Android入门之Gallery用法实例解析

本文实例介绍的Android的Gallery控件是个很不错的看图控件，可以大大减轻开发者对于看图功能的开发，并且效果也很美观。本文实例中的Gallery的用法，主要实现用反射机制来动态读取资源中的图片。

该实例代码运行的效果图如下：

main.xml源码如下:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  >
<Gallery android:id="@+id/gallery" android:layout_height="fill_parent" android:layout_width="fill_parent"></Gallery>
</LinearLayout>

Java程序源码如下：

package com.testImageView; 

import java.lang.reflect.Field;
import java.util.ArrayList; 

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;
import android.widget.AdapterView.OnItemClickListener; 

public class testImageView extends Activity {
  private Gallery mGallery;
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main); 

    mGallery = (Gallery)findViewById(R.id.gallery);
    try {
      mGallery.setAdapter(new ImageAdapter(this));
    } catch (IllegalArgumentException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    } catch (IllegalAccessException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
    mGallery.setOnItemClickListener(new OnItemClickListener() {
      public void onItemClick(AdapterView parent, View v, int position, long id) {
        testImageView.this.setTitle(String.valueOf(position));
      }
    });
  } 

  /*
   * class ImageAdapter is used to control gallery source and operation.
   */
  private class ImageAdapter extends BaseAdapter{
    private Context mContext;
    private ArrayList<Integer> imgList=new ArrayList<Integer>();
    private ArrayList<Object> imgSizes=new ArrayList<Object>();
    public ImageAdapter(Context c) throws IllegalArgumentException, IllegalAccessException{
      mContext = c; 

      //用反射机制来获取资源中的图片ID和尺寸
      Field[] fields = R.drawable.class.getDeclaredFields();
      for (Field field : fields)
      {
        if (!"icon".equals(field.getName()))//除了icon之外的图片
        {
          int index=field.getInt(R.drawable.class);
          //保存图片ID
          imgList.add(index);
          //保存图片大小
          int size[]=new int[2];
          Bitmap bmImg=BitmapFactory.decodeResource(getResources(),index);
          size[0]=bmImg.getWidth();size[1]=bmImg.getHeight();
          imgSizes.add(size);
        }
      }
    }
    @Override
    public int getCount() {
      // TODO Auto-generated method stub 

      return imgList.size();
    } 

    @Override
    public Object getItem(int position) {
      // TODO Auto-generated method stub 

      return position;
    } 

    @Override
    public long getItemId(int position) {
      // TODO Auto-generated method stub 

      return position;
    } 

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
      // TODO Auto-generated method stub 

      ImageView i = new ImageView (mContext);
      //从imgList取得图片ID
      i.setImageResource(imgList.get(position).intValue());
      i.setScaleType(ImageView.ScaleType.FIT_XY);
      //从imgSizes取得图片大小
      int size[]= new int[2];
      size=(int[]) imgSizes.get(position);
      i.setLayoutParams(new Gallery.LayoutParams(size[0], size[1]));
      return i;
    } 

  };
}