Android入門第十三篇之Gallery + ImageSwitcher

上次講了如何使用Gallery控件，這次就講Gallery 與ImageSwitcher的結合使用，本文實現一個簡單的浏覽圖片的功能。先貼出程序運行截圖：

除了Gallery可以拖拉切換圖片，我在ImageSwitcher控件加入了setOnTouchListener事件實現，使得ImageSwitcher也可以在拖拉中切換圖片。本例子依然使用JAVA的反射機制來自動讀取資源中的圖片。

main.xml的源碼如下:     

<?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> 
   

程序的源碼如下:

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>();//圖像ID     
         
    @Override    
    protected void onCreate(Bundle savedInstanceState) {     
        // TODO Auto-generated method stub     
        super.onCreate(savedInstanceState);     
        setContentView(R.layout.main);     
        //用反射機制來獲取資源中的圖片ID     
        Field[] fields = R.drawable.class.getDeclaredFields();     
        for (Field field : fields)     
        {     
            if (!"icon".equals(field.getName()))//除了icon之外的圖片     
            {        
                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();     
                }     
                //保存圖片ID     
                imgList.add(index);     
            }     
        }     
             
        //設置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控件上滑動可以切換圖片    
             */    
            @Override    
            public boolean onTouch(View v, MotionEvent event) {     
                if(event.getAction()==MotionEvent.ACTION_DOWN)     
                {     
                    downX=(int) event.getX();//取得按下時的坐標     
                    return true;     
                }     
                else if(event.getAction()==MotionEvent.ACTION_UP)     
                {     
                    upX=(int) event.getX();//取得松開時的坐標     
                    int index=0;     
                    if(upX-downX>100)//從左拖到右，即看前一張     
                    {     
                        //如果是第一，則去到尾部     
                        if(gallery.getSelectedItemPosition()==0)     
                           index=gallery.getCount()-1;     
                        else    
                            index=gallery.getSelectedItemPosition()-1;     
                    }     
                    else if(downX-upX>100)//從右拖到左，即看後一張     
                    {     
                        //如果是最後，則去到第一     
                        if(gallery.getSelectedItemPosition()==(gallery.getCount()-1))     
                            index=0;     
                        else    
                            index=gallery.getSelectedItemPosition()+1;     
                    }     
                    //改變gallery圖片所選，自動觸發ImageSwitcher的setOnItemSelectedListener     
                    gallery.setSelection(index, true);     
                    return true;     
                }     
                return false;     
            }     
                 
        });     
             
        //設置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     
            }     
                 
        });     
    }     
    //設置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(//自適應圖片大小     
                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;     
    }     
    
}