Android 使用Bitmap将自身保存为文件，BitmapFactory从File中解析图片并防止OOM

1、使用Bitmap将自身保存为文件

public boolean saveBitmapAsFile(String name, Bitmap bitmap) {

        File saveFile = new File(cacheDirectory, name);

        boolean saved = false;

        FileOutputStream os = null;

        try {

            Log.d("FileCache", "Saving File To Cache " + saveFile.getPath());

            os = new FileOutputStream(saveFile);

            bitmap.compress(CompressFormat.PNG, , os);

            os.flush();

            os.close();

            saved = true;

        } catch (FileNotFoundException e) {

            e.printStackTrace();

        } catch (IOException e) {

            e.printStackTrace();

        }

        return saved;

    }

2、BitmapFactory从File中解析图片并防止OOM

/** 获得与需要的比例最接近的比例 */

    static int calculateInSampleSize(BitmapFactory.Options bitmapOptions, int reqWidth, int reqHeight) {

        final int height = bitmapOptions.outHeight;

        final int width = bitmapOptions.outWidth;

        int sampleSize = ;

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

            final int heightRatio = Math.round((float) height / (float) reqHeight);

            final int widthRatio = Math.round((float) width / (float) reqWidth);

            sampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;

        }

        return sampleSize;

    }

    public static Bitmap decodeImage(String filePath) {

        /** Decode image size */

        BitmapFactory.Options o = new BitmapFactory.Options();

        /** 只取宽高防止oom */

        o.inJustDecodeBounds = true;

        BitmapFactory.decodeFile(filePath, o);

        int scale=calculateInSampleSize(o, displayStats.maxItemWidthHeight, displayStats.maxItemWidthHeight);

        BitmapFactory.Options options=new BitmapFactory.Options();

        /** Decode with inSampleSize，比直接算出options中的使用更少的内存*/

        options.inSampleSize=scale;

        /** 内存不足的时候可被擦除 */

        options.inPurgeable = true;

        /** 深拷贝 */

        options.inInputShareable = true;

        synchronized (DDGControlVar.DECODE_LOCK) {

            Bitmap result = BitmapFactory.decodeFile(filePath, options);

            return result;

        }

    }