我的Android第五章

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);  
    }  
}