OSC首发：android中的左右滑屏实现By ViewPager

先看效果，就是左右滑屏的效果

具体实现详解

android compatibility package, revision 3在7月份发布后，其中有个ViewPager引起了我的注意

官方的描述：

 请参考：http://developer.android.com/sdk/compatibility-library.html#Notes

ViewPager的下载与安装

首先通过SDK Manager更新最新版android compatibility package, revision 3

更新后，在eclipse中工程上点击右键，选择android tools -> add compatibility library即可完成安装

实际上就是一个jar包，手工导到工程中也可

jar包所在位置是\android-sdk\extras\android\compatibility\v4\android-support-v4.jar

至此准备环境已经ok

下边还是通过代码进行说话吧

准备布局文件

viewpager_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" android:orientation="vertical">
<!-- 此处需要给出全路径 -->
<android.support.v4.view.ViewPager
    android:id="@+id/viewpagerLayout" android:layout_height="fill_parent" android:layout_width="fill_parent"/>
</LinearLayout>

layout1.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" android:orientation="vertical">
    <TextView android:textAppearance="?android:attr/textAppearanceLarge" android:layout_height="wrap_content" android:id="@+id/textView1" android:layout_width="fill_parent" android:text="第一页"></TextView>
    <EditText android:layout_width="match_parent" android:layout_height="wrap_content" android:id="@+id/editText1">
        <requestFocus></requestFocus>
    </EditText>
</LinearLayout>

layout2.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" android:orientation="vertical">
    <TextView android:textAppearance="?android:attr/textAppearanceLarge" android:layout_height="wrap_content" android:id="@+id/textView1" android:layout_width="fill_parent" android:text="第二页"></TextView>
    <EditText android:layout_width="match_parent" android:layout_height="wrap_content" android:id="@+id/editText1">
        <requestFocus></requestFocus>
    </EditText>
</LinearLayout>

layout3.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" android:orientation="vertical">
    <TextView android:textAppearance="?android:attr/textAppearanceLarge" android:layout_height="wrap_content" android:id="@+id/textView1" android:layout_width="fill_parent" android:text="第三页"></TextView>
    <EditText android:layout_width="match_parent" android:layout_height="wrap_content" android:id="@+id/editText1">
        <requestFocus></requestFocus>
    </EditText>
</LinearLayout>

主程序

package a.b;

import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.os.Bundle;
import android.os.Parcelable;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.EditText;

public class TestViewPager extends Activity {
	private ViewPager myViewPager;

	private MyPagerAdapter myAdapter;
	
	private LayoutInflater mInflater;
	private List<View> mListViews;
	private View layout1 = null;
	private View layout2 = null;
	private View layout3 = null;
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.viewpager_layout);
		myAdapter = new MyPagerAdapter();
		myViewPager = (ViewPager) findViewById(R.id.viewpagerLayout);
		myViewPager.setAdapter(myAdapter);
        
        mListViews = new ArrayList<View>();
        mInflater = getLayoutInflater();
        layout1 = mInflater.inflate(R.layout.layout1, null);
        layout2 = mInflater.inflate(R.layout.layout2, null);
        layout3 = mInflater.inflate(R.layout.layout3, null);
       
        mListViews.add(layout1);
        mListViews.add(layout2);
        mListViews.add(layout3);
        
        //初始化当前显示的view
        myViewPager.setCurrentItem(1);
        
        //初始化第二个view的信息
        EditText v2EditText = (EditText)layout2.findViewById(R.id.editText1);
        v2EditText.setText("动态设置第二个view的值");
        
        myViewPager.setOnPageChangeListener(new OnPageChangeListener() {
			
			@Override
			public void onPageSelected(int arg0) {
				Log.d("k", "onPageSelected - " + arg0);
				//activity从1到2滑动，2被加载后掉用此方法
				View v = mListViews.get(arg0);
				EditText editText = (EditText)v.findViewById(R.id.editText1);
				editText.setText("动态设置#"+arg0+"edittext控件的值");
			}
			
			@Override
			public void onPageScrolled(int arg0, float arg1, int arg2) {
				Log.d("k", "onPageScrolled - " + arg0);
				//从1到2滑动，在1滑动前调用
			}
			
			@Override
			public void onPageScrollStateChanged(int arg0) {
				Log.d("k", "onPageScrollStateChanged - " + arg0);
				//状态有三个0空闲，1是增在滑行中，2目标加载完毕
				/**
			     * Indicates that the pager is in an idle, settled state. The current page
			     * is fully in view and no animation is in progress.
			     */
			    //public static final int SCROLL_STATE_IDLE = 0;
			    /**
			     * Indicates that the pager is currently being dragged by the user.
			     */
			    //public static final int SCROLL_STATE_DRAGGING = 1;
			    /**
			     * Indicates that the pager is in the process of settling to a final position.
			     */
			    //public static final int SCROLL_STATE_SETTLING = 2;

			}
		});
        
	}
	
    private class MyPagerAdapter extends PagerAdapter{

		@Override
		public void destroyItem(View arg0, int arg1, Object arg2) {
			Log.d("k", "destroyItem");
			((ViewPager) arg0).removeView(mListViews.get(arg1));
		}

		@Override
		public void finishUpdate(View arg0) {
			Log.d("k", "finishUpdate");
		}

		@Override
		public int getCount() {
			Log.d("k", "getCount");
			return mListViews.size();
		}

		@Override
		public Object instantiateItem(View arg0, int arg1) {
			Log.d("k", "instantiateItem");
			((ViewPager) arg0).addView(mListViews.get(arg1),0);
			return mListViews.get(arg1);
		}

		@Override
		public boolean isViewFromObject(View arg0, Object arg1) {
			Log.d("k", "isViewFromObject");
			return arg0==(arg1);
		}

		@Override
		public void restoreState(Parcelable arg0, ClassLoader arg1) {
			Log.d("k", "restoreState");
		}

		@Override
		public Parcelable saveState() {
			Log.d("k", "saveState");
			return null;
		}

		@Override
		public void startUpdate(View arg0) {
			Log.d("k", "startUpdate");
		}
    	
    }
	
}

在实机上测试后，非常流畅，这也就是说官方版的左右滑屏控件已经实现

目前，关于viewpager的文章非常少，本文是通过阅读viewpager源代码分析出的写法

当然此文章仅是抛砖引玉，而且属于框架式程序，目的就是让读者了解API的基本用法

希望这篇原创文章对大家有帮助

欢迎感兴趣的朋友一起讨论

共同学习，共同进步

另外，ViewPager的注释上有这么一段话，大体意思是该控件目前属于早期实现，后续会有修改

/**
 * Layout manager that allows the user to flip left and right
 * through pages of data.  You supply an implementation of a
 * {@link PagerAdapter} to generate the pages that the view shows.
 *
 * <p>Note this class is currently under early design and
 * development.  The API will likely change in later updates of
 * the compatibility library, requiring changes to the source code
 * of apps when they are compiled against the newer version.</p>
 */