Android Studioにて、KotlinでのLogin

前提

C言語は勉強済み
Kotlinを勉強し始めたばかりで、長澤太郎著「Kotlinスタートブック」を見ながら勉強しています。
ある団体でアプリを作成しようとしているのですが、そのログイン画面を作ろうとしています。

伺いたいこと

Android StudioのLogin_activityのファイル「LoginActivity.kt」のコードを解読しているのですが、本には記載されていないコード（11行目のsuperなど）があり、どのような仕組みになっているのか分かりません。一部分であったり、簡単にでも大丈夫ですので、何が書かれているのか教えていただきたいです。コードが凄く長文ですいません。

該当のソースコード

Kotlin
1
2class LoginActivity : AppCompatActivity(), LoaderCallbacks<Cursor> {
3
4    private var mAuthTask: UserLoginTask? = null
5
6    override fun onCreate(savedInstanceState: Bundle?) {
7        super.onCreate(savedInstanceState)
8        setContentView(R.layout.activity_login)
9        // Set up the login form.
10        populateAutoComplete()
11        password.setOnEditorActionListener(TextView.OnEditorActionListener { _, id, _ ->
12            if (id == EditorInfo.IME_ACTION_DONE || id == EditorInfo.IME_NULL) {
13                attemptLogin()
14                return@OnEditorActionListener true
15            }
16            false
17        })
18
19        email_sign_in_button.setOnClickListener { attemptLogin() }
20    }
21
22    private fun populateAutoComplete() {
23        if (!mayRequestContacts()) {
24            return
25        }
26
27        loaderManager.initLoader(0, null, this)
28    }
29
30    private fun mayRequestContacts(): Boolean {
31        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {
32            return true
33        }
34        if (checkSelfPermission(READ_CONTACTS) == PackageManager.PERMISSION_GRANTED) {
35            return true
36        }
37        if (shouldShowRequestPermissionRationale(READ_CONTACTS)) {
38            Snackbar.make(email, R.string.permission_rationale, Snackbar.LENGTH_INDEFINITE)
39                .setAction(android.R.string.ok,
40                    { requestPermissions(arrayOf(READ_CONTACTS), REQUEST_READ_CONTACTS) })
41        } else {
42            requestPermissions(arrayOf(READ_CONTACTS), REQUEST_READ_CONTACTS)
43        }
44        return false
45    }
46
47    override fun onRequestPermissionsResult(
48        requestCode: Int, permissions: Array<String>,
49        grantResults: IntArray
50    ) {
51        if (requestCode == REQUEST_READ_CONTACTS) {
52            if (grantResults.size == 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
53                populateAutoComplete()
54            }
55        }
56    }
57
58    private fun attemptLogin() {
59        if (mAuthTask != null) {
60            return
61        }
62
63        // Reset errors.
64        email.error = null
65        password.error = null
66
67        // Store values at the time of the login attempt.
68        val emailStr = email.text.toString()
69        val passwordStr = password.text.toString()
70
71        var cancel = false
72        var focusView: View? = null
73
74        // Check for a valid password, if the user entered one.
75        if (!TextUtils.isEmpty(passwordStr) && !isPasswordValid(passwordStr)) {
76            password.error = getString(R.string.error_invalid_password)
77            focusView = password
78            cancel = true
79        }
80
81        // Check for a valid email address.
82        if (TextUtils.isEmpty(emailStr)) {
83            email.error = getString(R.string.error_field_required)
84            focusView = email
85            cancel = true
86        } else if (!isEmailValid(emailStr)) {
87            email.error = getString(R.string.error_invalid_email)
88            focusView = email
89            cancel = true
90        }
91
92        if (cancel) {
93            // There was an error; don't attempt login and focus the first
94            // form field with an error.
95            focusView?.requestFocus()
96        } else {
97            // Show a progress spinner, and kick off a background task to
98            // perform the user login attempt.
99            showProgress(true)
100            mAuthTask = UserLoginTask(emailStr, passwordStr)
101            mAuthTask!!.execute(null as Void?)
102        }
103    }
104
105    private fun isEmailValid(email: String): Boolean {
106        //TODO: Replace this with your own logic
107        return email.contains("@")
108    }
109
110    private fun isPasswordValid(password: String): Boolean {
111        //TODO: Replace this with your own logic
112        return password.length > 4
113    }
114
115    @TargetApi(Build.VERSION_CODES.HONEYCOMB_MR2)
116    private fun showProgress(show: Boolean) {
117        // On Honeycomb MR2 we have the ViewPropertyAnimator APIs, which allow
118        // for very easy animations. If available, use these APIs to fade-in
119        // the progress spinner.
120        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB_MR2) {
121            val shortAnimTime = resources.getInteger(android.R.integer.config_shortAnimTime).toLong()
122
123            login_form.visibility = if (show) View.GONE else View.VISIBLE
124            login_form.animate()
125                .setDuration(shortAnimTime)
126                .alpha((if (show) 0 else 1).toFloat())
127                .setListener(object : AnimatorListenerAdapter() {
128                    override fun onAnimationEnd(animation: Animator) {
129                        login_form.visibility = if (show) View.GONE else View.VISIBLE
130                    }
131                })
132
133            login_progress.visibility = if (show) View.VISIBLE else View.GONE
134            login_progress.animate()
135                .setDuration(shortAnimTime)
136                .alpha((if (show) 1 else 0).toFloat())
137                .setListener(object : AnimatorListenerAdapter() {
138                    override fun onAnimationEnd(animation: Animator) {
139                        login_progress.visibility = if (show) View.VISIBLE else View.GONE
140                    }
141                })
142        } else {
143            // The ViewPropertyAnimator APIs are not available, so simply show
144            // and hide the relevant UI components.
145            login_progress.visibility = if (show) View.VISIBLE else View.GONE
146            login_form.visibility = if (show) View.GONE else View.VISIBLE
147        }
148    }
149
150    override fun onCreateLoader(i: Int, bundle: Bundle?): Loader<Cursor> {
151        return CursorLoader(
152            this,
153            // Retrieve data rows for the device user's 'profile' contact.
154            Uri.withAppendedPath(
155                ContactsContract.Profile.CONTENT_URI,
156                ContactsContract.Contacts.Data.CONTENT_DIRECTORY
157            ), ProfileQuery.PROJECTION,
158
159            // Select only email addresses.
160            ContactsContract.Contacts.Data.MIMETYPE + " = ?", arrayOf(
161                ContactsContract.CommonDataKinds.Email
162                    .CONTENT_ITEM_TYPE
163            ),
164
165            // Show primary email addresses first. Note that there won't be
166            // a primary email address if the user hasn't specified one.
167            ContactsContract.Contacts.Data.IS_PRIMARY + " DESC"
168        )
169    }
170
171    override fun onLoadFinished(cursorLoader: Loader<Cursor>, cursor: Cursor) {
172        val emails = ArrayList<String>()
173        cursor.moveToFirst()
174        while (!cursor.isAfterLast) {
175            emails.add(cursor.getString(ProfileQuery.ADDRESS))
176            cursor.moveToNext()
177        }
178
179        addEmailsToAutoComplete(emails)
180    }
181
182    override fun onLoaderReset(cursorLoader: Loader<Cursor>) {
183
184    }
185
186    private fun addEmailsToAutoComplete(emailAddressCollection: List<String>) {
187        //Create adapter to tell the AutoCompleteTextView what to show in its dropdown list.
188        val adapter = ArrayAdapter(
189            this@LoginActivity,
190            android.R.layout.simple_dropdown_item_1line, emailAddressCollection
191        )
192
193        email.setAdapter(adapter)
194    }
195
196    object ProfileQuery {
197        val PROJECTION = arrayOf(
198            ContactsContract.CommonDataKinds.Email.ADDRESS,
199            ContactsContract.CommonDataKinds.Email.IS_PRIMARY
200        )
201        val ADDRESS = 0
202        val IS_PRIMARY = 1
203    }
204
205    inner class UserLoginTask internal constructor(private val mEmail: String, private val mPassword: String) :
206        AsyncTask<Void, Void, Boolean>() {
207
208        override fun doInBackground(vararg params: Void): Boolean? {
209            // TODO: attempt authentication against a network service.
210
211            try {
212                // Simulate network access.
213                Thread.sleep(2000)
214            } catch (e: InterruptedException) {
215                return false
216            }
217
218            return DUMMY_CREDENTIALS
219                .map { it.split(":") }
220                .firstOrNull { it[0] == mEmail }
221                ?.let {
222                    // Account exists, return true if the password matches.
223                    it[1] == mPassword
224                }
225                ?: true
226        }
227
228        override fun onPostExecute(success: Boolean?) {
229            mAuthTask = null
230            showProgress(false)
231
232            if (success!!) {
233                finish()
234            } else {
235                password.error = getString(R.string.error_incorrect_password)
236                password.requestFocus()
237            }
238        }
239
240        override fun onCancelled() {
241            mAuthTask = null
242            showProgress(false)
243        }
244    }
245
246    companion object {
247
248        private val REQUEST_READ_CONTACTS = 0
249
250        private val DUMMY_CREDENTIALS = arrayOf("foo@example.com:hello", "bar@example.com:world")
251    }
252}