I've tried following this example for creating and using a BoundService: https://developer.android.com/guide/components/bound-services#Binder

The issue is, that it won't connect to the service for me. I have an existing project with some fragment stuff in it, but in case this messes something up I've also copied it. That's my MainActivity.kt:

import android.content.ComponentName
import android.content.Context
import android.content.Intent
import android.content.ServiceConnection
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.os.IBinder
import android.util.Log
import android.view.MenuItem
import android.view.View
import android.widget.Button
import android.widget.TextView
import android.widget.Toast
import androidx.appcompat.app.ActionBarDrawerToggle
import androidx.drawerlayout.widget.DrawerLayout
import androidx.fragment.app.Fragment
import com.google.android.material.navigation.NavigationView
import com.google.android.material.tabs.TabLayout

class MainActivity : AppCompatActivity() {

    lateinit var toggle : ActionBarDrawerToggle
    lateinit var drawerLayout: DrawerLayout

    private lateinit var mService: LocalService
    private var mBound: Boolean = false

    /** Defines callbacks for service binding, passed to bindService()  */
    private val connection = object : ServiceConnection {

        override fun onServiceConnected(className: ComponentName, service: IBinder) {
            // We've bound to LocalService, cast the IBinder and get LocalService instance
            Log.w("test", "test")
            val binder = service as LocalService.LocalBinder
            mService = binder.getService()
            mBound = true
        }

        override fun onServiceDisconnected(arg0: ComponentName) {
            mBound = false
        }
    }

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

        drawerLayout = findViewById(R.id.drawerLayout)
        val navView : NavigationView = findViewById(R.id.nav_view)

        toggle = ActionBarDrawerToggle(this, drawerLayout, R.string.open, R.string.close)
        drawerLayout.addDrawerListener(toggle)
        toggle.syncState()

        supportActionBar?.setDisplayHomeAsUpEnabled(true)

        navView.setNavigationItemSelectedListener {


            // Highlight the current selected Item
            it.isChecked = true

            // Switch Fragments when user clicks on Items in NavDrawer
            when(it.itemId) {
                R.id.nav_home -> replaceFragment(HomeFragment(), it.title.toString())
                R.id.nav_import -> replaceFragment(ImportFragment(), it.title.toString())
                R.id.nav_export -> replaceFragment(ExportFragment(), it.title.toString())
                R.id.nav_share -> replaceFragment(ShareFragment(), it.title.toString())
            }

            true
        }



        // Default Page is Home
        replaceFragment(HomeFragment(), "Home")
    }

    // Method for replacing fragments
    private fun replaceFragment(fragment: Fragment, title : String) {
        val fragmentManager = supportFragmentManager
        val fragmentTransaction = fragmentManager.beginTransaction()
        fragmentTransaction.replace(R.id.frameLayout, fragment)
        fragmentTransaction.commit()

        // Close Drawer when user clicks on it
        drawerLayout.closeDrawers()

        // Set the correct title of current fragment
        setTitle(title)
    }

    override fun onOptionsItemSelected(item: MenuItem): Boolean {

        if(toggle.onOptionsItemSelected(item)) {
            return true
        }

        return super.onOptionsItemSelected(item)
    }

    override fun onStart() {
        super.onStart()
        // Bind to LocalService
        Intent(this, LocalService::class.java).also { intent ->
            bindService(intent, connection, Context.BIND_AUTO_CREATE)
        }
    }

    override fun onStop() {
        super.onStop()
        unbindService(connection)
        mBound = false
    }

    /** Called when a button is clicked (the button in the layout file attaches to
     * this method with the android:onClick attribute)  */
    fun onButtonClick(v: View) {
        if (mBound) {
            // Call a method from the LocalService.
            // However, if this call were something that might hang, then this request should
            // occur in a separate thread to avoid slowing down the activity performance.
            val num: Int = mService.randomNumber
            Toast.makeText(this, "number: $num", Toast.LENGTH_SHORT).show()
        }
    }

}

The Button with the onButtonClick Listener is in the Home Fragment and calls the function correctly (I assume as e.g. a Toast with a testmessage then gets displayed). However, mBound always keeps the value "false" and as a result the onButtonClick function does nothing. Where is my error?

To make it completet, that's the LocalService.kt:

import android.app.Service
import android.content.Intent
import android.os.Binder
import android.os.IBinder
import java.util.*

class LocalService : Service() {
    // Binder given to clients
    private val binder = LocalBinder()

    // Random number generator
    private val mGenerator = Random()

    /** method for clients  */
    val randomNumber: Int
        get() = mGenerator.nextInt(100)

    /**
     * Class used for the client Binder.  Because we know this service always
     * runs in the same process as its clients, we don't need to deal with IPC.
     */
    inner class LocalBinder : Binder() {
        // Return this instance of LocalService so clients can call public methods
        fun getService(): LocalService = this@LocalService
    }

    override fun onBind(intent: Intent): IBinder {
        return binder
    }
}

CodePudding user response：

Did you declare the Service in your Android Manifest file? Try to use getApplicationContext().bindService instead of just bindService on your activity. It is using the higher level application context. I hope help you.