GridView简单应用

package com.example.gridviewdemo;

import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import android.os.Bundle;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.SimpleAdapter;

public class MainActivity extends Activity {
    private GridView gd;
    private List<Map<String, Integer>> list = new ArrayList<Map<String, Integer>>();
    private SimpleAdapter sa;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        gd = (GridView) findViewById(R.id.gd);
        Field[] fieds = R.drawable.class.getDeclaredFields();//利用反射得到图片
        for (int i = 0; i < fieds.length; i++) {
            Map<String, Integer> map = new HashMap<String, Integer>();
            try {
                if(fieds[i].getName().startsWith("pic"))//判断图片开头是不是pic
                map.put("img", fieds[i].getInt(R.drawable.class));//放进map里
            } catch (IllegalAccessException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IllegalArgumentException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            list.add(map);
        }
        sa = new SimpleAdapter(MainActivity.this, list, R.layout.grid_layout,
                new String[] { "img" }, new int[] { R.id.img });
        gd.setAdapter(sa);
        //给网格视图设置点击事件
        gd.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view,
                    int position, long id) {
                ImageView showImg = new ImageView(MainActivity.this);
                Map<String, Integer> map1 = (Map<String, Integer>) sa
                        .getItem(position);
                showImg.setImageResource(map1.get("img"));
                //设置图片大小
                showImg.setLayoutParams(new LinearLayout.LayoutParams(
                        LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
            //把这个图片用对话框显示出来
                new AlertDialog.Builder(MainActivity.this)
                .setTitle("选择的图片是")
                .setView(showImg)
                .setPositiveButton("确定", new DialogInterface.OnClickListener() {

                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        // TODO Auto-generated method stub

                    }
                }).show();
            }
        });

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}