和谐共生（3）

今天实现了Android轮播图效果，将会把它插入到整体的项目中

实现效果是这样的

这个效果是根据网上资料来的，边学边做。

核心代码

package com.example.loopviewdemo;

import android.content.Context;

import android.support.v4.view.ViewPager;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.widget.ImageView;

import android.widget.LinearLayout;

import android.widget.TextView;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

    private ViewPager viewPager;  //轮播图模块

    private int[] mImg;

    private int[] mImg_id;

    private String[] mDec;

    private ArrayList<ImageView> mImgList;

    private LinearLayout ll_dots_container;

    private TextView loop_dec;

    private int previousSelectedPosition = 0;

    boolean isRunning = false;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        initLoopView();  //实现轮播图

    }

    private void initLoopView() {

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

        ll_dots_container = (LinearLayout)findViewById(R.id.ll_dots_loop);

        loop_dec = (TextView)findViewById(R.id.loop_dec);

        // 图片资源id数组

        mImg = new int[]{

                R.drawable.test3,

                R.drawable.test3,

                R.drawable.test3,

                R.drawable.test3,

                R.drawable.test3

        };

        // 文本描述

        mDec = new String[]{

                "Test1",

                "Test2",

                "Test3",

                "Test4",

                "Test5"

        };

        mImg_id = new int[]{

                R.id.pager_img1,

                R.id.pager_img2,

                R.id.pager_img3,

                R.id.pager_img4,

                R.id.pager_img5

        };

        // 初始化要展示的5个ImageView

        mImgList = new ArrayList<ImageView>();

        ImageView imageView;

        View dotView;

        LinearLayout.LayoutParams layoutParams;

        for(int i=0;i<mImg.length;i++){

            //初始化要显示的图片对象

            imageView = new ImageView(this);

            imageView.setBackgroundResource(mImg[i]);

            imageView.setId(mImg_id[i]);

            imageView.setOnClickListener(new pagerOnClickListener(getApplicationContext()));

            mImgList.add(imageView);

            //加引导点

            dotView = new View(this);

            dotView.setBackgroundResource(R.drawable.dot);

            layoutParams = new LinearLayout.LayoutParams(10,10);

            if(i!=0){

                layoutParams.leftMargin=10;

            }

            //设置默认所有都不可用

            dotView.setEnabled(false);

            ll_dots_container.addView(dotView,layoutParams);

        }

        ll_dots_container.getChildAt(0).setEnabled(true);

        loop_dec.setText(mDec[0]);

        previousSelectedPosition=0;

        //设置适配器

        viewPager.setAdapter(new LoopViewAdapter(mImgList));

        // 把ViewPager设置为默认选中Integer.MAX_VALUE / t2，从十几亿次开始轮播图片，达到无限循环目的;

        int m = (Integer.MAX_VALUE / 2) %mImgList.size();

        int currentPosition = Integer.MAX_VALUE / 2 - m;

        viewPager.setCurrentItem(currentPosition);

        viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {

            @Override

            public void onPageScrolled(int i, float v, int i1) {

            }

            @Override

            public void onPageSelected(int i) {

                int newPosition = i % mImgList.size();

                loop_dec.setText(mDec[newPosition]);

                ll_dots_container.getChildAt(previousSelectedPosition).setEnabled(false);

                ll_dots_container.getChildAt(newPosition).setEnabled(true);

                previousSelectedPosition = newPosition;

            }

            @Override

            public void onPageScrollStateChanged(int i) {

            }

        });

        // 开启轮询

        new Thread(){

            public void run(){

                isRunning = true;

                while(isRunning){

                    try{

                        Thread.sleep(5000);

                    } catch (InterruptedException e) {

                        e.printStackTrace();

                    }

                    //下一条

                    runOnUiThread(new Runnable() {

                        @Override

                        public void run() {

                            viewPager.setCurrentItem(viewPager.getCurrentItem()+1);

                        }

                    });

                }

            }

        }.start();

    }

}

import android.support.annotation.NonNull;import android.support.v4.view.PagerAdapter;import android.view.View;import android.view.ViewGroup;import android.widget.ImageView;

import java.util.ArrayList;

class LoopViewAdapter extends PagerAdapter{

    private ArrayList<ImageView> imageViewList;

    public LoopViewAdapter(ArrayList<ImageView> mImgList){

        imageViewList = mImgList;

    }

    // 1. 返回要显示的条目内容, 创建条目    @NonNull

    @Override

    public Object instantiateItem(@NonNull ViewGroup container, int position) {

        // container: 容器: ViewPager

        // position: 当前要显示条目的位置 0 -> 4

        //newPosition = position % 5

        int newPosition = position % imageViewList.size();

        ImageView img = imageViewList.get(newPosition);

        // a. 把View对象添加到container中        container.addView(img);

        // b. 把View对象返回给框架, 适配器

        return img;

    }

    @Override

    public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {

        container.removeView((View)object);

    }

    @Override

    public int getCount() {

        return Integer.MAX_VALUE;   //返回一个无限大的值，可以 无限循环!!!!!    }

    /**

     * 判断是否使用缓存, 如果返回的是true, 使用缓存. 不去调用instantiateItem方法创建一个新的对象

     */

    @Override

    public boolean isViewFromObject(@NonNull View view, @NonNull Object o) {

        return view == o ;

    }

}