android中如何使用一张图片适配不同尺寸的APP引导页(http://blog.csdn.net/sahadev_/article/details/48475217)

ScaleBitmap.java

private static void scaleImage(final Activity activity, final View view, int drawableResId) {
		// 获取屏幕的高宽
		Point outSize = new Point();
		if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB_MR2) {
			activity.getWindow().getWindowManager().getDefaultDisplay().getSize(outSize);
		} else {
			outSize.x = activity.getWindow().getWindowManager().getDefaultDisplay().getWidth();
			outSize.y = activity.getWindow().getWindowManager().getDefaultDisplay().getHeight();
		}

		// 解析将要被处理的图片
		Bitmap resourceBitmap = BitmapFactory.decodeResource(activity.getResources(), drawableResId);

		if (resourceBitmap == null) {
			return;
		}

		// 开始对图片进行拉伸或者缩放

		// 使用图片的缩放比例计算将要放大的图片的高度
		int bitmapScaledHeight = Math.round(resourceBitmap.getHeight() * outSize.x * 1.0f / resourceBitmap.getWidth());

		// 以屏幕的宽度为基准，如果图片的宽度比屏幕宽，则等比缩小，如果窄，则放大
		final Bitmap scaledBitmap = Bitmap.createScaledBitmap(resourceBitmap, outSize.x, bitmapScaledHeight, false);

		view.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
			@Override
			public void onGlobalLayout() {
				// 当UI绘制完毕，我们对图片进行处理
				int viewHeight = view.getMeasuredHeight();

				// 计算将要裁剪的图片的顶部以及底部的偏移量
				int offset = (scaledBitmap.getHeight() - viewHeight) / 2;

				// 对图片以中心进行裁剪，裁剪出的图片就是非常适合做引导页的图片了
				Bitmap finallyBitmap = Bitmap.createBitmap(scaledBitmap, 0, offset, scaledBitmap.getWidth(),
						scaledBitmap.getHeight() - offset * 2);

				// 设置图片显示

				if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
					view.setBackground(new BitmapDrawable(activity.getResources(), finallyBitmap));
				} else {
					view.setBackgroundDrawable(new BitmapDrawable(activity.getResources(), finallyBitmap));
				}
			}
		});
	}