Android之Activity，Fragment生命周期探知

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Android之Activity，Fragment生命周期探知 - sin@ - 博客频道 - CSDN.NET

根据官方文档，本人手画了一下Activity和Fragment的整个生命周期执行顺序图：

Activity生命周期执行顺序图：

Fragment生命周期执行顺序图：

?

一个Activity在它的整个生命周期里面分三个状态，分别是活动周期，可见周期，以及生命周期。 一个Fragment是依附于Activity之上，它的整个生命周期里面也分三个状态，分别是活动周期，可见周期，以及生命周期。 现在我们来分析一下这些状态的实际执行顺序，我们通过日志的方式来打印每个函数的执行过程，新建一个android工程，Activity代码和Fragment代码如下：

[java] view plaincopyprint?

1. public?class?MainActivity?extends?Activity?{??
2. ??
3. ????private?static?String?TAG?=?"chenjianjun";??
4. ??????
5. ????private?static?Button?mybtnButton;??
6. ??????
7. ????@Override??
8. ????public?boolean?onCreateOptionsMenu(Menu?menu)?{??
9. ????????//?Inflate?the?menu;?this?adds?items?to?the?action?bar?if?it?is?present.??
10. ????????getMenuInflater().inflate(R.menu.main,?menu);??
11. ????????return?true;??
12. ????}??
13. ??????
14. ????/**??
15. ?????*?在完整生存期开始时调用?
16. ?????*?@see?android.app.Activity#onCreate(android.os.Bundle)?
17. ?????*/??
18. ????@Override??
19. ????protected?void?onCreate(Bundle?savedInstanceState)?{??
20. ????????super.onCreate(savedInstanceState);??
21. ????????setContentView(R.layout.activity_main);??
22. ??????????
23. ????????mybtnButton?=?(Button)findViewById(R.id.btn);??
24. ????????mybtnButton.setOnClickListener(new?View.OnClickListener()?{??
25. ??????????????
26. ????????????@Override??
27. ????????????public?void?onClick(View?v)?{??
28. ????????????????Intent?bintent?=?new?Intent(MainActivity.this,?SecondActivity.class);??
29. ????????????????startActivity(bintent);??
30. ????????????}??
31. ????????});??
32. ??????????
33. ????????Log.i(TAG,?"onCreate?is?call.......");??
34. ????}??
35. ??
36. ????/**?
37. ?????*?在onCreate方法后调用，用于恢复UI状态?
38. ?????*?@see?android.app.Activity#onRestoreInstanceState(android.os.Bundle)?
39. ?????*/??
40. ????@Override??
41. ????protected?void?onRestoreInstanceState(Bundle?savedInstanceState)??
42. ????{??
43. ????????Log.i(TAG,?"onRestoreInstanceState?is?call?start.......");??
44. ????????super.onRestoreInstanceState(savedInstanceState);??
45. ????????/**?
46. ?????????*?从savedInstanceState恢复UI状态?
47. ?????????*?这个savedInstanceState也被传递给了onCreate?
48. ?????????*?自Activity上次可见之后，只有当系统终止了该Activity时，才会被调用?
49. ?????????*?在随后的Activity进程的可见生存期之前被调用?
50. ?????????*/??
51. ????????Log.i(TAG,?"onRestoreInstanceState?is?call?end.......");??
52. ????}??
53. ??????
54. ????/**?
55. ?????*?在可见生存期开始时调用?
56. ?????*?@see?android.app.Activity#onStart()?
57. ?????*/??
58. ????@Override??
59. ????protected?void?onStart()??
60. ????{??
61. ????????Log.i(TAG,?"onStart?is?call?start.......");??
62. ????????super.onStart();??
63. ????????/**?
64. ?????????*?既然Activity可见，就应用任何要求的UI变化?
65. ?????????*/??
66. ????????Log.i(TAG,?"onStart?is?call?end.......");??
67. ????}??
68. ??????
69. ????/**?
70. ?????*?在Activity活动状态生存期开始时调用?
71. ?????*?@see?android.app.Activity#onResume()?
72. ?????*/??
73. ????@Override??
74. ????protected?void?onResume()??
75. ????{??
76. ????????Log.i(TAG,?"onResume?is?call?start.......");??
77. ????????super.onResume();??
78. ????????/**?
79. ?????????*?恢复Activity处于不活动状态时被挂起的，暂停的UI更新，线程，进程?
80. ?????????*/??
81. ????????Log.i(TAG,?"onResume?is?call?end.......");??
82. ????}??
83. ??????
84. ????/*?
85. ?????*?把UI状态保存到outState中?
86. ?????*?@see?android.app.Activity#onSaveInstanceState(android.os.Bundle)?
87. ?????*/??
88. ????@Override??
89. ????protected?void?onSaveInstanceState(Bundle?savedInstanceState)??
90. ????{??
91. ????????Log.i(TAG,?"onSaveInstanceState?is?call?start.......");??
92. ????????/**?
93. ?????????*?保存UI的状态?
94. ?????????*?如果进程被运行时终止并重启，那么这个Bundle会被传递给onCreate和onRestoreInstanceState?
95. ?????????*/??
96. ????????super.onSaveInstanceState(savedInstanceState);??
97. ????????Log.i(TAG,?"onSaveInstanceState?is?call?end.......");??
98. ????}??
99. ??????
100. ????/**?
101. ?????*?在Activity活动状态生存期结束时被调用?
102. ?????*/??
103. ????@Override??
104. ????protected?void?onPause()??
105. ????{??
106. ????????Log.i(TAG,?"onPause?is?call?start.......");??
107. ????????/**?
108. ?????????*?挂起UI更新，线程或者CPU密集的进程?
109. ?????????*/??
110. ????????super.onPause();??
111. ????????Log.i(TAG,?"onPause?is?call?end.......");??
112. ????}??
113. ??????
114. ????@Override??
115. ????protected?void?onStop()??
116. ????{??
117. ????????Log.i(TAG,?"onStop?is?call?start.......");??
118. ????????/**?
119. ?????????*?挂起UI更新，线程或者处理?
120. ?????????*?当Activity不可见时，保存所有的编辑或者状态改变?
121. ?????????*?调用这个方法后，进程可能会被终止?
122. ?????????*/??
123. ????????super.onStop();??
124. ??????????
125. ????????Log.i(TAG,?"onStop?is?callv?end.......");??
126. ????}??
127. ??????
128. ????@Override??
129. ????protected?void?onDestroy()??
130. ????{??
131. ????????Log.i(TAG,?"onDestroy?is?call?start.......");??
132. ????????/**?
133. ?????????*?清理所有的资源，包括结束线程，关闭数据库连接等?
134. ?????????*/??
135. ????????super.onDestroy();??
136. ??????????
137. ????????Log.i(TAG,?"onDestroy?is?call?end.......");??
138. ????}??
139. ??????
140. ????@Override??
141. ????protected?void?onRestart()??
142. ????{??
143. ????????Log.i(TAG,?"onRestart?is?call?start.......");??
144. ????????super.onRestart();??
145. ????????/**?
146. ?????????*?加装载改变，知道Activity在此进程中已经可见?
147. ?????????*/??
148. ????????Log.i(TAG,?"onRestart?is?call?end.......");??
149. ????}??
150. }??

public class MainActivity extends Activity {

	private static String TAG = "chenjianjun";

	private static Button mybtnButton;

	@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;
	}

	/**
	 * 在完整生存期开始时调用
	 * @see android.app.Activity#onCreate(android.os.Bundle)
	 */
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		mybtnButton = (Button)findViewById(R.id.btn);
		mybtnButton.setOnClickListener(new View.OnClickListener() {

			@Override
			public void onClick(View v) {
				Intent bintent = new Intent(MainActivity.this, SecondActivity.class);
				startActivity(bintent);
			}
		});

		Log.i(TAG, "onCreate is call.......");
	}

	/**
	 * 在onCreate方法后调用，用于恢复UI状态
	 * @see android.app.Activity#onRestoreInstanceState(android.os.Bundle)
	 */
	@Override
	protected void onRestoreInstanceState(Bundle savedInstanceState)
	{
		Log.i(TAG, "onRestoreInstanceState is call start.......");
		super.onRestoreInstanceState(savedInstanceState);
		/**
		 * 从savedInstanceState恢复UI状态
		 * 这个savedInstanceState也被传递给了onCreate
		 * 自Activity上次可见之后，只有当系统终止了该Activity时，才会被调用
		 * 在随后的Activity进程的可见生存期之前被调用
		 */
		Log.i(TAG, "onRestoreInstanceState is call end.......");
	}

	/**
	 * 在可见生存期开始时调用
	 * @see android.app.Activity#onStart()
	 */
	@Override
	protected void onStart()
	{
		Log.i(TAG, "onStart is call start.......");
		super.onStart();
		/**
		 * 既然Activity可见，就应用任何要求的UI变化
		 */
		Log.i(TAG, "onStart is call end.......");
	}

	/**
	 * 在Activity活动状态生存期开始时调用
	 * @see android.app.Activity#onResume()
	 */
	@Override
	protected void onResume()
	{
		Log.i(TAG, "onResume is call start.......");
		super.onResume();
		/**
		 * 恢复Activity处于不活动状态时被挂起的，暂停的UI更新，线程，进程
		 */
		Log.i(TAG, "onResume is call end.......");
	}

	/*
	 * 把UI状态保存到outState中
	 * @see android.app.Activity#onSaveInstanceState(android.os.Bundle)
	 */
	@Override
	protected void onSaveInstanceState(Bundle savedInstanceState)
	{
		Log.i(TAG, "onSaveInstanceState is call start.......");
		/**
		 * 保存UI的状态
		 * 如果进程被运行时终止并重启，那么这个Bundle会被传递给onCreate和onRestoreInstanceState
		 */
		super.onSaveInstanceState(savedInstanceState);
		Log.i(TAG, "onSaveInstanceState is call end.......");
	}

	/**
	 * 在Activity活动状态生存期结束时被调用
	 */
	@Override
	protected void onPause()
	{
		Log.i(TAG, "onPause is call start.......");
		/**
		 * 挂起UI更新，线程或者CPU密集的进程
		 */
		super.onPause();
		Log.i(TAG, "onPause is call end.......");
	}

	@Override
	protected void onStop()
	{
		Log.i(TAG, "onStop is call start.......");
		/**
		 * 挂起UI更新，线程或者处理
		 * 当Activity不可见时，保存所有的编辑或者状态改变
		 * 调用这个方法后，进程可能会被终止
		 */
		super.onStop();

		Log.i(TAG, "onStop is callv end.......");
	}

	@Override
	protected void onDestroy()
	{
		Log.i(TAG, "onDestroy is call start.......");
		/**
		 * 清理所有的资源，包括结束线程，关闭数据库连接等
		 */
		super.onDestroy();

		Log.i(TAG, "onDestroy is call end.......");
	}

	@Override
	protected void onRestart()
	{
		Log.i(TAG, "onRestart is call start.......");
		super.onRestart();
		/**
		 * 加装载改变，知道Activity在此进程中已经可见
		 */
		Log.i(TAG, "onRestart is call end.......");
	}
}

?

[java] view plaincopyprint?

1. public?class?MyStateFragment?extends?Fragment?{??
2. ??
3. ????private?static?String?TAG?=?"chenjianjun";??
4. ????/**?
5. ?????*?调用该方法时，Fragment会被连接到它的父Activity上?
6. ?????*/??
7. ????@Override??
8. ????public?void?onAttach(Activity?activity)??
9. ????{??
10. ????????Log.i(TAG,?"-----onAttach?is?call?start.......");??
11. ????????super.onAttach(activity);??
12. ????????/**?
13. ?????????*?获取对父Activity的引用?
14. ?????????*/??
15. ????????Log.i(TAG,?"-----onAttach?is?call?end.......");??
16. ????}??
17. ??????
18. ????/**?
19. ?????*?调用该方法来进行Fragment的初始创建?
20. ?????*/??
21. ????@Override??
22. ????public?void?onCreate(Bundle?savedInstanceState)??
23. ????{??
24. ????????Log.i(TAG,?"-----onCreate?is?call?start.......");??
25. ????????super.onCreate(savedInstanceState);??
26. ????????/**?
27. ?????????*?初期化Fragment?
28. ?????????*/??
29. ????????Log.i(TAG,?"-----onCreate?is?call?end.......");??
30. ????}??
31. ??????
32. ????/**?
33. ?????*?一旦Fragment已被创建，要创建它自己的用户界面时调用该方法?
34. ?????*/??
35. ????@Override??
36. ????public?View?onCreateView(LayoutInflater?inflater,?ViewGroup?container,?Bundle?savedInstanceState)??
37. ????{??
38. ????????Log.i(TAG,?"-----onCreateView?is?call?start.......");??
39. ????????/**?
40. ?????????*?创建，或者填充Fragment的UI，并返回它?
41. ?????????*?如果这个Fragment没有UI，那么返回null?
42. ?????????*/??
43. ????????View?view?=?inflater.inflate(R.layout.my_state_fragment,?container,?false);??
44. ??????????
45. ????????Log.i(TAG,?"-----onCreateView?is?call?end.......");??
46. ????????return?view;??
47. ????}??
48. ??????
49. ????/**?
50. ?????*?一旦父Activity和Fragment的UI已经被创建，则调用该方法?
51. ?????*/??
52. ????@Override??
53. ????public?void?onActivityCreated(Bundle?savedInstanceState)??
54. ????{??
55. ????????Log.i(TAG,?"-----onActivityCreated?is?call?start.......");??
56. ????????super.onActivityCreated(savedInstanceState);??
57. ????????/**?
58. ?????????*?完成Fragment的初期化----那些父Activity和Fragment的View被完全填充后才能做的事情?
59. ?????????*/??
60. ????????Log.i(TAG,?"-----onActivityCreated?is?call?end.......");??
61. ????}??
62. ??????
63. ????/**?
64. ?????*?在可见生命周期的开始时被调用?
65. ?????*/??
66. ????@Override??
67. ????public?void?onStart()??
68. ????{??
69. ????????Log.i(TAG,?"-----onStart?is?call?start.......");??
70. ????????super.onStart();??
71. ????????/**?
72. ?????????*?应用所有需要的UI变化，现在Fragment是可见的?
73. ?????????*/??
74. ????????Log.i(TAG,?"-----onStart?is?call?end.......");??
75. ????}??
76. ??????
77. ????/**?
78. ?????*?在活动生命周期开始时被调用?
79. ?????*/??
80. ????@Override??
81. ????public?void?onResume()??
82. ????{??
83. ????????Log.i(TAG,?"-----onResume?is?call?start.......");??
84. ????????super.onResume();??
85. ????????/**?
86. ?????????*?恢复所有暂停的事物，如UI更新，线程或者进程等?
87. ?????????*/??
88. ????????Log.i(TAG,?"-----onResume?is?call?end.......");??
89. ????}??
90. ??????
91. ????/**?
92. ?????*?在活动生命周期结束时被调用?
93. ?????*/??
94. ????@Override??
95. ????public?void?onPause()??
96. ????{??
97. ????????Log.i(TAG,?"-----onPause?is?call?start.......");??
98. ????????/**?
99. ?????????*?需要暂停父Activity不是活动的前台Activity时，需要暂停的事物，如UI更新，线程或者进程等?
100. ?????????*/??
101. ????????super.onPause();??
102. ????????Log.i(TAG,?"-----onPause?is?call?end.......");??
103. ????}??
104. ??????
105. ????/**?
106. ?????*??在活动生命周期结束时被调用,保存UI的状态变化?
107. ?????*/??
108. ????@Override??
109. ????public?void?onSaveInstanceState(Bundle?savedInstanceState)??
110. ????{??
111. ????????Log.i(TAG,?"-----onSaveInstanceState?is?call?start.......");??
112. ????????/**?
113. ?????????*?将UI的变化信息保存到savedInstanceState中?
114. ?????????*?这个savedInstanceState会被传递到onCreate，onCreateView和onActivityCreated（如果它的父Activity被终止并且重新启动）方法中?
115. ?????????*/??
116. ????????super.onSaveInstanceState(savedInstanceState);??
117. ????????Log.i(TAG,?"-----onSaveInstanceState?is?call?end.......");??
118. ????}??
119. ??????
120. ????/**?
121. ?????*?在可见生命周期结束时调用该方法?
122. ?????*/??
123. ????@Override??
124. ????public?void?onStop()??
125. ????{??
126. ????????Log.i(TAG,?"-----onStop?is?call?start.......");??
127. ????????/**?
128. ?????????*?当Fragment不可见时，暂停其余的事物，如UI更新，线程或者进程等?
129. ?????????*/??
130. ????????super.onStop();??
131. ????????Log.i(TAG,?"-----onStop?is?call?end.......");??
132. ????}??
133. ??????
134. ????/**?
135. ?????*?当Fragment的view被分离时，调用该方法?
136. ?????*/??
137. ????@Override??
138. ????public?void?onDestroyView()??
139. ????{??
140. ????????Log.i(TAG,?"-----onDestroyView?is?call?start.......");??
141. ????????/**?
142. ?????????*?清除资源相关的view?
143. ?????????*/??
144. ????????super.onDestroyView();??
145. ????????Log.i(TAG,?"-----onDestroyView?is?call?end.......");??
146. ????}??
147. ??????
148. ????/**?
149. ?????*?在整个生命周期结束的时候调用?
150. ?????*/??
151. ????@Override??
152. ????public?void?onDestroy()??
153. ????{??
154. ????????Log.i(TAG,?"-----onDestroy?is?call?start.......");??
155. ????????/**?
156. ?????????*?清除所有的资源，包括线程和关闭数据库连接等?
157. ?????????*/??
158. ????????super.onDestroy();??
159. ????????Log.i(TAG,?"-----onDestroy?is?call?end.......");??
160. ????}??
161. ??????
162. ????/**?
163. ?????*?当Fragment从它的父Activity上分离时调用?
164. ?????*/??
165. ????@Override??
166. ????public?void?onDetach()??
167. ????{??
168. ????????Log.i(TAG,?"-----onDetach?is?call?start.......");??
169. ????????super.onDetach();??
170. ????????Log.i(TAG,?"-----onDetach?is?call?end.......");??
171. ????}??
172. }??

public class MyStateFragment extends Fragment {

	private static String TAG = "chenjianjun";
	/**
	 * 调用该方法时，Fragment会被连接到它的父Activity上
	 */
	@Override
	public void onAttach(Activity activity)
	{
		Log.i(TAG, "-----onAttach is call start.......");
		super.onAttach(activity);
		/**
		 * 获取对父Activity的引用
		 */
		Log.i(TAG, "-----onAttach is call end.......");
	}

	/**
	 * 调用该方法来进行Fragment的初始创建
	 */
	@Override
	public void onCreate(Bundle savedInstanceState)
	{
		Log.i(TAG, "-----onCreate is call start.......");
		super.onCreate(savedInstanceState);
		/**
		 * 初期化Fragment
		 */
		Log.i(TAG, "-----onCreate is call end.......");
	}

	/**
	 * 一旦Fragment已被创建，要创建它自己的用户界面时调用该方法
	 */
	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
	{
		Log.i(TAG, "-----onCreateView is call start.......");
		/**
		 * 创建，或者填充Fragment的UI，并返回它
		 * 如果这个Fragment没有UI，那么返回null
		 */
		View view = inflater.inflate(R.layout.my_state_fragment, container, false);

		Log.i(TAG, "-----onCreateView is call end.......");
		return view;
	}

	/**
	 * 一旦父Activity和Fragment的UI已经被创建，则调用该方法
	 */
	@Override
	public void onActivityCreated(Bundle savedInstanceState)
	{
		Log.i(TAG, "-----onActivityCreated is call start.......");
		super.onActivityCreated(savedInstanceState);
		/**
		 * 完成Fragment的初期化----那些父Activity和Fragment的View被完全填充后才能做的事情
		 */
		Log.i(TAG, "-----onActivityCreated is call end.......");
	}

	/**
	 * 在可见生命周期的开始时被调用
	 */
	@Override
	public void onStart()
	{
		Log.i(TAG, "-----onStart is call start.......");
		super.onStart();
		/**
		 * 应用所有需要的UI变化，现在Fragment是可见的
		 */
		Log.i(TAG, "-----onStart is call end.......");
	}

	/**
	 * 在活动生命周期开始时被调用
	 */
	@Override
	public void onResume()
	{
		Log.i(TAG, "-----onResume is call start.......");
		super.onResume();
		/**
		 * 恢复所有暂停的事物，如UI更新，线程或者进程等
		 */
		Log.i(TAG, "-----onResume is call end.......");
	}

	/**
	 * 在活动生命周期结束时被调用
	 */
	@Override
	public void onPause()
	{
		Log.i(TAG, "-----onPause is call start.......");
		/**
		 * 需要暂停父Activity不是活动的前台Activity时，需要暂停的事物，如UI更新，线程或者进程等
		 */
		super.onPause();
		Log.i(TAG, "-----onPause is call end.......");
	}

	/**
	 *  在活动生命周期结束时被调用,保存UI的状态变化
	 */
	@Override
	public void onSaveInstanceState(Bundle savedInstanceState)
	{
		Log.i(TAG, "-----onSaveInstanceState is call start.......");
		/**
		 * 将UI的变化信息保存到savedInstanceState中
		 * 这个savedInstanceState会被传递到onCreate，onCreateView和onActivityCreated（如果它的父Activity被终止并且重新启动）方法中
		 */
		super.onSaveInstanceState(savedInstanceState);
		Log.i(TAG, "-----onSaveInstanceState is call end.......");
	}

	/**
	 * 在可见生命周期结束时调用该方法
	 */
	@Override
	public void onStop()
	{
		Log.i(TAG, "-----onStop is call start.......");
		/**
		 * 当Fragment不可见时，暂停其余的事物，如UI更新，线程或者进程等
		 */
		super.onStop();
		Log.i(TAG, "-----onStop is call end.......");
	}

	/**
	 * 当Fragment的view被分离时，调用该方法
	 */
	@Override
	public void onDestroyView()
	{
		Log.i(TAG, "-----onDestroyView is call start.......");
		/**
		 * 清除资源相关的view
		 */
		super.onDestroyView();
		Log.i(TAG, "-----onDestroyView is call end.......");
	}

	/**
	 * 在整个生命周期结束的时候调用
	 */
	@Override
	public void onDestroy()
	{
		Log.i(TAG, "-----onDestroy is call start.......");
		/**
		 * 清除所有的资源，包括线程和关闭数据库连接等
		 */
		super.onDestroy();
		Log.i(TAG, "-----onDestroy is call end.......");
	}

	/**
	 * 当Fragment从它的父Activity上分离时调用
	 */
	@Override
	public void onDetach()
	{
		Log.i(TAG, "-----onDetach is call start.......");
		super.onDetach();
		Log.i(TAG, "-----onDetach is call end.......");
	}
}

activity_main.xml：

[html] view plaincopyprint?

1. <RelativeLayout?xmlns:android="http://schemas.android.com/apk/res/android"??
2. ????xmlns:tools="http://schemas.android.com/tools"??
3. ????android:layout_width="match_parent"??
4. ????android:layout_height="match_parent"??
5. ????android:paddingBottom="@dimen/activity_vertical_margin"??
6. ????android:paddingLeft="@dimen/activity_horizontal_margin"??
7. ????android:paddingRight="@dimen/activity_horizontal_margin"??
8. ????android:paddingTop="@dimen/activity_vertical_margin"??
9. ????tools:context=".MainActivity"?>??
10. ??
11. ????<fragment???
12. ????????android:name="com.xuexi.mystateactivity.fragment.MyStateFragment"??
13. ????????android:id="@+id/ToDoListFragment"??
14. ????????android:layout_width="match_parent"??
15. ????????android:layout_height="wrap_content"??
16. ????????android:visibility="gone"???
17. ????????/>??
18. ??????
19. ????<Button??
20. ????????android:id="@+id/btn"??
21. ????????android:layout_width="wrap_content"??
22. ????????android:layout_height="wrap_content"??
23. ????????android:layout_alignLeft="@+id/ToDoListFragment"??
24. ????????android:layout_below="@+id/ToDoListFragment"??
25. ????????android:layout_marginTop="44dp"??
26. ????????android:text="@string/btn_name"?/>??
27. ??
28. </RelativeLayout>??

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <fragment
        android:name="com.xuexi.mystateactivity.fragment.MyStateFragment"
        android:id="@+id/ToDoListFragment"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:visibility="gone"
        />

    <Button
        android:id="@+id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/ToDoListFragment"
        android:layout_below="@+id/ToDoListFragment"
        android:layout_marginTop="44dp"
        android:text="@string/btn_name" />

</RelativeLayout>

编译运行，启动程序打印日志如下：

切换到后台，日志如下：

从后台切换到前台，日志如下：

切换到其他的activity，日志如下：

从其他的activity切换回来，日志如下：

按home键退出，日志如下：

综上，大家对照代码查看日志的，我们展现了在每种情况下，Activity和Fragment的周期处于那种状态。理解好Activity和Fragment的生命周期，对于我们开发好一个app程序

有很大的帮助。

这里有个问题，跟文档上面有一点不相符的，就是Activity的onSaveInstanceState调用，在切换到后台和切换到其他Activity的时候有调用，但是都是在onPause和onStop之间，

书中的文字表述也是这样来说的，不知道为什么图是这样来画的！

Android之Activity，Fragment生命周期探知

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原文地址：http://www.cnblogs.com/seven1979/p/4345121.html