AlertDialog Extensions

This is custom AlertDialog which can easily invoke from Activity or from Fragment.

AlertDialog Kotlin Extension

import android.annotation.SuppressLint
import android.app.Activity
import android.content.Context
import android.view.LayoutInflater
import android.view.View
import android.widget.Button
import android.widget.TextView
import androidx.annotation.StringRes
import androidx.appcompat.app.AlertDialog
import androidx.fragment.app.Fragment
import au.com.elegantmedia.presentation.R


/**
 * Created by Chathura Wijesinghe 
 * [email protected]
 */


inline fun Activity.alert(title: CharSequence? = null, message: CharSequence? = null, func: AlertDialogHelper.() -> Unit): AlertDialog {
    return AlertDialogHelper(this, title, message).apply {
        func()
    }.create()
}

inline fun Activity.alert(titleResource: Int = 0, messageResource: Int = 0, func: AlertDialogHelper.() -> Unit): AlertDialog {
    val title = if (titleResource == 0) null else getString(titleResource)
    val message = if (messageResource == 0) null else getString(messageResource)
    return AlertDialogHelper(this, title, message).apply {
        func()
    }.create()
}

inline fun Fragment.alert(title: CharSequence? = null, message: CharSequence? = null, func: AlertDialogHelper.() -> Unit): AlertDialog {
    return AlertDialogHelper(this.context!!, title, message).apply {
        func()
    }.create()
}

inline fun Fragment.alert(titleResource: Int = 0, messageResource: Int = 0, func: AlertDialogHelper.() -> Unit): AlertDialog {
    val title = if (titleResource == 0) null else getString(titleResource)
    val message = if (messageResource == 0) null else getString(messageResource)
    return AlertDialogHelper(this.context!!, title, message).apply {
        func()
    }.create()
}

@SuppressLint("InflateParams")
class AlertDialogHelper(context: Context, title: CharSequence?, message: CharSequence?) {

    private val dialogView: View by lazyFast {
        LayoutInflater.from(context).inflate(R.layout.dialog_info, null)
    }

    private val builder: AlertDialog.Builder = AlertDialog.Builder(context)
        .setView(dialogView)

    private val title: TextView by lazyFast {
        dialogView.findViewById<TextView>(R.id.dialogInfoTitleTextView)
    }

    private val message: TextView by lazyFast {
        dialogView.findViewById<TextView>(R.id.dialogInfoMessageTextView)
    }

    private val positiveButton: Button by lazyFast {
        dialogView.findViewById<Button>(R.id.dialogInfoPositiveButton)
    }

    private val negativeButton: Button by lazyFast {
        dialogView.findViewById<Button>(R.id.dialogInfoNegativeButton)
    }

    private var dialog: AlertDialog? = null

    var cancelable: Boolean = true

    init {
        this.title.text = title
        this.message.text = message
    }

    fun positiveButton(@StringRes textResource: Int, func: (() -> Unit)? = null) {
        with(positiveButton) {
            text = builder.context.getString(textResource)
            setClickListenerToDialogButton(func)
        }
    }

    fun positiveButton(text: CharSequence, func: (() -> Unit)? = null) {
        with(positiveButton) {
            this.text = text
            setClickListenerToDialogButton(func)
        }
    }

    fun negativeButton(@StringRes textResource: Int, func: (() -> Unit)? = null) {
        with(negativeButton) {
            text = builder.context.getString(textResource)
            setClickListenerToDialogButton(func)
        }
    }

    fun negativeButton(text: CharSequence, func: (() -> Unit)? = null) {
        with(negativeButton) {
            this.text = text
            setClickListenerToDialogButton(func)
        }
    }

    fun onCancel(func: () -> Unit) {
        builder.setOnCancelListener { func() }
    }

    fun create(): AlertDialog {
        title.goneIfTextEmpty()
        message.goneIfTextEmpty()
        positiveButton.goneIfTextEmpty()
        negativeButton.goneIfTextEmpty()

        dialog = builder
            .setCancelable(cancelable)
            .create()
        return dialog!!
    }

    private fun TextView.goneIfTextEmpty() {
        visibility = if (text.isNullOrEmpty()) {
            View.GONE
        } else {
            View.VISIBLE
        }
    }

    private fun Button.setClickListenerToDialogButton(func: (() -> Unit)?) {
        setOnClickListener {
            func?.invoke()
            dialog?.dismiss()
        }
    }
}

/**
 * Implementation of lazy that is not thread safe. Useful when you know what thread you will be
 * executing on and are not worried about synchronization.
 */
fun <T> lazyFast(operation: () -> T): Lazy<T> = lazy(LazyThreadSafetyMode.NONE) {
    operation()
}

You can simply show AlertDialog using bellow pease of code

alert("Title", "Message: Are you sure") {
      positiveButton("Ok") {
          // Do positive stuff here 
      }
      negativeButton("Cancel"){
          // Do negative stuff here 
      }
  }.show()

OR

 alert(R.string.title, R.string.message) {
     positiveButton(R.string.ok) {
         // Do positive stuff here 
     }
     negativeButton(R.string.cancel){
         // Do negative stuff here 
     }
 }.show()

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