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 <?xmlversion="1.0"encoding="utf-8"?>
02 <Buttonxmlns: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 <?xmlversion="1.0"encoding="utf-8"?>
02 <RelativeLayoutxmlns: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 publicclassViewSwitcherExampleextendsListActivity
02 implementsOnClickListener {
03
04 //sample list items
05 staticfinalString[] ITEMS =newString[]
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 privateViewSwitcher switcher;
14
15 /** Called when the activity is first created. */
16 @Override
17 publicvoidonCreate(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 =newViewSwitcher(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(newArrayAdapter(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 protectedvoidonPostExecute(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 <?xmlversion="1.0"encoding="utf-8"?>
02 <ViewSwitcherxmlns: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

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