不记得什么时候,我留意到到美团网首页有使用ViewPager+GridView实现左右滑动查看更多分类的一个功能,感觉它很有趣,于是想着自己动手也实现这样一个功能,和往常一样,主要是想总结一下我在学习过程中的一些笔记以及需要注意的地方。
其中需要注意的有如下几个点:
一:使用GridView作为每个ViewPager的页面,也就是说每个ViewPager的页面都是inflate出一个GridView新实例
二:如何将GridView和ViewPager关联起来:在刚刚第一点所说的,有多少个ViewPager的页面就会inflate出多少个GridView作为每页的VIew加入集合中,并将这个集合作为ViewPager的数据源传给ViewPager的Adapter
//总的页数=总数/每页数量,并取整pageCount = (int) Math.ceil(mDatas.size() * 1.0 / pageSize);mPagerList = new ArrayList<View>();for (int i = 0; i < pageCount; i++) {// 每个页面都是inflate出一个新实例GridView gridView = (GridView) inflater.inflate(R.layout.gridview, mPager, false);gridView.setAdapter(new GridViewAdapter(this, mDatas, i, pageSize));mPagerList.add(gridView);gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {@Overridepublic void onItemClick(AdapterView<?> parent, View view, int position, long id) {Toast.makeText(MainActivity.this, mDatas.get((int) id).getName(), Toast.LENGTH_SHORT).show();});}
三:在ViewPager翻页时,如何让GridView显示正确的数据:
(1)给GridView设置Adapter时,除了需要传入总数据集mDatas之外,还需要传入当前页数以及每一页显示的个数,然后经过计算得出正确的count和应该显示的View的数据
(2)在GridView中Adapter中修改getCount()方法:
/*** 先判断数据集的大小是否足够显示满本页,如果够,则直接返回每一页显示的最大条目个数pageSize,如果不够,则有几项就返回几,(也就是最后一页的时候就显示剩余item)*/@Overridepublic int getCount() {return mDatas.size() > (curIndex + 1) * pageSize ? pageSize : (mDatas.size() - curIndex * pageSize);}
(3)修改getView()方法:
在给View绑定显示的数据时,根据当前下标curIndex和每页显示最大数pageSize ,计算一下正确的position = position + curIndex * pageSize
@Overridepublic View getView(int position, View convertView, ViewGroup parent) {ViewHolder viewHolder = null;if (convertView == null) {convertView = inflater.inflate(R.layout.item_gridview, parent, false);viewHolder = new ViewHolder();viewHolder.tv = (TextView) convertView.findViewById(R.id.textView);viewHolder.iv = (ImageView) convertView.findViewById(R.id.imageView);convertView.setTag(viewHolder);} else {viewHolder = (ViewHolder) convertView.getTag();}/*** 在给View绑定显示的数据时,计算正确的position = position + curIndex * pageSize*/int pos = position + curIndex * pageSize;viewHolder.tv.setText(mDatas.get(pos).name);viewHolder.iv.setImageResource(mDatas.get(pos).iconRes);return convertView;}
(4)修改getItem()和getItemId()方法
@Overridepublic Object getItem(int position) {return mDatas.get(position + curIndex * pageSize);}@Overridepublic long getItemId(int position) {return position + curIndex * pageSize;}
四、如何在ViewPager翻页时,正确显示目前选中的是那一页呢,也就是说在左右滑动时,下面小圆点的状态也要相应地做出改变:
/*** 设置圆点*/public void setOvalLayout() {for (int i = 0; i < pageCount; i++) {mLlDot.addView(inflater.inflate(R.layout.dot, null));}// 默认显示第一页mLlDot.getChildAt(0).findViewById(R.id.v_dot).setBackgroundResource(R.drawable.dot_selected);mPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {public void onPageSelected(int position) {// 取消圆点选中mLlDot.getChildAt(curIndex).findViewById(R.id.v_dot).setBackgroundResource(R.drawable.dot_normal);// 圆点选中mLlDot.getChildAt(position).findViewById(R.id.v_dot).setBackgroundResource(R.drawable.dot_selected);curIndex = position;}public void onPageScrolled(int arg0, float arg1, int arg2) {}public void onPageScrollStateChanged(int arg0) {}});}
五、在初始化数据源时,如何动态获取资源ID:
/*** 初始化数据源*/private void initDatas() {mDatas = new ArrayList<Model>();for (int i = 0; i < titles.length; i++) {//动态获取资源ID,第一个参数是资源名,第二个参数是资源类型例如drawable,string等,第三个参数包名int imageId = getResources().getIdentifier("ic_category_" + i, "mipmap", getPackageName());mDatas.add(new Model(titles[i], imageId));}}
就这五点吧,现在我们先来看看美团网首页使用ViewPager+GridView实现左右滑动查看更多分类的效果图:
再来看一下我们最终效果图:
现在我们来看下项目结构图
现在我把完整的代码贴出来,由于代码都有注释,下面就不进行一一解释啦
1、MainActivity
package per.lijuan.meituan;import android.os.Bundle;import android.support.v4.view.ViewPager;import android.support.v7.app.AppCompatActivity;import android.view.LayoutInflater;import android.view.View;import android.widget.AdapterView;import android.widget.GridView;import android.widget.LinearLayout;import android.widget.Toast;import java.util.ArrayList;import java.util.List;public class MainActivity extends AppCompatActivity {private String[] titles = {"美食", "电影", "酒店住宿", "休闲娱乐", "外卖", "自助餐", "KTV", "机票/火车票", "周边游", "美甲美睫","火锅", "生日蛋糕", "甜品饮品", "水上乐园", "汽车服务", "美发", "丽人", "景点", "足疗按摩", "运动健身", "健身", "超市", "买菜","今日新单", "小吃快餐", "面膜", "洗浴/汗蒸", "母婴亲子", "生活服务", "婚纱摄影", "学习培训", "家装", "结婚", "全部分配"};private ViewPager mPager;private List<View> mPagerList;private List<Model> mDatas;private LinearLayout mLlDot;private LayoutInflater inflater;/*** 总的页数*/private int pageCount;/*** 每一页显示的个数*/private int pageSize = 10;/*** 当前显示的是第几页*/private int curIndex = 0;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);mPager = (ViewPager) findViewById(R.id.viewpager);mLlDot = (LinearLayout) findViewById(R.id.ll_dot);//初始化数据源initDatas();inflater = LayoutInflater.from(this);//总的页数=总数/每页数量,并取整pageCount = (int) Math.ceil(mDatas.size() * 1.0 / pageSize);mPagerList = new ArrayList<View>();for (int i = 0; i < pageCount; i++) {// 每个页面都是inflate出一个新实例GridView gridView = (GridView) inflater.inflate(R.layout.gridview, mPager, false);gridView.setAdapter(new GridViewAdapter(this, mDatas, i, pageSize));mPagerList.add(gridView);gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {@Overridepublic void onItemClick(AdapterView<?> parent, View view, int position, long id) {Toast.makeText(MainActivity.this, mDatas.get((int) id).getName(), Toast.LENGTH_SHORT).show();}});}//设置适配器mPager.setAdapter(new ViewPagerAdapter(mPagerList));//设置圆点setOvalLayout();}/*** 初始化数据源*/private void initDatas() {mDatas = new ArrayList<Model>();for (int i = 0; i < titles.length; i++) {//动态获取资源ID,第一个参数是资源名,第二个参数是资源类型例如drawable,string等,第三个参数包名int imageId = getResources().getIdentifier("ic_category_" + i, "mipmap", getPackageName());mDatas.add(new Model(titles[i], imageId));}}/*** 设置圆点*/public void setOvalLayout() {for (int i = 0; i < pageCount; i++) {mLlDot.addView(inflater.inflate(R.layout.dot, null));}// 默认显示第一页mLlDot.getChildAt(0).findViewById(R.id.v_dot).setBackgroundResource(R.drawable.dot_selected);mPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {public void onPageSelected(int position) {// 取消圆点选中mLlDot.getChildAt(curIndex).findViewById(R.id.v_dot).setBackgroundResource(R.drawable.dot_normal);// 圆点选中mLlDot.getChildAt(position).findViewById(R.id.v_dot).setBackgroundResource(R.drawable.dot_selected);curIndex = position;}public void onPageScrolled(int arg0, float arg1, int arg2) {}public void onPageScrollStateChanged(int arg0) {}});}}
2、activity_main.xml
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:background="#D4D3D3"android:orientation="vertical"><RelativeLayout android:layout_width="match_parent"android:layout_height="180dp"android:background="#FFFFFF"><android.support.v4.view.ViewPager android:id="@+id/viewpager"android:layout_width="match_parent"android:layout_height="wrap_content" /><LinearLayout android:id="@+id/ll_dot"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_alignParentBottom="true"android:layout_marginBottom="8dp"android:gravity="center"android:orientation="horizontal" /></RelativeLayout></LinearLayout>
分析下布局结构:
(1)首先是一个ViewPager,用于结合GridView实现左右滑动查看更多分类;
(2)下面是一个LinearLayout,有多少个ViewPager的页面就会inflate出多少个小圆点,并且在ViewPager翻页时,也就是说在左右滑动时,下面小圆点的状态也要相应地做出改变
3、GridViewAdapter
package per.lijuan.meituan;import android.content.Context;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.BaseAdapter;import android.widget.ImageView;import android.widget.TextView;import java.util.List;/*** Created by lijuan on /9/12.*/public class GridViewAdapter extends BaseAdapter {private List<Model> mDatas;private LayoutInflater inflater;/*** 页数下标,从0开始(当前是第几页)*/private int curIndex;/*** 每一页显示的个数*/private int pageSize;public GridViewAdapter(Context context, List<Model> mDatas, int curIndex, int pageSize) {inflater = LayoutInflater.from(context);this.mDatas = mDatas;this.curIndex = curIndex;this.pageSize = pageSize;}/*** 先判断数据集的大小是否足够显示满本页,如果够,则直接返回每一页显示的最大条目个数pageSize,如果不够,则有几项就返回几,(也就是最后一页的时候就显示剩余item)*/@Overridepublic int getCount() {return mDatas.size() > (curIndex + 1) * pageSize ? pageSize : (mDatas.size() - curIndex * pageSize);}@Overridepublic Object getItem(int position) {return mDatas.get(position + curIndex * pageSize);}@Overridepublic long getItemId(int position) {return position + curIndex * pageSize;}@Overridepublic View getView(int position, View convertView, ViewGroup parent) {ViewHolder viewHolder = null;if (convertView == null) {convertView = inflater.inflate(R.layout.item_gridview, parent, false);viewHolder = new ViewHolder();viewHolder.tv = (TextView) convertView.findViewById(R.id.textView);viewHolder.iv = (ImageView) convertView.findViewById(R.id.imageView);convertView.setTag(viewHolder);} else {viewHolder = (ViewHolder) convertView.getTag();}/*** 在给View绑定显示的数据时,计算正确的position = position + curIndex * pageSize*/int pos = position + curIndex * pageSize;viewHolder.tv.setText(mDatas.get(pos).name);viewHolder.iv.setImageResource(mDatas.get(pos).iconRes);return convertView;}class ViewHolder {public TextView tv;public ImageView iv;}}
4、ViewPagerAdapter
package per.lijuan.meituan;import android.support.v4.view.PagerAdapter;import android.view.View;import android.view.ViewGroup;import java.util.List;/*** Created by lijuan on /9/12.*/public class ViewPagerAdapter extends PagerAdapter {private List<View> mViewList;public ViewPagerAdapter(List<View> mViewList) {this.mViewList = mViewList;}@Overridepublic void destroyItem(ViewGroup container, int position, Object object) {container.removeView(mViewList.get(position));}@Overridepublic Object instantiateItem(ViewGroup container, int position) {container.addView(mViewList.get(position));return (mViewList.get(position));}@Overridepublic int getCount() {if (mViewList == null)return 0;return mViewList.size();}@Overridepublic boolean isViewFromObject(View view, Object object) {return view == object;}}
5、Model
package per.lijuan.meituan;/*** Created by lijuan on /9/12.*/public class Model {public String name;public int iconRes;public Model(String name, int iconRes) {this.name = name;this.iconRes = iconRes;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getIconRes() {return iconRes;}public void setIconRes(int iconRes) {this.iconRes = iconRes;}}
布局文件就不一一贴出来啦,大家可以点击源码下载:Android 仿美团网,探索利用ViewPager+GridView实现左右滑动查看更多分类的功能
好了,本篇文章已经全部写完了,有什么疑问的,请在下面留言,存在总结不到位的地方还望指导,感谢^_^