ViewPager 无限轮播自动轮播

- 日理万妓 2022-06-08 00:11 306阅读 0赞

**1、ViewPager的应用 **

ViewPager应用很简单，只需使用android.support.v4.view.ViewPager组件即可，同ListView一样，需要给它指定一个适配器。 
    四大函数略。 2、实现无限循环 
    当banner位于1屏，向左滑动，此时位于最后一屏， 
    当banner位于最后一屏，向右滑动，此时位于第一屏。

package com.example.myapplication;
    
    import android.app.Activity;
    import android.content.Context;
    import android.os.AsyncTask;
    import android.os.Bundle;
    import android.os.Handler;
    import android.support.v4.view.PagerAdapter;
    import android.support.v4.view.ViewPager;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.view.Window;
    import android.widget.ImageView;
    
    public class MainActivity extends Activity {
    
    
        private ViewPager mBanner;
        private ImageView[] mPositionViews;
        private BannerAdapter mAdapter;
        private int currentPosition = 0;
        private final int Max_Size = 100;
        private final int Default_Size = 3;
        private int[] mImageSrc = {
                R.mipmap.b,
                R.mipmap.c,
                R.mipmap.d };
    
        private Handler mHandler = new Handler();
        private long lasttime;
        private Runnable mRunnable = new Runnable() {
    
            @Override public void run() {
                // TODO Auto-generated method stub if (System.currentTimeMillis() - lasttime > 3000) {
                    currentPosition++;
                    viewHandler.sendEmptyMessage(currentPosition);
                    lasttime = System.currentTimeMillis();
                }
                mHandler.postDelayed(mRunnable, 3000);
            }
        };
    
        private Handler viewHandler = new Handler() {
            public void handleMessage(android.os.Message msg) {
                mBanner.setCurrentItem(msg.what);
            }
        };
    
        @Override protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            requestWindowFeature(Window.FEATURE_NO_TITLE);
            setContentView(R.layout.activity_main);
            init();
        }
    
        private void setBannerPosition(int position) {
    
            position %= Default_Size;
            for (ImageView imageView : mPositionViews) {
                imageView.setImageResource(R.mipmap.point_mormal);
            }
            mPositionViews[position].setImageResource(R.mipmap.point_selected);
        }
    
        private void init() {
    
            mPositionViews = new ImageView[]{
                    (ImageView) findViewById(R.id.position_1),
                    (ImageView) findViewById(R.id.position_2),
                    (ImageView) findViewById(R.id.position_3),
            };
            mBanner = (ViewPager) findViewById(R.id.banner);
            mAdapter = new BannerAdapter(this);
            mBanner.setAdapter(mAdapter);
            mHandler.postDelayed(mRunnable, 3000);
            mBanner.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
    
                @Override public void onPageSelected(int arg0) {
                    currentPosition = arg0;
                    setBannerPosition(currentPosition);
                }
    
                @Override public void onPageScrolled(int arg0, float arg1, int arg2) {
    
                }
    
                @Override public void onPageScrollStateChanged(int arg0) {
    
                }
            });
    
        }
    
        private class BannerAdapter extends PagerAdapter {
    
            private LayoutInflater mInflater;
    
            public BannerAdapter(Context context) {
                mInflater = LayoutInflater.from(context);
            }
    
            @Override public int getCount() {
                return Max_Size;
            }
    
    
            @Override public boolean isViewFromObject(View arg0, Object arg1) {
                return arg0 == arg1;
            }
    
            @Override public Object instantiateItem(ViewGroup container, int position) {
                position %= Default_Size;
                View view = mInflater.inflate(R.layout.item, container, false);
                ImageView imageView = (ImageView) view.findViewById(R.id.image);
                imageView.setImageResource(mImageSrc[position]);
                container.addView(view);
                return view;
            }
    
            @Override public void destroyItem(ViewGroup container, int position, Object object) {
                container.removeView((View) object);
            }
    
            @Override public void finishUpdate(ViewGroup container) {
                //获取当前banner的索引 int position = mBanner.getCurrentItem();
                //屏幕0切换为屏幕3 if (position == 0) {
                    currentPosition = Default_Size;
                    //banner设置当前索引 mBanner.setCurrentItem(currentPosition, false);
                }
                //当下标达到99时，将其切换到第2屏 else if (position == Max_Size - 1) {
                    currentPosition = Default_Size - 1;
                    mBanner.setCurrentItem(currentPosition, false);
                }
                super.finishUpdate(container);
            }
    
        }
    
    
    }

布局文件

<?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
        android:layout_height="match_parent" tools:context="com.example.myapplication.MainActivity">
    
        <android.support.v4.view.ViewPager android:id="@+id/banner"
            android:layout_height="match_parent"
            android:layout_width="match_parent"
             />
    
        <ImageView android:id="@+id/position_2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@mipmap/point_mormal"
            android:layout_alignParentBottom="true"
            android:layout_centerHorizontal="true"
            />
        <ImageView android:id="@+id/position_1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@mipmap/point_mormal"
            android:layout_alignParentBottom="true"
            android:layout_toLeftOf="@+id/position_2"
            />
        <ImageView android:id="@+id/position_3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@mipmap/point_mormal"
            android:layout_toRightOf="@+id/position_2"
            android:layout_alignParentBottom="true"
            />
    
    
    </RelativeLayout>