#1 Activity：

Activity是一个交互界面，可以布满整个窗口，或者悬浮于其他窗口上

一个程序由多个Activity组成，Manifest中指明了主Activity

<activity
 <span style="white-space:pre">	</span>android:label="@string/app_name"
<span style="white-space:pre">	</span>android:name=".MainActivity" >
	  <intent-filter >
	 <span style="white-space:pre">	</span><action android:name="android.intent.action.MAIN" />
	 <span style="white-space:pre">	</span><category android:name="android.intent.category.LAUNCHER" />
	   </intent-filter>
</activity>

Activity是一个互相调用关系，以栈的形式存取

#2 生命周期

voidonCreate(BundlesavedInstanceState) 
voidonStart() 
voidonRestart() 
voidonResume() 
voidonPause() 
voidonStop() 
voidonDestroy()

开始Activity：onCreate、onStart和onResume方法。
Activity失去焦点：onPause、onStop
Activity重新获得焦点：onRestart、onStart和onResume
关闭Activity：onPause、onStop和onDestory

#3 测试代码

package com.android.mylife;


import android.app.Activity;
import android.os.Bundle;

import android.util.Log;


public class Main extends Activity {
	
/** Called when the activity is first created. */
	
	private final String TAG = "Main";


	@Override

	public void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);

		setContentView(R.layout.main);

		Log.i(TAG, "onCreate Method is executed");

	}
	@Override
	protected void onStart() {

		// TODO Auto-generated method stub

		super.onStart();

		Log.i(TAG, "onStart Method is executed");

	}
	@Override

	protected void onRestart() {

		// TODO Auto-generated method stub

		super.onRestart();

		Log.i(TAG, "onRestart Method is executed");

	}
	@Override
	protected void onResume() {

		// TODO Auto-generated method stub

		super.onResume();

		Log.i(TAG, "onResume Method is executed");

	}
	@Override
	protected void onStop() {

		// TODO Auto-generated method stub

		super.onStop();

		Log.i(TAG, "onStop Method is executed");

	}
	@Override
	protected void onPause() {

		// TODO Auto-generated method stub

		super.onPause();

		Log.i(TAG, "onPause Method is executed");

	}
	@Override
	protected void onDestroy() {

		// TODO Auto-generated method stub

		super.onDestroy();

		Log.i(TAG, "onDestroy Method is executed");

	}

}