Android使用Bit地图Factory.Options解决加载大图片内存溢出有关问题

public?Bitmap getBitmapFromFile(File?dst,?int?width,?int?height)?{
? ??if?(null?!=?dst?&&?dst.exists())?{
? ? ? ? BitmapFactory.Options?opts?=?null;
? ? ? ??if?(width?>?0?&&?height?>?0)?{
? ? ? ? ? ? opts?=?new?BitmapFactory.Options();
? ? ? ? ? ? opts.inJustDecodeBounds?=?true;
? ? ? ? ? ? BitmapFactory.decodeFile(dst.getPath(), opts);
? ? ? ? ? ??// 计算图片缩放比例
? ? ? ? ? ??final?int?minSideLength?=?Math.min(width, height);
? ? ? ? ? ? opts.inSampleSize?=?computeSampleSize(opts, minSideLength,
? ? ? ? ? ? ? ? ? ? width?*?height);
? ? ? ? ? ? opts.inJustDecodeBounds?=?false;
? ? ? ? ? ? opts.inInputShareable?=?true;
? ? ? ? ? ? opts.inPurgeable?=?true;
? ? ? ??}
? ? ? ??try?{
? ? ? ? ? ??return?BitmapFactory.decodeFile(dst.getPath(), opts);
? ? ? ??}?catch?(OutOfMemoryError?e)?{
? ? ? ? ? ? e.printStackTrace();
? ? ? ??}
? ??}
? ??return?null;
}

public?static?int?computeSampleSize(BitmapFactory.Options?options,
? ? ? ??int?minSideLength,?int?maxNumOfPixels)?{
? ??int?initialSize?=?computeInitialSampleSize(options, minSideLength,
? ? ? ? ? ? maxNumOfPixels);

? ??int?roundedSize;
? ??if?(initialSize?<=?8)?{
? ? ? ? roundedSize?=?1;
? ? ? ??while?(roundedSize?<?initialSize)?{
? ? ? ? ? ? roundedSize?<<=?1;
? ? ? ??}
? ??}?else?{
? ? ? ? roundedSize?=?(initialSize?+?7)?/?8?*?8;
? ??}

? ??return?roundedSize;
}

private?static?int?computeInitialSampleSize(BitmapFactory.Options?options,
? ? ? ??int?minSideLength,?int?maxNumOfPixels)?{
? ??double?w?=?options.outWidth;
? ??double?h?=?options.outHeight;

? ??int?lowerBound?=?(maxNumOfPixels?==?-1)???1?:?(int)?Math.ceil(Math
? ? ? ? ? ? .sqrt(w?*?h?/?maxNumOfPixels));
? ??int?upperBound?=?(minSideLength?==?-1)???128?:?(int)?Math.min(Math
? ? ? ? ? ? .floor(w?/?minSideLength),?Math.floor(h?/?minSideLength));

? ??if?(upperBound?<?lowerBound)?{
? ? ? ??// return the larger one when there is no overlapping zone.
? ? ? ??return?lowerBound;
? ??}

? ??if?((maxNumOfPixels?==?-1)?&&?(minSideLength?==?-1))?{
? ? ? ??return?1;
? ??}?else?if?(minSideLength?==?-1)?{
? ? ? ??return?lowerBound;
? ??}?else?{
? ? ? ??return?upperBound;
? ??}
}