How do I remove a row from recyclerview using room?

Question

I\'m trying to delete an row of recyclerview using room.im doing swipe to delete a particular row....

Here is my Address table-->

@Entity(tableName          


        

Answer 1

Follow my simple steps to solve your issue,

Step 1: Check once CustomApplication name mentioned or not in AndroidManifest.xml,

otherwise you get this issue

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myapplication/com.example.myapplication.AddressActivity}: java.lang.ClassCastException: android.app.Application cannot be cast to com.example.myapplication.CustomApplication

Step 2: Check your module level build.gradle file

apply this changes

apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
apply plugin: 'kotlin-kapt'

check dependencies -- For Kotlin use kapt instead of annotationProcessor

implementation "androidx.room:room-runtime:2.2.5"
kapt "androidx.room:room-compiler:2.2.5"

otherwise you get this issue

java.lang.RuntimeException: cannot find implementation for com.example.myapplication.Database. Database_Impl does not exist

Step 3: check your AddressDao interface, add this function

 @Delete
 suspend fun deleteAddress(address: Address)

Step 4:

in AddressAdapter class, add this listener,

interface ItemListener {
    fun onItemClicked(address: Address, position: Int)
}

add listener variable and setListener function

private lateinit var listener: ItemListener

interface ItemListener {
    fun onItemClicked(address: Address, position: Int)
}

fun setListener(listener: ItemListener) {
    this.listener = listener;
}

then update your code in tvDelete.setOnClickListener method

    viewHolder.tvDelete.setOnClickListener(View.OnClickListener { view ->
        mItemManger.removeShownLayouts(viewHolder.swipelayout)
        addresses.removeAt(position)

        listener.onItemClicked(fl, position)
        
        notifyDataSetChanged()
     //   notifyItemRemoved(position)
     //   notifyItemRangeChanged(position, addresses.size)
        mItemManger.closeAllItems()
        Toast.makeText(
            view.context,
            "Deleted " + viewHolder.tv.getText().toString(),
            Toast.LENGTH_SHORT
        ).show()
    })

Step 5: In AddressActivity class, do this changes

Implement listener here,

class AddressActivity : AppCompatActivity(), AddressAdapter.ItemListener {

then override method

override fun onItemClicked(address: Address, position: Int) {
    
}

then set listener for adapter

        recyclerView.layoutManager = LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false)
        recyclerView.adapter = adapter
        adapter.setListener(this)

then update code in override method

override fun onItemClicked(address: Address, position: Int) {
    lifecycleScope.launch {
        val application = application as CustomApplication
        application.database.AddressDao().deleteAddress(address)
    }
}

here I used coroutine otherwise you can use AsycTask also

for coroutine add this dependencies in your module build.gradle file

implementation "android.arch.lifecycle:extensions:1.1.1"
kapt "android.arch.lifecycle:compiler:1.1.1"
implementation "androidx.lifecycle:lifecycle-runtime-ktx:2.2.0"
implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.0'

if you directly called deleteAddress method in UI class, you get this issue

java.lang.IllegalStateException: Cannot access database on the main thread since it may potentially lock the UI for a long period of time.

so use such methods in background thread,

If you really want to execute in main UI thread, do this changes in your code

in AddressDao interface,

@Delete
fun deleteAddress(address: Address)

in CustomApplication class, add allowMainThreadQueries()

class CustomApplication : Application() {
    lateinit var database: Database
        private set
    lateinit var addressDao: AddressDao
        private set

    override fun onCreate() {
        super.onCreate()

        this.database = Room.databaseBuilder(
            applicationContext,
            Database::class.java, "database"
        ).allowMainThreadQueries().build()
        addressDao = database.AddressDao()
    }
}