Using Anko in Kotlin

Using Anko in Kotlin

Anko is a Kotlin library that makes Android application development faster and easier. Let’s explore how to use Anko for creating layouts programmatically.

Project Setup

Add Dependencies

// build.gradle.kts
dependencies {
    implementation("org.jetbrains.anko:anko:0.10.8")
    implementation("org.jetbrains.anko:anko-commons:0.10.8")
    implementation("org.jetbrains.anko:anko-design:0.10.8")
    implementation("org.jetbrains.anko:anko-sdk25:0.10.8")
}

Basic Layouts

Simple Layout

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        verticalLayout {
            padding = dip(16)

            textView {
                text = "Hello, Anko!"
                textSize = 24f
                textColor = Color.BLACK
            }

            button {
                text = "Click Me"
                onClick { toast("Button clicked!") }
            }
        }
    }
}

Complex Layout

class UserProfileActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        verticalLayout {
            padding = dip(16)

            imageView {
                imageResource = R.drawable.profile_placeholder
                scaleType = ImageView.ScaleType.CENTER_CROP
            }.lparams(width = matchParent, height = dip(200))

            textView {
                text = "John Doe"
                textSize = 24f
                textColor = Color.BLACK
            }.lparams {
                topMargin = dip(16)
                gravity = Gravity.CENTER
            }

            textView {
                text = "john.doe@example.com"
                textSize = 16f
                textColor = Color.GRAY
            }.lparams {
                topMargin = dip(8)
                gravity = Gravity.CENTER
            }

            button {
                text = "Edit Profile"
                onClick { startActivity<EditProfileActivity>() }
            }.lparams {
                topMargin = dip(16)
                width = matchParent
            }
        }
    }
}

Layout Components

Form Layout

class LoginActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        verticalLayout {
            padding = dip(16)

            textView {
                text = "Login"
                textSize = 24f
                textColor = Color.BLACK
            }.lparams {
                gravity = Gravity.CENTER
                bottomMargin = dip(32)
            }

            val emailEdit = editText {
                hint = "Email"
                inputType = InputType.TYPE_TEXT_VARIATION_EMAIL_ADDRESS
            }.lparams(width = matchParent) {
                bottomMargin = dip(16)
            }

            val passwordEdit = editText {
                hint = "Password"
                inputType = InputType.TYPE_TEXT_VARIATION_PASSWORD
            }.lparams(width = matchParent) {
                bottomMargin = dip(24)
            }

            button {
                text = "Login"
                onClick {
                    val email = emailEdit.text.toString()
                    val password = passwordEdit.text.toString()
                    login(email, password)
                }
            }.lparams(width = matchParent)
        }
    }
}

List Layout

class UserListActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        verticalLayout {
            padding = dip(16)

            textView {
                text = "Users"
                textSize = 24f
                textColor = Color.BLACK
            }.lparams {
                gravity = Gravity.CENTER
                bottomMargin = dip(16)
            }

            val recyclerView = recyclerView {
                layoutManager = LinearLayoutManager(context)
                adapter = UserAdapter(getUsers())
            }.lparams(width = matchParent, height = matchParent)
        }
    }
}

Anko Commons

Dialogs

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        verticalLayout {
            button {
                text = "Show Dialog"
                onClick {
                    alert("Are you sure?", "Confirmation") {
                        positiveButton("Yes") {
                            toast("Confirmed!")
                        }
                        negativeButton("No") {
                            toast("Cancelled!")
                        }
                    }.show()
                }
            }
        }
    }
}

Intents

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        verticalLayout {
            button {
                text = "Open URL"
                onClick {
                    browse("https://www.example.com")
                }
            }

            button {
                text = "Send Email"
                onClick {
                    email("recipient@example.com", "Subject", "Body")
                }
            }

            button {
                text = "Make Call"
                onClick {
                    makeCall("1234567890")
                }
            }
        }
    }
}

Anko SQLite

Database Operations

class DatabaseHelper(ctx: Context) : ManagedSQLiteOpenHelper(ctx, "database.db", null, 1) {
    companion object {
        private var instance: DatabaseHelper? = null

        @Synchronized
        fun getInstance(ctx: Context): DatabaseHelper {
            if (instance == null) {
                instance = DatabaseHelper(ctx.applicationContext)
            }
            return instance!!
        }
    }

    override fun onCreate(db: SQLiteDatabase) {
        db.createTable("users", true,
            "id" to INTEGER + PRIMARY_KEY + AUTOINCREMENT,
            "name" to TEXT,
            "email" to TEXT
        )
    }

    override fun onUpgrade(db: SQLiteDatabase, oldVersion: Int, newVersion: Int) {
        db.dropTable("users", true)
    }
}

// Usage
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val db = DatabaseHelper.getInstance(this)

        db.use {
            insert("users",
                "name" to "John Doe",
                "email" to "john@example.com"
            )

            val users = select("users").exec {
                parseList(UserParser())
            }
        }
    }
}

Anko Coroutines

Async Operations

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        verticalLayout {
            button {
                text = "Load Data"
                onClick {
                    doAsync {
                        val result = URL("https://api.example.com/data").readText()
                        uiThread {
                            toast("Data loaded: $result")
                        }
                    }
                }
            }
        }
    }
}

Best Practices

Layout Organization

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        MainUI().setContentView(this)
    }
}

class MainUI : AnkoComponent<MainActivity> {
    override fun createView(ui: AnkoContext<MainActivity>) = with(ui) {
        verticalLayout {
            padding = dip(16)

            titleView()
            contentView()
            actionButtons()
        }
    }

    private fun _LinearLayout.titleView() {
        textView {
            text = "Main Screen"
            textSize = 24f
            textColor = Color.BLACK
        }.lparams {
            gravity = Gravity.CENTER
            bottomMargin = dip(16)
        }
    }

    private fun _LinearLayout.contentView() {
        // Content implementation
    }

    private fun _LinearLayout.actionButtons() {
        // Buttons implementation
    }
}

Common Patterns

RecyclerView with Anko

class UserAdapter(private val users: List<User>) : RecyclerView.Adapter<UserAdapter.ViewHolder>() {
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        return ViewHolder(UserItemUI().createView(AnkoContext.create(parent.context, parent)))
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.bind(users[position])
    }

    override fun getItemCount() = users.size

    class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
        private val nameView = view.find<TextView>(R.id.name)
        private val emailView = view.find<TextView>(R.id.email)

        fun bind(user: User) {
            nameView.text = user.name
            emailView.text = user.email
        }
    }
}

class UserItemUI : AnkoComponent<ViewGroup> {
    override fun createView(ui: AnkoContext<ViewGroup>) = with(ui) {
        linearLayout {
            orientation = LinearLayout.VERTICAL
            padding = dip(16)

            textView {
                id = R.id.name
                textSize = 16f
                textColor = Color.BLACK
            }

            textView {
                id = R.id.email
                textSize = 14f
                textColor = Color.GRAY
            }
        }
    }
}

Conclusion

Anko helps you:

• Create layouts programmatically
• Simplify Android development
• Write more concise code
• Improve code readability

Remember:

• Use appropriate layouts
• Follow best practices
• Keep code organized
• Handle configuration changes

Stay tuned for more Kotlin tips and tricks!