Launcher is unable to update

This has been happening to me for a while, so basically whenever I open my Minecraft Launcher it crashes right after a small 'updating launcher' window opens. That window stays for maybe only half a second before crashing. I have been turning off my wifi whenever I open it to prevent updates, then once it's open I simply turn it back on. This allows me to play past versions. I have tried reinstalling but it won't work, I have tried downloading the latest java but it won't work