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;
    }

}