Android学习之Gallery

在Android中，画廊控件Gallery用来显示图片列表，可以用手指直接拖动图片左右移动。Gallery只能水平显示一行，且Gallery列表中的图片会根据不同的拖动情况向左或向右移动，直到显示到最后一个图片为止

1.XML布局

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:orientation="vertical" >

     <ImageView
         android:id="@+id/imageView"
         android:layout_width="match_parent"
         android:layout_height="650dp" >
     </ImageView>

     <Gallery
         android:id="@+id/gallery"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:spacing="5dp" >
     </Gallery>

 </LinearLayout>

在Gallery属性标签中，android:spacing="5dp"属性用于指定Gallery列表图片之间的间隔为2dp。

2.实现适配器

要实现Gallery画廊控件功能，需要一个容器来存放Gallery显示的图片。我们可以使用一个继承自BaseAdapter类的派生类ImageAdapter来装这些图片。

代码如：

 package com.example.gallery;

 import android.os.Bundle;
 import android.app.Activity;
 import android.content.Context;
 import android.view.Menu;
 import android.view.View;
 import android.view.ViewGroup;
 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 ImageView mImageView;
     private Gallery mGallery;
     private int[] images = { R.drawable.m1, R.drawable.m2, R.drawable.m3,
             R.drawable.m4, R.drawable.m5, };

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         mImageView = (ImageView) this.findViewById(R.id.imageView);
         mGallery = (Gallery) this.findViewById(R.id.gallery);
         mGallery.setAdapter(new ImagesAdapter(this));
         mGallery.setOnItemClickListener(new OnItemClickListener() {
             @Override
             public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
                     long arg3) {
                 mImageView.setBackgroundResource(images[arg2]);
             }
         });
     }

     public class ImagesAdapter extends BaseAdapter {
         private Context context;

         public ImagesAdapter(Context context) {
             this.context = context;
         }

         @Override
         public int getCount() {
             // TODO Auto-generated method stub
             return images.length;
         }

         @Override
         public Object getItem(int position) {
             // TODO Auto-generated method stub
             return images[position];
         }

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

         @Override
         public View getView(int position, View arg1, ViewGroup arg2) {
             ImageView imageView = new ImageView(context);
             imageView.setImageResource(images[position]);
             imageView.setLayoutParams(new Gallery.LayoutParams(200, 200));
             imageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
             return imageView;
         }
     }

     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         // Inflate the menu; this adds items to the action bar if it is present.
         getMenuInflater().inflate(R.menu.main, menu);
         return true;
     }

 }