onBackPressed() 已弃用，有什么替代方案？

Question

I have upgraded targetSdkVersion and compileSdkVersion to 33 .

Now getting warning onBackPressed is deprecated.

It is suggested to use use OnBackInvokedCallback or androidx.activity.OnBackPressedCallback to handle back navigation instead. Anyone can help me to use the updated method.

Example:

Use Case: I use if (isTaskRoot) {} inside onBackPressed(){} method to check activity is last on the activity-stack.

override fun onBackPressed() {
    if (isTaskRoot) { // Check this activity is last on the activity-stack.(Check Whether This activity opened from Push-Notification)
        startActivity(Intent(mContext, Dashboard::class.java))
        finish()
    } else {
        finishWithResultOK()
    }
}

Answer 1

Replace onBackPressed() with below code.

onBackPressedDispatcher.onBackPressed()

Answer 2

With a combination of top answers. Here is a solution:

1. When you need to press the back button, copy this:

Note: it will automatically destroy your activity.

button.setOnClickListener {
    onBackPressedDispatcher.onBackPressed()
}

2. When you need to handle the back button pressed, copy this:

onBackPressedDispatcher.addCallback(this, object: OnBackPressedCallback(true) {
    override fun handleOnBackPressed() {
        // Whatever you want
        // when back pressed
        println("Back button pressed")
        finish()
    }
})

Answer 3

In Kotlin , this way is working

1- Remove onBackPressed()

2- below onCreate(savedInstanceState: Bundle?) add these lines:

 if (Build.VERSION.SDK_INT >= 33) {
        onBackInvokedDispatcher.registerOnBackInvokedCallback(
            OnBackInvokedDispatcher.PRIORITY_DEFAULT
        ) {
           
            exitOnBackPressed()
        }
    } else {
        onBackPressedDispatcher.addCallback(
            this,
            object : OnBackPressedCallback(true) {
                override fun handleOnBackPressed() {
                  
                    Log.i("TAG", "handleOnBackPressed: Exit")
                    exitOnBackPressed()
                }
            })
    }

3- Define a new function for handling

fun exitOnBackPressed() {
}

Answer 4

According your API level register:

• onBackInvokedDispatcher.registerOnBackInvokedCallback for API level 33+
• onBackPressedDispatcher callback for backword compatibility "API level 13+"

This requires to at least use appcompat:1.6.0-alpha03 ; the current is 1.6.0-alpha04 :

 implementation 'androidx.appcompat:appcompat:1.6.0-alpha04'

if (BuildCompat.isAtLeastT()) {
    onBackInvokedDispatcher.registerOnBackInvokedCallback(
        OnBackInvokedDispatcher.PRIORITY_DEFAULT
    ) {
        // Back is pressed... Finishing the activity
        finish()
    }
} else {
    onBackPressedDispatcher.addCallback(
        this, // lifecycle owner
        object : OnBackPressedCallback(true) {
            override fun handleOnBackPressed() {
                // Back is pressed... Finishing the activity
                finish()
            }
        })
}

UPDATE:

Thanks to @ianhanniballake comment; you can just use OnBackPressedDispatcher even in API level 33+

The OnBackPressedDispatcher is already going to be using the Android T specific API internally when using Activity 1.6+,

So, you can just do:

onBackPressedDispatcher.addCallback(
    this, // lifecycle owner
    object : OnBackPressedCallback(true) {
        override fun handleOnBackPressed() {
            // Back is pressed... Finishing the activity
            finish()
        }
    })

Note that you shouldn't override the onBackPressed() as that will make the onBackPressedDispatcher callback not to fire; check this answer for clarifying that.

Answer 5

Simply replace

override fun onBackPressed() {
      super.onBackPressed() //Replace this is deprecated line
}

with

override fun onBackPressed() {
      onBackPressedDispatcher.onBackPressed() //with this line
}

Answer 6

You can use the OnBackInvokedCallback

as described in the documentation and follow this guide here to update your code

Answer 7

Here is the extension function to implement OnBackPressedCallback in activity.

fun AppCompatActivity.addOnBackPressedDispatcher(onBackPressed: () -> Unit = { finish() }) {
    onBackPressedDispatcher.addCallback(
        this,
        object : OnBackPressedCallback(true) {
            override fun handleOnBackPressed() {
                onBackPressed.invoke()
            }
        }
    )
}

Usage:

addOnBackPressedDispatcher {
    //doSomething()
}

Answer 8

You could use the onBackPressedDispatcher

onBackPressedDispatcher.addCallback(this, object : OnBackPressedCallback(true) {
    override fun handleOnBackPressed() {
        finish() //finshes the activity when back pressed.simillar to the super.onbackpressed
    }
})

in here "this" means the lifeCycleOwner

Answer 9

Use like below,

 override fun onClick(v: View?) { when (v?.id) { R.id.iv_back -> onBackPressedMethod() } }

and now create that method for handling back event

 private fun onBackPressedMethod(){ if (Build.VERSION.SDK_INT >= 33) { onBackInvokedDispatcher.registerOnBackInvokedCallback( OnBackInvokedDispatcher.PRIORITY_DEFAULT) { // back button pressed... finishing the activity finish() } } else { onBackPressedDispatcher.addCallback( this, object: OnBackPressedCallback(true) { override fun handleOnBackPressed() { // back button pressed... finishing the activity finish() } }) } }

That's it!

Answer 10

Bonus: To close DrawerLayout when onBackPressed use like below (according to this I/O talk ),

val callback = onBackPressedDispatcher.addCallback(this, false) {
    binding.drawerLayout.closeDrawer(GravityCompat.START)
}
            
binding.drawerLayout.addDrawerListener(object : DrawerListener {  
        
    override fun onDrawerOpened(drawerView: View) {
        callback.isEnabled = true
    }
        
    override fun onDrawerClosed(drawerView: View) {
        callback.isEnabled = false
    }

    override fun onDrawerSlide(drawerView: View, slideOffset: Float) = Unit    
    override fun onDrawerStateChanged(newState: Int) = Unit
})

Answer 11

use onBackPressedDispatcher.onBackPressed() instead of super.onBackPressed()

Answer 12

override the onDismiss() function for BottomSheets.

override fun onDismiss(dialog: DialogInterface) {
   super.onDismiss(dialog)
   //TODO your logic.
   }