This tutorial explains how to
show a message box on button click of an Android application.
Create a new Android project:
Create a new project as in the
Hello World Android tutorial.
Application Name: Message Alert
Project Name: MessageAlert
Package Name: com.skk.messagealert
Minimum SDK: API 8
Target SDK: API 20
Compile With: API 20
Theme: Holo Light with Dark Action
Bar
Activity Name: Message_Alert
1) Remove
the existing TextView “HelloWorld”
2) Drag
and drop a button from the Forms Widget Pallet to Android Screen and rename the
Text properties to “Show Alert”
3) Response
for the button click in Android can be done via any of the two following ways,
a. By
setting onClick event:
In the properties of the button change the onClick event value to sendMessage. This will update the XML as
below
android:onClick="sendMessage"
Complete XML File:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.skk.messagealert.MessageAlert" >
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginLeft="98dp"
android:layout_marginTop="46dp"
android:onClick="sendMessage"
android:text="Show Alert" />
</RelativeLayout>
Now we need to write the code for showing the Message on button
click i.e the event, go to the java file MessageAlert.java
under src\com.skk.messageAlert\ add the following method in MessageAlert class
public void sendMessage(View
view) {
Toast.makeText(getApplicationContext(), "You have
clicked me!", Toast.LENGTH_LONG).show();
}
Typically in this method we set the text that needs to be
displayed when button is clicked, and how long it should be shown and show the
message to the user.
b. Using
onClickListener event:
In this method we set the Listener event for the button. The below
is the code for the same.
@Override
protected void onCreate(Bundle
savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_message_alert);
Button bt1 = (Button)
findViewById(R.id.button1);
bt1.setOnClickListener(new
View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(getApplicationContext(),
"You have clicked me!", Toast.LENGTH_LONG).show();
}
});
}
Here we create a local variable to refer the button and add the
EventHandler for that and on click of that we show the message using Toast.
4) After
creating the code as in any one of the methods above, save and run the code as
Android Application Project. This will launch the android application. Once you
click the button you should be able to see the message being show.
Successfully we have created and deployed the sample message box
in Android.
Additional Details:
Toast: Toast
is used to show a small popup upon a specific action in Android, while the
current activity remains visible and interactable.
makeText(): This is used to
create the text message that needs to be displayed , duration and the application
context.
show(): This
method is called to displayed the created text message.
R.java:
This is an auto generated
file for all the Android project, it creates a unique ID for all the elements
in the Android application i.e Button, title, logo etc. Sample value below.
public static final int button1=0x7f05003c;
Note:
The value of the button might differ for you.
