Android Application Development Programming
- 1. 1 Android Programming T.ABIRAMI/KEC Dr.T.Abirami Associate Professor Department of IT Kongu Engineering College [email protected]
- 2. XML in Android XML stands for Extensible Markup Language. XML is a markup language much like HTML used to describe data XML tags are not predefined T.ABIRAMI/KEC 2
- 3. XML Syntax //This line is called the XML prolog: <?xml version="1.0" encoding="UTF-8"?> <root> <child> <subchild>.....</subchild> </child> </root> T.ABIRAMI/KEC 3
- 4. XML Elements An XML element is everything from (including) the element's start tag to (including) the element's end tag. An element can contain: text attributes other elements or a mix of the above T.ABIRAMI/KEC 4
- 5. XML Naming Rules XML elements must follow these naming rules: Element names are case-sensitive Element names must start with a letter or underscore Element names cannot start with the letters xml (or XML, or Xml, etc) Element names can contain letters, digits, hyphens, underscores, and periods Element names cannot contain spaces Any name can be used, no words are reserved T.ABIRAMI/KEC 5
- 6. xmlns:android Defines the Android namespace. Namespaces are how you access all the Android attributes and tags that are defined by Google This attribute should always be set to "http://schemas.android.com/apk/res/android". In your example, the Namespace Prefix is "android" and the Namespace URI is "http://schemas.android.com/apk/res/android" T.ABIRAMI/KEC 6 xmlns:android
- 7. xmlns:android The xmlns attribute declares an XML Namespace. Namespaces are used to avoid conflicts between element names when mixing XML languages. Name Space in order to specify that the attributes listed below, belongs to Android. Thus they starts with "android:" T.ABIRAMI/KEC 7
- 11. Understanding the default activity Code MainActivity: It is the name of the class we are having. It is also named as your activity name. If you remember the project creation we have given this name. ActionBarActivity : Our class MainActivity is extending this class. onCreate(Bundle savedInstanceState): This is an overridden method. It is inside the ActionBarActivity class. This method will be executed when the app is opened (the activity is created). So basically you can think that it is the main method. Bundle: It is another predefined class. It is basically used for passing data between android activities. setContentView(R.layout.activity_main): This method takes a layout and it set the view as the layout to the activity. We created a layout named activity_main.xml. As I told you before that all the ids for all the components are generated automatically and stored inside R.java file. We are selecting the id of our layout from R.java file (R.layout.activity_main). T.ABIRAMI/KEC 11
- 12. View class It is a superclass for all GUI components in Android. Commonly used Views are : EditText ImageView TextView Button ImageButton CheckBox etc… T.ABIRAMI/KEC 12
- 13. Initializing a View predefined class named View in android. For initializing a View from XML layout file, we have a method findViewById(). T.ABIRAMI/KEC 13
- 14. findViewById(int id) R is a Class in android that are having the id’s of all the view’s. findViewById() is a call to a function by a reference of View class findViewById is a method that finds the view from the layout resource file that are attached with current Activity. to find xml id T.ABIRAMI/KEC 14
- 15. Syntax Declaration of UI UIclassname objectname=(Uiclassname) findViewById(R.id.UniqueUI _ID); Button button = (Button) findViewById(R.id.button_send);
- 16. Button It represents a push button. A Push buttons can be clicked, or pressed by the user to perform an action. There are different types of buttons used in android such as CompoundButton, ToggleButton, RadioButton , ImageButton etc.. Android buttons are GUI components which are sensible to taps (clicks) by the user. It perform different actions or events like click event, pressed event, touch event etc. T.ABIRAMI/KEC 16
- 17. Button View is the superclass for all widgets and the OnClickListener interface belongs to this class Button Create the button object Use OnClickListner to make it listen to the user's click Use onClick to execute actions after the user clicks the button T.ABIRAMI/KEC 17
- 18. Handling Click events in Button | Android There are 2 ways to handle the click event in button 1. Onclick in xml layout 2. Using an OnClickListener interface T.ABIRAMI/KEC 18
- 19. Onclick in XML layout When the user clicks a button, the Button object receives an on-click event. To make click event work add android:onClick attribute to the Button element in your XML layout. The value for this attribute must be the name of the method you want to call in response to a click event. T.ABIRAMI/KEC 19
- 20. Onclick in xml layout <Button android:id="@+id/button_send" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/button_send" android:onClick="sendMessage" /> T.ABIRAMI/KEC 20
- 21. In MainActivity class : Onclick in xml layout /** Called when the user touches the button */ public void sendMessage(View view) { // Do something in response to button click } T.ABIRAMI/KEC 21 Make sure that your sendMessage method should have the following : •Be public •Return void •Define a View as its only parameter (this will be the View that was clicked)
- 22. Using an OnClickListener : Operation on button button.setOnClickListener ( new View.OnClickListener() { public void onClick(View v) { // Do something in response to button click } } ); T.ABIRAMI/KEC 22
- 23. public class MainActivity extends ActionBarActivity {Button b; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); b=(Button)findViewById(R.id.button1); b.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View arg0) { // TODO Auto-generated method stub } }); } } T.ABIRAMI/KEC 23
- 24. Handling EditText getText(): This method returns an Editable instance. And it contains the text from the EditText. So for storing the Text into a String object, use the toString() method to convert it into String. setText(String s):This method takes a string and set the string to EditText. T.ABIRAMI/KEC 24
- 25. Input From user 1. using setText() tt.setText(Integer.toString(z)); 2.using getText() x=Integer.parseInt(amount1.getText().toString());
- 26. private void showMessage(){ String s = editText.getText().toString(); String greeting = "Hello "+s; editText.setText(greeting); } T.ABIRAMI/KEC 26
- 27. Android Toast class Toast can be used to display information for the short period of time. Toast class is used to show notification for a particular interval of time. After sometime it disappears. It doesn't block the user interaction. A toast contains message to be displayed quickly and disappears after sometime. android.widget.Toast class is the subclass of java.lang.Object class. T.ABIRAMI/KEC 27
- 28. Constants of Toast class Constant Description public static final int LENGTH_LONG displays view for the long duration of time. public static final int LENGTH_SHORT displays view for the short duration of time. T.ABIRAMI/KEC 28
- 29. Methods of Toast class Method Description public static Toast makeText(Context context, CharSequence text, int duration) makes the toast containing text and duration. public void show() displays toast. public void setMargin (float horizontalMargin, float verticalMargin) changes the horizontal and vertical margin difference. T.ABIRAMI/KEC 29
- 31. Toast toast=Toast.makeText(getApplicatio nContext(),"Hello Javatpoint",Toast.LENGT H_SHORT); toast.setMargin(50,50); toast.show(); T.ABIRAMI/KEC 31
- 32. DDMS (Dalvik Debug Monitor Server) It is integrated into Eclipse and is also shipped in the tools/ directory of the SDK. It works with both the emulator and a connected device. If both are connected and running simultaneously, DDMS defaults to the emulator. The service could include message formation, call spoofing, capturing screenshot, exploring internal threads and file systems etc.. T.ABIRAMI/KEC 32
- 33. TextView UI control / Class To display text on the screen Class Heirarchy: java.lang.Object ↳ android.view.View ↳ android.widget.TextView T.ABIRAMI/KEC 33
- 34. Xml code <TextView android:id="@+id/text_view_id" android:layout_height="wrap_content" android:layout_width="wrap_content" android:text=“Test" /> T.ABIRAMI/KEC 34
- 35. Attributes android:typeface="sans" android:textColor="@color/colorPrimary“ textView.setTextSize(TypedValue.COMPLEX_UNIT_SP,15); textView.setTextColor(Color.RED); T.ABIRAMI/KEC 35
- 36. T.ABIRAMI/KEC 36 ATTRIBUTES DESCRIPTION android:text Sets text of the Textview android:id Gives a unique ID to the Textview android:cursorVisible Use this attribute to make cursor visible or invisible. Default value is visible. android:drawableBottom Sets images or other graphic assets to below of the Textview. android:drawableEnd Sets images or other graphic assets to end of Textview. android:drawableLeft Sets images or other graphic assets to left of Textview. android:drawablePadding Sets padding to the drawable(images or other graphic assets) in the Textview. android:autoLink This attribute is used to automatically detect url or emails and show it as clickable link. android:autoText Automatically correct spelling errors in text of the Textview. android:capitalize It automatically capitalize whatever the user types in the Textview. android:drawableRight Sets drawables to right of text in the Textview. android:drawableStart Sets drawables to start of text in the Textview. android:drawableTop Sets drawables to top of text in the Textview. android:ellipsize Use this attribute when you want text to be ellipsized if it is longer than the Textview width. android:ems Sets width of the Textview in ems. android:gravity We can align text of the Textview vertically or horizontally or both. android:height Use to set height of the Textview. android:hint Use to show hint when there is no text. android:inputType Use to set input type of the Textview. It can be Number, Password, Phone etc. android:lines Use to set height of the Textview by number of lines. android:maxHeight Sets maximum height of the Textview. android:minHeight Sets minimum height of the Textview. android:maxLength Sets maximum character length of the Textview. android:maxLines Sets maximum lines Textview can have. android:minLines Sets minimum lines Textview can have. android:maxWidth Sets maximum width Textview can have. android:minWidth Sets minimum lines Textview can have. android:textAllCaps Show all texts of the Textview in capital letters. android:textColor Sets color of the text. android:textSize Sets font size of the text. android:textStyle Sets style of the text. For example, bold, italic, bolditalic. android:typeface Sets typeface or font of the text. For example, normal, sans, serif etc android:width Sets width of the TextView.
- 37. Java Code TextView textView = (TextView) findViewById(R.id.textView); textView.setText("Android"); //set text for text view textView.setTextSize(20); textView.setBackgroundColor(Color.BLACK);//set background color T.ABIRAMI/KEC 37
- 38. EditText It is a user interface control It is used to allow the user to enter or modify the text. Package Stru.. java.lang.Object ↳android.view.View ↳android.widget.TextView ↳android.widget.EditText T.ABIRAMI/KEC 38
- 39. EditText :Attributes Inherited from TextView Class <EditText android:id="@+id/txtSub" android:layout_width="match_parent" android:layout_height="wrap_content" android:hint="Subject" android:inputType="text"/> T.ABIRAMI/KEC 39
- 40. EditText Attributes Attribute Description android:id It is used to uniquely identify the control android:gravity It is used to specify how to align the text like left, right, center, top, etc. android:text It is used to set the text. android:hint It is used to display the hint text when text is empty android:textColor It is used to change the color of the text. android:textColorHint It is used to change the text color of hint text. android:textSize It is used to specify the size of the text. android:textStyle It is used to change the style (bold, italic, bolditalic) of text. android:background It is used to set the background color for edit text control android:ems It is used to make the textview be exactly this many ems wide. android:width It makes the TextView be exactly this many pixels wide. android:height It makes the TextView be exactly this many pixels tall. android:maxWidth It is used to make the TextView be at most this many pixels wide. android:minWidth It is used to make the TextView be at least this many pixels wide. android:textAllCaps It is used to present the text in all CAPS android:typeface It is used to specify the Typeface (normal, sans, serif, monospace) for the text. android:textColorHighlight It is used to change the color of text selection highlight. android:inputType It is used to specify the type of text being placed in text fields. android:fontFamily It is used to specify the fontFamily for the text. android:editable If we set false, EditText won't allow us to enter or modify the text T.ABIRAMI/KEC 40
- 41. public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); EditText et = (EditText) findViewById(R.id.txtSub); String name = et.getText().toString(); } } T.ABIRAMI/KEC 41 EditText simpleEditText = (EditText) findViewById(R.id.et_simple); String strValue = simpleEditText.getText().toString();
- 42. Validating your Text if (name.getText().toString().isEmpty()|| password.getText().toString().isEmpty() || email.getText().toString().isEmpty() || dob.getText().toString().isEmpty() || phoneno.getText().toString().isEmpty()) { result.setText("Please Fill All the Details") } else { result.setText(name.getText().toString() + password.getText().toString() + email.getText().toString() + dob.getText().toString() + phoneno.getText().toString()) } T.ABIRAMI/KEC 42