下载缩略图然后再显示的问题

Question

我想从 URL 上下载一个图片再放到 SD card 中，再在 imageview 中显示它的缩略图：

try {
Download(URL);  //download picture to SD card/Download
File myfile = new File(Environment.getExternalStorageDirectory() + "/Download/", filename);
Drawable photo = null; 
photo = Drawable.createFromPath(myfile.getPath());
imageview.setBackgroundDrawable(photo);
}

它显示初始化照片，但是当图像放大就会发生内存错误。所以我想显示小点的图像。那么我该如何做能生成缩略图再显示呢？或者如何让 android 系统生成缩略图？

Answer 1

网上很多，随便找个地方copy了个给你

 private Bitmap getImageThumbnail(String imagePath, int width, int height) {  
        Bitmap bitmap = null;  
        BitmapFactory.Options options = new BitmapFactory.Options();  
        options.inJustDecodeBounds = true;  
        // 获取这个图片的宽和高，注意此处的bitmap为null  
        bitmap = BitmapFactory.decodeFile(imagePath, options);  
        options.inJustDecodeBounds = false; // 设为 false  
        // 计算缩放比  
        int h = options.outHeight;  
        int w = options.outWidth;  
        int beWidth = w / width;  
        int beHeight = h / height;  
        int be = 1;  
        if (beWidth < beHeight) {  
            be = beWidth;  
        } else {  
            be = beHeight;  
        }  
        if (be <= 0) {  
            be = 1;  
        }  
        options.inSampleSize = be;  
        // 重新读入图片，读取缩放后的bitmap，注意这次要把options.inJustDecodeBounds 设为 false  
        bitmap = BitmapFactory.decodeFile(imagePath, options);  
        // 利用ThumbnailUtils来创建缩略图，这里要指定要缩放哪个Bitmap对象  
        bitmap = ThumbnailUtils.extractThumbnail(bitmap, width, height,  
                ThumbnailUtils.OPTIONS_RECYCLE_INPUT);  
        return bitmap;  
    }