Can some one please help me.This code is not error but it does not show display

Support
1
2

Can you explain what your problem is? What exactly are you expecting your code to do? What does it do instead?
Also it would be helpful if you only share the relevant parts of the code. That way it’s far more likely that people actually want to help you. Going through someone else’s entire project is not that appealing.

1 Like
3

this is Mainactivity.kt

package com.example.android.navigation

import android.app.Activity
import android.content.Intent
import android.os.Bundle
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.databinding.DataBindingUtil
import androidx.drawerlayout.widget.DrawerLayout
import androidx.lifecycle.Observer
import androidx.lifecycle.ViewModelProvider
import androidx.navigation.findNavController
import androidx.navigation.ui.NavigationUI
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.example.android.navigation.databinding.ActivityMainBinding
import com.google.android.material.floatingactionbutton.FloatingActionButton

class MainActivity : AppCompatActivity() {
private lateinit var drawerLayout: DrawerLayout
private val newWordActivityRequestCode = 1
private lateinit var wordViewModel: WordViewModel

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

    val recyclerView = findViewById<RecyclerView>(R.id.recyclerview)
    val adapter = WordListAdapter(this)
    recyclerView.adapter = adapter
    recyclerView.layoutManager = LinearLayoutManager(this)

    // Get a new or existing ViewModel from the ViewModelProvider.
    wordViewModel = ViewModelProvider(this).get(WordViewModel::class.java)

    // Add an observer on the LiveData returned by getAlphabetizedWords.
    // The onChanged() method fires when the observed data changes and the activity is
    // in the foreground.
    wordViewModel.allWords.observe(this, Observer { words ->
        // Update the cached copy of the words in the adapter.
        words?.let { adapter.setWords(it) }
    })

    val fab = findViewById<FloatingActionButton>(R.id.fab)
    fab.setOnClickListener {
        val intent = Intent(this@MainActivity, NewWordActivity::class.java)
        startActivityForResult(intent, newWordActivityRequestCode)
    }
    val binding = DataBindingUtil.setContentView<ActivityMainBinding>(this, R.layout.activity_main)

    drawerLayout = binding.drawerLayout

    val navController = this.findNavController(R.id.myNavHostFragment)


    NavigationUI.setupActionBarWithNavController(this, navController, drawerLayout)

    NavigationUI.setupWithNavController(binding.navView, navController)


}

override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    super.onActivityResult(requestCode, resultCode, data)

    if (requestCode == newWordActivityRequestCode && resultCode == Activity.RESULT_OK) {
        data?.getStringExtra(NewWordActivity.EXTRA_REPLY)?.let {
            val word = Word(it)
            wordViewModel.insert(word)
        }
    } else {
        Toast.makeText(
                applicationContext,
                R.string.empty_not_saved,
                Toast.LENGTH_LONG).show()
    }
}


override fun onSupportNavigateUp(): Boolean {
    val navController = this.findNavController(R.id.myNavHostFragment)
    return NavigationUI.navigateUp(navController, drawerLayout)
}

}

4

and I add this recyclerView code to the MainActivity.kt.Display will not show on the phone screen

val recyclerView = findViewById(R.id.recyclerview)
val adapter = WordListAdapter(this)
recyclerView.adapter = adapter
recyclerView.layoutManager = LinearLayoutManager(this)

    // Get a new or existing ViewModel from the ViewModelProvider.
    wordViewModel = ViewModelProvider(this).get(WordViewModel::class.java)

    // Add an observer on the LiveData returned by getAlphabetizedWords.
    // The onChanged() method fires when the observed data changes and the activity is
    // in the foreground.
    wordViewModel.allWords.observe(this, Observer { words ->
        // Update the cached copy of the words in the adapter.
        words?.let { adapter.setWords(it) }
    })

    val fab = findViewById<FloatingActionButton>(R.id.fab)
    fab.setOnClickListener {
        val intent = Intent(this@MainActivity, NewWordActivity::class.java)
        startActivityForResult(intent, newWordActivityRequestCode)
    }
5

I want to add navigation contact to my firstApp use only ViewModel and Room database

6

It’s specific to Android, not Kotlin. Also, don’t expect anyone will do your homework.

2 Likes