ViewPager 自动切换

最新推荐文章于 2023-11-25 19:55:33 发布

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本文介绍了一个使用Android支持库实现的无限循环ViewPager示例。通过自定义PagerAdapter并利用Handler发送消息更新ViewPager当前页，实现了轮播广告的自动切换效果。

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package com.test.viewpagerdemo;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.Toast;

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

/**
 * ViewPager �无限循环自动切换
 */
public class MainActivity extends AppCompatActivity {

    private ViewPager viewPager;
    private List<ImageView> list;
    private int[] imageIds;
    private int num = 300;
    private ImageView imageView1, imageView2, imageView3;


    private final Handler viewHandler = new Handler() {

        @Override
        public void handleMessage(Message msg) {
            viewPager.setCurrentItem(msg.what);
            super.handleMessage(msg);
        }

    };

    private Handler mHandler = new Handler();
    private Runnable mRunnable = new Runnable() {
        @Override
        public void run() {
            mHandler.postDelayed(mRunnable, 1000 * 5);
            num++;
            viewHandler.sendEmptyMessage(num);

        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        requestWindowFeature(Window.FEATURE_NO_TITLE); //去掉标题

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        imageView1 = (ImageView) findViewById(R.id.ad1);
        imageView2 = (ImageView) findViewById(R.id.ad2);
        imageView3 = (ImageView) findViewById(R.id.ad3);

        list = new ArrayList<ImageView>();
        imageIds = new int[]{R.mipmap.shuangta, R.mipmap.shui, R.mipmap.xiangbi};

        LinearLayout linearLayout = (LinearLayout) findViewById(R.id.viewGroup);

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

        for (int i = 0; i < imageIds.length; i++) {
            ImageView imageView = new ImageView(this);
            imageView.setImageResource(imageIds[i]);

            list.add(imageView);
        }
        viewPager.setAdapter(new MyAdapter());
        viewPager.setOnPageChangeListener(new MyListener());
        viewPager.setCurrentItem(num);

        mHandler.postDelayed(mRunnable, 5000);
    }

    private class MyAdapter extends PagerAdapter {
        @Override
        public int getCount() {
            return Integer.MAX_VALUE;
        }

        @Override
        public boolean isViewFromObject(View view, Object object) {
            return view == object;
        }

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            // super.destroyItem(container, position, object);
        }

        @Override
        public int getItemPosition(Object object) {
            return super.getItemPosition(object);
        }

        @Override
        public Object instantiateItem(View container, int position) {
            try {
                // ((ViewPager) arg0).addView(list.get(arg1),0);
                ((ViewPager) container).addView((View) list.get(position % list.size()),
                        0);
            } catch (Exception e) {
                // TODO: handle exception
            }

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

    private class MyListener implements ViewPager.OnPageChangeListener {

        //当页面被滑动的时候 调用
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

        }

        @Override // 当新的页面被选中 调用
        public void onPageSelected(int position) {
            num = position;
            position = position % list.size();
            Toast.makeText(MainActivity.this, "当前的位置 : " + (position + 1), Toast.LENGTH_SHORT).show();

            switch (position) {
                case 0:
                    imageView1.setBackgroundResource(R.mipmap.ad1);
                    imageView2.setBackgroundResource(R.mipmap.ad2);
                    imageView3.setBackgroundResource(R.mipmap.ad2);
                    break;
                case 1:
                    imageView1.setBackgroundResource(R.mipmap.ad2);
                    imageView2.setBackgroundResource(R.mipmap.ad1);
                    imageView3.setBackgroundResource(R.mipmap.ad2);
                    break;
                case 2:
                    imageView1.setBackgroundResource(R.mipmap.ad2);
                    imageView2.setBackgroundResource(R.mipmap.ad2);
                    imageView3.setBackgroundResource(R.mipmap.ad1);
                    break;
            }
        }

        @Override
        public void onPageScrollStateChanged(int state) {

        }
    }
}