Android入门之Gallery+ImageSwitcher用法实例解析

继上一篇介绍了如何使用Gallery控件之后，本文就来讲一下Gallery 与ImageSwitcher的结合使用。本文所述实例代码将实现一个简单的浏览图片的功能。

先贴出程序运行截图如下：

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>

Java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;
 }
}