Android基础之Activity生命周期

package com.scott.lifecycle;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

public class LifeCycleActivity extends Activity {
	
	private static final String TAG = "LifeCycleActivity";
	private Context cOntext= this;
	private int param = 1;
	
	//Activity创建时被调用
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Log.i(TAG, "onCreate called.");
    
    setContentView(R.layout.lifecycle);
    
    Button btn = (Button) findViewById(R.id.btn);
    btn.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View v) {
				Intent intent = new Intent(context, TargetActivity.class);
				startActivity(intent);
			}
		});
  }
  
  //Activity创建或者从后台重新回到前台时被调用
  @Override
  protected void onStart() {
  	super.onStart();
  	Log.i(TAG, "onStart called.");
  }
  
  //Activity从后台重新回到前台时被调用
  @Override
  protected void onRestart() {
  	super.onRestart();
  	Log.i(TAG, "onRestart called.");
  }
  
  //Activity创建或者从被覆盖、后台重新回到前台时被调用
  @Override
  protected void onResume() {
  	super.onResume();
  	Log.i(TAG, "onResume called.");
  }
  
  //Activity窗口获得或失去焦点时被调用,在onResume之后或onPause之后
  /*@Override
  public void onWindowFocusChanged(boolean hasFocus) {
  	super.onWindowFocusChanged(hasFocus);
  	Log.i(TAG, "onWindowFocusChanged called.");
  }*/
  
  //Activity被覆盖到下面或者锁屏时被调用
  @Override
  protected void onPause() {
  	super.onPause();
  	Log.i(TAG, "onPause called.");
  	//有可能在执行完onPause或onStop后,系统资源紧张将Activity杀死,所以有必要在此保存持久数据
  }
  
  //退出当前Activity或者跳转到新Activity时被调用
  @Override
  protected void onStop() {
  	super.onStop();
  	Log.i(TAG, "onStop called.");	
  }
  
  //退出当前Activity时被调用,调用之后Activity就结束了
  @Override
  protected void onDestroy() {
  	super.onDestroy();
  	Log.i(TAG, "onDestory called.");
  }
  
  /**
   * Activity被系统杀死时被调用.
   * 例如:屏幕方向改变时,Activity被销毁再重建;当前Activity处于后台,系统资源紧张将其杀死.
   * 另外,当跳转到其他Activity或者按Home键回到主屏时该方法也会被调用,系统是为了保存当前View组件的状态.
   * 在onPause之前被调用.
   */
	@Override
	protected void onSaveInstanceState(Bundle outState) {
		outState.putInt("param", param);
		Log.i(TAG, "onSaveInstanceState called. put param: " + param);
		super.onSaveInstanceState(outState);
	}
	
	/**
	 * Activity被系统杀死后再重建时被调用.
	 * 例如:屏幕方向改变时,Activity被销毁再重建;当前Activity处于后台,系统资源紧张将其杀死,用户又启动该Activity.
	 * 这两种情况下onRestoreInstanceState都会被调用,在onStart之后.
	 */
	@Override
	protected void onRestoreInstanceState(Bundle savedInstanceState) {
		param = savedInstanceState.getInt("param");
		Log.i(TAG, "onRestoreInstanceState called. get param: " + param);
		super.onRestoreInstanceState(savedInstanceState);
	}
}

package com.scott.lifecycle;

import android.app.Activity;
import android.content.res.Configuration;
import android.os.Bundle;
import android.util.Log;

public class OrientationActivity extends Activity {
	
	private static final String TAG = "OrientationActivity";
	private int param = 1;
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.orientation_portrait);
		Log.i(TAG, "onCreate called.");
	}
	
	@Override
	protected void onStart() {
		super.onStart();
		Log.i(TAG, "onStart called.");
	}
	
	@Override
	protected void onRestart() {
		super.onRestart();
		Log.i(TAG, "onRestart called.");
	}
	
	@Override
	protected void onResume() {
		super.onResume();
		Log.i(TAG, "onResume called.");
	}
	
	@Override
	protected void onPause() {
		super.onPause();
		Log.i(TAG, "onPause called.");
	}
	
	@Override
	protected void onStop() {
		super.onStop();
		Log.i(TAG, "onStop called.");
	}
	
	@Override
	protected void onDestroy() {
		super.onDestroy();
		Log.i(TAG, "onDestory called.");
	}

	@Override
	protected void onSaveInstanceState(Bundle outState) {
		outState.putInt("param", param);
		Log.i(TAG, "onSaveInstanceState called. put param: " + param);
		super.onSaveInstanceState(outState);
	}
	
	@Override
	protected void onRestoreInstanceState(Bundle savedInstanceState) {
		param = savedInstanceState.getInt("param");
		Log.i(TAG, "onRestoreInstanceState called. get param: " + param);
		super.onRestoreInstanceState(savedInstanceState);
	}
	
	//当指定了android:cOnfigChanges="orientation"后,方向改变时onConfigurationChanged被调用
	@Override
	public void onConfigurationChanged(Configuration newConfig) {
		super.onConfigurationChanged(newConfig);
		Log.i(TAG, "onConfigurationChanged called.");
		switch (newConfig.orientation) {
		case Configuration.ORIENTATION_PORTRAIT:
			setContentView(R.layout.orientation_portrait);
			break;
		case Configuration.ORIENTATION_LANDSCAPE:
			setContentView(R.layout.orientation_landscape);
			break;
		}
	}
}