安卓官方解决加载图片内存溢出问题

水深无声 2022-09-25 13:18 205阅读 0赞

1.计算options.inSampleSize

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) {
    
            final int halfHeight = height / 2;
            final int halfWidth = width / 2;
    
            // Calculate the largest inSampleSize value that is a power of 2 and keeps both
            // height and width larger than the requested height and width.
            while ((halfHeight / inSampleSize) >= reqHeight
                    && (halfWidth / inSampleSize) >= reqWidth) {
                inSampleSize *= 2;
            }
        }
    
        return inSampleSize;
    }

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);
    }

3.使用

mImageView.setImageBitmap(
        decodeSampledBitmapFromResource(getResources(), R.id.myimage, 100, 100));

PS: [原文链接][Link 1]

4.可简写为：

private Bitmap decodeBitmap(File file){
            try{
                BitmapFactory.Options o = new BitmapFactory.Options();
                o.inJustDecodeBounds = true;
                BitmapFactory.decodeStream(new FileInputStream(file),null,o);
                final int REQYIRED_SIZE  = 70;
                int scale = 1;
                while (o.outWidth / 2 / scale >= REQYIRED_SIZE && o.outHeight / 2 /scale >= REQYIRED_SIZE){
                    scale *= 2;
                }
                Log.e(TAG, "decodeBitmap: scale---"+scale );
                BitmapFactory.Options options = new BitmapFactory.Options();
                options.inSampleSize = scale / 4;
                return BitmapFactory.decodeStream(new FileInputStream(file),null,options);
            }catch (Exception e){
                e.printStackTrace();
            }
            return null;
        }

[Link 1]: https://developer.android.com/training/displaying-bitmaps/load-bitmap.html