then once I've actually created the
toast object, I'll immediately display it with .show at the end of the
statement. And
so now, every time the user selects an item
from the Options menu, this code will be executed.
I'll run the app. And
once again, as the app comes to the
screen, I get the toast message, Activity Created. But
then I'll go to the Options menu and choose
Settings, and I see the message, You Selected Settings. When
the message goes away, I'll try it again, and see
that every time I choose an item from the menu, the
message is displayed. So
again, toast messages can be a really useful part of an
actual Android app, but they're also used for debugging simple events.
To find out when something has happened, without
having to dig through the Logcat view.