Android 仿美团网，探索使用ViewPager+GridView实现左右滑动查看更多分类的功能
oracle_java_zxh
8年前
<p>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。</p> <p>其中需要注意的有如下几个点：</p> <p>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</p> <p>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</p> <pre> <code class="language-java">//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() { @Override public void onItemClick(AdapterView<?> parent, View view, int position, long id) { int pos = position + curIndex * pageSize; Toast.makeText(MainActivity.this, mDatas.get(pos).getName(), Toast.LENGTH_SHORT).show(); } }); }</code></pre> <p>三：在ViewPager翻页时，如何让GridView显示正确的数据：</p> <p>（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</p> <p>（2）在GridView中Adapter中修改getCount()方法：</p> <pre> <code class="language-java">/** * 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) */ @Override public int getCount() { return mDatas.size() > (curIndex + 1) * pageSize ? pageSize : (mDatas.size() - curIndex * pageSize); }</code></pre> <p>（3）修改getView()方法：</p> <p>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</p> <pre> <code class="language-java">@Override public 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; }</code></pre> <p>（4）修改getItem()和getItemId()方法</p> <pre> <code class="language-java">@Override public Object getItem(int position) { return mDatas.get(position + curIndex * pageSize); } @Override public long getItemId(int position) { return position + curIndex * pageSize; }</code></pre> <p>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：</p> <pre> <code class="language-java">/** * 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) { } }); }</code></pre> <p>五、在初始化数据源时，如何动态获取资源ID：</p> <pre> <code class="language-java">/** * 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)); } }</code></pre> <p>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：</p> <p style="text-align:center"><img src="https://simg.open-open.com/show/7cdc5992d28c43d888f4215896bc852a.png"></p> <p style="text-align:center">这里写图片描述</p> <p>再来看一下我们最终效果图：</p> <p style="text-align:center"><img src="https://simg.open-open.com/show/9920b96e5add2289194ae2450deb24ec.gif"></p> <p style="text-align:center">这里写图片描述</p> <p>现在我们来看下项目结构图</p> <p style="text-align:center"><img src="https://simg.open-open.com/show/c15665d60f2647a977704e80a3d1fb53.png"></p> <p style="text-align:center">这里写图片描述</p> <p>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</p> <p>1、MainActivity</p> <pre> <code class="language-java">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; @Override protected 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() { @Override public void onItemClick(AdapterView<?> parent, View view, int position, long id) { int pos = position + curIndex * pageSize; Toast.makeText(MainActivity.this, mDatas.get(pos).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) { } }); } }</code></pre> <p>2、activity_main.xml</p> <pre> <code class="language-java"><?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/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></code></pre> <p>分析下布局结构：</p> <p>（1）首先是一个ViewPager，用于结合GridView实现左右滑动查看更多分类；</p> <p>（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</p> <p>3、GridViewAdapter</p> <pre> <code class="language-java">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 2016/9/12. */ 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) */ @Override public int getCount() { return mDatas.size() > (curIndex + 1) * pageSize ? pageSize : (mDatas.size() - curIndex * pageSize); } @Override public Object getItem(int position) { return mDatas.get(position + curIndex * pageSize); } @Override public long getItemId(int position) { return position + curIndex * pageSize; } @Override public 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; } }</code></pre> <p>4、ViewPagerAdapter</p> <pre> <code class="language-java">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 2016/9/12. */ public class ViewPagerAdapter extends PagerAdapter { private List<View> mViewList; public ViewPagerAdapter(List<View> mViewList) { this.mViewList = mViewList; } @Override public void destroyItem(ViewGroup container, int position, Object object) { container.removeView(mViewList.get(position)); } @Override public Object instantiateItem(ViewGroup container, int position) { container.addView(mViewList.get(position)); return (mViewList.get(position)); } @Override public int getCount() { if (mViewList == null) return 0; return mViewList.size(); } @Override public boolean isViewFromObject(View view, Object object) { return view == object; } }</code></pre> <p>5、Model</p> <pre> <code class="language-java">package per.lijuan.meituan; /** * Created by lijuan on 2016/9/12. */ 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; } }</code></pre> <p> </p> <p> </p> <p>来自：http://www.jianshu.com/p/1bb63a457292</p> <p> </p>