Basic Android Training : Learn to response to the Click

Simple Calculation

Create Android project named as AdditionApp.

Change the following files:

Main.xml

<?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" > <EditText         android:id="@+id/txtNum1"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:ems="10"         android:hint="@string/edit_message" >         <requestFocus />     </EditText>     <EditText         android:id="@+id/txtNum2"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:ems="10" />     <Button         android:id="@+id/btnCal"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="@string/btnCalLabel"         android:onClick="calculate"/>     <TextView         android:id="@+id/tvResult"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="TextView" /> </LinearLayout>

Strings.xml

<?xml version="1.0" encoding="utf-8"?> <resources>     <string name="hello">Hello World, MyFirstApp2!</string>     <string name="app_name">My First App 2</string>     <string name="edit_message">Edit here.</string>     <string name="btnCalLabel">Calculate</string> </resources>

AdditionApp.java

package com.kent; import android.app.Activity; import android.content.Intent; import android.os.Bundle; import android.util.Log; import android.view.View; import android.widget.EditText; import android.widget.TextView; public class AdditionApp extends Activity {                 @Override     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.main);     }         /** Called when the user click the Calculate button */     public void calculate(View view) {                         Log.i("MyFirstApp2", "calculate() ...start calculating...");                         // Get input from Number 1             EditText etNum1 = (EditText)findViewById(R.id.txtNum1);             int num1 = Integer.parseInt(etNum1.getText().toString());                         // Get input from Number 2             EditText etNum2 = (EditText)findViewById(R.id.txtNum2);             int num2 = Integer.parseInt(etNum2.getText().toString());                         // Show the result in TextView             TextView tvResult = (TextView)findViewById(R.id.tvResult);             tvResult.setText(String.valueOf(num1+num2));                         Log.i("MyFirstApp2", "Calculate done!");     } }

In this application, it takes in two input: num1 and num2, and add the two value then show it in a TextView object. It first turn the number entered as String into a integer value (using Integer.parseInt() method), then add them.

Then, using String.valueOf() method to turn the result back to a String value, and set this value to TextView tvResult object.

Android..cool!