android开发 怎么在应用中调取图片库 选择一张图片 返回自己的应用中

http://www.oschina.net/question/97402_33604

 

package demo.camera;  
import android.app.Activity;  
import android.database.Cursor;  
import android.graphics.Bitmap;  
import android.graphics.BitmapFactory;  
import android.os.Bundle;  
import android.provider.MediaStore.Images.Media;  
import android.util.Log;  
import android.view.View;  
import android.widget.ImageButton;  
import android.widget.TextView;  
/** 
 * 该类完成图片的检索，显示功能 
 * @author Administrator 
 * 
 */  
public class PhotoManager extends Activity {  
      
    public static final float DISPLAY_WIDTH = 200;  
    public static final float DISPLAY_HEIGHT = 200;  
      
    //这里采用ImageButton的原因是有Button的作用  
    private ImageButton photoView;  
    private TextView nameView;  
      
    private Cursor cursor;  
      
    private String photoPath; //存放某张图片对应的位置信息  
    private Bitmap currPhoto;  
      
    //这三个变量主要用来保存Media.DATA,Media.TITLE,Media.DISPLAY_NAME的索引号，来获取每列的数据  
    private int photoIndex;  
    //private int titleIndex;  
    private int nameIndex;  
      
    public void onCreate(Bundle savedInstanceState){  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.photo_view);  
          
        photoView = (ImageButton)this.findViewById(R.id.image_view);  
        photoView.setOnClickListener(clickListener);  
        nameView = (TextView)this.findViewById(R.id.view_name);  
          
        //指定获取的列  
        String columns[] = new String[]{  
                Media.DATA,Media._ID,Media.TITLE,Media.DISPLAY_NAME  
        };  
        //cursor = this.managedQuery(Media.EXTERNAL_CONTENT_URI, columns, null, null, null);  
        cursor = this.getContentResolver().query(Media.EXTERNAL_CONTENT_URI, columns, null, null, null);  
        photoIndex = cursor.getColumnIndexOrThrow(Media.DATA);  
        //titleIndex = cursor.getColumnIndexOrThrow(Media.TITLE);  
        nameIndex = cursor.getColumnIndexOrThrow(Media.DISPLAY_NAME);  
          
        Log.v("HERE First:", "First Debug");  
        //显示第一张图片，但是首先要判断一下，Cursor是否有值  
        if(cursor.moveToFirst()){  
            showImage();  
        }  
    }  
      
    private View.OnClickListener clickListener = new View.OnClickListener() {  
          
        @Override  
        public void onClick(View v) {  
              
            if(cursor.moveToNext()){  
                showImage();  
            }  
        }  
    };  
      
    /** 
     * 显示图像信息 
     */  
    private void showImage(){  
        photoPath = cursor.getString(photoIndex); //这里获取到的就是图片存储的位置信息  
        //这里怎样获取图片呢？看decodeBitmap  
        Log.v("Photo Path:", photoPath);  
        currPhoto = decodeBitmap(photoPath);  
        photoView.setImageBitmap(currPhoto);  
        nameView.setText(cursor.getString(nameIndex));        
    }  
      
    /** 
     * 从path中获取图片信息 
     * @param path 
     * @return 
     */  
    private Bitmap decodeBitmap(String path){  
        BitmapFactory.Options op = new BitmapFactory.Options();  
        op.inJustDecodeBounds = true;  
        Bitmap bmp = BitmapFactory.decodeFile(path, op); //获取尺寸信息  
        //获取比例大小  
        int wRatio = (int)Math.ceil(op.outWidth/DISPLAY_WIDTH);  
        int hRatio = (int)Math.ceil(op.outHeight/DISPLAY_HEIGHT);  
        //如果超出指定大小，则缩小相应的比例  
        if(wRatio > 1 && hRatio > 1){  
            if(wRatio > hRatio){  
                op.inSampleSize = wRatio;  
            }else{  
                op.inSampleSize = hRatio;  
            }  
        }  
        op.inJustDecodeBounds = false;  
        bmp = BitmapFactory.decodeFile(path, op);  
        return bmp;  
    }  
      
}