缩放图标以适合Imageview Android

时间:2013-07-31 10:33:59

标签: android android-ui

我的应用程序中有一个列表,其中包含所有已安装的应用程序及其图标,我能够渲染已安装的应用程序和图标,但它消耗了很多内存,因为它将已安装的应用程序的drawables(icons)加载到内存中。

我想缩小图标然后加载到内存中以减少应用程序的内存使用量。谁能告诉我如何实现这一目标。

注意:如果是PNG格式,那么它就不会压缩您的图片,因为PNG是一种无损格式。 和应用程序图标采用PNG格式

任何减少图标内存分配的方法??

2 个答案:

答案 0 :(得分:1)

是的,所有这些都在文档中:

http://developer.android.com/training/displaying-bitmaps/index.html

计算样本大小,即所需位图的大小:

public static int calculateInSampleSize(
            BitmapFactory.Options options, int reqWidth, int reqHeight) {
    // Raw height and width of image
    final int height = options.outHeight;
    final int width = options.outWidth;
    int inSampleSize = 1;

    if (height > reqHeight || width > reqWidth) {

        // Calculate ratios of height and width to requested height and width
        final int heightRatio = Math.round((float) height / (float) reqHeight);
        final int widthRatio = Math.round((float) width / (float) reqWidth);

        // Choose the smallest ratio as inSampleSize value, this will guarantee
        // a final image with both dimensions larger than or equal to the
        // requested height and width.
        inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;
    }

    return inSampleSize;
}

以这个大小解码你的位图:

public static Bitmap decodeSampledBitmapFromResource(Resources res, int resId,
        int reqWidth, int reqHeight) {

    // First decode with inJustDecodeBounds=true to check dimensions
    final BitmapFactory.Options options = new BitmapFactory.Options();
    options.inJustDecodeBounds = true;
    BitmapFactory.decodeResource(res, resId, options);

    // Calculate inSampleSize
    options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);

    // Decode bitmap with inSampleSize set
    options.inJustDecodeBounds = false;
    return BitmapFactory.decodeResource(res, resId, options);
}

这应该都是在UI线程之外完成的:

http://developer.android.com/training/displaying-bitmaps/process-bitmap.html

然后,您可以缓存位图,这样您就不必多次执行此操作:

http://developer.android.com/training/displaying-bitmaps/cache-bitmap.html

答案 1 :(得分:1)

使用BitmapFactory.Options中的inSampleSize

    BitmapFactory.Options options = new BitmapFactory.Options();
 options.inSampleSize = 2; //Downsample 10x