转：基础总结篇之一：Activity生命周期

  1 package com.scott.lifecycle;
  2 
  3 import android.app.Activity;
  4 import android.content.Context;
  5 import android.content.Intent;
  6 import android.os.Bundle;
  7 import android.util.Log;
  8 import android.view.View;
  9 import android.widget.Button;
 10 
 11 public class LifeCycleActivity extends Activity {
 12     
 13     private static final String TAG = "LifeCycleActivity";
 14     private Context context = this;
 15     private int param = 1;
 16     
 17     //Activity创建时被调用
 18     @Override
 19     public void onCreate(Bundle savedInstanceState) {
 20         super.onCreate(savedInstanceState);
 21         Log.i(TAG, "onCreate called.");
 22         
 23         setContentView(R.layout.lifecycle);
 24         
 25         Button btn = (Button) findViewById(R.id.btn);
 26         btn.setOnClickListener(new View.OnClickListener() {
 27             @Override
 28             public void onClick(View v) {
 29                 Intent intent = new Intent(context, TargetActivity.class);
 30                 startActivity(intent);
 31             }
 32         });
 33     }
 34     
 35     //Activity创建或者从后台重新回到前台时被调用
 36     @Override
 37     protected void onStart() {
 38         super.onStart();
 39         Log.i(TAG, "onStart called.");
 40     }
 41     
 42     //Activity从后台重新回到前台时被调用
 43     @Override
 44     protected void onRestart() {
 45         super.onRestart();
 46         Log.i(TAG, "onRestart called.");
 47     }
 48     
 49     //Activity创建或者从被覆盖、后台重新回到前台时被调用
 50     @Override
 51     protected void onResume() {
 52         super.onResume();
 53         Log.i(TAG, "onResume called.");
 54     }
 55     
 56     //Activity窗口获得或失去焦点时被调用,在onResume之后或onPause之后
 57     /*@Override
 58     public void onWindowFocusChanged(boolean hasFocus) {
 59         super.onWindowFocusChanged(hasFocus);
 60         Log.i(TAG, "onWindowFocusChanged called.");
 61     }*/
 62     
 63     //Activity被覆盖到下面或者锁屏时被调用
 64     @Override
 65     protected void onPause() {
 66         super.onPause();
 67         Log.i(TAG, "onPause called.");
 68         //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
 69     }
 70     
 71     //退出当前Activity或者跳转到新Activity时被调用
 72     @Override
 73     protected void onStop() {
 74         super.onStop();
 75         Log.i(TAG, "onStop called.");    
 76     }
 77     
 78     //退出当前Activity时被调用,调用之后Activity就结束了
 79     @Override
 80     protected void onDestroy() {
 81         super.onDestroy();
 82         Log.i(TAG, "onDestory called.");
 83     }
 84     
 85     /**
 86      * Activity被系统杀死时被调用.
 87      * 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.
 88      * 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.
 89      * 在onPause之前被调用.
 90      */
 91     @Override
 92     protected void onSaveInstanceState(Bundle outState) {
 93         outState.putInt("param", param);
 94         Log.i(TAG, "onSaveInstanceState called. put param: " + param);
 95         super.onSaveInstanceState(outState);
 96     }
 97     
 98     /**
 99      * Activity被系统杀死后再重建时被调用.
100      * 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.
101      * 这两种情况下onRestoreInstanceState都会被调用,在onStart之后.
102      */
103     @Override
104     protected void onRestoreInstanceState(Bundle savedInstanceState) {
105         param = savedInstanceState.getInt("param");
106         Log.i(TAG, "onRestoreInstanceState called. get param: " + param);
107         super.onRestoreInstanceState(savedInstanceState);
108     }
109 }

 1 package com.scott.lifecycle;
 2 
 3 import android.app.Activity;
 4 import android.content.res.Configuration;
 5 import android.os.Bundle;
 6 import android.util.Log;
 7 
 8 public class OrientationActivity extends Activity {
 9     
10     private static final String TAG = "OrientationActivity";
11     private int param = 1;
12     
13     @Override
14     protected void onCreate(Bundle savedInstanceState) {
15         super.onCreate(savedInstanceState);
16         setContentView(R.layout.orientation_portrait);
17         Log.i(TAG, "onCreate called.");
18     }
19     
20     @Override
21     protected void onStart() {
22         super.onStart();
23         Log.i(TAG, "onStart called.");
24     }
25     
26     @Override
27     protected void onRestart() {
28         super.onRestart();
29         Log.i(TAG, "onRestart called.");
30     }
31     
32     @Override
33     protected void onResume() {
34         super.onResume();
35         Log.i(TAG, "onResume called.");
36     }
37     
38     @Override
39     protected void onPause() {
40         super.onPause();
41         Log.i(TAG, "onPause called.");
42     }
43     
44     @Override
45     protected void onStop() {
46         super.onStop();
47         Log.i(TAG, "onStop called.");
48     }
49     
50     @Override
51     protected void onDestroy() {
52         super.onDestroy();
53         Log.i(TAG, "onDestory called.");
54     }
55 
56     @Override
57     protected void onSaveInstanceState(Bundle outState) {
58         outState.putInt("param", param);
59         Log.i(TAG, "onSaveInstanceState called. put param: " + param);
60         super.onSaveInstanceState(outState);
61     }
62     
63     @Override
64     protected void onRestoreInstanceState(Bundle savedInstanceState) {
65         param = savedInstanceState.getInt("param");
66         Log.i(TAG, "onRestoreInstanceState called. get param: " + param);
67         super.onRestoreInstanceState(savedInstanceState);
68     }
69     
70     //当指定了android:configChanges="orientation"后,方向改变时onConfigurationChanged被调用
71     @Override
72     public void onConfigurationChanged(Configuration newConfig) {
73         super.onConfigurationChanged(newConfig);
74         Log.i(TAG, "onConfigurationChanged called.");
75         switch (newConfig.orientation) {
76         case Configuration.ORIENTATION_PORTRAIT:
77             setContentView(R.layout.orientation_portrait);
78             break;
79         case Configuration.ORIENTATION_LANDSCAPE:
80             setContentView(R.layout.orientation_landscape);
81             break;
82         }
83     }
84 }