android 获取本地图片的缩略图，显示到imageview并保存缩略图到本地某一文件夹下

Activity:

public class ButtonFiveActivity extends AppCompatActivity {
    private ImageView imageOne;
    private ImageView imageTwo;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_five);
        imageOne = findViewById(R.id.imageOne);
        imageTwo = findViewById(R.id.imageTwo);
        Bitmap bmp = null;
        try {
            bmp = PictureProcessingUtil.revitionImageSize(Environment.getExternalStorageDirectory()+"/文件夹名称/FCEB0E51-6118-497B-B3EE-22F420F91054.jpeg",400,400);
            PictureProcessingUtil.saveBitmap(bmp,this);
        } catch (IOException e) {
            e.printStackTrace();
        }
        imageOne.setImageBitmap(bmp);
        String  userImagePath = Environment.getExternalStorageDirectory().getAbsolutePath() + "/文件夹名称/FCEB0E51-6118-497B-B3EE-22F420F91054.jpeg";
        boolean fileExist = PictureProcessingUtil.fileIsExists(userImagePath);
        if(fileExist){
              imageTwo.setImageBitmap(PictureProcessingUtil.saveBitmapFile(userImagePath));
        }
    }
}

布局简单，即两个imageView,一个用于显示缩略图，一个显示原图，用于对比。

PictureProcessingUtil：

public class PictureProcessingUtil {
    //获取缩略图
    public static Bitmap revitionImageSize(String path, int maxWidth, int maxHeight) throws IOException {
        Bitmap bitmap = null;
        try {
            BufferedInputStream in = new BufferedInputStream(new FileInputStream(
                    new File(path)));
            BitmapFactory.Options options = new BitmapFactory.Options();
            options.inJustDecodeBounds = true;
            BitmapFactory.decodeStream(in, null, options);
            in.close();
            int i = 0;
            while (true) {
                if ((options.outWidth >> i <= maxWidth)
                        && (options.outHeight >> i <= maxHeight)) {
                    in = new BufferedInputStream(
                            new FileInputStream(new File(path)));
                    options.inSampleSize = (int) Math.pow(2.0D, i);
                    options.inJustDecodeBounds = false;
                    bitmap = BitmapFactory.decodeStream(in, null, options);
                    break;
                }
                i += 1;
            }
        } catch (Exception e) {
            return null;
        }
        return bitmap;
    }

    public static Bitmap saveBitmapFile(String filePath) {
        File file = new  File(filePath);
        return BitmapFactory.decodeFile(file.toString());
    }
    //判断文件是否存在
    public static boolean fileIsExists(String strFile) {
        try {
            File f = new File(strFile);
            if (!f.exists()) {
                return false;
            }
        } catch (Exception e) {
            return false;
        }
        return true;
    }

    // 图片存放路径
    public static String sdCardDir = Environment.getExternalStorageDirectory() + "/文件夹名称/";
    /**
     * 保存图片
     *
     * @param bitmap
     */
    public static void saveBitmap(Bitmap bitmap, Context context) {
        try {
            File dirFile = new File(sdCardDir);
            if (!dirFile.exists()) {              //如果不存在，那就建立这个文件夹
                dirFile.mkdirs();
            }
            File file = new File(sdCardDir,  "FCEB0E51-6118-497B-B3EE-22F420F91054little.jpeg");//加little用于名称区分
            FileOutputStream fos = new FileOutputStream(file);
            bitmap.compress(Bitmap.CompressFormat.JPEG, 100, fos);
            fos.flush();
            fos.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        // 把文件插入到系统图库
//        try {
//            MediaStore.Images.Media.insertImage(context.getContentResolver(),
//                    file.getAbsolutePath(), fileName, null);
//        } catch (FileNotFoundException e) {
//            e.printStackTrace();
//        }
//        // 通知图库更新
//        context.sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE,
//                Uri.parse("file://" + "/sdcard/namecard/")));
    }
}