Android - UI Controls

2021-12-07 14:05 Android开发

<blockquote > Input controls are the interactive components in your app's user interface. Android provides a wide variety of controls you can use in your UI, such as buttons, text fields, seek bars, check box, zoom buttons, toggle buttons, and many more. </blockquote> <img alt="UI Control" src="http://www.tutorialspoint.com/android/images/ui_control.jpg" /> <h4 align="center" >UI ELEMENTS</h4> AViewis an object that draws something on the screen that the user can interact with and aViewGroupis an object that holds other View (and ViewGroup) objects in order to define the layout of the user interface. You define your layout in an XML file which offers a human-readable structure for the layout, similar to HTML. For example, a simple vertical layout with a text view and a button looks like this − <pre class="prettyprint notranslate prettyprinted" > <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <TextView android:id="@+id/text" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="I am a TextView" /> <Button android:id="@+id/button" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="I am a Button" /> </LinearLayout></pre> <h2 >Android UI Controls</h2> There are number of UI controls provided by Android that allow you to build the graphical user interface for your app. <table class="table table-bordered" > <tbody > <tr > <th >S.N.</th> <th >UI Control & Description</th> </tr> <tr > <td >1</td> <td ><a alt="Android TextView Control" href="http://www.tutorialspoint.com/android/android_textview_control.htm" >TextView</a> This control is used to display text to the user. </td> </tr> <tr > <td >2</td> <td ><a alt="Android EditText Control" href="http://www.tutorialspoint.com/android/android_edittext_control.htm" >EditText</a> EditText is a predefined subclass of TextView that includes rich editing capabilities. </td> </tr> <tr > <td >3</td> <td ><a alt="Android AutoCompleteTextView Control" href="http://www.tutorialspoint.com/android/android_autocompletetextview_control.htm" >AutoCompleteTextView</a> The AutoCompleteTextView is a view that is similar to EditText, except that it shows a list of completion suggestions automatically while the user is typing. </td> </tr> <tr > <td >4</td> <td ><a alt="Android Button Control" href="http://www.tutorialspoint.com/android/android_button_control.htm" >Button</a> A push-button that can be pressed, or clicked, by the user to perform an action. </td> </tr> <tr > <td >5</td> <td ><a alt="Android ImageButton Control" href="http://www.tutorialspoint.com/android/android_imagebutton_control.htm" >ImageButton</a> AbsoluteLayout enables you to specify the exact location of its children. </td> </tr> <tr > <td >6</td> <td ><a alt="Android CheckBox Control" href="http://www.tutorialspoint.com/android/android_checkbox_control.htm" >CheckBox</a> An on/off switch that can be toggled by the user. You should use check box when presenting users with a group of selectable options that are not mutually exclusive. </td> </tr> <tr > <td >7</td> <td ><a alt="Android ToggleButton Control" href="http://www.tutorialspoint.com/android/android_togglebutton_control.htm" >ToggleButton</a> An on/off button with a light indicator. </td> </tr> <tr > <td >8</td> <td ><a alt="Android RadioButton Control" href="http://www.tutorialspoint.com/android/android_radiobutton_control.htm" >RadioButton</a> The RadioButton has two states: either checked or unchecked. </td> </tr> <tr > <td >9</td> <td ><a alt="Android RadioGroup Control" href="http://www.tutorialspoint.com/android/android_radiogroup_control.htm" >RadioGroup</a> A RadioGroup is used to group together one or more RadioButtons. </td> </tr> <tr > <td >10</td> <td ><a alt="Android ProgressBar Control" href="http://www.tutorialspoint.com/android/android_progressbar.htm" >ProgressBar</a> The ProgressBar view provides visual feedback about some ongoing tasks, such as when you are performing a task in the background. </td> </tr> <tr > <td >11</td> <td ><a alt="Android Spinner Control" href="http://www.tutorialspoint.com/android/android_spinner_control.htm" >Spinner</a> A drop-down list that allows users to select one value from a set. </td> </tr> <tr > <td >12</td> <td ><a alt="Android TimePicker Control" href="http://www.tutorialspoint.com/android/android_timepicker_control.htm" >TimePicker</a> The TimePicker view enables users to select a time of the day, in either 24-hour mode or AM/PM mode. </td> </tr> <tr > <td >13</td> <td ><a alt="Android DatePicker Control" href="http://www.tutorialspoint.com/android/android_datepicker_control.htm" >DatePicker</a> The DatePicker view enables users to select a date of the day. </td> </tr> </tbody> </table> <h2 >Create UI Controls</h2> Input controls are the interactive components in your app's user interface. Android provides a wide variety of controls you can use in your UI, such as buttons, text fields, seek bars, check box, zoom buttons, toggle buttons, and many more. As explained in previous chapter, a view object may have a unique ID assigned to it which will identify the View uniquely within the tree. The syntax for an ID, inside an XML tag is − <pre class="prettyprint notranslate prettyprinted" > android:id="@+id/text_id"</pre> To create a UI Control/View/Widget you will have to define a view/widget in the layout file and assign it a unique ID as follows − <pre class="prettyprint notranslate prettyprinted" > <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <TextView android:id="@+id/text_id" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="I am a TextView" /> </LinearLayout></pre> Then finally create an instance of the Control object and capture it from the layout, use the following − <pre class="prettyprint notranslate prettyprinted" > TextView myText = (TextView) findViewById(R.id.text_id);</pre>