团队项目——和谐共生（2）

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 ;
    }
}