使用ViewPager实现欢迎页面左右拖动效果

今天用ViewPager 这个类实现欢迎页面左右拖动效果。ViewPager是实现左右两个屏幕平滑地切换的一个类，它是Google提供的。使用ViewPager首先需要引入android-support-v4.jar这个jar包。具体ViewPager的用法，这里不做介绍，自己从网上搜索吧！

下面先看一下效果：

首先是layout下面的main.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <android.support.v4.view.ViewPager
        android:id="@+id/viewPager"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical" >

        <LinearLayout
            android:id="@+id/viewGroup"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:layout_marginBottom="30dp"
            android:gravity="center_horizontal"
            android:orientation="horizontal" >
        </LinearLayout>
    </RelativeLayout>

</FrameLayout>

接下来为每一个切换界面设置布局item1.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" >

    <ImageView
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:background="@drawable/guide01" >
    </ImageView>

</LinearLayout>

其他的几个界面布局和这个一样 ，就是修改下背景图片，所以不再复述

import java.util.ArrayList;


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.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.view.Window;
import android.widget.ImageView;

public class MainActivity extends Activity {
    ViewPager viewPager;
    ArrayList<View> list;
    ViewGroup main, group;
    ImageView imageView;
    ImageView[] imageViews;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        this.requestWindowFeature(Window.FEATURE_NO_TITLE);
        LayoutInflater inflater = getLayoutInflater();
        list = new ArrayList<View>();
        list.add(inflater.inflate(R.layout.item1, null));
        list.add(inflater.inflate(R.layout.item2, null));
        list.add(inflater.inflate(R.layout.item3, null));
        list.add(inflater.inflate(R.layout.item4, null));
        list.add(inflater.inflate(R.layout.item5, null));

        imageViews = new ImageView[list.size()];
        ViewGroup main = (ViewGroup) inflater.inflate(R.layout.main, null);
        // group是R.layou.main中的负责包裹小圆点的LinearLayout.
        ViewGroup group = (ViewGroup) main.findViewById(R.id.viewGroup);

        viewPager = (ViewPager) main.findViewById(R.id.viewPager);

        for (int i = 0; i < list.size(); i++) {
            imageView = new ImageView(MainActivity.this);
            imageView.setLayoutParams(new LayoutParams(10,10));
            imageView.setPadding(10, 0, 10, 0);
            imageViews[i] = imageView;
            if (i == 0) {
                // 默认进入程序后第一张图片被选中;
                imageViews[i].setBackgroundResource(R.drawable.guide_dot_white);
            } else {
                imageViews[i].setBackgroundResource(R.drawable.guide_dot_black);
            }
            group.addView(imageView);
        }

        setContentView(main);

        viewPager.setAdapter(new MyAdapter());
        viewPager.setOnPageChangeListener(new MyListener());
    }

    class MyAdapter extends PagerAdapter {

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

        @Override
        public boolean isViewFromObject(View arg0, Object arg1) {
            return arg0 == arg1;
        }

        @Override
        public int getItemPosition(Object object) {
            // TODO Auto-generated method stub
            return super.getItemPosition(object);
        }

        @Override
        public void destroyItem(View arg0, int arg1, Object arg2) {
            // TODO Auto-generated method stub
            ((ViewPager) arg0).removeView(list.get(arg1));
        }

        @Override
        public Object instantiateItem(View arg0, int arg1) {
            // TODO Auto-generated method stub
            ((ViewPager) arg0).addView(list.get(arg1));
            return list.get(arg1);
        }

        @Override
        public void restoreState(Parcelable arg0, ClassLoader arg1) {
            // TODO Auto-generated method stub

        }

        @Override
        public Parcelable saveState() {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public void startUpdate(View arg0) {
            // TODO Auto-generated method stub

        }

        @Override
        public void finishUpdate(View arg0) {
            // TODO Auto-generated method stub

        }
    }

    class MyListener implements OnPageChangeListener {

        @Override
        public void onPageScrollStateChanged(int arg0) {
            // TODO Auto-generated method stub

        }

        @Override
        public void onPageScrolled(int arg0, float arg1, int arg2) {
            // TODO Auto-generated method stub

        }

        @Override
        public void onPageSelected(int arg0) {
            for (int i = 0; i < imageViews.length; i++) {
                imageViews[arg0]
                        .setBackgroundResource(R.drawable.guide_dot_white);
                if (arg0 != i) {
                    imageViews[i]
                            .setBackgroundResource(R.drawable.guide_dot_black);
                }
            }

        }

    }
}

好了，就这么简单，最后在提醒一句，不要忘记加入android-support-v4.jar这个jar包。