viewpager的轮播图

package com.example.news.viewpagerdeamo;

import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

    private ViewPager viewPager;
    private LinearLayout point_group;
    private TextView image_desc;
    // 图片资源id
    private final int[] images = {R.drawable.a, R.drawable.b, R.drawable.c,
            R.drawable.d, R.drawable.e};
    // 图片标题集合
    private final String[] imageDescriptions = {"第一张图片",
            "第二张图片", "第三张图片", "第四张图片", "第五张图片"};

    private ArrayList<ImageView> imageList;
    // 上一个页面的位置
    protected int lastPosition = 0;

    // 判断是否自动滚动viewPager
    private boolean isRunning = true;
    private Handler handler = new Handler() {
        public void handleMessage(android.os.Message msg) {
            // 执行滑动到下一个页面
            viewPager.setCurrentItem(viewPager.getCurrentItem() + 1);
            if (isRunning) {
                // 在发一个handler延时
                handler.sendEmptyMessageDelayed(0, 5000);
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        viewPager = (ViewPager) findViewById(R.id.viewPager);
        point_group = (LinearLayout) findViewById(R.id.point_group);
        image_desc = (TextView) findViewById(R.id.image_desc);
        image_desc.setText(imageDescriptions[0]);

        // 初始化图片资源
        imageList = new ArrayList<ImageView>();
        for (int i : images) {
            // 初始化图片资源
            ImageView imageView = new ImageView(this);
            imageView.setBackgroundResource(i);
            imageList.add(imageView);

            // 添加指示小点
            ImageView point = new ImageView(this);
            LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(100,
                    15);
            params.rightMargin = 20;
            params.bottomMargin = 10;
            point.setLayoutParams(params);
            point.setBackgroundResource(R.drawable.point_bg);
            if (i == R.drawable.a) {
                //默认聚焦在第一张
                point.setBackgroundResource(R.drawable.point_bg_focus);
                point.setEnabled(true);
            } else {
                point.setEnabled(false);
            }

            point_group.addView(point);
        }

        viewPager.setAdapter(new MyPageAdapter());
        // 设置当前viewPager的位置
        viewPager.setCurrentItem(Integer.MAX_VALUE / 2
                - (Integer.MAX_VALUE / 2 % imageList.size()));
        viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {

            @Override
            public void onPageSelected(int position) {
                // 页面切换后调用， position是新的页面位置

                // 实现无限制循环播放
                position %= imageList.size();

                image_desc.setText(imageDescriptions[position]);

                // 把当前点设置为true,将上一个点设为false；并设置point_group图标
                point_group.getChildAt(position).setEnabled(true);
                point_group.getChildAt(position).setBackgroundResource(R.drawable.point_bg_focus);//设置聚焦时的图标样式
                point_group.getChildAt(lastPosition).setEnabled(false);
                point_group.getChildAt(lastPosition).setBackgroundResource(R.drawable.point_bg);//上一张恢复原有图标
                lastPosition = position;

            }

            @Override
            public void onPageScrolled(int position, float positionOffset,
                                       int positionOffsetPixels) {
                // 页面正在滑动时间回调

            }

            @Override
            public void onPageScrollStateChanged(int state) {
                // 当pageView 状态发生改变的时候，回调

            }
        });

        /**
         * 自动循环： 1.定时器：Timer 2.开子线程：while true循环 3.ClockManger
         * 4.用Handler发送延时信息，实现循环，最简单最方便
         *
         */

        handler.sendEmptyMessageDelayed(0, 3000);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        menu.add(0, 0, 0, "分享");
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        /*int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }*/

        switch (item.getItemId()) {
            case 0:
                Intent intent = new Intent(Intent.ACTION_SEND);
                intent.setType("text/plain");
                intent.putExtra(Intent.EXTRA_SUBJECT, "分享");
                intent.putExtra(Intent.EXTRA_TEXT, "I would like to share this with you...");
                startActivity(Intent.createChooser(intent, getTitle()));
                return true;
        }

//        return super.onOptionsItemSelected(item);
        return false;
    }

    @Override
    protected void onDestroy() {
// 停止滚动
        isRunning = false;
        super.onDestroy();
    }

    private class MyPageAdapter extends PagerAdapter {
        // 需要实现以下四个方法

        @Override
        public int getCount() {
            // 获得页面的总数
            return Integer.MAX_VALUE;
        }

        @Override
        public boolean isViewFromObject(View view, Object object) {
            // 判断view和Object对应是否有关联关系
            if (view == object) {
                return true;
            } else {
                return false;
            }
        }

        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            // 获得相应位置上的view； container view的容器，其实就是viewpage自身,
            // position: viewpager上的位置
            // 给container添加内容
            container.addView(imageList.get(position % imageList.size()));

            return imageList.get(position % imageList.size());
        }

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            // 销毁对应位置上的Object
            // super.destroyItem(container, position, object);
            container.removeView((View) object);
            object = null;
        }

    }
}