Android使用Gallery实现照片拖动的特效

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;
import com.example.memorydemo.R;

public class SimpleGallery extends Activity {

  private static final String TAG = "SimpleGallery";

  @Override
  protected void onCreate(Bundle onSavedInstance) {
    super.onCreate(onSavedInstance);
    setContentView(R.layout.simple_gallery_layout);

    Gallery gallery = findViewById(R.id.gallery);
    gallery.setAdapter(new ImageAdapter(this));
  }

  private class ImageAdapter extends BaseAdapter {

    // 这里我们使用Android原生的资源图标
    private int[] imageIds = {
        android.R.drawable.btn_minus,
        android.R.drawable.btn_radio,
        android.R.drawable.ic_lock_idle_low_battery,
        android.R.drawable.ic_menu_camera };

    private Context mContext;

    public ImageAdapter(Context context) {
      mContext = context;
    }

    @Override
    public int getCount() {
      return imageIds.length;
    }

    @Override
    public Object getItem(int position) {
      return imageIds[position];
    }

    @Override
    public long getItemId(int position) {
      return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
      ImageView imageView;
      if (convertView == null) {
        Log.i(TAG, "convertView is null, create new imageview");
        imageView = new ImageView(mContext);
      } else {
        Log.i(TAG, "Cast convertView to ImageView");
        imageView = (ImageView) convertView;
      }

      imageView.setImageResource(imageIds[position]);
      imageView.setScaleType(ImageView.ScaleType.FIT_XY);
						
		  // 注意这里要用Gallery.LayoutParams作为布局参数类型，源码中给出了建议（Views given to the Gallery should use 
			// Gallery.LayoutParams s their ayout parameters type）
			// 由于Android原生图片很小，我将高度设置为 500，方便看效果
      imageView.setLayoutParams(new Gallery.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, 500));
      return imageView;
    }
  }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       android:layout_width="match_parent"
       android:layout_height="match_parent">

  <Gallery
      android:id="@+id/gallery"
      android:layout_width="match_parent"
      android:layout_height="match_parent" />

</LinearLayout>