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As we have already learned the basics about Button now we discuss about the CheckBox in Android

Read Working with Buttons in Android

Working With CheckBox is similar to that of Button.

Create a new Project and drag and drop a Checkbox

Then after that type the following code


isChecked   is a Boolean variable which gives two results on clicking the checkbox it gives true and when it is unchecked it gives false.

The Output will be





Read How to Develop a BMI calculator App.

Download the Source Code for this BMI calculator

Downlod APK

I make this post simple as possible in the coding point of view.

You can read what is BMI and what is the formula to calculate our Body Mass Index.

I am simply explaining how to develop a BMI Calculator Android App.

Just read my previous posts like How to work with Buttons, How to add two numbers in Android and a Simple Calculator app.

If you have practiced the above examples it will be easy for you to do this BMI calculator app.

Create a new Project, drag and drop 2 Edittext to enter the height and weight, a button to calculate and a TextView to display the result also use the Hint.



After register the button, Edittext and Textview in MainActivity.java



After that write the below code inside the onClick()

@Override
    public void onClick(View arg0)
    {
       
       
        final DecimalFormat df2 = new DecimalFormat(".##");
        Double weight,height,heightinmeter,bmi,finalht;
        weight=Double.parseDouble(wt.getText().toString());
        height=Double.parseDouble(ht.getText().toString());
        heightinmeter=height*0.3048;
        finalht=heightinmeter*heightinmeter;
        bmi=weight/finalht;
        bmival.setText(""+df2.format(bmi));
       
        if(bmi<18.5)
         {
             res.setText("underweight");
         }
         else if(bmi>18.5&&bmi<24.9)
         {
             res.setText("normal weight");
         }
         else if(bmi>25&&bmi<29.9)
         {
             res.setText("overweight");
         }
         else if(bmi>30&&bmi<39.9)
         {
             res.setText("obesity");
         }
         else if(bmi>40)
         {
             res.setText("severe obesity");
         }
       
       
    }



  final DecimalFormat df2 = new DecimalFormat(".##");

this line is used to print only two digits after the dot for ex: 21.23 

heightinmeter=height*0.3048;
this line will convert your height in feet to height in meter

  Formula for calculating:

        heightinmeter=height*0.3048;// meter=feet*0.3048
        finalht=heightinmeter*heightinmeter;// height=meter*meter
        bmi=weight/finalht; // bmi=weight/height

Download Source Code of this Example

Read

How to Use Image as a Button in Android 

 

Working with multiple buttons in Android 

Download Source Code

Still now we have learned to work with buttons, now we will learn to use images as buttons , as we see now a days in our mobiles.

Its just copy pasting a image in a drawable folder which is under the res folder and adding it in the  activity_main.xml file.



Let us see in detail.

Create a New Android Application Project, and drag and drop a Button in the  layout.


Now create a New Folder in the res folder named as drawable. 


Right click on the res folder and click New---> Folder and name the folder as drawable and click Finish.




Now the created drawable folder can be seen below the res folder.


Now copy any image that you want use as button and paste in the drawable folder.

Copy image from your computer


and right click on the drwable folder and paste it.


Now you can see that the image has been pasted inside the drawable folder.


Now open activity_main.xml file and delete the  android:text="Button" since we do not need any text for our image.


then add the following code    android:background="@drawable/music"  as in the image


Then save it and open the Graphics Layout .


Now the button is changed into an image, but it is too big, we can resize it by using the width and height property in the activity_main.xml file.

I am using 100 dp for both width and height.


save it and open Graphics layout


Now we can see the resized image button.

Now we want make some action for that button, we can simply use a Toast message for that.

Open MainActivity.java and register the button , implement the listener interface and add the unimplemented methods as we saw in the post How to use Buttons in Android .



Then write the Toast message code


Now save and run the program.

Read 

How to use Android Phone as an Emulator

You can try with multiple buttons using images as we saw in the post
Working with Multiple Buttons in Android  


You can try the combinations of these example and make your own example.

 Also Read:

How to change Background Color in Android

Changing the background color of the Layout or screen in android is very simple to do.

Open a New Project in Android Eclipse


Enter the Project Name For Ex:  BackgroundColor


and click Next till the Finish comes and also click Finish.

The new Project will be created


Click the activity_main.xml below this image to open the xml file.


Add the following line inside the Relative layout tag

 android:background="#EACC00"

How to change Button color in Android

It is very easy to change the Button color in android with just one line of code.

Open New Android Application project and drag and drop the button in the UI interface .






Then double click on the button it will take you to the activity_main.xml in which you can see the button coding


In that add the following code

 android:background="any html color code"

After typing the code save it and click the Graphical Layout to see the change of the button color.


You can get the HTML color code in the internet.

It ranges from 0-9 and A-F , combination of these 6 digits will make a color.

Also Read:

Working with Buttons