Objectives

Complete the presenter pattern implementation, introducing BaseView & BasePresenter classes

Solutions

Exercise 1

Convert the PlacemarkMaps Activity into PlacemarkMapView + PlacemarkPresenter. Perhaps aim for this final structure:

Exercise 1 Solution

PlacemarkMapPresenter

package org.wit.placemark.views.map

import com.google.android.gms.maps.CameraUpdateFactory
import com.google.android.gms.maps.GoogleMap
import com.google.android.gms.maps.model.LatLng
import com.google.android.gms.maps.model.Marker
import com.google.android.gms.maps.model.MarkerOptions
import org.wit.placemark.main.MainApp

class PlacemarkMapPresenter(val view: PlacemarkMapView) {

  var app: MainApp

  init {
    app = view.application as MainApp
  }

  fun doPopulateMap(map: GoogleMap) {
    map.uiSettings.setZoomControlsEnabled(true)
    map.setOnMarkerClickListener(view)
    app.placemarks.findAll().forEach {
      val loc = LatLng(it.lat, it.lng)
      val options = MarkerOptions().title(it.title).position(loc)
      map.addMarker(options).tag = it.id
      map.moveCamera(CameraUpdateFactory.newLatLngZoom(loc, it.zoom))
    }
  }

  fun doMarkerSelected(marker: Marker) {
    val tag = marker.tag as Long
    val placemark = app.placemarks.findById(tag)
    if (placemark != null) view.showPlacemark(placemark)
  }
}

PlacemarkMapView

package org.wit.placemark.views.map

import android.os.Bundle
import android.support.v7.app.AppCompatActivity
import com.google.android.gms.maps.GoogleMap
import com.google.android.gms.maps.model.Marker
import org.wit.placemark.R
import kotlinx.android.synthetic.main.activity_placemark_map.*
import kotlinx.android.synthetic.main.content_placemark_map.*
import org.wit.placemark.helpers.readImageFromPath
import org.wit.placemark.models.PlacemarkModel

class PlacemarkMapView : AppCompatActivity(), GoogleMap.OnMarkerClickListener {

  lateinit var presenter: PlacemarkMapPresenter

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_placemark_map)
    setSupportActionBar(toolbarMaps)
    presenter = PlacemarkMapPresenter(this)

    mapView.onCreate(savedInstanceState);
    mapView.getMapAsync {
      presenter.doPopulateMap(it)
    }
  }

  fun showPlacemark(placemark: PlacemarkModel) {
    currentTitle.text = placemark.title
    currentDescription.text = placemark.description
    imageView.setImageBitmap(readImageFromPath(this, placemark.image))
  }

  override fun onMarkerClick(marker: Marker): Boolean {
    presenter.doMarkerSelected(marker)
    return true
  }

  override fun onDestroy() {
    super.onDestroy()
    mapView.onDestroy()
  }

  override fun onLowMemory() {
    super.onLowMemory()
    mapView.onLowMemory()
  }

  override fun onPause() {
    super.onPause()
    mapView.onPause()
  }

  override fun onResume() {
    super.onResume()
    mapView.onResume()
  }

  override fun onSaveInstanceState(outState: Bundle?) {
    super.onSaveInstanceState(outState)
    mapView.onSaveInstanceState(outState)
  }
}

AndroidManifest.xml

    <activity
      android:name=".views.map.PlacemarkMapView"
      android:label="@string/title_activity_placemark_maps"
      android:theme="@style/AppTheme"></activity>

activity_placemark_map.xml

<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  tools:context="org.wit.placemark.views.map.PlacemarkMapView">

  ...
  <include layout="@layout/content_placemark_map" />
  ...

content_placemark_map.xml

<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  app:layout_behavior="@string/appbar_scrolling_view_behavior"
  tools:context="org.wit.placemark.views.map.PlacemarkMapView"
  tools:showIn="@layout/activity_placemark_map">
...

Solutions

Exercise 2:

Simplify the UX for PlacemarkActivity, removing the Add Placemark button, and including a save menu option to perform equivalent functionality:

Solution

strings.xml

  <string name="menu_savePlacemark">Save</string>

menu_placemark.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto">

  <item
    android:id="@+id/item_save"
    android:title="@string/menu_savePlacemark"
    app:showAsAction="always"/>
  <item
    android:id="@+id/item_delete"
    android:title="@string/menu_deletePlacemark"
    app:showAsAction="always"/>
</menu>

activity_placemark

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  tools:context="org.wit.placemark.views.placemark.PlacemarkView">

  <android.support.design.widget.AppBarLayout
    android:id="@+id/appBarLayout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@color/colorAccent"
    android:fitsSystemWindows="true"
    app:elevation="0dip"
    app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

    <android.support.v7.widget.Toolbar
      android:id="@+id/toolbarAdd"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      app:titleTextColor="@color/colorPrimary" />

  </android.support.design.widget.AppBarLayout>

  <android.support.constraint.ConstraintLayout
    android:layout_width="match_parent"
    android:layout_height="600dp"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent">

    <EditText
      android:id="@+id/placemarkTitle"
      android:layout_width="365dp"
      android:layout_height="wrap_content"
      android:layout_marginEnd="8dp"
      android:layout_marginStart="8dp"
      android:layout_marginTop="64dp"
      android:ems="10"
      android:hint="@string/hint_placemarkTitle"
      android:inputType="text"
      app:layout_constraintEnd_toEndOf="parent"
      app:layout_constraintHorizontal_bias="0.503"
      app:layout_constraintStart_toStartOf="parent"
      app:layout_constraintTop_toTopOf="parent" />

    <EditText
      android:id="@+id/description"
      android:layout_width="365dp"
      android:layout_height="wrap_content"
      android:layout_marginEnd="8dp"
      android:layout_marginStart="8dp"
      android:layout_marginTop="8dp"
      android:ems="10"
      android:hint="@string/hint_placemarkDescription"
      android:inputType="textPersonName"
      app:layout_constraintEnd_toEndOf="parent"
      app:layout_constraintStart_toStartOf="parent"
      app:layout_constraintTop_toBottomOf="@+id/placemarkTitle" />

    <Button
      android:id="@+id/chooseImage"
      android:layout_width="158dp"
      android:layout_height="wrap_content"
      android:layout_marginStart="8dp"
      android:text="@string/button_addImage"
      app:layout_constraintStart_toStartOf="parent"
      app:layout_constraintTop_toBottomOf="@+id/description" />

    <Button
      android:id="@+id/placemarkLocation"
      android:layout_width="167dp"
      android:layout_height="wrap_content"
      android:layout_marginEnd="8dp"
      android:text="@string/button_location"
      app:layout_constraintEnd_toEndOf="parent"
      app:layout_constraintTop_toBottomOf="@+id/description" />

    <ImageView
      android:id="@+id/placemarkImage"
      android:layout_width="0dp"
      android:layout_height="0dp"
      android:layout_marginStart="8dp"
      android:layout_marginTop="8dp"
      android:layout_marginEnd="8dp"
      android:layout_marginBottom="8dp"
      app:layout_constraintBottom_toBottomOf="parent"
      app:layout_constraintEnd_toEndOf="parent"
      app:layout_constraintHorizontal_bias="0.555"
      app:layout_constraintStart_toStartOf="parent"
      app:layout_constraintTop_toBottomOf="@+id/placemarkLocation"
      app:layout_constraintVertical_bias="0.173"
      app:srcCompat="@drawable/ic_launcher_background" />

  </android.support.constraint.ConstraintLayout>

</android.support.constraint.ConstraintLayout>

PlacemarkView

package org.wit.placemark.views.placemark

import android.content.Intent
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.view.Menu
import android.view.MenuItem
import kotlinx.android.synthetic.main.activity_placemark.*
import org.jetbrains.anko.AnkoLogger
import org.jetbrains.anko.toast
import org.wit.placemark.R
import org.wit.placemark.helpers.readImageFromPath
import org.wit.placemark.models.PlacemarkModel

class PlacemarkView : AppCompatActivity(), AnkoLogger {

  lateinit var presenter: PlacemarkPresenter
  var placemark = PlacemarkModel()

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_placemark)
    toolbarAdd.title = title
    setSupportActionBar(toolbarAdd)

    presenter = PlacemarkPresenter(this)

    chooseImage.setOnClickListener { presenter.doSelectImage() }

    placemarkLocation.setOnClickListener { presenter.doSetLocation() }
  }

  fun showPlacemark(placemark: PlacemarkModel) {
    placemarkTitle.setText(placemark.title)
    description.setText(placemark.description)
    placemarkImage.setImageBitmap(readImageFromPath(this, placemark.image))
    if (placemark.image != null) {
      chooseImage.setText(R.string.change_placemark_image)
    }
  }

  override fun onCreateOptionsMenu(menu: Menu): Boolean {
    menuInflater.inflate(R.menu.menu_placemark, menu)
    return super.onCreateOptionsMenu(menu)
  }

  override fun onOptionsItemSelected(item: MenuItem?): Boolean {
    when (item?.itemId) {
      R.id.item_delete -> {
        presenter.doDelete()
      }
      R.id.item_save -> {
        if (placemarkTitle.text.toString().isEmpty()) {
          toast(R.string.enter_placemark_title)
        } else {
          presenter.doAddOrSave(placemarkTitle.text.toString(), description.text.toString())
        }
      }
    }
    return super.onOptionsItemSelected(item)
  }

  override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    super.onActivityResult(requestCode, resultCode, data)
    if (data != null) {
      presenter.doActivityResult(requestCode, resultCode, data)
    }
  }

  override fun onBackPressed() {
    presenter.doCancel()
  }
}

BaseView/Presenter

These new classes will implement some commonality that can be extracted from our MVP implementation.

First, a base class for all Presenters:

BasePresenter

package org.wit.placemark.views

import android.content.Intent
import org.wit.placemark.main.MainApp

open class BasePresenter(var view: BaseView?) {

  var app: MainApp =  view?.application as MainApp

  open fun doActivityResult(requestCode: Int, resultCode: Int, data: Intent) {
  }

  open fun doRequestPermissionsResult(requestCode: Int, permissions: Array<String>, grantResults: IntArray) {
  }

  open fun onDestroy() {
    view = null
  }
}

Notice this is where we keep our app reference.

THen the base class for all Views:

BaseView

package org.wit.placemark.views

import android.content.Intent

import android.os.Parcelable
import android.support.v7.app.AppCompatActivity
import android.support.v7.widget.Toolbar
import org.jetbrains.anko.AnkoLogger

import org.wit.placemark.models.PlacemarkModel
import org.wit.placemark.views.editlocation.EditLocationView
import org.wit.placemark.views.map.PlacemarkMapView
import org.wit.placemark.views.placemark.PlacemarkView
import org.wit.placemark.views.placemarklist.PlacemarkListView

val IMAGE_REQUEST = 1
val LOCATION_REQUEST = 2

enum class VIEW {
  LOCATION, PLACEMARK, MAPS, LIST
}

open abstract class BaseView() : AppCompatActivity(), AnkoLogger {

  var basePresenter: BasePresenter? = null

  fun navigateTo(view: VIEW, code: Int = 0, key: String = "", value: Parcelable? = null) {
    var intent = Intent(this, PlacemarkListView::class.java)
    when (view) {
      VIEW.LOCATION -> intent = Intent(this, EditLocationView::class.java)
      VIEW.PLACEMARK -> intent = Intent(this, PlacemarkView::class.java)
      VIEW.MAPS -> intent = Intent(this, PlacemarkMapView::class.java)
      VIEW.LIST -> intent = Intent(this, PlacemarkListView::class.java)
    }
    if (key != "") {
      intent.putExtra(key, value)
    }
    startActivityForResult(intent, code)
  }

  fun initPresenter(presenter: BasePresenter): BasePresenter {
    basePresenter = presenter
    return presenter
  }

  fun init(toolbar: Toolbar) {
    toolbar.title = title
    setSupportActionBar(toolbar)
  }

  override fun onDestroy() {
    basePresenter?.onDestroy()
    super.onDestroy()
  }


  override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    super.onActivityResult(requestCode, resultCode, data)
    if (data != null) {
      basePresenter?.doActivityResult(requestCode, resultCode, data)
    }
  }

  override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<String>, grantResults: IntArray) {
    basePresenter?.doRequestPermissionsResult(requestCode, permissions, grantResults)
  }

  open fun showPlacemark(placemark: PlacemarkModel) {}
  open fun showPlacemarks(placemarks: List<PlacemarkModel>) {}
  open fun showProgress() {}
  open fun hideProgress() {}
}

This is more involved, including:

• utility method for launching activities
• some default lifecycle implementations
• shared initialisation of the toolbar
• stubbed specification of useful methods which concrete View classes will implement.

PlacemarkPresenter/View

Notice in this implementation that the view reference may be null, thus all access is via null safe calls.

PlacemarkPresenter

package org.wit.placemark.views.placemark

import android.content.Intent
import org.wit.placemark.helpers.showImagePicker
import org.wit.placemark.models.Location
import org.wit.placemark.models.PlacemarkModel
import org.wit.placemark.views.*

class PlacemarkPresenter(view: BaseView) : BasePresenter(view) {

  var placemark = PlacemarkModel()
  var defaultLocation = Location(52.245696, -7.139102, 15f)
  var edit = false;

  init {
    if (view.intent.hasExtra("placemark_edit")) {
      edit = true
      placemark = view.intent.extras.getParcelable<PlacemarkModel>("placemark_edit")
      view.showPlacemark(placemark)
    }
  }

  fun doAddOrSave(title: String, description: String) {
    placemark.title = title
    placemark.description = description
    if (edit) {
      app.placemarks.update(placemark)
    } else {
      app.placemarks.create(placemark)
    }
    view?.finish()
  }

  fun doCancel() {
    view?.finish()
  }

  fun doDelete() {
    app.placemarks.delete(placemark)
    view?.finish()
  }

  fun doSelectImage() {
     view?.let{
       showImagePicker(view!!, IMAGE_REQUEST)
     }
  }

  fun doSetLocation() {
    if (edit == false) {
      view?.navigateTo(VIEW.LOCATION, LOCATION_REQUEST, "location", defaultLocation)
    } else {
      view?.navigateTo(VIEW.LOCATION, LOCATION_REQUEST, "location", Location(placemark.lat, placemark.lng, placemark.zoom))
    }
  }

  override fun doActivityResult(requestCode: Int, resultCode: Int, data: Intent) {
    when (requestCode) {
      IMAGE_REQUEST -> {
        placemark.image = data.data.toString()
        view?.showPlacemark(placemark)
      }
      LOCATION_REQUEST -> {
        val location = data.extras.getParcelable<Location>("location")
        placemark.lat = location.lat
        placemark.lng = location.lng
        placemark.zoom = location.zoom
      }
    }
  }
}

This is the view:

PlacemarkView

import org.wit.placemark.views.BaseView

class PlacemarkView : BaseView(), AnkoLogger {

  lateinit var presenter: PlacemarkPresenter
  var placemark = PlacemarkModel()

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

    init(toolbarAdd)

    presenter = initPresenter (PlacemarkPresenter(this)) as PlacemarkPresenter

    chooseImage.setOnClickListener { presenter.doSelectImage() }

    placemarkLocation.setOnClickListener { presenter.doSetLocation() }
  }

  override fun showPlacemark(placemark: PlacemarkModel) {
    placemarkTitle.setText(placemark.title)
    description.setText(placemark.description)
    placemarkImage.setImageBitmap(readImageFromPath(this, placemark.image))
    if (placemark.image != null) {
      chooseImage.setText(R.string.change_placemark_image)
    }
  }

  override fun onCreateOptionsMenu(menu: Menu): Boolean {
    menuInflater.inflate(R.menu.menu_placemark, menu)
    return super.onCreateOptionsMenu(menu)
  }

  override fun onOptionsItemSelected(item: MenuItem?): Boolean {
    when (item?.itemId) {
      R.id.item_delete -> {
        presenter.doDelete()
      }
      R.id.item_save -> {
        if (placemarkTitle.text.toString().isEmpty()) {
          toast(R.string.enter_placemark_title)
        } else {
          presenter.doAddOrSave(placemarkTitle.text.toString(), description.text.toString())
        }
      }
    }
    return super.onOptionsItemSelected(item)
  }

  override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    super.onActivityResult(requestCode, resultCode, data)
    if (data != null) {
      presenter.doActivityResult(requestCode, resultCode, data)
    }
  }

  override fun onBackPressed() {
    presenter.doCancel()
  }
}

PlacemarkListView/Presenter

Notice in the presenter a more attractive signature for launching activities in the navigateTo method:

PlacemarkListPresenter

package org.wit.placemark.views.placemarklist

import org.wit.placemark.models.PlacemarkModel
import org.wit.placemark.views.BasePresenter
import org.wit.placemark.views.BaseView
import org.wit.placemark.views.VIEW

class PlacemarkListPresenter(view: BaseView) : BasePresenter(view) {

  fun doAddPlacemark() {
    view?.navigateTo(VIEW.PLACEMARK)
  }

  fun doEditPlacemark(placemark: PlacemarkModel) {
    view?.navigateTo(VIEW.PLACEMARK, 0, "placemark_edit", placemark)
  }

  fun doShowPlacemarksMap() {
    view?.navigateTo(VIEW.MAPS)
  }

  fun loadPlacemarks() {
    view?.showPlacemarks(app.placemarks.findAll())
  }
}

This is the view:

PlacemarkListView

package org.wit.placemark.views.placemarklist

import android.content.Intent
import android.os.Bundle
import android.support.v7.widget.LinearLayoutManager
import android.view.*
import kotlinx.android.synthetic.main.activity_placemark_list.*
import org.wit.placemark.R
import org.wit.placemark.models.PlacemarkModel
import org.wit.placemark.views.BaseView

class PlacemarkListView :  BaseView(), PlacemarkListener {

  lateinit var presenter: PlacemarkListPresenter

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_placemark_list)
    init(toolbarMain)

    presenter = initPresenter(PlacemarkListPresenter(this)) as PlacemarkListPresenter

    val layoutManager = LinearLayoutManager(this)
    recyclerView.layoutManager = layoutManager
    presenter.loadPlacemarks()
  }

  override fun showPlacemarks(placemarks: List<PlacemarkModel>) {
    recyclerView.adapter = PlacemarkAdapter(placemarks, this)
    recyclerView.adapter?.notifyDataSetChanged()
  }

  override fun onCreateOptionsMenu(menu: Menu?): Boolean {
    menuInflater.inflate(R.menu.menu_main, menu)
    return super.onCreateOptionsMenu(menu)
  }

  override fun onOptionsItemSelected(item: MenuItem?): Boolean {
    when (item?.itemId) {
      R.id.item_add -> presenter.doAddPlacemark()
      R.id.item_map -> presenter.doShowPlacemarksMap()
    }
    return super.onOptionsItemSelected(item)
  }

  override fun onPlacemarkClick(placemark: PlacemarkModel) {
    presenter.doEditPlacemark(placemark)
  }

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

Solution

Placemark application so far:

• archive.zip

Exercise 1

Using this lab as a guide, convert PlacemarkMapView/Presenter to use the PlacemarkView/Presenter base classes

Exercise 2

Also convert EditLoctionView/Presenter to use the base classes