In some android app, button will be enabled only when user input enough characters in EditText, for example user account register app. There are two methods to archive this. Use android.text.TextWatcher or listen android.view.KeyEvent event. This example will tell you how to implement this.
android.widget.ProgressBar is a sub class of android.view.View. It is the parent class of both AbsSeekBar, RatingBar, SeekBar and ContentLoadingProgressBar. This article will introduce ProgressBar properties and how to customize ProgressBar for your needs.
android.widget.ToggleButton class is used to implement toggle button in android application. This article will show you two examples about how to use it.