Java Source Code

---

The Java code is what drives everything. It is converted to Dalvik executable and runs your application. This application includes two screens/activities/classes: MainActivity.java and NextActivity.java. Notice that the class is based on the Activity class. An Activity is a single application entity that is used to perform actions. The onCreate method is called by the Android system when your Activity starts—it is where you should perform all initialization and UI setup. An activity is not required to have a user interface, but usually does.

Next Page ⇓     ⇑ Home Page

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 }