Android入门第十三篇之Gallery + ImageSwitcher

本文来自http://blog.csdn.net/hellogv/ ，引用必须注明出处！

上次讲了如何使用Gallery控件，这次就讲Gallery 与ImageSwitcher的结合使用，本文实现一个简单的浏览图片的功能。先贴出程序运行截图：

除了Gallery可以拖拉切换图片，我在ImageSwitcher控件加入了setOnTouchListener事件实现，使得ImageSwitcher也可以在拖拉中切换图片。本例子依然使用JAVA的反射机制来自动读取资源中的图片。

main.xml的源码如下:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent"> 
    
    <ImageSwitcher android:id="@+id/switcher"
        android:layout_width="match_parent" android:layout_height="match_parent"/>
    
    <Gallery android:id="@+id/gallery"
        android:background="#55000000"
        android:layout_width="match_parent"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        
        android:gravity="center_vertical"
        android:spacing="16dp" android:layout_height="100dp"/>
</RelativeLayout>
   

程序的源码如下:

package com.testImageView;
import java.lang.reflect.Field;
import java.util.ArrayList;
import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.ViewGroup;
import android.view.animation.AnimationUtils;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageSwitcher;
import android.widget.ImageView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.Gallery.LayoutParams;
import android.widget.ViewSwitcher.ViewFactory;
public class testImageView extends Activity implements ViewFactory {
	private ImageSwitcher is;
	private Gallery gallery;
	private int downX,upX;
    private ArrayList<Integer> imgList=new ArrayList<Integer>();//图像ID
    
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
        //用反射机制来获取资源中的图片ID
    	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 = 0;
				try {
					index = field.getInt(R.drawable.class);
				} catch (IllegalArgumentException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} catch (IllegalAccessException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
    			//保存图片ID
    			imgList.add(index);
    		}
    	}
    	
    	//设置ImageSwitcher控件
		is = (ImageSwitcher) findViewById(R.id.switcher);
		is.setFactory(this);
		is.setInAnimation(AnimationUtils.loadAnimation(this,
				android.R.anim.fade_in));
		is.setOutAnimation(AnimationUtils.loadAnimation(this,
				android.R.anim.fade_out));
		is.setOnTouchListener(new OnTouchListener(){
			/*
			 * 在ImageSwitcher控件上滑动可以切换图片
			 */
			@Override
			public boolean onTouch(View v, MotionEvent event) {
				if(event.getAction()==MotionEvent.ACTION_DOWN)
				{
					downX=(int) event.getX();//取得按下时的坐标
					return true;
				}
				else if(event.getAction()==MotionEvent.ACTION_UP)
				{
					upX=(int) event.getX();//取得松开时的坐标
					int index=0;
					if(upX-downX>100)//从左拖到右，即看前一张
					{
						//如果是第一，则去到尾部
						if(gallery.getSelectedItemPosition()==0)
						   index=gallery.getCount()-1;
						else
							index=gallery.getSelectedItemPosition()-1;
					}
					else if(downX-upX>100)//从右拖到左，即看后一张
					{
						//如果是最后，则去到第一
						if(gallery.getSelectedItemPosition()==(gallery.getCount()-1))
							index=0;
						else
							index=gallery.getSelectedItemPosition()+1;
					}
					//改变gallery图片所选，自动触发ImageSwitcher的setOnItemSelectedListener
					gallery.setSelection(index, true);
					return true;
				}
				return false;
			}
			
		});
		
		//设置gallery控件
		gallery = (Gallery) findViewById(R.id.gallery);
		gallery.setAdapter(new ImageAdapter(this));
		gallery.setOnItemSelectedListener(new OnItemSelectedListener(){
			@Override
			public void onItemSelected(AdapterView<?> arg0, View arg1,
					int position, long arg3) {
				is.setImageResource(imgList.get(position));
			}
			@Override
			public void onNothingSelected(AdapterView<?> arg0) {
				// TODO Auto-generated method stub
			}
			
		});
	}
	//设置ImgaeSwitcher
	@Override
	public View makeView() {
		ImageView i = new ImageView(this);
		i.setBackgroundColor(0xFF000000);
		i.setScaleType(ImageView.ScaleType.CENTER);//居中
		i.setLayoutParams(new ImageSwitcher.LayoutParams(//自适应图片大小
				LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
		return i;
	}
	public class ImageAdapter extends BaseAdapter {
		public ImageAdapter(Context c) {
			mContext = c;
		}
		public int getCount() {
			return imgList.size();
		}
		public Object getItem(int position) {
			return position;
		}
		public long getItemId(int position) {
			return position;
		}
		public View getView(int position, View convertView, ViewGroup parent) {
			ImageView i = new ImageView(mContext);
			i.setImageResource(imgList.get(position));
			i.setAdjustViewBounds(true);
			i.setLayoutParams(new Gallery.LayoutParams(
					LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
			return i;
		}
		private Context mContext;
	}

}