Android应用开发学习之画廊视图

作者：刘昊昱

博客：http://blog.csdn.net/liuhaoyutz

画廊视图Gallery能按水平方向显示一组图片，并可以拖动图片。下面我们来看一个使用画廊视图的例子，其运行效果如下：

先来看主布局文件main.xml，其内容如下：

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

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    android:orientation="vertical" >

    <TextView

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        android:textSize="20px"

        android:text="@string/hello" />

    <Gallery

        android:id="@+id/gallery"

        android:spacing="5px"

        android:unselectedAlpha="0.5"

        android:layout_width="match_parent"

        android:layout_height="wrap_content" />

</LinearLayout>

下面看主Activity文件，其内容如下：

package com.liuhaoyu;

import android.app.Activity;

import android.content.res.TypedArray;

import android.os.Bundle;

import android.view.View;

import android.view.ViewGroup;

import android.widget.AdapterView;

import android.widget.BaseAdapter;

import android.widget.Gallery;

import android.widget.ImageView;

import android.widget.Toast;

import android.widget.AdapterView.OnItemClickListener;

public class MainActivity extends Activity {

    /** Called when the activity is first created. */

	private int[] imageId = new int[] { R.drawable.img01, R.drawable.img02,

			R.drawable.img03, R.drawable.img04, R.drawable.img05,

			R.drawable.img06, R.drawable.img07, R.drawable.img08};

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

        Gallery gallery = (Gallery) findViewById(R.id.gallery);

		BaseAdapter adapter = new BaseAdapter() {

			@Override

			public View getView(int position, View convertView, ViewGroup parent) {

				ImageView imageview;

				if (convertView == null) {

					imageview = new ImageView(MainActivity.this);

					imageview.setScaleType(ImageView.ScaleType.FIT_XY);

					imageview.setLayoutParams(new Gallery.LayoutParams(180, 135));

					TypedArray typedArray = obtainStyledAttributes(R.styleable.Gallery);

					imageview.setBackgroundResource(typedArray.getResourceId(

							R.styleable.Gallery_android_galleryItemBackground,

							0));

					imageview.setPadding(5, 0, 5, 0);

				} else {

					imageview = (ImageView) convertView;

				}

				imageview.setImageResource(imageId[position]);

				return imageview;

			}

			@Override

			public long getItemId(int position) {

				return position;

			}

			@Override

			public Object getItem(int position) {

				return position;

			}

			@Override

			public int getCount() {

				return imageId.length;

			}

		};

		gallery.setAdapter(adapter);

		gallery.setSelection(imageId.length / 2);

		gallery.setOnItemClickListener(new OnItemClickListener() {

			@Override

			public void onItemClick(AdapterView<?> parent, View view,

					int position, long id) {

				Toast.makeText(MainActivity.this,

						"第" + String.valueOf(position+1) + "张图片被选中",

						Toast.LENGTH_SHORT).show();

			}

		});

    }

}

在res/values目录中，创建attr.xml文件，该文件用于自定义属性，其内容如下：

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

<resources>

    <declare-styleable name="Gallery">

        <attr name="android:galleryItemBackground" />

    </declare-styleable>

</resources>