Context?

개발하면서 항상 헷깔렸던 Context에 대해 공식문서와 구글 검색을 통해 정리를 해봤다.

정의

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문맥 또는 맥락은 언어학, 사회학에서 핵심이 되는 사건 주변의 실체

 

정의만 봤을 때 안드로이드에서 어떤 것이 Context인지 확실하지 않다.

개발자 사이트에선 뭐라고 적어놨을까?

 

Interface to global information about an application environment. This is an abstract class whose implementation is provided by the Android system. It allows access to application-specific resources and classes, as well as up-calls for application-level operations such as launching activities, broadcasting and receiving intents, etc.

번역하면

어플리케이션 환경의 글로벌 정보에 대한 인터페이스입니다. 이것은 안드로이드 시스템에 의해 구현되는 추상 클래스입니다. 이것은 어플레케이션 별 리소스 및 클래스에 대한 액세스와 함께, 시작 액티비티, 브로드캐스트 및 수신 인텐트 등과 같은 애플리케이션 수준의 운영에 대한 호출을 허용합니다.

번역만 봤을 땐 20% 부족하다. 글로벌 정보란 무엇이며 호출을 허용한다는 말이 어떤 건지 와닫지 않는다.

글로벌 정보가 뭘까? Context의 상속관계와 프로퍼티, 메서드에 힌트가 있을지도 모른다.

상속관계

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#Context의 상속관계

Object를 상속하고 있고 직간접적인 하위 클래스가 엄청 많다. 하위 클래스가 어떤 것들인지 감이 안 잡힐 수 있는데 우리가 자주 보는 AppCompatActivity() 클래스의 상속관계를 살펴보자.

AppCompatActivity의 상속관계

Context가 부모클래스에 있는 것을 확인할 수 있다.

상속관계로 알 수 있는 것은 Context는 자바 최상위 클래스인 오브젝트를 직접적으로 상속하는 클래스라는 것이다.

적용되는 범위가 글로벌한 것은 알겠는데 그렇다면 글로벌 정보는 뭘까?

프로퍼티, 메서드

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Context클래스의 프로퍼티와 메서드를 보면 글로벌 정보가 뭔지 알 수 있을지도 모른다.(길다)

package android.content;

public abstract class Context {
    public static final String ACCESSIBILITY_SERVICE = "accessibility";
    public static final String ACCOUNT_SERVICE = "account";
    public static final String ACTIVITY_SERVICE = "activity";
    public static final String ALARM_SERVICE = "alarm";
    public static final String APPWIDGET_SERVICE = "appwidget";
    public static final String APP_OPS_SERVICE = "appops";
    public static final String APP_SEARCH_SERVICE = "app_search";
    public static final String AUDIO_SERVICE = "audio";
    public static final String BATTERY_SERVICE = "batterymanager";
    public static final int BIND_ABOVE_CLIENT = 8;
    public static final int BIND_ADJUST_WITH_ACTIVITY = 128;
    public static final int BIND_ALLOW_OOM_MANAGEMENT = 16;
    public static final int BIND_AUTO_CREATE = 1;
    public static final int BIND_DEBUG_UNBIND = 2;
    public static final int BIND_EXTERNAL_SERVICE = -2147483648;
    public static final int BIND_IMPORTANT = 64;
    public static final int BIND_INCLUDE_CAPABILITIES = 4096;
    public static final int BIND_NOT_FOREGROUND = 4;
    public static final int BIND_NOT_PERCEPTIBLE = 256;
    public static final int BIND_WAIVE_PRIORITY = 32;
    public static final String BIOMETRIC_SERVICE = "biometric";
    public static final String BLOB_STORE_SERVICE = "blob_store";
    public static final String BLUETOOTH_SERVICE = "bluetooth";
    public static final String BUGREPORT_SERVICE = "bugreport";
    public static final String CAMERA_SERVICE = "camera";
    public static final String CAPTIONING_SERVICE = "captioning";
    public static final String CARRIER_CONFIG_SERVICE = "carrier_config";
    public static final String CLIPBOARD_SERVICE = "clipboard";
    public static final String COMPANION_DEVICE_SERVICE = "companiondevice";
    public static final String CONNECTIVITY_DIAGNOSTICS_SERVICE = "connectivity_diagnostics";
    public static final String CONNECTIVITY_SERVICE = "connectivity";
    public static final String CONSUMER_IR_SERVICE = "consumer_ir";
    public static final int CONTEXT_IGNORE_SECURITY = 2;
    public static final int CONTEXT_INCLUDE_CODE = 1;
    public static final int CONTEXT_RESTRICTED = 4;
    public static final String CROSS_PROFILE_APPS_SERVICE = "crossprofileapps";
    public static final String DEVICE_POLICY_SERVICE = "device_policy";
    public static final String DISPLAY_HASH_SERVICE = "display_hash";
    public static final String DISPLAY_SERVICE = "display";
    public static final String DOMAIN_VERIFICATION_SERVICE = "domain_verification";
    public static final String DOWNLOAD_SERVICE = "download";
    public static final String DROPBOX_SERVICE = "dropbox";
    public static final String EUICC_SERVICE = "euicc";
    public static final String FILE_INTEGRITY_SERVICE = "file_integrity";
    public static final String FINGERPRINT_SERVICE = "fingerprint";
    public static final String GAME_SERVICE = "game";
    public static final String HARDWARE_PROPERTIES_SERVICE = "hardware_properties";
    public static final String INPUT_METHOD_SERVICE = "input_method";
    public static final String INPUT_SERVICE = "input";
    public static final String IPSEC_SERVICE = "ipsec";
    public static final String JOB_SCHEDULER_SERVICE = "jobscheduler";
    public static final String KEYGUARD_SERVICE = "keyguard";
    public static final String LAUNCHER_APPS_SERVICE = "launcherapps";
    public static final String LAYOUT_INFLATER_SERVICE = "layout_inflater";
    public static final String LOCATION_SERVICE = "location";
    public static final String MEDIA_COMMUNICATION_SERVICE = "media_communication";
    public static final String MEDIA_METRICS_SERVICE = "media_metrics";
    public static final String MEDIA_PROJECTION_SERVICE = "media_projection";
    public static final String MEDIA_ROUTER_SERVICE = "media_router";
    public static final String MEDIA_SESSION_SERVICE = "media_session";
    public static final String MIDI_SERVICE = "midi";
    public static final int MODE_APPEND = 32768;
    public static final int MODE_ENABLE_WRITE_AHEAD_LOGGING = 8;
    /** @deprecated */
    @Deprecated
    public static final int MODE_MULTI_PROCESS = 4;
    public static final int MODE_NO_LOCALIZED_COLLATORS = 16;
    public static final int MODE_PRIVATE = 0;
    /** @deprecated */
    @Deprecated
    public static final int MODE_WORLD_READABLE = 1;
    /** @deprecated */
    @Deprecated
    public static final int MODE_WORLD_WRITEABLE = 2;
    public static final String NETWORK_STATS_SERVICE = "netstats";
    public static final String NFC_SERVICE = "nfc";
    public static final String NOTIFICATION_SERVICE = "notification";
    public static final String NSD_SERVICE = "servicediscovery";
    public static final String PEOPLE_SERVICE = "people";
    public static final String PERFORMANCE_HINT_SERVICE = "performance_hint";
    public static final String POWER_SERVICE = "power";
    public static final String PRINT_SERVICE = "print";
    public static final int RECEIVER_VISIBLE_TO_INSTANT_APPS = 1;
    public static final String RESTRICTIONS_SERVICE = "restrictions";
    public static final String ROLE_SERVICE = "role";
    public static final String SEARCH_SERVICE = "search";
    public static final String SENSOR_SERVICE = "sensor";
    public static final String SHORTCUT_SERVICE = "shortcut";
    public static final String STORAGE_SERVICE = "storage";
    public static final String STORAGE_STATS_SERVICE = "storagestats";
    public static final String SYSTEM_HEALTH_SERVICE = "systemhealth";
    public static final String TELECOM_SERVICE = "telecom";
    public static final String TELEPHONY_IMS_SERVICE = "telephony_ims";
    public static final String TELEPHONY_SERVICE = "phone";
    public static final String TELEPHONY_SUBSCRIPTION_SERVICE = "telephony_subscription_service";
    public static final String TEXT_CLASSIFICATION_SERVICE = "textclassification";
    public static final String TEXT_SERVICES_MANAGER_SERVICE = "textservices";
    public static final String TV_INPUT_SERVICE = "tv_input";
    public static final String UI_MODE_SERVICE = "uimode";
    public static final String USAGE_STATS_SERVICE = "usagestats";
    public static final String USB_SERVICE = "usb";
    public static final String USER_SERVICE = "user";
    public static final String VIBRATOR_MANAGER_SERVICE = "vibrator_manager";
    /** @deprecated */
    @Deprecated
    public static final String VIBRATOR_SERVICE = "vibrator";
    public static final String VPN_MANAGEMENT_SERVICE = "vpn_management";
    public static final String WALLPAPER_SERVICE = "wallpaper";
    public static final String WIFI_AWARE_SERVICE = "wifiaware";
    public static final String WIFI_P2P_SERVICE = "wifip2p";
    public static final String WIFI_RTT_RANGING_SERVICE = "wifirtt";
    public static final String WIFI_SERVICE = "wifi";
    public static final String WINDOW_SERVICE = "window";

    public Context() {
        throw new RuntimeException("Stub!");
    }

    public abstract AssetManager getAssets();

    public abstract Resources getResources();

    public abstract PackageManager getPackageManager();

    public abstract ContentResolver getContentResolver();

    public abstract Looper getMainLooper();

    public Executor getMainExecutor() {
        throw new RuntimeException("Stub!");
    }

    public abstract Context getApplicationContext();

    public void registerComponentCallbacks(ComponentCallbacks callback) {
        throw new RuntimeException("Stub!");
    }

    public void unregisterComponentCallbacks(ComponentCallbacks callback) {
        throw new RuntimeException("Stub!");
    }

    @NonNull
    public final CharSequence getText(int resId) {
        throw new RuntimeException("Stub!");
    }

    @NonNull
    public final String getString(int resId) {
        throw new RuntimeException("Stub!");
    }

    @NonNull
    public final String getString(int resId, Object... formatArgs) {
        throw new RuntimeException("Stub!");
    }

    public final int getColor(int id) {
        throw new RuntimeException("Stub!");
    }

    @Nullable
    public final Drawable getDrawable(int id) {
        throw new RuntimeException("Stub!");
    }

    @NonNull
    public final ColorStateList getColorStateList(int id) {
        throw new RuntimeException("Stub!");
    }

    public abstract void setTheme(int var1);

    @ExportedProperty(
        deepExport = true
    )
    public abstract Theme getTheme();

    @NonNull
    public final TypedArray obtainStyledAttributes(@NonNull int[] attrs) {
        throw new RuntimeException("Stub!");
    }

    @NonNull
    public final TypedArray obtainStyledAttributes(int resid, @NonNull int[] attrs) throws NotFoundException {
        throw new RuntimeException("Stub!");
    }

    @NonNull
    public final TypedArray obtainStyledAttributes(@Nullable AttributeSet set, @NonNull int[] attrs) {
        throw new RuntimeException("Stub!");
    }

    @NonNull
    public final TypedArray obtainStyledAttributes(@Nullable AttributeSet set, @NonNull int[] attrs, int defStyleAttr, int defStyleRes) {
        throw new RuntimeException("Stub!");
    }

    public abstract ClassLoader getClassLoader();

    public abstract String getPackageName();

    @NonNull
    public String getOpPackageName() {
        throw new RuntimeException("Stub!");
    }

    @Nullable
    public String getAttributionTag() {
        throw new RuntimeException("Stub!");
    }

    @NonNull
    public AttributionSource getAttributionSource() {
        throw new RuntimeException("Stub!");
    }

    @Nullable
    public ContextParams getParams() {
        throw new RuntimeException("Stub!");
    }

    public abstract ApplicationInfo getApplicationInfo();

    public abstract String getPackageResourcePath();

    public abstract String getPackageCodePath();

    public abstract SharedPreferences getSharedPreferences(String var1, int var2);

    public abstract boolean moveSharedPreferencesFrom(Context var1, String var2);

    public abstract boolean deleteSharedPreferences(String var1);

    public abstract FileInputStream openFileInput(String var1) throws FileNotFoundException;

    public abstract FileOutputStream openFileOutput(String var1, int var2) throws FileNotFoundException;

    public abstract boolean deleteFile(String var1);

    public abstract File getFileStreamPath(String var1);

    public abstract File getDataDir();

    public abstract File getFilesDir();

    public abstract File getNoBackupFilesDir();

    @Nullable
    public abstract File getExternalFilesDir(@Nullable String var1);

    public abstract File[] getExternalFilesDirs(String var1);

    public abstract File getObbDir();

    public abstract File[] getObbDirs();

    public abstract File getCacheDir();

    public abstract File getCodeCacheDir();

    @Nullable
    public abstract File getExternalCacheDir();

    public abstract File[] getExternalCacheDirs();

    /** @deprecated */
    @Deprecated
    public abstract File[] getExternalMediaDirs();

    public abstract String[] fileList();

    public abstract File getDir(String var1, int var2);

    public abstract SQLiteDatabase openOrCreateDatabase(String var1, int var2, CursorFactory var3);

    public abstract SQLiteDatabase openOrCreateDatabase(String var1, int var2, CursorFactory var3, @Nullable DatabaseErrorHandler var4);

    public abstract boolean moveDatabaseFrom(Context var1, String var2);

    public abstract boolean deleteDatabase(String var1);

    public abstract File getDatabasePath(String var1);

    public abstract String[] databaseList();

    /** @deprecated */
    @Deprecated
    public abstract Drawable getWallpaper();

    /** @deprecated */
    @Deprecated
    public abstract Drawable peekWallpaper();

    /** @deprecated */
    @Deprecated
    public abstract int getWallpaperDesiredMinimumWidth();

    /** @deprecated */
    @Deprecated
    public abstract int getWallpaperDesiredMinimumHeight();

    /** @deprecated */
    @Deprecated
    public abstract void setWallpaper(Bitmap var1) throws IOException;

    /** @deprecated */
    @Deprecated
    public abstract void setWallpaper(InputStream var1) throws IOException;

    /** @deprecated */
    @Deprecated
    public abstract void clearWallpaper() throws IOException;

    public abstract void startActivity(Intent var1);

    public abstract void startActivity(Intent var1, @Nullable Bundle var2);

    public abstract void startActivities(Intent[] var1);

    public abstract void startActivities(Intent[] var1, Bundle var2);

    public abstract void startIntentSender(IntentSender var1, @Nullable Intent var2, int var3, int var4, int var5) throws SendIntentException;

    public abstract void startIntentSender(IntentSender var1, @Nullable Intent var2, int var3, int var4, int var5, @Nullable Bundle var6) throws SendIntentException;

    public abstract void sendBroadcast(Intent var1);

    public abstract void sendBroadcast(Intent var1, @Nullable String var2);

    public void sendBroadcastWithMultiplePermissions(@NonNull Intent intent, @NonNull String[] receiverPermissions) {
        throw new RuntimeException("Stub!");
    }

    public abstract void sendOrderedBroadcast(Intent var1, @Nullable String var2);

    public abstract void sendOrderedBroadcast(@NonNull Intent var1, @Nullable String var2, @Nullable BroadcastReceiver var3, @Nullable Handler var4, int var5, @Nullable String var6, @Nullable Bundle var7);

    public abstract void sendBroadcastAsUser(Intent var1, UserHandle var2);

    public abstract void sendBroadcastAsUser(Intent var1, UserHandle var2, @Nullable String var3);

    public abstract void sendOrderedBroadcastAsUser(Intent var1, UserHandle var2, @Nullable String var3, BroadcastReceiver var4, @Nullable Handler var5, int var6, @Nullable String var7, @Nullable Bundle var8);

    public void sendOrderedBroadcast(@NonNull Intent intent, @Nullable String receiverPermission, @Nullable String receiverAppOp, @Nullable BroadcastReceiver resultReceiver, @Nullable Handler scheduler, int initialCode, @Nullable String initialData, @Nullable Bundle initialExtras) {
        throw new RuntimeException("Stub!");
    }

    /** @deprecated */
    @Deprecated
    public abstract void sendStickyBroadcast(Intent var1);

    /** @deprecated */
    @Deprecated
    public void sendStickyBroadcast(@NonNull Intent intent, @Nullable Bundle options) {
        throw new RuntimeException("Stub!");
    }

    /** @deprecated */
    @Deprecated
    public abstract void sendStickyOrderedBroadcast(Intent var1, BroadcastReceiver var2, @Nullable Handler var3, int var4, @Nullable String var5, @Nullable Bundle var6);

    /** @deprecated */
    @Deprecated
    public abstract void removeStickyBroadcast(Intent var1);

    /** @deprecated */
    @Deprecated
    public abstract void sendStickyBroadcastAsUser(Intent var1, UserHandle var2);

    /** @deprecated */
    @Deprecated
    public abstract void sendStickyOrderedBroadcastAsUser(Intent var1, UserHandle var2, BroadcastReceiver var3, @Nullable Handler var4, int var5, @Nullable String var6, @Nullable Bundle var7);

    /** @deprecated */
    @Deprecated
    public abstract void removeStickyBroadcastAsUser(Intent var1, UserHandle var2);

    @Nullable
    public abstract Intent registerReceiver(@Nullable BroadcastReceiver var1, IntentFilter var2);

    @Nullable
    public abstract Intent registerReceiver(@Nullable BroadcastReceiver var1, IntentFilter var2, int var3);

    @Nullable
    public abstract Intent registerReceiver(BroadcastReceiver var1, IntentFilter var2, @Nullable String var3, @Nullable Handler var4);

    @Nullable
    public abstract Intent registerReceiver(BroadcastReceiver var1, IntentFilter var2, @Nullable String var3, @Nullable Handler var4, int var5);

    public abstract void unregisterReceiver(BroadcastReceiver var1);

    @Nullable
    public abstract ComponentName startService(Intent var1);

    @Nullable
    public abstract ComponentName startForegroundService(Intent var1);

    public abstract boolean stopService(Intent var1);

    public abstract boolean bindService(Intent var1, @NonNull ServiceConnection var2, int var3);

    public boolean bindService(@NonNull Intent service, int flags, @NonNull Executor executor, @NonNull ServiceConnection conn) {
        throw new RuntimeException("Stub!");
    }

    public boolean bindIsolatedService(@NonNull Intent service, int flags, @NonNull String instanceName, @NonNull Executor executor, @NonNull ServiceConnection conn) {
        throw new RuntimeException("Stub!");
    }

    public boolean bindServiceAsUser(@NonNull Intent service, @NonNull ServiceConnection conn, int flags, @NonNull UserHandle user) {
        throw new RuntimeException("Stub!");
    }

    public void updateServiceGroup(@NonNull ServiceConnection conn, int group, int importance) {
        throw new RuntimeException("Stub!");
    }

    public abstract void unbindService(@NonNull ServiceConnection var1);

    public abstract boolean startInstrumentation(@NonNull ComponentName var1, @Nullable String var2, @Nullable Bundle var3);

    public abstract Object getSystemService(@NonNull String var1);

    public final <T> T getSystemService(@NonNull Class<T> serviceClass) {
        throw new RuntimeException("Stub!");
    }

    @Nullable
    public abstract String getSystemServiceName(@NonNull Class<?> var1);

    public abstract int checkPermission(@NonNull String var1, int var2, int var3);

    public abstract int checkCallingPermission(@NonNull String var1);

    public abstract int checkCallingOrSelfPermission(@NonNull String var1);

    public abstract int checkSelfPermission(@NonNull String var1);

    public abstract void enforcePermission(@NonNull String var1, int var2, int var3, @Nullable String var4);

    public abstract void enforceCallingPermission(@NonNull String var1, @Nullable String var2);

    public abstract void enforceCallingOrSelfPermission(@NonNull String var1, @Nullable String var2);

    public abstract void grantUriPermission(String var1, Uri var2, int var3);

    public abstract void revokeUriPermission(Uri var1, int var2);

    public abstract void revokeUriPermission(String var1, Uri var2, int var3);

    public abstract int checkUriPermission(Uri var1, int var2, int var3, int var4);

    @NonNull
    public int[] checkUriPermissions(@NonNull List<Uri> uris, int pid, int uid, int modeFlags) {
        throw new RuntimeException("Stub!");
    }

    public abstract int checkCallingUriPermission(Uri var1, int var2);

    @NonNull
    public int[] checkCallingUriPermissions(@NonNull List<Uri> uris, int modeFlags) {
        throw new RuntimeException("Stub!");
    }

    public abstract int checkCallingOrSelfUriPermission(Uri var1, int var2);

    @NonNull
    public int[] checkCallingOrSelfUriPermissions(@NonNull List<Uri> uris, int modeFlags) {
        throw new RuntimeException("Stub!");
    }

    public abstract int checkUriPermission(@Nullable Uri var1, @Nullable String var2, @Nullable String var3, int var4, int var5, int var6);

    public abstract void enforceUriPermission(Uri var1, int var2, int var3, int var4, String var5);

    public abstract void enforceCallingUriPermission(Uri var1, int var2, String var3);

    public abstract void enforceCallingOrSelfUriPermission(Uri var1, int var2, String var3);

    public abstract void enforceUriPermission(@Nullable Uri var1, @Nullable String var2, @Nullable String var3, int var4, int var5, int var6, @Nullable String var7);

    public abstract Context createPackageContext(String var1, int var2) throws NameNotFoundException;

    public abstract Context createContextForSplit(String var1) throws NameNotFoundException;

    public abstract Context createConfigurationContext(@NonNull Configuration var1);

    public abstract Context createDisplayContext(@NonNull Display var1);

    @NonNull
    public Context createWindowContext(int type, @Nullable Bundle options) {
        throw new RuntimeException("Stub!");
    }

    @NonNull
    public Context createWindowContext(@NonNull Display display, int type, @Nullable Bundle options) {
        throw new RuntimeException("Stub!");
    }

    @NonNull
    public Context createContext(@NonNull ContextParams contextParams) {
        throw new RuntimeException("Stub!");
    }

    @NonNull
    public Context createAttributionContext(@Nullable String attributionTag) {
        throw new RuntimeException("Stub!");
    }

    public abstract Context createDeviceProtectedStorageContext();

    @Nullable
    public Display getDisplay() {
        throw new RuntimeException("Stub!");
    }

    public boolean isRestricted() {
        throw new RuntimeException("Stub!");
    }

    public abstract boolean isDeviceProtectedStorage();

    public boolean isUiContext() {
        throw new RuntimeException("Stub!");
    }
}

메서드를 살펴보면 액티비티와 뷰를 수정하기 위해 사용하던 메서드를 볼 수 있다. Context의 메서드는 하위 클래스에 의해 오버라이딩 되며 실제로 사용하는 것은 오버라이딩 된 메서드이다. 따라서 글로벌 정보란 Context를 상속하고 있는 클래스의 메서드라고 볼 수 있다. 

 

위 두 내용을 종합해보면 Context는 어플리케이션, 액티비티 등의 추상 클래스이다.

개념적으로 Context는 메모리에 적재되있는 어플리케이션, 액티비티등 이 가지고 있는 정보(프로퍼티, 메서드)라고 볼 수 있다.

getContext(), getApplicationContext()과 같은 메서드를 통해 어플리케이션, 액티비티의 정보를 가져올 수 있다.

Context 종류

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크게 2가지로 나뉜다.

1. Application Context

ApplicationContext는 메모리에 있는 어플리케이션 객체의 정보이다. 싱글톤인 인스턴스이며 getApplicationContext()를 통해 접근할 수 있다.  어플리케이션이므로 어플리케이션 자체의 생명주기에 영향받는다. 따라서 Activity보다 큰 Context를 요구하는 패러미터에 사용하는 Context이다. Application Context가 필요한 패러미터에 Activity Context를 전달하면 액티비티에 대한 참조가 유지되고 가비지 콜렉트가 되지 않으므로 메모리 누수를 초래한다.

만약, 라이브러리를 액티비티에서 초기화 해야하는 경우 항상 Activity Context가 아닌 Application Context를 전달해줘야 한다.

getApplicationContext() 또는 applicationContext로 참조할 수 있다.

사용 예 : 어플리케이션에 대한 싱글톤 객체를 만들어야 하고 해당 객체에 Context가 필요한 경우 Application Context를 전달해야한다. Activity Context를 주게되면 해당 액티비티가 사용되지 않더라도 참조가 유지되기 때문에 메모리 누수가 생기기 때문이다.

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2. Activity Context

이 Context는 액티비티에서 사용할 수 있다. 또한 이 Context는 액티비티의 수명주기와 연결된다. 액티비티에서 Context를 전달하거나 현재 Context에 라이프 사이클이 연결된 Context가 필요할 때 Activity Context를 사용해야 한다.

getContext() 또는 context로 참조할 수 있다.

사용 예 : 수명주기가 액티비티에 연결된 객체를 생성해야 하는 경우 또는 알림 대화상자 등 UI작업에 Context가 필요한 경우 Activity Context를 사용할 수 있다.

계층 구조는 다음과 같다. 

Context 계층구조

3. ContentProvider의 getContext()

이 Context는 Application Context이며 Application Context로 사용할 수 있다.

참고

https://blog.mindorks.com/understanding-context-in-android-application-330913e32514

https://developer.android.com/reference/android/content/Context

Understanding Context In Android Application