Up Navigation in android-CodePudding

When I'm pressing the back button on phone or the support action bar, it's exiting the application. How can I fix it to return to the main activity In login code:

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_login)
    
    supportActionBar?.setDisplayShowHomeEnabled(true) 
.... }
override fun onOptionsItemSelected(item: MenuItem): Boolean {
    when (item.itemId) {
        android.R.id.home -> {
            NavUtils.navigateUpFromSameTask(this)
            return true
        }
    }
    return super.onOptionsItemSelected(item)
}

And in the manifest file:

<activity
        android:name=".LoginActivity"
        android:label="Login"
        android:parentActivityName=".MainActivity">
    <meta-data
        android:name="android.support.PARENT_ACTIVITY"
        android:value="com.example.food_bank.MainActivity"/>
</activity>

CodePudding user response：

what works for me:

MainActivity:

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val button = findViewById<Button>(R.id.button)
        button.setOnClickListener{
            startActivity(Intent(this, LoginActivity::class.java))
        }
    }
}

LoginActivity:

class LoginActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_login)
        supportActionBar?.setDisplayHomeAsUpEnabled(true)
    }
// no onOptionsSelected here
}

Manifest:

(...)
        <activity
            android:name="LoginActivity"
            android:exported="false"
            android:label="@string/title_activity_login"
            android:parentActivityName=".MainActivity"/>
(...)

I guess switching from two times supportActionBar?.setDisplayShowHomeEnabled(true) to supportActionBar?.setDisplayHomeAsUpEnabled(true) has something to do with it

CodePudding user response：

Change your onOptionsItemSelected like this

android.R.id.home -> {
    onBackPressed()
    return true
}

and override onBackPressed method on your activity like this

override fun onBackPressed() {
    super.onBackPressed()
    NavUtils.navigateUpFromSameTask(this)
}