Android中利用ViewPager实现视图切换

在为ViewFlipper视图切换增加动画和Android中实现视图随手势移动中实现了视图随手势切换，现在Android中Compatibility Package提供了ViewPager可以更简便的实现视图切换,实现的效果如下:

效果和ViewGroup一样,但是实现过程更简单.新版的Android Market和Google+都是用了ViewPager.

说一下实现过程:

工程目录如下:

MyPagerActivity的onCreate方法如下:

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
initPageContent();
awesomeAdapter = new MyPagerAdapter();
awesomePager = (ViewPager) findViewById(R.id.awesomepager);
awesomePager.setAdapter(awesomeAdapter);
}

其中main.xml布局文件引入了ViewPager:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#a4c639">
<android.support.v4.view.ViewPager
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/awesomepager"/>
</LinearLayout>

MyPagerAdapter继承了PagerAdapter:

private class MyPagerAdapter extends PagerAdapter{

@Override
public int getCount() {
return imageS.length;
}

/**
* Create the page for the given position. The adapter is responsible
* for adding the view to the container given here, although it only
* must ensure this is done by the time it returns from
* {@link #finishUpdate()}.
*
* @param container The containing View in which the page will be shown.
* @param position The page position to be instantiated.
* @return Returns an Object representing the new page. This does not
* need to be a View, but can be some other container of the page.
*/
@Override
public Object instantiateItem(View collection, int position) {

View view = getLayoutInflater().inflate(R.layout.page,null);
ImageView imageView =(ImageView) view.findViewById(R.id.imageId);
imageView.setImageDrawable(imageS[position]);
((ViewPager) collection).addView(view,0);
return view;
}

/**
* Remove a page for the given position. The adapter is responsible
* for removing the view from its container, although it only must ensure
* this is done by the time it returns from {@link #finishUpdate()}.
*
* @param container The containing View from which the page will be removed.
* @param position The page position to be removed.
* @param object The same object that was returned by
* {@link #instantiateItem(View, int)}.
*/
@Override
public void destroyItem(View collection, int position, Object view) {
((ViewPager) collection).removeView((View) view);
}

@Override
public boolean isViewFromObject(View view, Object object) {
return view==((View)object);
}

/**
* Called when the a change in the shown pages has been completed. At this
* point you must ensure that all of the pages have actually been added or
* removed from the container as appropriate.
* @param container The containing View which is displaying this adapter’s
* page views.
*/
@Override
public void finishUpdate(View arg0) {}

@Override
public void restoreState(Parcelable arg0, ClassLoader arg1) {}

@Override
public Parcelable saveState() {
return null;
}

@Override
public void startUpdate(View arg0) {}
}

其中红色代码部分负责加载Layout和想layout中填充View.这样就实现了视图的随手势切换.

源代码见:http://bigcateasymorse.googlecode.com/svn/trunk/android-viewpager0.1/

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