自定义后退按钮-Android导航 [英] custom back button - Android Navigation

问题描述

我有一个表单，希望在用户离开之前得到用户的确认消息.

I have a form and want to get a confirmation message from the user before the user leaves it.

我想在用户触摸此按钮时提供自定义后退按钮:

i want provide custom back button when user touch this button:

我试试这个:

val onBackPressedCallback = object : OnBackPressedCallback(true) {
            override fun handleOnBackPressed() {
            }
        }
requireActivity().onBackPressedDispatcher.addCallback(this,onBackPressedCallback)

但似乎只能为内置的软件/硬件后退按钮提供自定义后退行为，而不是后退箭头按钮

but only seems to work for providing custom back behavior to the built-in software/hardware back button and not the back arrow button

我该怎么做?

推荐答案

使用 onSupportNavigateUp ，并将 yourCurrentFragmentID 替换为当前的片段ID.所有这些都应在MainActivity中完成.

Use onSupportNavigateUp, and replace yourCurrentFragmentID to your current fragment id. All these should be done in MainActivity.

 navController = findNavController(R.id.nav_host_fragment)

 setupActionBarWithNavController(navController!!)

 override fun onSupportNavigateUp(): Boolean {
        return when(navController?.currentDestination?.id) {
            R.id.yourCurrentFragmentID -> {
                showDialog()
                true
            }
            else -> navController?.navigateUp()!!
        }
    }

修改

如果您的片段已使用 onOptionsItemSelected ，则可以通过检查 itemId 来处理逻辑.

If your fragment already use onOptionsItemSelected, you can handle the logic by checking itemId.

 override fun onOptionsItemSelected(item: MenuItem): Boolean {
        val id = item.itemId
        if (id == R.id.save) {
           // your save button code logic 
        }else if(id ==android.R.id.home){ 
            // display confirmation message
        }
        return super.onOptionsItemSelected(item)
    }

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