自定义控件——改造已有的控件——不滚动的列表视图

以你之姓@ 2024-04-07 12:40 29阅读 0赞

不滚动的列表视图

把ListView放入ScrollView会产生问题，因为ScrollView和ListView都允许滚动，那么在双方的重叠区域，上下滑动的手势究竟表示要滚动哪个视图？

Android的处理对策是：如果ListView的高度被设置为wrap\_content，则此时列表视图只显示一行的高度，然后整个界面只支持滚动ScrollView。

但如此一来， ScrollView内部的ListView无法显示完整的列表。

public class NoScrollListView extends ListView {
        public NoScrollListView(Context context) {
            super(context);
        }
        public NoScrollListView(Context context, AttributeSet attrs) {
            super(context, attrs);
        }
        public NoScrollListView(Context context, AttributeSet attrs, int defStyle) {
            super(context, attrs, defStyle);
        }
     
        // 重写onMeasure方法，以便自行设定视图的高度
    public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
            // 将高度设为最大值，即所有项加起来的总高度
            int expandSpec = MeasureSpec.makeMeasureSpec(
                    Integer.MAX_VALUE >> 2, MeasureSpec.AT_MOST);
            super.onMeasure(widthMeasureSpec, expandSpec);  // 按照新的高度规格重新测量视图尺寸
        }
    }

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布局：

![07fe52595da81240be410e760f8ecd75.png][]

![5750db46c07643b454c0c75414e4668c.png][]

NoScrollListView

package com.example.myapplication.widget;
    
    import android.content.Context;
    import android.util.AttributeSet;
    import android.widget.ListView;
    
    public class NoScrollListView extends ListView 
    {
    
        public NoScrollListView(Context context)
        {
            super(context);
        }
    
        public NoScrollListView(Context context, AttributeSet attrs)
        {
            super(context, attrs);
        }
    
        public NoScrollListView(Context context, AttributeSet attrs, int defStyle)
        {
            super(context, attrs, defStyle);
        }
    
        // 重写onMeasure方法，以便自行设定视图的高度
        @Override
        public void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
        {
            // 将高度设为最大值，即所有项加起来的总高度
            int expandSpec = MeasureSpec.makeMeasureSpec(Integer.MAX_VALUE >> 2, MeasureSpec.AT_MOST);
            super.onMeasure(widthMeasureSpec, expandSpec); // 按照新的高度规格重新测量视图尺寸
        }
    }

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Planet

package com.example.myapplication.bean;
    
    import com.example.myapplication.R;
    import java.util.ArrayList;
    import java.util.List;
    
    public class Planet {
        public int image; // 行星图标
        public String name; // 行星名称
        public String desc; // 行星描述
    
        public Planet(int image, String name, String desc) {
            this.image = image;
            this.name = name;
            this.desc = desc;
        }
    
        private static int[] iconArray = {R.drawable.shuixing, R.drawable.jinxing, R.drawable.diqiu,
                R.drawable.huoxing, R.drawable.muxing, R.drawable.tuxing};
        private static String[] nameArray = {"水星", "金星", "地球", "火星", "木星", "土星"};
        private static String[] descArray = {
                "水星是太阳系八大行星最内侧也是最小的一颗行星，也是离太阳最近的行星",
                "金星是太阳系八大行星之一，排行第二，距离太阳0.725天文单位",
                "地球是太阳系八大行星之一，排行第三，也是太阳系中直径、质量和密度最大的类地行星，距离太阳1.5亿公里",
                "火星是太阳系八大行星之一，排行第四，属于类地行星，直径约为地球的53%",
                "木星是太阳系八大行星中体积最大、自转最快的行星，排行第五。它的质量为太阳的千分之一，但为太阳系中其它七大行星质量总和的2.5倍",
                "土星为太阳系八大行星之一，排行第六，体积仅次于木星"
        };
    
        public static List<Planet> getDefaultList() {
            List<Planet> planetList = new ArrayList<Planet>();
            for (int i = 0; i < iconArray.length; i++) {
                planetList.add(new Planet(iconArray[i], nameArray[i], descArray[i]));
            }
            return planetList;
        }
    }

![2dd4b4a854837b09cec0a223274816ae.png][]

PlanetListAdapter

package com.example.myapplication.adapter;
    
    import android.annotation.SuppressLint;
    import android.content.Context;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.AdapterView;
    import android.widget.AdapterView.OnItemClickListener;
    import android.widget.AdapterView.OnItemLongClickListener;
    import android.widget.BaseAdapter;
    import android.widget.ImageView;
    import android.widget.TextView;
    import android.widget.Toast;
    import com.example.myapplication.R;
    import com.example.myapplication.bean.Planet;
    import java.util.List;
    
    @SuppressLint("DefaultLocale")
    public class PlanetListAdapter extends BaseAdapter implements
            OnItemClickListener, OnItemLongClickListener {
        private Context mContext; // 声明一个上下文对象
        private List<Planet> mPlanetList; // 声明一个行星信息列表
    
        // 行星适配器的构造方法，传入上下文与行星列表
        public PlanetListAdapter(Context context, List<Planet> planet_list) {
            mContext = context;
            mPlanetList = planet_list;
        }
    
        // 获取列表项的个数
        public int getCount() {
            return mPlanetList.size();
        }
    
        // 获取列表项的数据
        public Object getItem(int arg0) {
            return mPlanetList.get(arg0);
        }
    
        // 获取列表项的编号
        public long getItemId(int arg0) {
            return arg0;
        }
    
        // 获取指定位置的列表项视图
        public View getView(final int position, View convertView, ViewGroup parent) {
            ViewHolder holder;
            if (convertView == null) { // 转换视图为空
                holder = new ViewHolder(); // 创建一个新的视图持有者
                // 根据布局文件item_list.xml生成转换视图对象
                convertView = LayoutInflater.from(mContext).inflate(R.layout.item_list, null);
                holder.iv_icon = convertView.findViewById(R.id.iv_icon);
                holder.tv_name = convertView.findViewById(R.id.tv_name);
                holder.tv_desc = convertView.findViewById(R.id.tv_desc);
                convertView.setTag(holder); // 将视图持有者保存到转换视图当中
            } else { // 转换视图非空
                // 从转换视图中获取之前保存的视图持有者
                holder = (ViewHolder) convertView.getTag();
            }
            Planet planet = mPlanetList.get(position);
            holder.iv_icon.setImageResource(planet.image); // 显示行星的图片
            holder.tv_name.setText(planet.name); // 显示行星的名称
            holder.tv_desc.setText(planet.desc); // 显示行星的描述
            holder.iv_icon.requestFocus();
            return convertView;
        }
    
        // 定义一个视图持有者，以便重用列表项的视图资源
        public final class ViewHolder {
            public ImageView iv_icon; // 声明行星图片的图像视图对象
            public TextView tv_name; // 声明行星名称的文本视图对象
            public TextView tv_desc; // 声明行星描述的文本视图对象
        }
    
        // 处理列表项的点击事件，由接口OnItemClickListener触发
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            String desc = String.format("您点击了第%d个行星，它的名字是%s", position + 1,
                    mPlanetList.get(position).name);
            Toast.makeText(mContext, desc, Toast.LENGTH_LONG).show();
        }
    
        // 处理列表项的长按事件，由接口OnItemLongClickListener触发
        public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
            String desc = String.format("您长按了第%d个行星，它的名字是%s", position + 1,
                    mPlanetList.get(position).name);
            Toast.makeText(mContext, desc, Toast.LENGTH_LONG).show();
            return true;
        }
    }

主代码：

package com.example.myapplication;
    
    import androidx.appcompat.app.AppCompatActivity;
    import androidx.viewpager.widget.ViewPager;
    import android.os.Bundle;
    import android.widget.ListView;
    import android.widget.Toast;
    import com.example.myapplication.adapter.ImagePagerAdapater;
    import com.example.myapplication.adapter.PlanetListAdapter;
    import com.example.myapplication.bean.GoodsInfo;
    import com.example.myapplication.bean.Planet;
    import com.example.myapplication.widget.NoScrollListView;
    
    import java.util.ArrayList;
    
    public class MainActivity extends AppCompatActivity
    {
    
        private ArrayList<GoodsInfo> mGoodsList; // 手机商品列表
    
        @Override
        protected void onCreate(Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
    
            PlanetListAdapter adapter1 = new PlanetListAdapter(this, Planet.getDefaultList());
            
            // 从布局文件中获取名叫lv_planet的列表视图
            // lv_planet是系统自带的ListView，被ScrollView嵌套只能显示一行
            ListView lv_planet = findViewById(R.id.lv_planet);
            
            lv_planet.setAdapter(adapter1); // 设置列表视图的行星适配器
            lv_planet.setOnItemClickListener(adapter1);
            lv_planet.setOnItemLongClickListener(adapter1);
            
            PlanetListAdapter adapter2 = new PlanetListAdapter(this, Planet.getDefaultList());
            
            // 从布局文件中获取名叫nslv_planet的不滚动列表视图
            // nslv_planet是自定义控件NoScrollListView，会显示所有行
            NoScrollListView nslv_planet = findViewById(R.id.nslv_planet);
            
            nslv_planet.setAdapter(adapter2); // 设置不滚动列表视图的行星适配器
            nslv_planet.setOnItemClickListener(adapter2);
            nslv_planet.setOnItemLongClickListener(adapter2);
        }
    }

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