Java Source Code (Cont.)

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intent( Context packageContext, Class<?> cls )

It is a constructor of the class Intent, an abstract description of an operation to be performed, and creates an intent:

• “Context packageContext,” which is a Context of the application package implementing this class. Context is an interface to information about an application environment.


• “Class<?> cls,” which is the component class that is to be used for the intent

i.putExtra( String name, String[ ] value ) method

Add extended data to the intent, where

• name, which is the name of the extra data, such as "name", and
• value, which is the String array data value, such as name.getText( ).toString( ).

startActivity( Intent )

It is a method of Context and launches a new activity. In this case, it will launch the NextPageActivity activity.

onCreateOptionsMenu( Menu menu )

Initialize the contents of the Activity’s standard options menu. This is only called once, the first time the options menu is displayed.

getMenuInflater( ).inflate( R.menu.menu_main, menu );

Inflate a menu hierarchy from the specified XML resource.

onOptionsItemSelected( MenuItem item )

It is called whenever an item in your options menu is selected.

int id = item.getItemId( );

Return the identifier for this menu item.

HelloWorld/app/src/main/java/com/example/wenchen/helloworld/MainActivity.java

view source print? 01 package com.example.wenchen.helloworld; 02   03 import android.app.Activity; 04 import android.content.Intent; 05 import android.os.Bundle; 06 import android.view.View; 07 import android.widget.Button; 08 import android.widget.EditText; 09 import android.support.v7.app.AppCompatActivity; 10 import android.view.Menu; 11 import android.view.MenuItem; 12   13 public class MainActivity extends AppCompatActivity { 14   @Override 15   protected void onCreate( Bundle savedInstanceState ) { 16     super.onCreate( savedInstanceState ); 17     setContentView( R.layout.activity_main ); 18     final EditText name = (EditText) findViewById( R.id.name ); 19     final Button button = (Button)   findViewById( R.id.next ); 20     button.setOnClickListener( 21       new View.OnClickListener( ) { 22         public void onClick( View v ) { 23           /** Here i calls a new screen. **/ 24           Intent i = new Intent( MainActivity.this, NextActivity.class ); 25           i.putExtra( "name", name.getText( ).toString( ) ); 26           startActivity( i ); 27         } 28       } 29     ); 30   } 31   32   @Override 33   public boolean onCreateOptionsMenu( Menu menu ) { 34     // Inflate the menu; this adds items to the action bar if it is present. 35     getMenuInflater( ).inflate( R.menu.menu_main, menu ); 36     return true; 37   } 38   39   @Override 40   public boolean onOptionsItemSelected( MenuItem item ) { 41     // Handle action bar item clicks here.  The action bar will 42     // automatically handle clicks on the Home/Up button, so long 43     // as you specify a parent activity in AndroidManifest.xml. 44     int id = item.getItemId( ); 45   46     // noinspection SimplifiableIfStatement 47     if ( id == R.id.action_settings ) { 48       return true; 49     } 50     else if ( id == R.id.next ) { 51       Intent i = new Intent( MainActivity.this, NextActivity.class ); 52       startActivity( i ); 53     } 54     return super.onOptionsItemSelected( item ); 55   } 56 }