[Android开发学习31]Gallery之初体验--实现手指直接拖动图片移动

13-04-06 来源：[db:作者]

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一、基础知识:

要实现这一效果，需要一个容器来存放Gallrey显示的图片，这里使用一个继承自BaseAdapter类的派生类来装这些图片。
我们需要监听其事件setOnItemClickListener,从而确定用户当前选中的是哪一张图片。
首先，需要将所有要显示的图片的索引存放在一个int型数组中，然后通过setImageResource方法来设置ImageView要显示的图片资源，最后将
每张图片的ImageView显示在屏幕上。

二、代码展示:

1."main.xml"

[html]
<?xml version="1.0" encoding="utf-8"?>
<Gallery
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/Gallery01"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
/>

<?xml version="1.0" encoding="utf-8"?>
<Gallery
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/Gallery01"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
/>

2."Activity01.java"

[java] view plaincopyprint?package com.yarin.android.XX;

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

public class Activity01 extends Activity
{
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        //获得Gallery对象
        Gallery g = (Gallery) findViewById(R.id.Gallery01);

        //添加ImageAdapter给Gallery对象
        g.setAdapter(new ImageAdapter(this));

        //设置Gallery的背景
        g.setBackgroundResource(R.drawable.bg0);

        //设置Gallery的事件监听
        g.setOnItemClickListener(new OnItemClickListener() {
            public void onItemClick(AdapterView<?> parent, View v, int position, long id)
            {
                Toast.makeText(Activity01.this,"你选择了"+(position+1)+" 号图片",
                    Toast.LENGTH_SHORT).show();
            }
        });
    }
}

package com.yarin.android.XX;

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

public class Activity01 extends Activity
{
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

//获得Gallery对象
Gallery g = (Gallery) findViewById(R.id.Gallery01);

//添加ImageAdapter给Gallery对象
g.setAdapter(new ImageAdapter(this));

  //设置Gallery的背景
  g.setBackgroundResource(R.drawable.bg0);

  //设置Gallery的事件监听
  g.setOnItemClickListener(new OnItemClickListener() {
   public void onItemClick(AdapterView<?> parent, View v, int position, long id)
   {
          Toast.makeText(Activity01.this,"你选择了"+(position+1)+" 号图片",
              Toast.LENGTH_SHORT).show();
   }
  });
}
}

3."ImageAdapter.java"

[java]
package com.yarin.android.XX;

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

public class ImageAdapter extends BaseAdapter
{
    // 定义Context
    private Context     mContext;
    // 定义整型数组即图片源
    private Integer[]   mImageIds =
    {
            R.drawable.img1,
            R.drawable.img2,
            R.drawable.img3,
            R.drawable.img4,
            R.drawable.img5,
            R.drawable.img6,
            R.drawable.img7,
            R.drawable.img8,
    };

    // 声明 ImageAdapter
    public ImageAdapter(Context c)
    {
        mContext = c;
    }

    // 获取图片的个数
    public int getCount()
    {
        return mImageIds.length;
    }

    // 获取图片在库中的位置
    public Object getItem(int position)
    {
        return position;
    }

    // 获取图片ID
    public long getItemId(int position)
    {
        return position;
    }

    public View getView(int position, View convertView, ViewGroup parent)
    {
        ImageView imageview = new ImageView(mContext);

        // 给ImageView设置资源
        imageview.setImageResource(mImageIds[position]);
        // 设置布局图片120×120显示
        imageview.setLayoutParams(new Gallery.LayoutParams(120, 120));
        // 设置显示比例类型
        imageview.setScaleType(ImageView.ScaleType.FIT_CENTER);
        return imageview;
    }
}

package com.yarin.android.XX;

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

public class ImageAdapter extends BaseAdapter
{
// 定义Context
private Context  mContext;
// 定义整型数组即图片源
private Integer[] mImageIds =
{
   R.drawable.img1,
   R.drawable.img2,
   R.drawable.img3,
   R.drawable.img4,
   R.drawable.img5,
   R.drawable.img6,
   R.drawable.img7,
   R.drawable.img8,
};

// 声明 ImageAdapter
public ImageAdapter(Context c)
{
mContext = c;
}

// 获取图片的个数
public int getCount()
{
return mImageIds.length;
}

// 获取图片在库中的位置
public Object getItem(int position)
{
return position;
}

// 获取图片ID
public long getItemId(int position)
{
return position;
}

public View getView(int position, View convertView, ViewGroup parent)
{
ImageView imageview = new ImageView(mContext);

  // 给ImageView设置资源
  imageview.setImageResource(mImageIds[position]);
  // 设置布局图片120×120显示
  imageview.setLayoutParams(new Gallery.LayoutParams(120, 120));
  // 设置显示比例类型
  imageview.setScaleType(ImageView.ScaleType.FIT_CENTER);
  return imageview;
}
}

三、效果展示:

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