The document discusses the author's experience creating an Android app using Kotlin. It begins with introductions and then describes how to set up Kotlin for Android development. The author then shows code examples from an app that makes the device sleep when tapped. A comparison is made between the Kotlin and Java versions of the code, noting that the Kotlin code is more concise. In summary, the author finds that Kotlin reduces the amount of coding needed compared to Java.

1. Kotlin で Android アプリを作ってみた
bina1204
1

2. アジェンダ
• 自己紹介
• Kotlin で Android アプリを作ってみた
• Java と Kotlin の比較
• まとめ
2

3. 自己紹介
3

4. プロフィール
びな
@bina1204
http://gsbina.com
4

5. Kotlin 初心者です
5

6. Kotlin で Android アプリを作ってみた
6

7. Kotlin を覚える
Kotlin Advent Calendar 2012 (全部俺) : ATND
http://atnd.org/events/34627
7

8. Kotlin の Android アプリ開発の準備
8.2 Androidアプリ開発 - プログラミング言語Kotlin
解説
https://sites.google.com/site/tarokotlin/chap8/sec82
8

9. アプリを作ってみた
タップすると
スリープする
9

10. アプリを作ってみた
10

11. Java と Kotlin の比較
11

12. AdminReceiver.Java
package com.gsbina.android.sleepnow;
import android.app.admin.DeviceAdminReceiver;
public class AdminReceiver extends DeviceAdminReceiver {
}
12

13. AdminReceiver.kt
package com.gsbina.android.sleepnow
import android.app.admin.DeviceAdminReceiver
public class AdminReceiver: DeviceAdminReceiver() {
}
13

14. CreateShortcutActivity.Java
@Override
protected void onResume() {
super.onResume();
final Intent sleepIntent = new Intent(PhoneSleepActivity.ACTION_SLEEP);
final Intent shortcutIntent = new Intent("com.android.launcher.action.INSTALL_SHORTCUT");
shortcutIntent.putExtra(Intent.EXTRA_SHORTCUT_INTENT, sleepIntent);
shortcutIntent.putExtra(Intent.EXTRA_SHORTCUT_NAME, "Sleep Now");
shortcutIntent.putExtra(Intent.EXTRA_SHORTCUT_ICON_RESOURCE, R.drawable.ic_launcher);
sendBroadcast(shortcutIntent);
finish();
}
14

15. CreateShortcutActivity.Kt
protected override fun onResume() {
super<Activity>.onResume()
val sleepIntent = Intent(PhoneSleepActivity.ACTION_SLEEP)
val shortcutIntent = Intent("com.android.launcher.action.INSTALL_SHORTCUT")
shortcutIntent.putExtra(Intent.EXTRA_SHORTCUT_INTENT, sleepIntent)
shortcutIntent.putExtra(Intent.EXTRA_SHORTCUT_NAME, "Sleep Now");
shortcutIntent.putExtra(Intent.EXTRA_SHORTCUT_ICON_RESOURCE, R.drawable.ic_launcher)
sendBroadcast(shortcutIntent)
finish()
}
15

16. PhoneSleepActivity.java
@Override
protected void onResume() {
super.onResume();
final DevicePolicyManager dpm = (DevicePolicyManager)getSystemService(DEVICE_POLICY_SERVICE);
if (dpm.isAdminActive(new AdminReceiver().getWho(this))) {
// スリープする
dpm.lockNow();
} else {
Toast.makeText(this, "Cannot sleep", Toast.LENGTH_SHORT).show();
startActivity(new Intent(this, MainActivity.class));
}
finish();
}
public static final String ACTION_SLEEP = "com.gsbina.android.sleepnow.action.SLEEP";
16

17. PhoneSleepActivity.Kt
protected override fun onResume() {
super<Activity>.onResume()
val dpm = getSystemService(Context.DEVICE_POLICY_SERVICE) as DevicePolicyManager
if (dpm.isAdminActive(AdminReceiver().getWho(this))) {
// スリープする
dpm.lockNow();
} else {
Toast.makeText(this, "Cannot sleep", Toast.LENGTH_SHORT)?.show()
startActivity(Intent(this, javaClass<MainActivity>()))
}
finish()
}
class object {
val ACTION_SLEEP = "com.gsbina.android.sleepnow.action.SLEEP"
}
17

18. MainActivity.java
private final MainActivity mSelf = this;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
setUpView();
}
private DevicePolicyManager mDevicePolicyManager;
private void setUpView() {
findViewById(R.id.device_admin).setOnClickListener(new OnClickDeviceAdmin());
findViewById(R.id.btn_create_shortcut).setOnClickListener(new OnClickCreateShortcut());
findViewById(R.id.btn_display_notification).setOnClickListener(new OnClickDisplayNotification());
findViewById(R.id.btn_hide_notification).setOnClickListener(new OnClickHideNotification());
findViewById(R.id.btn_sleep).setOnClickListener(new OnClickSleep());
findViewById(R.id.btn_uninstall).setOnClickListener(new OnClickUninstall());
}
18

19. MainActivity.kt
val mSelf = this
protected override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.main)
setUpView()
}
var mDevicePolicyManager: DevicePolicyManager? = null
private fun setUpView() {
findViewById(R.id.device_admin)?.setOnClickListener(OnClickDeviceAdmin())
findViewById(R.id.btn_create_shortcut)?.setOnClickListener(OnClickCreateShortcut())
findViewById(R.id.btn_display_notification)?.setOnClickListener(OnClickDisplayNotification())
findViewById(R.id.btn_hide_notification)?.setOnClickListener(OnClickHideNotification())
findViewById(R.id.btn_sleep)?.setOnClickListener(OnClickSleep())
findViewById(R.id.btn_uninstall)?.setOnClickListener(OnClickUninstall())
}
19

20. MainActivity.java
private class OnClickDeviceAdmin implements OnClickListener {
@Override
public void onClick(View v) {
final Switch s = (Switch) v;
if (s.isChecked()) {
activateDeviceAdmin();
} else {
mDevicePolicyManager.removeActiveAdmin(new AdminReceiver().getWho(mSelf));
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
updateView();
}
}, 250);
}
}
private void activateDeviceAdmin() {
final Intent intent = new Intent(DevicePolicyManager.ACTION_ADD_DEVICE_ADMIN);
final ComponentName name = new AdminReceiver().getWho(mSelf);
intent.putExtra(DevicePolicyManager.EXTRA_DEVICE_ADMIN, name);
startActivity(intent);
}
}
20

21. MainActivity.kt
inner class OnClickDeviceAdmin(): OnClickListener {
public override fun onClick(v: View?) {
val s = v as Switch
if (s.isChecked()) {
activateDeviceAdmin()
} else {
mDevicePolicyManager?.removeActiveAdmin(AdminReceiver().getWho(mSelf))
Handler().postDelayed(Runnable {
updateView()
}, 250)
}
}
private fun activateDeviceAdmin() {
val intent = Intent(DevicePolicyManager.ACTION_ADD_DEVICE_ADMIN)
val name = AdminReceiver().getWho(mSelf)
intent.putExtra(DevicePolicyManager.EXTRA_DEVICE_ADMIN, name)
startActivity(intent)
}
}
21

22. APK ファイルの比較
22

23. サイズ
Java
約 229KB
Kotlin
約 467KB
23

24. classes.dex
Java
android
com
Kotlin
android
com
jet
kotlin
org
24

25. AdminReceiver.class(Java)
package com.gsbina.android.sleepnow;
import android.app.admin.DeviceAdminReceiver;
public class AdminReceiver extends DeviceAdminReceiver
{
public AdminReceiver()
{
}
}
25

26. AdminReceiver.class(Kotlin)
package com.gsbina.android.sleepnow;
import android.app.admin.DeviceAdminReceiver;
import jet.JetObject;
public final class AdminReceiver extends DeviceAdminReceiver
implements JetObject
{
public AdminReceiver()
{
}
}
26

27. CreateShortcutActivity.class(Java)
protected void onResume()
{
super.onResume();
Intent intent = new Intent("com.gsbina.android.sleepnow.action.SLEEP");
Intent intent1 = new Intent("com.android.launcher.action.INSTALL_SHORTCUT");
Intent intent2 = intent1.putExtra("android.intent.extra.shortcut.INTENT", intent);
Intent intent3 = intent1.putExtra("android.intent.extra.shortcut.NAME", "Sleep Now");
Intent intent4 = intent1.putExtra("android.intent.extra.shortcut.ICON_RESOURCE", 0x7f020000);
sendBroadcast(intent1);
finish();
}
27

28. CreateShortcutActivity.class(Kotlin)
protected void onResume()
{
super.onResume();
String s = PhoneSleepActivity.object$.getACTION_SLEEP();
Intent intent = new Intent(s);
Intent intent1 = new Intent("com.android.launcher.action.INSTALL_SHORTCUT");
String s1 = Intent.EXTRA_SHORTCUT_INTENT;
Intrinsics.checkFieldIsNotNull(s1, "Intent", "EXTRA_SHORTCUT_INTENT");
Parcelable parcelable = (Parcelable)intent;
Intent intent2 = intent1.putExtra(s1, parcelable);
String s2 = Intent.EXTRA_SHORTCUT_NAME;
Intrinsics.checkFieldIsNotNull(s2, "Intent", "EXTRA_SHORTCUT_NAME");
Intent intent3 = intent1.putExtra(s2, "Sleep Now");
String s3 = Intent.EXTRA_SHORTCUT_ICON_RESOURCE;
Intrinsics.checkFieldIsNotNull(s3, "Intent", "EXTRA_SHORTCUT_ICON_RESOURCE");
int i = R.drawable.ic_launcher;
Intent intent4 = intent1.putExtra(s3, i);
sendBroadcast(intent1);
finish();
}
28

29. PhoneSleepActivity.class(Java)
protected void onResume()
{
super.onResume();
DevicePolicyManager devicepolicymanager = (DevicePolicyManager)getSystemService("device_policy");
android.content.ComponentName componentname = (new AdminReceiver()).getWho(this);
if(devicepolicymanager.isAdminActive(componentname)
{
devicepolicymanager.lockNow();
} else
{
Toast.makeText(this, "Cannot sleep", 0).show();
Intent intent = new Intent(this, com/gsbina/android/sleepnow/MainActivity);
startActivity(intent);
}
finish();
}
public static final String ACTION_SLEEP = "com.gsbina.android.sleepnow.action.SLEEP";
29

30. PhoneSleepActivity.class(Kotlin)
protected void onResume()
{
super.onResume();
String s = Context.DEVICE_POLICY_SERVICE;
Intrinsics.checkFieldIsNotNull(s, "Context", "DEVICE_POLICY_SERVICE");
Object obj = getSystemService(s);
if(obj == null)
throw new TypeCastException("jet.Any? cannot be cast to android.app.admin.DevicePolicyManager");
DevicePolicyManager devicepolicymanager = (DevicePolicyManager)obj;
android.content.ComponentName componentname = (new AdminReceiver()).getWho(this);
if(devicepolicymanager.isAdminActive(componentname))
{
devicepolicymanager.lockNow();
} else
{
Context context = getApplicationContext();
CharSequence charsequence = (CharSequence)"Cannot sleep";
int i = Toast.LENGTH_SHORT;
Toast toast = Toast.makeText(context, charsequence, i);
if(toast != null)
toast.show();
Intent intent = new Intent(this, com/gsbina/android/sleepnow/MainActivity);
startActivity(intent);
}
finish();
}
30

31. PhoneSleepActivity.class(Kotlin)
public static final class object
implements JetObject
{
public final String getACTION_SLEEP()
{
return ACTION_SLEEP;
}
private final String ACTION_SLEEP = "com.gsbina.android.sleepnow.action.SLEEP";
object()
{
}
}
public static final object object$ = new object();
31

32. まとめ
32

33. まとめ
33
final Intent intent = new Intent(this, MainActivity.class);
val intent = Intent(this, javaClass<MainActivity>());

34. まとめ
34
new Runnable() {
@Override
public void run() {
// 処理
}
}
Runnable {
// 処理
}

35. まとめ(定数)
35
public static final String ACTION_SLEEP =
"com.gsbina.android.sleepnow.action.SLEEP";
class object {
val ACTION_SLEEP = "com.gsbina.android.sleepnow.action.SLEEP"
}

36. まとめ
コーディングの量が減る
36
Java Kotlin
MainActivity 3773 3395
AdminReceiver 131 125
CreateShortcutActivity 594 566
PhoneSleepActivity 631 635
[文字数]