//声明为主活动
<intent-filter>
    <action android:name="android.intent.action.MAIN"/>
    <category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>

//不显示标题栏
requestWindowFeature(Window.FEATURE_NO_TITLE);

//显示提示
Toast.makeText(FirstActivity.this, "fuck me", Toast.LENGTH_SHORT).show();

//按钮注册监听器
button = (Button) findViewById(R.id.button);
button.setOnClickListener(new OnClickListener() {

	@Override
	public void onClick(View arg0) {
		// TODO Auto-generated method stub
		
	}
	
});

//线性布局
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
	xmlns:tools="http://schemas.android.com/tools"
</LinearLayout>

//表格布局里占两列
android:layout_span="2"