简单的图片二次采样

刚开始会出现加载不出控件的情况，获取width和height可能为0，所以放在onWindowFocusChanged方法中

    @Override
    public void onWindowFocusChanged(boolean hasFocus) {

        super.onWindowFocusChanged(hasFocus);

        // ImageView 的实际大小
        int width = img.getWidth();
        int height = img.getHeight();
        Log.e(TAG, "initView: " + "width:" + width + ",height:" + height);

        // 不二次采样bitmap大小
        Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.bb);
        Log.e(TAG, "init: " +"不二次采样bitmap大小: "+bitmap.getAllocationByteCount() );

        // 设置为true,加载图片时不会获取到bitmap对象,但是可以拿到图片的宽高
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeResource(getResources(), R.drawable.bb, options);

        // 获取图像的宽高值
        int outWidth = options.outWidth;
        int outHeight = options.outHeight;
        Log.e(TAG, "init: " + "outWidth: "+outWidth+",outHeight:"+outHeight);

        // 计算宽度比和高度比
        float widthRatio = outWidth * 1.0f / width;
        float heightRatio = outHeight * 1.0f / height;
        Log.e(TAG, "init: " + "widthRatio: "+widthRatio+",heightRatio:"+heightRatio);

        // 计算采样率
        float max = Math.max(widthRatio, heightRatio);
        int inSampleSize = (int) Math.ceil(max);
        Log.e(TAG, "init: " + "inSampleSize: "+inSampleSize);

        // 设置通过采样率更改压缩图片，加载图片显示
        options.inJustDecodeBounds=false;
        options.inSampleSize = inSampleSize;

        // 二次采样bitmap大小
        Bitmap bitmap1 = BitmapFactory.decodeResource(getResources(), R.drawable.bb, options);

        // 显示压缩后的图片
        img.setImageBitmap(bitmap1);
    }