Android4.0开发学习之ImageSwitcher

这次主要介绍Android4.0图片转换的功能，具体运行效果如下:

要实现这个效果主要用到两个控件ImageView和Gallery，具体的界面布局文件代码如下：

<?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"
	 android:orientation="vertical">

	<ImageView 
	    android:id="@+id/myImageView"
	    android:layout_width="wrap_content"
		android:layout_height="wrap_content"
		android:layout_above="@+id/picGallery"
		android:src="@drawable/girl_1"/>
	<Gallery  
	    android:id="@+id/picGallery"
		android:layout_width="match_parent"
		android:layout_height="wrap_content"
		android:layout_alignParentBottom="true"
		/>
</RelativeLayout>

新建values\attrs.xml文件：

<?xml version="1.0" encoding="utf-8"?>

<resources>
    <!-- These are the attributes that we want to retrieve from the theme
         in view/Gallery1.java -->
    <declare-styleable name="Gallery1">
        <attr name="android:galleryItemBackground" />
    </declare-styleable>
    
</resources>

具体的实现JAVA代码如下：

import android.app.Activity;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;

public class MainActivity extends Activity {

	private Gallery picGallery;
	private ImageView myImageView;
	private Integer[] images = {
            R.drawable.girl_1,
            R.drawable.girl_2,
            R.drawable.girl_3,
            R.drawable.girl_4,
            R.drawable.girl_5,
            R.drawable.girl_6,
            R.drawable.girl_7,
            R.drawable.girl_8,
    };
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		requestWindowFeature(Window.FEATURE_NO_TITLE);
		setContentView(R.layout.activity_main);
		
		picGallery = (Gallery) findViewById(R.id.picGallery);
		myImageView = (ImageView) findViewById(R.id.myImageView);
		picGallery.setAdapter(new ImageAdapter(this));
		picGallery.setOnItemClickListener(listener);
	}

	
	 private OnItemClickListener listener = new OnItemClickListener() {

		@Override
		public void onItemClick(AdapterView<?> parent, View view, int position,long id) 
		{
			Drawable drawable = MainActivity.this.getResources().getDrawable(images[position]);
			myImageView.setImageDrawable(drawable);
		}
	};
	 public class ImageAdapter extends BaseAdapter {
	        private static final int ITEM_WIDTH = 136;
	        private static final int ITEM_HEIGHT = 88;

	        private final int mGalleryItemBackground;
	        private final Context mContext;

	        private final Integer[] mImageIds = {
	                R.drawable.girl_1,
	                R.drawable.girl_2,
	                R.drawable.girl_3,
	                R.drawable.girl_4,
	                R.drawable.girl_5,
	                R.drawable.girl_6,
	                R.drawable.girl_7,
	                R.drawable.girl_8,
	        };

	        private final float mDensity;

	        public ImageAdapter(Context c) {
	            mContext = c;
	            // See res/values/attrs.xml for the <declare-styleable> that defines
	            // Gallery1.
	            TypedArray a = obtainStyledAttributes(R.styleable.Gallery1);
	            mGalleryItemBackground = a.getResourceId(
	                    R.styleable.Gallery1_android_galleryItemBackground, 0);
	            a.recycle();

	            mDensity = c.getResources().getDisplayMetrics().density;
	        }

	        public int getCount() {
	            return mImageIds.length;
	        }

	        public Object getItem(int position) {
	            return position;
	        }

	        public long getItemId(int position) {
	            return position;
	        }

	        public View getView(int position, View convertView, ViewGroup parent) {
	            ImageView imageView;
	            if (convertView == null) {
	                convertView = new ImageView(mContext);

	                imageView = (ImageView) convertView;
	                imageView.setScaleType(ImageView.ScaleType.FIT_XY);
	                imageView.setLayoutParams(new Gallery.LayoutParams(
	                        (int) (ITEM_WIDTH * mDensity + 0.5f),
	                        (int) (ITEM_HEIGHT * mDensity + 0.5f)));
	            
	                // The preferred Gallery item background
	                imageView.setBackgroundResource(mGalleryItemBackground);
	            } else {
	                imageView = (ImageView) convertView;
	            }

	            imageView.setImageResource(mImageIds[position]);

	            return imageView;
	        }
	    }
}