[转]高仿优酷Android客户端图片左右滑动（自动切换）

本例是用ViewPager去做的实现，支持自动滑动和手动滑动，不仅优酷网，实际上有很多商城和门户网站都有类似的实现:

具体思路如下：

1. 首先工程中需要添加android-support-v4.jar,才能使用ViewPager控件.

2. 图片的自动切换: 可使用Timer或者ScheduledExecutorService,这个有多重方式可以实现.

    同时要切换底部的dots（圆点）

3.Handler+Message机制更新UI,这个相信大家都很熟练，不再描述

4. 实现的一些细节:注意本例中的优化：图片的自动切换启动了其他的线程，要在Activity在可见到不可见的状态,也就是在onStop()方法中将线程停止，在onStart()方法中开启线程。否则，Timer没有停止，或者反复开启，会引起较大的内存消耗，时间一长就程序就会崩掉。 还有，就是在跳转到其他Activity的过程中会出现画面的卡顿。

下面看一下效果图和具体代码:

          

具体的布局文件及代码实现：

<?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:background="#FFFFFF"
    android:orientation="vertical" >

    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="40dip"
        android:background="@drawable/title_bk" >

        <ImageButton
            android:id="@+id/btn_back"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:background="@drawable/btn_back_selector"
            android:src="@drawable/btn_back" />

        <View
            android:id="@+id/line0"
            android:layout_width="1px"
            android:layout_height="fill_parent"
            android:layout_toRightOf="@id/btn_back"
            android:background="#aa11264f" />

        <View
            android:layout_width="1px"
            android:layout_height="fill_parent"
            android:layout_toRightOf="@id/line0"
            android:background="#009ad6" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerInParent="true"
            android:text="优酷客户端"
            android:textColor="#FFFFFF"
            android:textSize="20sp" />
    </RelativeLayout>

    <FrameLayout
        android:layout_width="fill_parent"
        android:layout_height="140dip" >

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

        <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="35dip"
            android:layout_gravity="bottom"
            android:background="#33000000"
            android:gravity="center"
            android:orientation="vertical" >

            <TextView
                android:id="@+id/tv_title"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="中国家庭院校园区域名字体现"
                android:textColor="#ffffff" />

            <LinearLayout
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginTop="3dip"
                android:gravity="center" >

                <View
                    android:id="@+id/v_dot0"
                    style="@style/dot_style"
                    android:background="@drawable/dot_focused" />

                <View
                    android:id="@+id/v_dot1"
                    style="@style/dot_style" />

                <View
                    android:id="@+id/v_dot2"
                    style="@style/dot_style" />

                <View
                    android:id="@+id/v_dot3"
                    style="@style/dot_style" />

                <View
                    android:id="@+id/v_dot4"
                    style="@style/dot_style" />
            </LinearLayout>
        </LinearLayout>
    </FrameLayout>

</LinearLayout>

MyViewPagerActivity:

package com.tony.viewpager;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;


import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
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.View;
import android.widget.ImageView;
import android.widget.ImageView.ScaleType;
import android.widget.TextView;

/**
 * 仿优酷Android客户端图片左右滑动
 * 
 */
public class MyViewPagerActivity extends Activity {
    private ViewPager viewPager; // android-support-v4中的滑动组件
    private List<ImageView> imageViews; // 滑动的图片集合

    private String[] titles; // 图片标题
    private int[] imageResId; // 图片ID
    private List<View> dots; // 图片标题正文的那些点

    private TextView tv_title;
    private int currentItem = 0; // 当前图片的索引号

    // An ExecutorService that can schedule commands to run after a given delay,
    // or to execute periodically.
    private ScheduledExecutorService scheduledExecutorService;

    // 切换当前显示的图片
    private Handler handler = new Handler() {
        public void handleMessage(android.os.Message msg) {
            viewPager.setCurrentItem(currentItem);// 切换当前显示的图片
        };
    };

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        imageResId = new int[] { R.drawable.a, R.drawable.b, R.drawable.c, R.drawable.d, R.drawable.e };
        titles = new String[imageResId.length];
        titles[0] = "巩俐不低俗，我就不能低俗";
        titles[1] = "扑树又回来啦！再唱经典老歌引万人大合唱";
        titles[2] = "揭秘北京电影如何升级";
        titles[3] = "乐视网TV版大派送";
        titles[4] = "热血屌丝的反杀";

        imageViews = new ArrayList<ImageView>();

        // 初始化图片资源
        for (int i = 0; i < imageResId.length; i++) {
            ImageView imageView = new ImageView(this);
            imageView.setImageResource(imageResId[i]);
            imageView.setScaleType(ScaleType.CENTER_CROP);
            imageViews.add(imageView);
        }

        
        dots = new ArrayList<View>();
        dots.add(findViewById(R.id.v_dot0));
        dots.add(findViewById(R.id.v_dot1));
        dots.add(findViewById(R.id.v_dot2));
        dots.add(findViewById(R.id.v_dot3));
        dots.add(findViewById(R.id.v_dot4));

        tv_title = (TextView) findViewById(R.id.tv_title);
        tv_title.setText(titles[0]);//

        viewPager = (ViewPager) findViewById(R.id.vp);
        viewPager.setAdapter(new MyAdapter());// 设置填充ViewPager页面的适配器
        // 设置一个监听器，当ViewPager中的页面改变时调用
        viewPager.setOnPageChangeListener(new MyPageChangeListener());

    }

    @Override
    protected void onStart() {
        scheduledExecutorService = Executors.newSingleThreadScheduledExecutor();
        // 当Activity显示出来后，每两秒钟切换一次图片显示
        scheduledExecutorService.scheduleAtFixedRate(new ScrollTask(), 1, 2, TimeUnit.SECONDS);
        super.onStart();
    }

    @Override
    protected void onStop() {
        // 当Activity不可见的时候停止切换
        scheduledExecutorService.shutdown();
        super.onStop();
    }

    /**
     * 换行切换任务
     * 
     * @author Administrator
     * 
     */
    private class ScrollTask implements Runnable {

        public void run() {
            synchronized (viewPager) {
                System.out.println("currentItem: " + currentItem);
                currentItem = (currentItem + 1) % imageViews.size();
                handler.obtainMessage().sendToTarget(); // 通过Handler切换图片
            }
        }

    }

    /**
     * 当ViewPager中页面的状态发生改变时调用
     * 
     * @author Administrator
     * 
     */
    private class MyPageChangeListener implements OnPageChangeListener {
        private int oldPosition = 0;

        /**
         * This method will be invoked when a new page becomes selected.
         * position: Position index of the new selected page.
         */
        public void onPageSelected(int position) {
            currentItem = position;
            tv_title.setText(titles[position]);
            dots.get(oldPosition).setBackgroundResource(R.drawable.dot_normal);
            dots.get(position).setBackgroundResource(R.drawable.dot_focused);
            oldPosition = position;
        }

        public void onPageScrollStateChanged(int arg0) {

        }

        public void onPageScrolled(int arg0, float arg1, int arg2) {

        }
    }

    /**
     * 填充ViewPager页面的适配器
     * 
     * @author Administrator
     * 
     */
    private class MyAdapter extends PagerAdapter {

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

        @Override
        public Object instantiateItem(View arg0, int arg1) {
            ((ViewPager) arg0).addView(imageViews.get(arg1));
            return imageViews.get(arg1);
        }

        @Override
        public void destroyItem(View arg0, int arg1, Object arg2) {
            ((ViewPager) arg0).removeView((View) arg2);
        }

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

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

        }

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

        @Override
        public void startUpdate(View arg0) {

        }

        @Override
        public void finishUpdate(View arg0) {

        }
    }
}

Drawable目录下
btn_back_selector.xml:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:drawable="@drawable/btn_top_pressed" android:state_focused="true"></item>
    <item android:drawable="@drawable/btn_top_pressed" android:state_pressed="true"></item>
    <item android:drawable="@drawable/btn_top_pressed" android:state_selected="true"></item>
    <item android:drawable="@drawable/title_bk"></item>

</selector>

btn_top_pressed.xml:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle" >

    <gradient
        android:angle="270"
        android:endColor="#009ad6"
        android:startColor="#11264f" />

</shape>

dot_focused.xml:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="oval" >

    <solid android:color="#aaFFFFFF" />

    <corners android:radius="5dip" />

</shape>

dot_normal.xml:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="oval" >

    <solid android:color="#33000000" />

    <corners android:radius="5dip" />

</shape>

title_bk.xml:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle" >

    <gradient
        android:angle="270"
        android:endColor="#11264f"
        android:startColor="#009ad6" />

</shape>

不过，发现有一个问题，@style/dot_style找不到，不知道是什么样式，于是改了改。修改如下：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <FrameLayout
        android:layout_width="fill_parent"  
        android:layout_height="140dp" >  
  
        <android.support.v4.view.ViewPager  
            android:id="@+id/vp"  
            android:layout_width="fill_parent"  
            android:layout_height="fill_parent" />  
  
            <LinearLayout  
                android:layout_width="match_parent"  
                android:layout_height="20dp"  
                android:layout_gravity="bottom"
                android:layout_marginBottom="5dp"
                android:gravity="center"
                android:orientation="horizontal">  
  
                <View  
                    android:id="@+id/v_dot0" 
                    android:layout_width="18dp"
                    android:layout_height="18dp"
                    android:background="@drawable/dot_focused" />  
  
                <View  
                    android:id="@+id/v_dot1" 
                    android:layout_width="18dp"
                    android:layout_height="18dp"
                    android:background="@drawable/dot_unfocused" />  
                    
                <View  
                    android:id="@+id/v_dot2"  
                    android:layout_width="18dp"
                    android:layout_height="18dp"
                    android:background="@drawable/dot_unfocused" />  
  
                <View  
                    android:id="@+id/v_dot3"  
                    android:layout_width="18dp"
                    android:layout_height="18dp"
                    android:background="@drawable/dot_unfocused" />  
                     
            </LinearLayout>  
    </FrameLayout>  

</LinearLayout>

如有不足之处，请多多指正！