When an application starts up for the first time, the ActivityManagerService creates a special kind of window token called an application window token, which uniquely identifies the application’s top-level container window.

Without window tokens, this necessary identification step wouldn’t be possible and the window manager wouldn’t be able to protect itself from malicious applications. If the tokens don’t match, the window manager rejects the request and throws a BadTokenException.

The window manager protects against this by requiring applications to pass their application’s window token as part of each request to add or remove a window. Window tokens are important for security reasons because they make it impossible for malicious applications to draw on top of the windows of other applications. WindowManagerService (WMS) is a system service that manages the windows on Android.Īs the name suggest, a window token is a special type of Binder token used by window manager to uniquely identify a window in the system.

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