由於最近專案需要做，一個簡單的unity3d上面連結android原生相簿獲取圖片的外掛，於是乎簡單的瞭解了一下，以下是實現步驟:

1.從unity3d的專案路徑中拷出jar包unity3D5.0\u3d\Unity\Editor\Data\PlaybackEngines\androidplayer\release\bin\classess

2.新建一個acitivity把classes.jre包放入libs資料夾，並建立一個繼承自UnityPlayerActivity的類

2.1匯入classes.jar

2.2建立繼承自UnityPlayerActivity的類

public class Main extends UnityPlayerActivity{
	
	private String photoPath="";
		
	public static String FILE_NAME = "image.png";
	
	public static final int CHOOSE_PICTURE=4;
	
	private String newPath="";
    
	private String headPath="";
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
	}
}
 

public void Main()
	{
	Intent openAlbumIntent = new Intent(Intent.ACTION_GET_CONTENT);  
		
    	openAlbumIntent.setType("image/*");  
        
    	startActivityForResult(openAlbumIntent, CHOOSE_PICTURE);  
	}
	
	 public void RefreshPic(String oldpath)
	 {
		 photoPath="/mnt/sdcard/DCIM/Camera/";
		 SimpleDateFormat sDateFormat=new SimpleDateFormat("yyyyMMddhhmmss");     
		 FILE_NAME="p"+sDateFormat.format(new java.util.Date())+".png"; 
		 copyFile(oldpath, photoPath);
		 myDeleteFile(oldpath);
		 Intent intent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE); 
		 Uri uri = Uri.fromFile(new File(photoPath+FILE_NAME)); 
		 intent.setData(uri); 
		 sendBroadcast(intent);  
	 }
 

 @Override
	protected void onActivityResult(int requestCode, int resultCode, Intent data) {
		    // 拍照  
	        if(requestCode==CHOOSE_PICTURE)
	        {
	             Uri originalUri = data.getData();  
	             String[] proj = {MediaStore.Images.Media.DATA};
				 Cursor cursor = getContentResolver().query(originalUri, proj, null, null, null); 
				 int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
				 cursor.moveToFirst();
			     //判斷遊標是否為空
				 if(cursor.getString(column_index)!=null)
				 {
			     //得到選擇圖片的原始路徑
				 String oldpath = cursor.getString(column_index); 
				 //儲存原始圖片的路徑
				 newPath="/mnt/sdcard/Android/data/com.unitypluginstest.main/files/sourcefiles";
				 //儲存壓縮後圖片的路徑
				 headPath="/mnt/sdcard/Android/data/com.unitypluginstest.main/files/headfiles";
				 SimpleDateFormat sDateFormat=new SimpleDateFormat("yyyyMMddhhmmss");     
				 FILE_NAME="p"+sDateFormat.format(new java.util.Date())+".png";  
				 //將選擇的圖片檔案複製到新的路徑
				 copyFile(oldpath, newPath);
				 //點陣圖工廠模式開啟對圖片進行壓縮設定
				 BitmapFactory.Options options = new BitmapFactory.Options();
	             options.inSampleSize =2;
	             Bitmap b = BitmapFactory.decodeFile(newPath+"/"+FILE_NAME, options);
	        	 BitmapFactory.Options options1 = new BitmapFactory.Options();
	             options1.inSampleSize =getSuitableSize(b.getWidth()*2,b.getHeight()*2);
	             Bitmap b1= BitmapFactory.decodeFile(newPath+"/"+FILE_NAME, options1);
	             saveBitmap(headPath, b1);
	             }
	             else
	             {
	 			 Toast.makeText(getApplicationContext(), "當前的路徑不存在", Toast.LENGTH_SHORT).show();
	             }
	        }
		super.onActivityResult(requestCode, resultCode, data);
	}
 

 public void copyFile(String oldPath, String newPath) {   
	       try {   
	           int bytesum = 0;   
	           int byteread = 0;   
	           File oldfile = new File(oldPath); 
	           File newfile=new File(newPath);
	           if(!newfile.exists())
	           {
	        	   newfile.mkdirs();
	           }
	           if (oldfile.exists()) { 
	               InputStream inStream = new FileInputStream(oldPath); //讀入原檔案   
	               FileOutputStream fs = new FileOutputStream(newPath+"/"+FILE_NAME);   
	               byte[] buffer = new byte[1024];   
	               while ( (byteread = inStream.read(buffer)) != -1) {   
	                   bytesum += byteread; 
	                   fs.write(buffer, 0, byteread);   
	               }   
	               Log.e("tag", "success!");
	               inStream.close();   
	               fs.close();
	           }   
	       }   
	       catch (Exception e) {   
	           e.printStackTrace();   
	  
	       }   
	   }   
	 
	 public boolean myDeleteFile(String path)
	 {
		 File file=new File(path);
		 if(file.exists())
		 {
			 file.delete();
			 return true;
		 }else
		 {
			 return false;
		 }
	 }
private int getSuitableSize(int width, int height) {
			int suitableSize = 16;
			if(width>height)
			{
				suitableSize=Math.round(width/128);
			}else if(height>width) 
			{
				suitableSize=Math.round(height/128);
			}else 
			{
				suitableSize=Math.round(width/128);
			}
			return suitableSize;
		}
		
		public void saveBitmap(String filePath,Bitmap bmp) { 
			File file = new File(filePath); 
			if(!file.exists())
			{
				file.mkdirs();
			}
			try { 
			FileOutputStream out = new FileOutputStream(file+"/"+FILE_NAME); 
			bmp.compress(Bitmap.CompressFormat.PNG, 30, out); 
			out.flush(); 
			out.close(); 
			} catch (FileNotFoundException e) { 
			// TODO Auto-generated catch block 
			e.printStackTrace(); 
			} catch (IOException e) { 
			// TODO Auto-generated catch block 
			e.printStackTrace(); 
			} 
			}