Added in [API level 18](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

# ViewTreeObserver.OnWindowFocusChangeListener

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` public static interface ViewTreeObserver.OnWindowFocusChangeListener `   
` `

|---|
| android.view.ViewTreeObserver.OnWindowFocusChangeListener |

<br />

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Interface definition for a callback to be invoked when the view hierarchy's window focus state changes.

## Summary

| ### Public methods ||
|---|---|
| ` abstract void` | ` https://developer.android.com/reference/android/view/ViewTreeObserver.OnWindowFocusChangeListener#onWindowFocusChanged(boolean)(boolean hasFocus) ` Callback method to be invoked when the window focus changes in the view tree. |

## Public methods

### onWindowFocusChanged

Added in [API level 18](https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels)

```
public abstract void onWindowFocusChanged (boolean hasFocus)
```

Callback method to be invoked when the window focus changes in the view tree.

<br />

| Parameters ||
|---|---|
| `hasFocus` | `boolean`: Set to true if the window is gaining focus, false if it is losing focus. <br /> |