viewpage广告条的制作

 

package com.itheima27.viewpagerdemo;

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

import android.app.Activity;
import android.os.Bundle;
import android.os.SystemClock;
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.view.ViewGroup;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.LinearLayout.LayoutParams;
import android.widget.TextView;

public class MainActivity extends Activity implements OnPageChangeListener {

    private List<ImageView> imageViewList;
    private TextView tvDescription;
    private LinearLayout llPointGroup;
    private int previousEnabledPosition = 0;        // 前一个被选中的"点"的索引, 默认情况下: 0
    
    private String[] imageDescriptionArray = {
            "巩俐不低俗，我就不能低俗",
            "扑树又回来啦！再唱经典老歌引万人大合唱",
            "揭秘北京电影如何升级",
            "乐视网TV版大派送",
            "热血屌丝的反杀"
    };
    private ViewPager mViewPager;
    
    private boolean isStop = false;        // 是否停止子线程, 不会停止
    

    @Override
    protected void onDestroy() {
        isStop = true;
        super.onDestroy();
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        init();
        
        // 开启线程无限自动移动
        Thread mThread = new Thread(new Runnable() {
            @Override
            public void run() {
                while(!isStop) {
                    // 每隔2秒钟, 发送一条消息到主线程, 更新viewpager的界面
                    SystemClock.sleep(2000);
                    
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            // 此方法是在主线程中执行
                            mViewPager.setCurrentItem(mViewPager.getCurrentItem() + 1);
                        }
                    });
                }
            }
        });
        mThread.start();
    }

    private void init() {
        mViewPager = (ViewPager) findViewById(R.id.viewpager);
        llPointGroup = (LinearLayout) findViewById(R.id.ll_point_group);
        tvDescription = (TextView) findViewById(R.id.tv_image_description);
        
        imageViewList = new ArrayList<ImageView>();
        
        int[] imageResIDs = {
                R.drawable.a,
                R.drawable.b,
                R.drawable.c,
                R.drawable.d,
                R.drawable.e
        };
        
        ImageView iv;
        View view;
        LayoutParams params;
        for (int id : imageResIDs) {
            iv = new ImageView(this);
            iv.setBackgroundResource(id);
            imageViewList.add(iv);
            
            
            // 每循环一次, 添加一个点到Linearlayout中
            view = new View(this);
            view.setBackgroundResource(R.drawable.point_background);
            params = new LayoutParams(5, 5);
            params.leftMargin = 5;
            view.setEnabled(false);
            view.setLayoutParams(params);
            
            llPointGroup.addView(view);        // 向线性布局中添加"点"
        }
        
        mViewPager.setAdapter(new MyAdapter());
        mViewPager.setOnPageChangeListener(this);
        
        // 初始化图片描述, 和哪一个点被选中
//        tvDescription.setText(imageDescriptionArray[0]);
//        llPointGroup.getChildAt(0).setEnabled(true);
        
        
        // 初始化ViewPager的默认position为Integer.Max_value的一半
        int index = (Integer.MAX_VALUE / 2) - (Integer.MAX_VALUE / 2 % imageViewList.size());
        mViewPager.setCurrentItem(index);        // 设置当前viewpager选中的pager页, 会触发OnPageChangeListener.onPagerSelected
        
    }

    class MyAdapter extends PagerAdapter {

        @Override
        public int getCount() {
            return Integer.MAX_VALUE;
        }

        /**
         * 复用对象.
         * true 复用对象
         * false 用的是object
         */
        @Override
        public boolean isViewFromObject(View arg0, Object arg1) {
            return arg0 == arg1;
        }

        /**
         * 销毁对象
         * @param position 将要被销毁对象的索引位置
         */
        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            container.removeView(imageViewList.get(position % imageViewList.size()));
        }

        /**
         * 初始化一个view对象
         * @param position 将要被创建的对象的索引位置
         */
        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            // 先把对象添加到viewpager中, 再返回当前对象
            container.addView(imageViewList.get(position % imageViewList.size()));
            return imageViewList.get(position % imageViewList.size());
        }
    }

    @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 position) {
        
        // 取余后的索引
        int newPosition = position % imageViewList.size();
        
        // 根据索引设置图片的描述
        tvDescription.setText(imageDescriptionArray[newPosition]);
        
        // 把上一个点设置为未选中
        llPointGroup.getChildAt(previousEnabledPosition).setEnabled(false);
        
        // 根据索引设置哪一个点被选中
        llPointGroup.getChildAt(newPosition).setEnabled(true);
        
        previousEnabledPosition = newPosition;
    }
}