Lets make a Temperature Converter Application. If you’ve read my previous blog on Hello World, this blog might not be a rocket science, but you would need some previous knowledge on the layouts and the controls! I’ll try explaining things as I go along!
Step1: File → New → Project → Android Project → [Name the project: TemperatueConverter] → [Select Build Target: Android 2.2 for me for now! ] → [Package Name:com.aniXification.temperatureConverter, Minimum SDK:8for me for now] → FINISH.
New Android project
Step2: The final Temperature Converter will look somewhat like this! The following is the main.xml layout view.
final App
Its xml data is:
<?xml version=“1.0″ encoding=“utf-8″?>
<LinearLayout xmlns:android=“http://schemas.android.com/apk/res/android”
android:layout_width=“fill_parent”
android:layout_height=“fill_parent”
android:orientation=“vertical” >
<LinearLayout
android:id=“@+id/linearLayout1″
android:layout_width=“match_parent”
android:layout_height=“wrap_content” >
<EditText
android:id=“@+id/editTextTemp”
android:layout_width=“wrap_content”
android:layout_height=“wrap_content”
android:layout_weight=“0.39″
android:inputType=“numberDecimal|numberSigned” >
</EditText>
<Button
android:id=“@+id/up”
android:layout_width=“wrap_content”
android:layout_height=“wrap_content”
android:onClick=“onUpButtonClicked”
android:text=“@string/up” />
<Button
android:id=“@+id/down”
android:layout_width=“wrap_content”
android:layout_height=“wrap_content”
android:onClick=“onDownButtonClicked”
android:text=“@string/down” />
</LinearLayout>
<RadioGroup
android:id=“@+id/radioGroup1″
android:layout_width=“wrap_content”
android:layout_height=“wrap_content” >
<RadioButton
android:id=“@+id/celsiusRButton”
android:layout_width=“wrap_content”
android:layout_height=“wrap_content”
android:checked=“true”
android:text=“@string/toCelsius” />
<RadioButton
android:id=“@+id/fahrenheitRButton”
android:layout_width=“wrap_content”
android:layout_height=“wrap_content”
android:text=“@string/toFahrenheit” />
</RadioGroup>
<Button
android:id=“@+id/convertButton”
android:layout_width=“wrap_content”
android:layout_height=“wrap_content”
android:onClick=“onConverterButtonClicked”
android:text=“@string/convert” />
</LinearLayout>
The layout consists of:
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The parent Vetrical LinearLayout
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The subparent Horizontal Layout
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A EditText
-
Up Button
-
Down Button
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RadioGroup
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to Celsius RadioButton
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to Fahrenheit RadioButton
-
Convert Button
If you see in the buttons above the onClick event is called which will be handled in our main Java class.
Before using the above xml file, copy the following xml file to strings.xml in res → values
<?xml version=“1.0″ encoding=“utf-8″?>
<resources>
<string name=“hello”>Hello World, TemperatureConverterActivity!</string>
<string name=“app_name”>TemperatureConverter</string>
<string name=“up”>up</string>
<string name=“down”>down</string>
<string name=“toCelsius”>to Celsius</string>
<string name=“toFahrenheit”>to Fahrenheit</string>
<string name=“convert”>Convert</string>
<string name=“temtToConvert”>Enter the temperature</string>
</resources>
These are the strings names used for the controls in the main.xml
Step3: Now. Lets look into the TemperatureConverterActivity.java class. Its is the main java class for me.
package com.aniXification.temperatureConverter;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.RadioButton;
import android.widget.Toast;
public class TemperatureConverterActivity extends Activity {
/** Called when the activity is first created. */
private EditText editTextGetTemp;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
editTextGetTemp = (EditText)findViewById(R.id.editTextTemp);
}
//The Convert Button Event Handler
public void onConverterButtonClicked(View view){
switch(view.getId()){
case R.id.convertButton:
RadioButton celsiusRButton = (RadioButton)findViewById(R.id.celsiusRButton);
RadioButton fahrenheitRButton = (RadioButton)findViewById(R.id.fahrenheitRButton);
//when the user clicks the button with empty EditText
if (editTextGetTemp.getText().length() == 0){
Toast.makeText(this, “Please enter some valid value”,Toast.LENGTH_LONG).show();
return;
}
//when valid value is entered
float inputTemp = Float.parseFloat(editTextGetTemp.getText().toString());
if(celsiusRButton.isChecked()){
editTextGetTemp.setText(String.valueOf(convertFahrenheitToCelsius(inputTemp)));
celsiusRButton.setChecked(false);
fahrenheitRButton.setChecked(true);
}
else{
editTextGetTemp.setText(String.valueOf(convertCelsiusToFahrenheit(inputTemp)));
fahrenheitRButton.setChecked(false);
celsiusRButton.setChecked(true);
}
}
}
//On Up Button Clicked
public void onUpButtonClicked(View view){
//when the user clicks the button with empty EditText
if (editTextGetTemp.getText().length() == 0){
Toast.makeText(this, “Please enter some valid value first”,Toast.LENGTH_LONG).show();
return;
}
else{
float inputTemp = Float.parseFloat(editTextGetTemp.getText().toString());
inputTemp ++ ;
editTextGetTemp.setText(“”+ inputTemp);
}
}
//On Down Button Clicked
public void onDownButtonClicked(View view){
//when the user clicks the button with empty EditText
if (editTextGetTemp.getText().length() == 0){
Toast.makeText(this, “Please enter some valid value first”,Toast.LENGTH_LONG).show();
return;
}
else{
float inputTemp = Float.parseFloat(editTextGetTemp.getText().toString());
inputTemp –;
editTextGetTemp.setText(“”+ inputTemp);
}
}
//Convert Fahrenheit to celsius
private float convertFahrenheitToCelsius(float fahrenheit){
return ((fahrenheit -32)*5/9);
}
//Convert to Fahrenheit to Celsius
private float convertCelsiusToFahrenheit(float celsius){
return ((9*celsius)/5)+ 32;
}
}
Now lets look what the above piece of code does,
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The EditText must not NULL to increase the counter, decrease the counter and the Temperature Conversion
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Enter any decimal or integer to the EditText check the radioButton to convert the temperature to and click the convert Button. And have the temperature converted!
The snapshot of the final application.
Final Application
Download the pdf version in here! temperature converter
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