Hot reload on save | 易学教程

问题

I'm currently using a terminal and vim on OSX as a development environment for Flutter. Things are going pretty well except that the app does not reload when I save any dart files. Is there a way to trigger that behavior?Currently I have to go to the terminal and hit "r" to see my changes.

回答1:

Sorry for the plug, but I wrote a very simple plugin to handle this.

It makes use of Flutter's --pid-file command line flag to send it a SIGUSR1 signal.

You can achieve the same result as my two-line plugin by adding this to an autocmd

silent execute '!kill -SIGUSR1 "$(cat /tmp/flutter.pid)"'

And launching Flutter with the --pid-file flag.

回答2:

I made a vim plugin hankchiutw/flutter-reload.vim based on killing with SIGUSR1.

You don't have to use --pid-file flag with this plugin. (Thanks to the pgrep :))

Simply execute flutter run, modify your *.dart file and see the reloading.

回答3:

I did it with the excellent little tool called entr. On OS/X you can install it from brew: brew install entr. The home page of the tool is at http://eradman.com/entrproject/

Then you start flutter run with the pidfile as @nobody_nowhere suggests.

How do you run entr depends on the level of service. In the simplest case you just do find lib/ -name '*.dart' | entr -p kill -USR1 $(cat /tmp/flutter.pid)

But such invocation will not detect new files in the source tree (because find builds a list of files to watch only once, at the start). You can get away with slightly more complex one-liner:

while true
do
    find lib/ -name '*.dart' | \
        entr -d -p kill -USR1 $(cat /tmp/flutter.pid)
done

The -d option makes entr exit when it does detect a new file in one of the directories and the loop runs again.

I personally use even more complex approach. I use Redux and change to middleware or other state files does not work with hot reload, it doesn't pick up these changes. So you need to resort to hot restart. I have a script hotrestarter.sh:

#!/bin/bash

set -euo pipefail
PIDFILE="/tmp/flutter.pid"

if [[ "${1-}" != "" && -e $PIDFILE ]]; then
    if [[ "$1" =~ \/state\/ ]]; then
        kill -USR2 $(cat $PIDFILE)
    else
        kill -USR1 $(cat $PIDFILE)
    fi
fi

It checks if the modified file lives in /state subdirectory and if true does hot restart or else hot reload. I call the script like that:

while true
do
    find lib/ -name '*.dart' | entr -d -p ./hotreloader.sh /_
done

The /_ parameter makes entr to pass the name of the file to the program being invoked.

回答4:

You don't say what platform, but all platforms have a "watcher" app that can run a command when any file in a tree changes. You'll need to run one of those.

回答5:

The following will trigger a Flutter reload on each *.dart file write (added to .vimrc):

function! HotReload() abort
  if !empty(glob("/tmp/flutter.pid"))
    silent execute '!kill -SIGUSR1 "$(cat /tmp/flutter.pid)"'
  endif
endfunction
autocmd BufWritePost *.dart call HotReload()

If you're also using :terminal in NeoVim, you can create a custom command to run Flutter with the --pid-file flag, directly in NeoVim. Something like:

command! FlutterRun :8split +terminal flutter run --pid-file /tmp/flutter.pid

This creates a :FlutterRun command that will open up a new terminal instance in a split and run Flutter automatically (with hot reloading).

回答6:

vscode has this feature. If you don't mind moving to vscode you can get it out of the box. You could also reach out to the author and see if they have any suggestions on how you could do it in vim or check the source directly. Most likely vim will have a mechanism to do so.

来源：https://stackoverflow.com/questions/49340508/hot-reload-on-save

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hot-reload