Activity----生命周期的理解

创建两个Activity，在两个Activity中各添加一个按钮，实现Activity之间的跳转，在LogCa中新建一个关于System的Filter logcat messages，然后观察，当启动一个Activity时，它的生命周期是怎么样变化的。



mainActivity.java

package cn.bzu.l2.l2_activitylifecycle;

import android.net.Uri;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;

public class MainActivity extends Activity {

	/**
	 * Activity第1次创建时调用
	 */
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		System.out.println("FirstActivity->onCreate");
	}
	
			
	public void enter2(View view){
		Intent intent=new Intent();
		intent.setClass(MainActivity.this, SecondActivity.class);
		startActivity(intent);
	}

	/**
	 * 1.在代码中明确调用了finish方法
	 * 2.Android系统资源不够用时，会优先销毁第1个不可见的Activity
	 */
	@Override
	protected void onDestroy() {
		super.onDestroy();
		System.out.println("FirstActivity->onDestroy");
	}

    /**
     * 当启动另外一个Activity时，就会调用第1个Activity的onPause方法
     */
	@Override
	protected void onPause() {
		super.onPause();
		System.out.println("FirstActivity->onPause");
	}

	@Override
	protected void onRestart() {
		super.onRestart();
		System.out.println("FirstActivity->onRestart");
	}

	/**
	 * Activity获得用户焦点时，即与用户交互时
	 */
	@Override
	protected void onResume() {
		super.onResume();
		System.out.println("FirstActivity->onResume");
	}

	/**
	 * Activity能被看到时
	 */
	@Override
	protected void onStart() {
		super.onStart();
		System.out.println("FirstActivity->onStart");
	}

    /**
     * 完全被新的Activity遮挡住时调用
     */
	@Override
	protected void onStop() {
		super.onStop();
		System.out.println("FirstActivity->onStop");
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

}

ScendActivity.java

package cn.bzu.l2.l2_activitylifecycle;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;

public class SecondActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_second);
		System.out.println("SecondActivity->onCreate");

	}
	
	public void enter1(View view){
		Intent intent=new Intent();
		intent.setClass(SecondActivity.this, MainActivity.class);
		startActivity(intent);
	}

	@Override
	protected void onDestroy() {
		super.onDestroy();
		System.out.println("SecondActivity->onDestroy");
	}

	@Override
	protected void onPause() {
		super.onPause();
		System.out.println("SecondActivity->onPause");
	}

	@Override
	protected void onRestart() {
		super.onRestart();
		System.out.println("SecondActivity->onRestart");
	}

	@Override
	protected void onResume() {
		super.onResume();
		System.out.println("SecondActivity->onResume");
	}

	@Override
	protected void onStart() {
		super.onStart();
		System.out.println("SecondActivity->onStart");
	}

	@Override
	protected void onStop() {
		super.onStop();
		System.out.println("SecondActivity->onStop");
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.second, menu);
		return true;
	}

}