测试 ListView 的效率 2

上面经过测试, 发现每次都要构造, 太浪费资源了. 所以进行如下改造.

java 代码如下:

package cn.powerise.test01;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import android.app.ListActivity;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

/**
 * 测试 ListView 的效率
 * @author R9(QQ:34351088)
 */
public class List_Efficiency_2 extends ListActivity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        List<HashMap<String, Object>> data = null;
        MyAdapter adapter = null;

        data = getData();

        adapter = new MyAdapter(this, data, R.layout.efficiency_item);
        setListAdapter(adapter);
    }

    private List<HashMap<String, Object>> getData() {
        List<HashMap<String, Object>> data = null;
        HashMap<String, Object> item = null;

        data = new ArrayList<HashMap<String, Object>>();
        for (int i = 10; i < 40; i++) {
            item = new HashMap<String, Object>();
            item.put("image", R.drawable.icon);
            item.put("id", i);
            item.put("name", "Name" + i);
            item.put("age", "Age" + i);
            item.put("phone", "139073100" + i);
            data.add(item);
        }

        return data;
    }

    class MyAdapter extends BaseAdapter {

        private List<HashMap<String, Object>> mData;
        private LayoutInflater mInflater;
        private int mResource;

        public MyAdapter(Context context, List<HashMap<String, Object>> data, int resource) {
            mData = data;
            mResource = resource;
            mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {

            View view = null;
            
            /**
             * 测试效率(改进)
             */
            if (convertView == null) {
                view = mInflater.inflate(mResource, null);
                System.out.println("-->" + position + " :: ");
            } else {
                view = convertView;
            }

            ImageView imageView = (ImageView) view.findViewById(R.id.iv_image);
            TextView idTextView = (TextView) view.findViewById(R.id.txt_id);
            TextView nameTextView = (TextView) view.findViewById(R.id.txt_name);
            TextView ageTextView = (TextView) view.findViewById(R.id.txt_age);
            TextView phoneTextView = (TextView) view.findViewById(R.id.txt_phone);

            HashMap<String, Object> dataSet = mData.get(position);

            imageView.setImageResource(R.drawable.icon);
            idTextView.setText(dataSet.get("id").toString());
            nameTextView.setText(dataSet.get("name").toString());
            ageTextView.setText(dataSet.get("age").toString());
            phoneTextView.setText(dataSet.get("phone").toString());

            return view;
        }

        @Override
        public int getCount() {
            return mData.size();
        }

        @Override
        public Object getItem(int position) {
            return mData.get(position);
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

    }
}

布局文件没有变, 还是前面那个. 现在再看看打印出来的信息:

然后, 我们再任意上下拖动 ListView, 看打印信息:

此时, 可以发现, 只有这10个 item, 并没有每次都重新构造 item 了, 效率大为提高了. 

因为核心代码:

if (convertView == null) {
　　view = mInflater.inflate(mResource, null);
　　System.out.println("-->" + position + " :: ");
} else {
　　view = convertView;
}

导致 item 可以复用了.