ViewPager-实现左右两个屏幕的切换

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     什么是ViewPager呢?
它是实现左右两个屏幕平滑地切换的一个类,它是Google提供的。
具体使用方法在<SDK_DOC_PATH>/sdk/compatibility-library.html(SDK_DOC_PATH是自带Android文档的位置,需要更新到最新的文档才有)。
    ViewPager提供了一个适配器,方便我们对各个View进行控制,下面介绍如何使用:
1、下载来Android SDK & AVD manager的更新:Available Packages -> Android Repository -> Android Compatibility Package, revision 3. 它将安装\extras\android\compatibility\v4文件下
2、建立一个Android项目,在上述安装目录下把 android-support-v4.jar添加进项目,如果是最新的ADT,只需要右击project->Android Tools->Add Compatibility Library
3、在Activity中使用ViewPager

4、如果ViewPager是用xml去定义的,需要写上全局的路径,如:

<android.support.v4.view.ViewPager
android:layout_width="match_parent" 
android:layout_height="match_parent" 
android:id="@+id/awesomepager"/>

5、建立一个PagerAdapter,实现如下方法:
getCount(), instantiateItem(), destroyItem(), isViewFromObject() 。

public class AwesomePagerActivity extends Activity {
    
	private ViewPager awesomePager;

	private Context cxt;
	private AwesomePagerAdapter awesomeAdapter;
	
	private LayoutInflater mInflater;
	private List<View> mListViews;
	
	/** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        cxt = this;
        
        awesomeAdapter = new AwesomePagerAdapter();
        awesomePager = (ViewPager) findViewById(R.id.awesomepager);
        awesomePager.setAdapter(awesomeAdapter);
        
        mListViews = new ArrayList<View>();
        mInflater = getLayoutInflater();
        mListViews.add(mInflater.inflate(R.layout.layout1, null));
        mListViews.add(mInflater.inflate(R.layout.layout2, null));
        mListViews.add(mInflater.inflate(R.layout.layout3, null));
        
    }
    
    private class AwesomePagerAdapter extends PagerAdapter{

		
		@Override
		public int getCount() {
			return mListViews.size();
		}

	    /**
	     * 从指定的position创建page
	     *
	     * @param container ViewPager容器
	     * @param position The page position to be instantiated.
	     * @return 返回指定position的page,这里不需要是一个view,也可以是其他的视图容器.
	     */
		@Override
		public Object instantiateItem(View collection, int position) {

			
			((ViewPager) collection).addView(mListViews.get(position),0);
			
			return mListViews.get(position);
		}

	    /**
	     * <span style="font-family:'Droid Sans';">从指定的position销毁page</span>
	     * 
	     * 
	     *<span style="font-family:'Droid Sans';">参数同上</span>
	     */
		@Override
		public void destroyItem(View collection, int position, Object view) {
			((ViewPager) collection).removeView(mListViews.get(position));
		}

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

		@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) {}
    	
    }
    
    
}

就这样,我们可以很容易就实现左右两个屏幕之间的切换。具体页面到内容就靠大家去发挥了!

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