Android4每日一例--第一天

HelloWorld
Helloworld,java
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;


public class HelloWorld extends Activity 
{
//當第一次創建該Activity時回調該方法
@Override
public void onCreate(Bundle savedInstanceState) 
{
super.onCreate(savedInstanceState);
//設置使用main.xml文件定義的頁面布局
setContentView(R.layout.main);
//獲取UI界面中ID為R.id.ok的按鈕
Button bn = (Button)findViewById(R.id.ok);
//為按鈕綁定一個單擊事件的監聽器
bn.setOnClickListener(new OnClickListener(){
public void  onClick(View v)   
{
//獲取UI界面中ID為R.id.show的文本框
final TextView show = (TextView)findViewById(R.id.show);
//改變文本框的文本內容
show.setText("Hello Android~" + new java.util.Date());
}
});        
}
}
點擊按鈕後文本框顯示Hello Android加當前時間。
自動生成的R文件，
public final class R {
    public static final class attr {
    }
    public static final class drawable {
        public static final int icon=0x7f020000;
    }
    public static final class id {
        public static final int ok=0x7f050001;
        public static final int show=0x7f050000;
    }
    public static final class layout {
        public static final int main=0x7f030000;
    }
    public static final class string {
        public static final int app_name=0x7f040000;
    }
}