Since the goal here is to demonstrate the problem of performing lengthy tasks on the main thread, the code will simply pause for 20 seconds before displaying different text on the TextView object: package Next, load the ThreadExampleActivity.java file into an editing panel and add code to implement the buttonClick() method which will be called when the Button view is touched by the user. Once completed, the XML file content should be similar to the following listing: With the button view still selected in the layout, locate the onClick property in the Properties panel and enter buttonClick as the method name. Extract the string to a resource named button_text. Double click on the TextView component and change the ID for the view to Next, click and drag the TextView so that it is positioned in the center of the display canvas.Īdd a Button view to the user interface, positioned directly beneath the existing TextView object as illustrated in Figure 35-1:ĭouble click on the button view and change the text to “Press Me”. Load the activity_thread_example.xml file for the project into the Designer tool. Continue to proceed through the screens, requesting the creation of a blank activity named ThreadExampleActivity, using the defaults for the layout and menu resource files. On the form factors screen, enable the Phone and Tablet option and set the minimum SDK setting to API 8: Android 2.2 (Froyo). Begin, therefore, by creating a new project in Android Studio, entering ThreadExample into the Application name field and as the Company Domain setting before clicking on the Next button. The first step will be to highlight the importance of performing time-consuming tasks in a separate thread from the main thread. The remainder of this chapter will work through some simple examples intended provide a basic introduction to threads.
In such a situation, this can be avoided simply by launching the task to be performed in a separate thread, allowing the main thread to continue unhindered with other tasks. Clearly, this is far from the desired behavior for any application. This will typically result in the operating system displaying an “Application is not responding” warning to the user.
Any additional components that are started within the application will, by default, also run on the main thread.Īny component within an application that performs a time consuming task using the main thread will cause the entire application to appear to lock up until the task is completed. The primary role of the main thread is to handle the user interface in terms of event handling and interaction with views in the user interface. This thread is generally referred to as the main thread. When an Android application is first started, the runtime system creates a single thread in which all application components will run by default. Report this ad The Application Main Thread
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