Dialog式的Activity(AndroidActivity生命週期)

概述

　　和普通的Activity跳轉稍微不一樣的是,當第1個Activity跳轉到第二個Activity後,若是點擊'back'按鈕(即Android鍵盤的按鈕,則不會調用調用第一個Activity的onStop方法,由於彈出對話框的時候,第1個Activity對用戶仍然是Visible(可見的).

　　以下,定義了兩個繼承Activity的java類:

 1 package com.example.activitydialog;
 2 
 3 import android.app.Activity;
 4 import android.content.Intent;
 5 import android.os.Bundle;
 6 import android.view.Menu;
 7 import android.view.View;
 8 import android.view.View.OnClickListener;
 9 import android.widget.Button;
10 
11 public class MainActivity extends Activity {
12 
13     private Button btn = null;
14     
15     @Override
16     protected void onCreate(Bundle savedInstanceState) {
17 System.out.println("MainActivity onCreate");
18         // TODO Auto-generated method stub
19         super.onCreate(savedInstanceState);
20         setContentView(R.layout.activity_main);
21         
22         btn = (Button)findViewById(R.id.btnMain);
23         //pop a dialog activity.
24         btn.setOnClickListener(new OnClickListener() {
25             
26             @Override
27             public void onClick(View v) {
28                 Intent intent = new Intent(MainActivity.this, DialogActivity.class);
29                 startActivity(intent);
30             }
31         });
32     }
33 
34     @Override
35     protected void onDestroy() {
36 System.out.println("MainActivity onDestroy");        
37         // TODO Auto-generated method stub
38         super.onDestroy();
39     }
40 
41     @Override
42     protected void onPause() {
43         System.out.println("MainActivity onPause");        
44         // TODO Auto-generated method stub
45         super.onPause();
46     }
47 
48     @Override
49     protected void onRestart() {
50         System.out.println("MainActivity onRestart");
51         // TODO Auto-generated method stub
52         super.onRestart();
53     }
54 
55     @Override
56     protected void onResume() {
57         System.out.println("MainActivity onResume");
58         // TODO Auto-generated method stub
59         super.onResume();
60     }
61 
62     @Override
63     protected void onStart() {
64         System.out.println("MainActivity onStart");
65         // TODO Auto-generated method stub
66         super.onStart();
67     }
68 
69     @Override
70     protected void onStop() {
71         System.out.println("MainActivity onStop");
72         // TODO Auto-generated method stub
73         super.onStop();
74     }
75 
76 
77     @Override
78     public boolean onCreateOptionsMenu(Menu menu) {
79         // Inflate the menu; this adds items to the action bar if it is present.
80         getMenuInflater().inflate(R.menu.main, menu);
81         return true;
82     }
83 
84 }

View Code

和

 1 package com.example.activitydialog;
 2 
 3 import android.app.Activity;
 4 import android.content.Intent;
 5 import android.os.Bundle;
 6 import android.view.View;
 7 import android.view.View.OnClickListener;
 8 import android.widget.Button;
 9 
10 public class DialogActivity extends Activity {
11 
12     private Button btn = null;
13 
14     @Override
15     protected void onCreate(Bundle savedInstanceState) {
16         System.out.println("DialogActivity onCreate");
17         // TODO Auto-generated method stub
18         super.onCreate(savedInstanceState);
19         setContentView(R.layout.activity_dialog);
20 
21         btn = (Button) findViewById(R.id.btnDialog);
22         //go to the previous activity when click on the button.
23         btn.setOnClickListener(new OnClickListener() {
24 
25             @Override
26             public void onClick(View v) {
27                 Intent intent = new Intent(DialogActivity.this, MainActivity.class);
28                 startActivity(intent);
29             }
30         });
31     }
32 
33     @Override
34     protected void onDestroy() {
35         System.out.println("DialogActivity onDestroy");
36         // TODO Auto-generated method stub
37         super.onDestroy();
38     }
39 
40     @Override
41     protected void onPause() {
42         System.out.println("DialogActivity onPause");
43         // TODO Auto-generated method stub
44         super.onPause();
45     }
46 
47     @Override
48     protected void onRestart() {
49         System.out.println("DialogActivity onRestart");
50         // TODO Auto-generated method stub
51         super.onRestart();
52     }
53 
54     @Override
55     protected void onResume() {
56         System.out.println("DialogActivity onResume");
57         // TODO Auto-generated method stub
58         super.onResume();
59     }
60 
61     @Override
62     protected void onStart() {
63         System.out.println("DialogActivity onStart");
64         // TODO Auto-generated method stub
65         super.onStart();
66     }
67 
68     @Override
69     protected void onStop() {
70         System.out.println("DialogActivity onStop");
71         // TODO Auto-generated method stub
72         super.onStop();
73     }
74 
75 }

View Code

　　並在layout中分別定義兩個不一樣的佈局xml文件:

(MainActivity對應的佈局)

 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     <Button
12         android:id="@+id/btnMain"
13         android:layout_width="wrap_content"
14         android:layout_height="wrap_content"
15         android:text="@string/second_activity" />
16 
17 </RelativeLayout>

View Code

和

(DialogActivity對應的佈局)

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     android:layout_width="match_parent"
 4     android:layout_height="match_parent"
 5     android:orientation="vertical" 
 6     >
 7     <Button 
 8         android:id="@+id/btnDialog"
 9         android:layout_width="fill_parent"
10         android:layout_height="fill_parent"
11         android:text="@string/second_activity"
12         />
13 </LinearLayout>

View Code

　　固然,若是使用第二個Activity的按鈕返回(而不是經過鍵盤的'返回'的話,仍是會調用第一個Activity的onStop方法).

　　這也充分說明了,官網對'Activity生命週期的這3段話):

There are three key loops you may be interested in monitoring within your activity:　　

• The entire lifetime of an activity happens between the first call to onCreate(Bundle) through to a single final call to onDestroy(). An activity will do all setup of "global" state in onCreate(), and release all remaining resources in onDestroy(). For example, if it has a thread running in the background to download data from the network, it may create that thread in onCreate() and then stop the thread in onDestroy().
• The visible lifetime of an activity happens between a call to onStart() until a corresponding call to onStop(). During this time the user can see the activity on-screen, though it may not be in the foreground and interacting with the user. Between these two methods you can maintain resources that are needed to show the activity to the user. For example, you can register a BroadcastReceiver in onStart() to monitor for changes that impact your UI, and unregister it in onStop() when the user no longer sees what you are displaying. The onStart() and onStop() methods can be called multiple times, as the activity becomes visible and hidden to the user.
• The foreground lifetime of an activity happens between a call to onResume() until a corresponding call to onPause(). During this time the activity is in front of all other activities and interacting with the user. An activity can frequently go between the resumed and paused states -- for example when the device goes to sleep, when an activity result is delivered, when a new intent is delivered -- so the code in these methods should be fairly lightweight.