The document describes how to create a simple Android calculator application. It includes code snippets for layout XML with EditText fields for input and a TextView for output, an Activity class to handle button clicks and perform calculations, and an enum to represent the different operations. The process method uses the operation and input values to calculate a result and update the output TextView.

1. ANDROID 세미나
FOR BEGINNER (2)
PoolC 홍철주
2012. 4. 18

2. RESOURCE -> SOURCE CODE
<?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" >
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/hello" />
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
</LinearLayout>

3. RESOURCE -> SOURCE CODE

4. RESOURCE -> SOURCE CODE
public class TestActivity extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button mButton = (Button)findViewById(R.id.button1);
}
}

5. RESOURCE -> SOURCE CODE
public final class R {
public static final class attr {
}
public static final class drawable {
public static final int ic_launcher=0x7f020000;
}
public static final class id {
public static final int button1=0x7f050000;
}
public static final class layout {
public static final int main=0x7f030000;
}
public static final class string {
public static final int app_name=0x7f040001;
public static final int hello=0x7f040000;
}
}

6. RESOURCE -> SOURCE CODE
{ResourceType} {Varible} = (ResourceType)findViewById(ResourceAddress);

7. RESOURCE -> SOURCE CODE
Button mButton = (Button)findViewById(R.id.button1);
// Button Listener : onClick -> call a function
mButton.setOnClickListener(new Button.OnClickListener(){
public void onClick(View v) {
// TODO Auto-generated method stub
Toast.makeText(getApplicationContext(), "Hello, World",
Toast.LENGTH_SHORT).show();
}
});

8. ACTIVITY
• 일단은 보이는 화면이라고 생각
• 당신은 화면 위에다가 터치도 하고 이것 저것한다
• 입력도 받고 출력도 받고
• 액티비티 주기를 볼 필요가 있긴 한데...

9. INTENT
• 안드로이드에서의 의사표현 수단
• 어떤 component를 부른다!
• 그리고 무엇을 해달라고 요청!

10. CONTEXT
• 어플리케이션 환경의 전역 정보에 접근하기 위한 인터페이
스
• 시스템 정보 접근, API 호출
• 액티비티간 리소스 공유 등..

11. INTENT -> NEW ACTIVITY!
Intent mIntent = new Intent(TestActivity.this, SecondActivity.class);
startActivity(mIntent);
Intent 의 생성자는 여러가지.
이는 그 중 하나.

12. SIMPLE CALCULATOR
op1
opr
op2
result

13. SIMPLE CALCULATOR
EditText op1, op2;
TextView opr, result;
Button plus, minus, mul, div;

14. SIMPLE CALCULATOR
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
op1 = (EditText)findViewById(R.id.op1);
op2 = (EditText)findViewById(R.id.op2);
opr = (TextView)findViewById(R.id.opr);
result = (TextView)findViewById(R.id.result);
plus = (Button)findViewById(R.id.plus);
plus.setOnClickListener(this);
minus = (Button)findViewById(R.id.minus);
minus.setOnClickListener(this);
mul = (Button)findViewById(R.id.mul);
mul.setOnClickListener(this);
div = (Button)findViewById(R.id.div);
div.setOnClickListener(this);
}
this? -> activity
public class TestActivity extends Activity implements View.OnClickListener

15. SIMPLE CALCULATOR
public void onClick(View v) {
// TODO Auto-generated method stub
switch(v.getId()) {
case R.id.plus:
process(Operator.plus);
break;
case R.id.minus:
process(Operator.minus);
break;
case R.id.mul:
process(Operator.mul);
break;
case R.id.div:
process(Operator.div);
break;
}
}

16. SIMPLE CALCULATOR
void process(Operator op)
{
int op1Num = Integer.parseInt(op1.getText().toString());
int op2Num = Integer.parseInt(op2.getText().toString());
double resultNum = 0;
switch(op)
{
case plus:
resultNum = op1Num + op2Num;
opr.setText("+");
break;
case minus:
resultNum = op1Num - op2Num;
opr.setText("-");
break;
case mul:
resultNum = op1Num * op2Num;
opr.setText("*");
break;
case div:
resultNum = (double)op1Num / op2Num;
opr.setText("/");
break;
}
result.setText(Double.toString(resultNum));