Android实战简易教程-第十枪（画廊组件Gallery实用研究）

Gallery组件用于拖拽浏览图片，下面我们就来看一下如何实现。

一、实现Gallery

1.布局文件很简单：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/MyLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#FFFFFF"
    android:orientation="vertical" >

    <Gallery
        android:id="@+id/myGallery"
        android:gravity="center_vertical"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

2.自定义适配器类，可以直接覆写BaseAdapter类中的几个方法。

package org.yayun.demo;

import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;
import android.widget.Gallery.LayoutParams;

public class ImageGalleryAdapter extends BaseAdapter {
	private Context context;
	private int imgRes[] = new int[] { R.drawable.ispic_a, R.drawable.ispic_b,
			R.drawable.ispic_c, R.drawable.ispic_d, R.drawable.ispic_e, };

	public ImageGalleryAdapter(Context c) {//构造方法，用于获取上下文对象
		this.context = c;
	}

	public int getCount() {

		return imgRes.length;
	}

	public Object getItem(int position) {
		return imgRes[position];
	}

	public long getItemId(int position) {
		return imgRes[position];
	}

	public View getView(int position, View convertView, ViewGroup parent) {
		ImageView img = new ImageView(this.context);
		img.setBackgroundColor(0xFFFFFFFF);
		img.setImageResource(this.imgRes[position]);//设置资源
		img.setScaleType(ImageView.ScaleType.CENTER);//居中显示
		img.setLayoutParams(new Gallery.LayoutParams(LayoutParams.WRAP_CONTENT,
				LayoutParams.WRAP_CONTENT));
		return img;
	}

}

3.MainActivity.java:

package org.yayun.demo;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Toast;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.Gallery;

public class MainActivity extends Activity {
	private Gallery gallery;

	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState); // 生命周期方法
		super.setContentView(R.layout.main); // 设置要使用的布局管理器
		gallery = (Gallery) findViewById(R.id.myGallery);
		gallery.setAdapter(new ImageGalleryAdapter(this));
		gallery.setOnItemClickListener(new OnItemClickListener() {

			public void onItemClick(AdapterView<?> parent, View view,
					int position, long id) {
				Toast.makeText(MainActivity.this,
						"您选择了第" + String.valueOf(position + 1) + "张图片",
						Toast.LENGTH_SHORT).show();

			}
		});
	}
}

4.运行实例如下：

二、Gallery和ImageSwitcher结合

这时的Gallery我们用SimpleAdapter类完成。

1.布局文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/MyLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#FFFFFF"
    android:gravity="bottom"
    android:orientation="vertical" >

    <ImageSwitcher
        android:id="@+id/imageSwitcher"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" >
    </ImageSwitcher>

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

</LinearLayout>

2.定义显示模板：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="#FFFFFF"
    android:orientation="horizontal" >

    <ImageView
        android:id="@+id/img"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:scaleType="center" />

</LinearLayout>

3.MainActivity.java程序：

package org.yayun.demo;

import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ImageSwitcher;
import android.widget.ImageView;
import android.widget.SimpleAdapter;
import android.widget.Toast;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.Gallery.LayoutParams;
import android.widget.Gallery;
import android.widget.ViewSwitcher.ViewFactory;

public class MainActivity extends Activity {
	private Gallery gallery;
	private List<Map<String, Integer>> list = new ArrayList<Map<String, Integer>>();
	private SimpleAdapter simpleAdapter;
	private ImageSwitcher imageSwitcher;

	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState); // 生命周期方法
		super.setContentView(R.layout.main); // 设置要使用的布局管理器
		initAdapter();
		gallery = (Gallery) findViewById(R.id.gallery);
		imageSwitcher = (ImageSwitcher) findViewById(R.id.imageSwitcher);
		imageSwitcher.setFactory(new ViewFactory() {

			public View makeView() {
				ImageView imageView = new ImageView(MainActivity.this);
				imageView.setBackgroundColor(0xFFFFFFFF);
				imageView.setScaleType(ImageView.ScaleType.CENTER);
				imageView.setLayoutParams(new ImageSwitcher.LayoutParams(
						LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
				return imageView;
			}
		});
		gallery.setAdapter(simpleAdapter);
		gallery.setOnItemClickListener(new OnItemClickListener() {

			public void onItemClick(AdapterView<?> parent, View view,
					int position, long id) {
				Map<String, Integer> map = (Map<String, Integer>) MainActivity.this.simpleAdapter
						.getItem(position);// 取出map
				MainActivity.this.imageSwitcher.setImageResource(map.get("img"));// 设置显示图片

			}
		});
	}

	private void initAdapter() {
		Field[] fields = R.drawable.class.getDeclaredFields();// Java反射机制获取所有资源图片
		for (int i = 0; i < fields.length; i++) {
			if (fields[i].getName().startsWith("ispic_")) {// 判断开头
				Map<String, Integer> map = new HashMap<String, Integer>();
				try {
					map.put("img", fields[i].getInt(R.drawable.class));
				} catch (IllegalArgumentException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} catch (IllegalAccessException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				this.list.add(map);
			}
		}
		simpleAdapter = new SimpleAdapter(this, this.list,
				R.layout.grid_layout, new String[] { "img" },
				new int[] { R.id.img });

	}
}

4.运行实例：