In android, CheckBox is a two-states button that can be either checked (ON) or unchecked (OFF) and it will allow users to toggle between the two states (ON / OFF) based on the requirements.
Generally, we can use multiple CheckBox controls in android application to allow users to select one or more options from the set of values.
Following is the pictorial representation of using CheckBox control in android applications.
By default, the android CheckBox will be in the OFF (Unchecked) state. We can change the default state of CheckBox by using android:checked attribute.
In case, if we want to change the state of CheckBox to ON (Checked), then we need to set android:checked = “true” in our XML layout file.
In android, we can create CheckBox control in two ways either in the XML layout file or create it in the Activity file programmatically.
Following is the sample way to define CheckBox control in XML layout file in android application.
If you observe above code snippet, here we defined CheckBox control and setting CheckBox state ON using android:checked attribute in xml layout file.
In android, we can create CheckBox control programmatically in activity file based on our requirements.
Following is the example of creating a CheckBox control dynamically in an activity file.
LinearLayout layout = (LinearLayout)findViewById(R.id.l_layout);
CheckBox cb = new CheckBox(this);
cb.setText("Tutlane");
cb.setChecked(true);
layout.addView(cb);
This is how we can define CheckBox in XML layout file or programmatically in activity file based on our requirements.
Generally, whenever the user clicks on CheckBox to Select or Deselect the CheckBox object will receive an on-click event.
In android, we can define the CheckBox click event in two ways either in the XML layout file or create it in the Activity file programmatically.
We can define a click event handler for button by adding the android:onClick attribute to the <CheckBox> element in our XML layout file.
The value of android:onClick attribute must be the name of method which we need to call in response to a click event and the Activity file which hosting XML layout must implement the corresponding method.
Following is the example of defining a CheckBox click event using android:onClick attribute in XML layout file.
android:onClick="onCheckBoxClick"/>
</LinearLayout>
In Activity that hosts our XML layout file, we need to implement click event method like as shown below.
public void onCheckboxClicked(View view) {
// Is the view now checked?
boolean checked = ((CheckBox) view).isChecked();
// Check which checkbox was clicked
switch(view.getId()) {
case R.id.chk1:
if (checked)
// Do your coding
else
// Do your coding
break;
// Perform your logic
}
}
In android, we can define CheckBox click event programmatically in Activity file rather than XML layout file.
To define checkbox click event programmatically, create View.OnClickListener object and assign it to the button by calling setOnClickListener(View.OnClickListener) like as shown below.
This is how we can handle CheckBox click events in android applications based on our requirements.
The following are some of the commonly used attributes related to CheckBox control in android applications.
| Attribute | Description |
|---|---|
| android:id | It is used to uniquely identify the control |
| android:checked | It is used to specify the current state of checkbox |
| android:gravity | It is used to specify how to align the text like left, right, center, top, etc. |
| android:text | It is used to set the text for a checkbox. |
| android:textColor | It is used to change the color of text. |
| android:textSize | It is used to specify the size of text. |
| android:textStyle | It is used to change the style (bold, italic, bolditalic) of text. |
| android:background | It is used to set the background color for checkbox control. |
| android:padding | It is used to set the padding from left, right, top and bottom. |
| android:onClick | It’s the name of the method to invoke when the checkbox clicked. |
| android:visibility | It is used to control the visibility of control. |
Following is the example of defining multiple CheckBox controls and one Button control in LinearLayout to get the selected values of CheckBox controls when we click on Button in the android application.
Create a new android application using android studio and give names as CheckBoxExample. In case if you are not aware of creating an app in android studio check this article Android Hello World App.
Now open an activity_main.xml file from \res\layout path and write the code like as shown below
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<CheckBox
android:id="@+id/chkJava"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="10dp"
android:layout_marginTop="150dp"
android:layout_marginLeft="100dp"
android:text="Java"
android:onClick="onCheckboxClicked"/>
<CheckBox
android:id="@+id/chkPython"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="10dp"
android:layout_marginLeft="100dp"
android:text="Python"
android:onClick="onCheckboxClicked"/>
<CheckBox
android:id="@+id/chkAndroid"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="10dp"
android:layout_marginLeft="100dp"
android:text="Android"
android:onClick="onCheckboxClicked"/>
<CheckBox
android:id="@+id/chkAngular"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="10dp"
android:layout_marginLeft="100dp"
android:text="AngularJS"
android:onClick="onCheckboxClicked"/>
<Button
android:id="@+id/getBtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="100dp"
android:text="Get Details" />
</LinearLayout>
If you observe above code we created a multiple CheckBox controls and one Button control in XML Layout file.
Once we are done with the creation of layout with required controls, we need to load the XML layout resource from our activity onCreate() callback method, for that open main activity file MainActivity.java from \java\com.tutlane.checkboxexample path and write the code like as shown below.
package com.tutlane.checkboxexample;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
CheckBox android, java, angular, python;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
android = (CheckBox)findViewById(R.id.chkAndroid);
angular = (CheckBox)findViewById(R.id.chkAngular);
java = (CheckBox)findViewById(R.id.chkJava);
python = (CheckBox)findViewById(R.id.chkPython);
Button btn = (Button)findViewById(R.id.getBtn);
btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String result = "Selected Courses";
if(android.isChecked()){
result += "\nAndroid";
}
if(angular.isChecked()){
result += "\nAngularJS";
}
if(java.isChecked()){
result += "\nJava";
}
if(python.isChecked()){
result += "\nPython";
}
Toast.makeText(getApplicationContext(), result, Toast.LENGTH_SHORT).show();
}
});
}
public void onCheckboxClicked(View view) {
boolean checked = ((CheckBox) view).isChecked();
String str="";
// Check which checkbox was clicked
switch(view.getId()) {
case R.id.chkAndroid:
str = checked?"Android Selected":"Android Deselected";
break;
case R.id.chkAngular:
str = checked?"AngularJS Selected":"AngularJS Deselected";
break;
case R.id.chkJava:
str = checked?"Java Selected":"Java Deselected";
break;
case R.id.chkPython:
str = checked?"Python Selected":"Python Deselected";
break;
}
Toast.makeText(getApplicationContext(), str, Toast.LENGTH_SHORT).show();
}
}
If you observe above code we are calling our layout using setContentView method in the form of R.layout.layout_file_name in our activity file. Here our xml file name is activity_main.xml so we used file name activity_main and we are getting the status of CheckBox controls when they Select / Deselect and getting the selected CheckBox control values on Button click.
Generally, during the launch of our activity, onCreate() callback method will be called by android framework to get the required layout for an activity.
When we execute the above example using the android virtual device (AVD) we will get a result like as shown below.
If you observe above result, we are able to get the status of checkboxes while selecting / deselecting and getting all the selected CheckBox values on button click.
This is how we can use CheckBox control in android applications to allow users to select one or more options based on our requirements.