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：