Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels) Summary: [Fields](https://developer.android.com/reference/android/database/Observable#lfields) \| [Ctors](https://developer.android.com/reference/android/database/Observable#pubctors) \| [Methods](https://developer.android.com/reference/android/database/Observable#pubmethods) \| [Inherited Methods](https://developer.android.com/reference/android/database/Observable#inhmethods)

# Observable

*** ** * ** ***


`
public


abstract
class
Observable
`


`

extends https://developer.android.com/reference/java/lang/Object


`

`


`

|---|---|
| [java.lang.Object](https://developer.android.com/reference/java/lang/Object) ||
| ↳ | android.database.Observable\<T\> |

|---|
| Known direct subclasses [ContentObservable](https://developer.android.com/reference/android/database/ContentObservable), [DataSetObservable](https://developer.android.com/reference/android/database/DataSetObservable) |---|---| | [ContentObservable](https://developer.android.com/reference/android/database/ContentObservable) | A specialization of `https://developer.android.com/reference/android/database/Observable` for `https://developer.android.com/reference/android/database/ContentObserver` that provides methods for sending notifications to a list of `https://developer.android.com/reference/android/database/ContentObserver` objects. | | [DataSetObservable](https://developer.android.com/reference/android/database/DataSetObservable) | A specialization of `https://developer.android.com/reference/android/database/Observable` for `https://developer.android.com/reference/android/database/DataSetObserver` that provides methods for sending notifications to a list of `https://developer.android.com/reference/android/database/DataSetObserver` objects. | |

<br />

*** ** * ** ***

Provides methods for registering or unregistering arbitrary observers in an `https://developer.android.com/reference/java/util/ArrayList`.

This abstract class is intended to be subclassed and specialized to maintain
a registry of observers of specific types and dispatch notifications to them.

## Summary

| ### Fields ||
|---|---|
| ` protected final https://developer.android.com/reference/java/util/ArrayList<T>` | `https://developer.android.com/reference/android/database/Observable#mObservers` The list of observers. |

| ### Public constructors ||
|---|---|
| ` https://developer.android.com/reference/android/database/Observable#Observable()() ` |

| ### Public methods ||
|---|---|
| ` void` | ` https://developer.android.com/reference/android/database/Observable#registerObserver(T)(T observer) ` Adds an observer to the list. |
| ` void` | ` https://developer.android.com/reference/android/database/Observable#unregisterAll()() ` Remove all registered observers. |
| ` void` | ` https://developer.android.com/reference/android/database/Observable#unregisterObserver(T)(T observer) ` Removes a previously registered observer. |

| ### Inherited methods |
|---|---|
| From class ` https://developer.android.com/reference/java/lang/Object ` |---|---| | ` https://developer.android.com/reference/java/lang/Object` | ` https://developer.android.com/reference/java/lang/Object#clone()() ` Creates and returns a copy of this object. | | ` boolean` | ` https://developer.android.com/reference/java/lang/Object#equals(java.lang.Object)(https://developer.android.com/reference/java/lang/Object obj) ` Indicates whether some other object is "equal to" this one. | | ` void` | ` https://developer.android.com/reference/java/lang/Object#finalize()() ` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. | | ` final https://developer.android.com/reference/java/lang/Class<?>` | ` https://developer.android.com/reference/java/lang/Object#getClass()() ` Returns the runtime class of this `Object`. | | ` int` | ` https://developer.android.com/reference/java/lang/Object#hashCode()() ` Returns a hash code value for the object. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#notify()() ` Wakes up a single thread that is waiting on this object's monitor. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#notifyAll()() ` Wakes up all threads that are waiting on this object's monitor. | | ` https://developer.android.com/reference/java/lang/String` | ` https://developer.android.com/reference/java/lang/Object#toString()() ` Returns a string representation of the object. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait(long,%20int)(long timeoutMillis, int nanos) ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*, or until a certain amount of real time has elapsed. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait(long)(long timeoutMillis) ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*, or until a certain amount of real time has elapsed. | | ` final void` | ` https://developer.android.com/reference/java/lang/Object#wait()() ` Causes the current thread to wait until it is awakened, typically by being *notified* or *interrupted*. | ||

## Fields

### mObservers

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
protected final ArrayList<T> mObservers
```

The list of observers. An observer can be in the list at most
once and will never be null.

<br />

## Public constructors

### Observable

```
public Observable ()
```

<br />

<br />

## Public methods

### registerObserver

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public void registerObserver (T observer)
```

Adds an observer to the list. The observer cannot be null and it must not already
be registered.

<br />

| Parameters ||
|---|---|
| `observer` | `T`: the observer to register <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | the observer is null |
| `https://developer.android.com/reference/java/lang/IllegalStateException` | the observer is already registered |

### unregisterAll

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public void unregisterAll ()
```

Remove all registered observers.

<br />

### unregisterObserver

Added in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public void unregisterObserver (T observer)
```

Removes a previously registered observer. The observer must not be null and it
must already have been registered.

<br />

| Parameters ||
|---|---|
| `observer` | `T`: the observer to unregister <br /> |

| Throws ||
|---|---|
| `https://developer.android.com/reference/java/lang/IllegalArgumentException` | the observer is null |
| `https://developer.android.com/reference/java/lang/IllegalStateException` | the observer is not yet registered |