Showing posts with label TUTORIALS. Show all posts
Showing posts with label TUTORIALS. Show all posts

Working with CheckBox in Android

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 open MainActivity.java and register the 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.

How to Create BMI Calculator Android App

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

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

This is the BMI standard

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");
}

The output will be

You can also add some colors to your app like this

I have used directly meter in this above example.

How to Change Button image when button is clicked

How to Use Image as a Button in Android

After practicing the above example you can do this example.

Changing Button image when the button is clicked is popular in may android applications.

For example : In Movie tickets booking application , if we select a seat it's image will be changed to different color or image.

We are going to do the same in our Example.

First create a new project drag and drop a button, copy a chair image from your computer and paste it in new drawable folder under res directory and do the xml coding part required to set the image to the button as you have practiced in the last example.

Till that you will get the result as:

Then also copy and paste another chair image which is in different color. i have choosen red color chair.

Then Open MainActivity.java and register the Button part and also include a boolean variable to check the button is clicked or not clicked.

Then use switch staement and type the code as in the image

public class MainActivity extends Activity implements OnClickListener {

Button chair;
Boolean b=false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
chair=(Button)findViewById(R.id.button1);
chair.setOnClickListener(this);

}

@Override
public void onClick(View v)
{
switch (v.getId()) {
case R.id.button1:
if(b)
{
chair.setBackgroundResource(R.drawable.ch);
b=false;
}
else
{
chair.setBackgroundResource(R.drawable.redchair);
b=true;
}
break;

default:
break;
}

}
}

In the above code i have used the if conditon to check whether the chair is clicked or not.

If the chair is not clicked the black chair will appear or if it is clicked red chair will appear, if the chair is clicked again the black chair will appear.

This condition will be useful in real time application because, the user may want to select a chair first but later he can choose a different chair, the application must be user friendly, thus we are using such a code.

the setBackgroundResource is similar to that setting background in xml file.

The output will be

When clicked again

You can try out with your own ideas also you can combine this with

Working with multiple buttons in Android

use switch statement with different button id's and with the help of if else conditon you can change multiple button's images.

Practice the previous examples well.

How to Use Image as a Button in Android

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.

we used color code inside the android:background="#EAAC00"  instead of the color code we are typing the location of the image ex: android:background= "@drawable/imagename" .

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.

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.

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"

Then save the file and open the Graphics Layout you can see the background color has been changed.

The #EAAC00 is HTML color code , you get more colors from the internet.

You can choose your desired background colors for your android app.

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.