检索Android的图片库，并显示

学习如何检索并显示媒体库中的图片

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;
    }

}

转自http://blog.csdn.net/chenjie19891104/article/details/6320664