android ViewSwitcher详解

ViewSwitcher 的作用简单来说就是：在两个视图间转换时显示动画

它的两个子类应该很熟悉，ImageSwitcher：转换图片时增加动画效果; TextSwitcher： 转换文字时增加动画效果; 其实例见apidemos中ImageSwitcher实例和TextSwitcher实例

但不要忽略ViewSwicher,在一些场合还是很有用的

在android里视图切换是一个很常见的需求，比如说加载view和后台背景，当后台加载数据时，loding view显示，数据View隐藏，加载完成，反向此过程。使用ViewSwicher提供了简单的逻辑，产生更可读的代码。

举个最常见的例子，列表底部加载

Button more

01 <?xml version="1.0" encoding="utf-8"?>
02 <Button xmlns:android="http://schemas.android.com/apk/res/android"
03     android:id="@+id/btn_loadmorecontacts"
04     android:text="Load More Items"
05     android:layout_width="fill_parent"
06     android:layout_height="wrap_content"
07     android:textAppearance="?android:attr/textAppearanceLarge"
08     android:minHeight="?android:attr/listPreferredItemHeight"
09     android:textColor="#FFFFFF"
10     android:background="<a href="http://my.oschina.net/asia" rel="nofollow"target="_blank">@android</a> :drawable/list_selector_background"
11     android:clickable="true"
12     android:onClick="onClick" />

大致是这样子

 

加载中视图：

01 <?xml version="1.0" encoding="utf-8"?>
02 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
03     android:layout_width="wrap_content"
04     android:layout_height="wrap_content"
05     android:gravity="center_horizontal"
06     android:minHeight="?android:attr/listPreferredItemHeight">
07
08     <ProgressBar
09         android:id="@+id/progressbar"
10         android:layout_width="wrap_content"
11         android:layout_height="wrap_content"
12         android:layout_centerVertical="true" />
13
14     <TextView
15         android:text="Loading…"
16         android:textAppearance="?android:attr/textAppearanceLarge"
17         android:layout_height="wrap_content"
18         android:layout_width="wrap_content"
19         android:layout_toRightOf="@+id/progressbar"
20         android:layout_centerVertical="true"
21         android:gravity="center"
22         android:padding="10dip"
23         android:textColor="#FFFFFF" />
24 </RelativeLayout>

 

01 public class ViewSwitcherExample extends ListActivity
02                  implements OnClickListener {
03
04     //sample list items
05     static final String[] ITEMS = new String[]
06           { "List Item 1", "List Item 2",
07             "List Item 3", "List Item 4",
08             "List Item 5", "List Item 6",
09             "List Item 7", "List Item 8",
10             "List Item 9", "List Item 10" };
11
12     //the ViewSwitcher
13     private ViewSwitcher switcher;
14
15     /** Called when the activity is first created. */
16     @Override
17     public void onCreate(Bundle savedInstanceState) {
18       super.onCreate(savedInstanceState);
19
20       //no window title
21       requestWindowFeature(Window.FEATURE_NO_TITLE);
22
23       //create the ViewSwitcher in the current context
24       switcher = new ViewSwitcher(this);
25
26       //底部 Button: see XML1
27       Button footer = (Button)View.inflate(this, R.layout.btn_loadmore, null);
28
29       //进度条View: see XML2
30       View progress = View.inflate(this, R.layout.loading_footer, null);
31
32       //向viewSwitcher加入view (first added will show first)
33       switcher.addView(footer);
34       switcher.addView(progress);
35
36       //listview底部加入swicher
37       getListView().addFooterView(switcher);
38
39       //add items to the ListView
40       setListAdapter(new ArrayAdapter(this,
41               android.R.layout.simple_list_item_1, ITEMS));
42     }
43
44     @Override /* Load More Button Was Clicked */
45     public void onClick(View arg0) {
46         //first view is showing, show the second progress view
47         switcher.showNext();
48         //and start background work
49         new getMoreItems().execute();
50     }
51
52     /** Background Task To Get More Items**/
53     private class getMoreItems extends AsyncTask {
54         @Override
55         protected Object doInBackground(Void… params) {
56             //code to add more items
57             //...
58             try {
59                 Thread.sleep(3000); //only to demonstrate
60             } catch (InterruptedException e) {
61                 e.printStackTrace();
62             }
63             return null;
64         }
65
66         @Override /* Background Task is Done */
67         protected void onPostExecute(Object result) {
68             //go back to the first view
69             switcher.showPrevious();
70                         //update the ListView
71         }
72     }
73 }

 

1 switcher.showNext();  // Switches to the next view
2 switcher.showPrevious();  // Switches to the previous view

当然你也可以使用xml形式构造ViewSwicher,这里加上了系统自带的切换效果@android:anim/slide_in_left和@android:anim/slide_out_right

 

01 <?xml version="1.0" encoding="utf-8"?>
02 <ViewSwitcher xmlns:android="http://schemas.android.com/apk/res/android"
03     android:id="@+id/profileSwitcher"
04     android:layout_width="fill_parent"
05     android:layout_height="fill_parent"
06     android:inAnimation="@android:anim/slide_in_left"
07     android:outAnimation="@android:anim/slide_out_right">
08 <RelativeLayout
09     android:layout_width="wrap_content"
10     android:layout_height="wrap_content">
11     <ProgressBar
12         android:id="@+id/progressbar"
13         android:layout_width="wrap_content"
14         android:layout_height="wrap_content"
15         android:layout_centerVertical="true" />
16     <TextView
17         android:text="Loading…"
18         android:layout_height="wrap_content"
19         android:layout_width="wrap_content"
20         android:layout_toRightOf="@+id/progressbar"
21         android:gravity="center"/>
22 </RelativeLayout>
23
24 <RelativeLayout
25     android:layout_width="wrap_content"
26     android:layout_height="wrap_content"
27     android:gravity="center_horizontal" >
28     <TextView
29         android:text="Finished!"
30         android:layout_height="wrap_content"
31         android:layout_width="wrap_content"
32         android:layout_centerVertical="true" />
33 </RelativeLayout>
34
35 </ViewSwitcher>

 你喜欢的话可以加入动画效果，使用View gone、Visible方式还是ViewSwicher还是看自己喜好了