The user might then decide to quit your application and uninstall itĪdditionally, the Android UI toolkit is not thread-safe. (about 5 seconds currently) the user is presented with the infamous " application not Even worse, if the UI thread is blocked for more than a few seconds From the user's perspective, theĪpplication appears to hang. When the thread is blocked, no events can be dispatched, Specifically, ifĮverything is happening in the UI thread, performing long operations such as network access orĭatabase queries will block the whole UI. When your app performs intensive work in response to user interaction, this single thread modelĬan yield poor performance unless you implement your application properly. The UI thread dequeues the request and notifies the widget that it should redraw Touch event to the widget, which in turn sets its pressed state and posts an invalidate request to Or a lifecycle callback method) always run in the UI thread of the process.įor instance, when the user touches a button on the screen, your app's UI thread dispatches the Consequently, methods that respond to systemĬallbacks (such as onKeyDown() to report user actions AllĬomponents that run in the same process are instantiated in the UI thread, and system calls toĮach component are dispatched from that thread. The system does not create a separate thread for each instance of a component. Thread might not be its UI thread for more information, see Thread However, under special circumstances, an app's main As such, the main thread is also sometimesĬalled the UI thread. It is alsoĪlmost always the thread in which your application interacts with componentsįrom the Android UI toolkit (components from the android.widget andĪndroid.view packages). The appropriate user interface widgets, including drawing events. When an application is launched, the system creates a thread of execution for the application,Ĭalled "main." This thread is very important because it is in charge of dispatching events to The details of the process lifecycle and its relationship to application states are discussed in Terminate a process, therefore, depends on the state of the components running in that process.
Visible on screen, compared to a process hosting visible activities. For example, it more readily shuts down a process hosting activities that are no longer When deciding which processes to kill, the Android system weighs their relative importance to A process is startedĪgain for those components when there's again work for them to do. ApplicationĬomponents running in the process that's killed are consequently destroyed. Required by other processes that are more immediately serving the user. The element also supports an android:process attribute, to set aĭefault value that applies to all components.Īndroid might decide to shut down a process at some point, when resources are Process-provided that the applications share the same Linux user ID and are signed with the You can also setĪndroid:process so that components of different applications run in the same In its own process or so that some components share a process while others do not. You can set this attribute so that each component runs Process in which that component should run. The manifest entry for each type of component element-, ,, and -supports an android:process attribute that can specify a
However, if you find that you need to control which process a certainĬomponent belongs to, you can do so in the manifest file. Processesīy default, all components of the same application run in the same process and most applications This document discusses how processes and threads work in an Android application. However, you can arrange forĭifferent components in your application to run in separate processes, and you can create additional Started within that process and uses the same thread of execution. If an application component starts and there already exists a processįor that application (because another component from the application exists), then the component is By default, all components of the same application run in the same process and thread Running, the Android system starts a new Linux process for the application with a single thread ofĮxecution. When an application component starts and the application does not have any other components
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