Kotlin 图标设置在服务中

Question

In the application I wrote with kotlin, I get status information from the server with the service every minute. I want to change the menu icon according to the status information from the server. I created a static global menu variable for this, but the icon changes only once, even if the status information from the server changes, the icon does not change.

MainActivitiy.kt

companion object {
    lateinit var menum: Menu
}

    override fun onCreateOptionsMenu(menu: Menu): Boolean {
    menuInflater.inflate(R.menu.menu_main, menu)
    menum = menu;
    ....
    ....
}

Service.kt

    fun sync_check(){
    if(LocalDbHash==SrvDbHash){
        MainActivity.menum.findItem(R.id.sync_btn).setIcon(R.drawable.ic_edit)
    }else{
        MainActivity.menum.findItem(R.id.sync_btn).setIcon(R.drawable.ic_delete)
    }
}

Answer 1

You want onPrepareOptionsMenu instead :

After the system calls onCreateOptionsMenu() , it retains an instance of the Menu you populate and will not call onCreateOptionsMenu() again unless the menu is invalidated for some reason. However, you should use onCreateOptionsMenu() only to create the initial menu state and not to make changes during the activity lifecycle .

If you want to modify the options menu based on events that occur during the activity lifecycle, you can do so in the onPrepareOptionsMenu() method. This method passes you the Menu object as it currently exists so you can modify it, such as add, remove, or disable items.

On Android 3.0 and higher, the options menu is considered to always be open when menu items are presented in the app bar. When an event occurs and you want to perform a menu update, you must call invalidateOptionsMenu() to request that the system call onPrepareOptionsMenu()

So syncCheck should just set a "current icon" variable, and call invalidateOptionsMenu() . onPrepareOptionsMenu will be passed the current Menu and you can do your update there. Something like:

var syncButtonEdits = true

override fun onCreateOptionsMenu(menu: Menu): Boolean {
    // inflate the basic menu
    menuInflater.inflate(R.menu.menu_main, menu)
}

// this is called just before the menu is displayed
override fun onPrepareOptionsMenu(menu: Menu): Boolean {
    menu.findItem(R.id.sync_btn).setIcon(
        // set this icon according to the current state
        if (syncButtonEdits) R.drawable.ic_edit else R.drawable.ic_delete
    )
}

fun sync_check(){
    syncButtonEdits = LocalDbHash==SrvDbHash
    // calls onPrepareOptionsMenu, which will check the value of syncButtonEdits
    invalidateOptionsMenu()
}