EVENTS HANDLING

Events are a useful way to collect data about a user's interaction with interactive components of Applications. Like button presses or screen touch etc.

The Android framework maintains an event queue as first-in, first-out (FIFO) basis.

Event Listeners

An event listener is an interface in the View class that contains a single callback method. These methods will be called by the Android framework when the View to which the listener has been registered is triggered by user interaction with the item in the UI.

Included in the event listener interfaces are the following callback methods:

onClick()

From View.OnClickListener. This is called when the user either touches the item (when in touch mode), or focuses upon the item with the navigation-keys or trackball and presses the suitable "enter" key or presses down on the trackball.

onLongClick()

From View.OnLongClickListener. This is called when the user either touches and holds the item (when in touch mode), or focuses upon the item with the navigation-keys or trackball and presses and holds the suitable "enter" key or presses and holds down on the trackball (for one second).

onFocusChange()

From View.OnFocusChangeListener. This is called when the user navigates onto or away from the item, using the navigation-keys or trackball.

onKey()

From View.OnKeyListener. This is called when the user is focused on the item and presses or releases a hardware key on the device.

onTouch()

From View.OnTouchListener. This is called when the user performs an action qualified as a touch event, including a press, a release, or any movement gesture on the screen (within the bounds of the item).

onCreateContextMenu()

From View.OnCreateContextMenuListener. This is called when a Context Menu is being built (as the result of a sustained "long click"). See the discussion on context menus in the Menus developer guide.

Example 1 : create new project

onClick()

activity_main.xml

<?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" >

    <Button

        android:id="@+id/button1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="open sajidtutorials" />

</LinearLayout>

OnClickActivity.java

import android.net.Uri;

import android.os.Bundle;

import android.widget.Button;

import android.view.View;

import android.view.View.OnClickListener;

public class OnClickActivity extends Activity {

         Button button;

         @Override

         public void onCreate(Bundle savedInstanceState) {

                 super.onCreate(savedInstanceState);

                 setContentView(R.layout.activity_main);

                 addListenerOnButton();

         }

         public void addListenerOnButton() {

                 button = (Button) findViewById(R.id.button1);

                 button.setOnClickListener(new OnClickListener() {

                          @Override

                          public void onClick(View arg0) {

                            Intent intent =

                            new Intent(Intent.ACTION_VIEW, Uri.parse("http://sajidtutorials.blogspot.com/"));

                              startActivity(intent);

                          }

                 });

         }

}

Screen Shots:

Example 2 onLongClick/Ontouch: create new project LongClickExample

MainActivity.java

package com. Long.click.example;

import android.app.Activity;

import android.os.Bundle;

import android.view.Gravity;

import android.view.Menu;

import android.view.MotionEvent;

import android.view.View;

import android.view.View.OnLongClickListener;

import android.widget.Button;

import android.widget.EditText;

import android.widget.ImageView;

import android.widget.TextView;

import android.widget.Toast;

public class MainActivity extends Activity {

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        final TextView myText = (TextView)findViewById(R.id.textView1);

        final EditText myInput = (EditText)findViewById(R.id.editText1);

        Button lButton = (Button) findViewById(R.id.buttonl);

        ImageView imgv= (ImageView)findViewById(R.id.image);

                 ImageView imgvv = (ImageView) findViewById(R.id.image1);

     

        // -- register click event with  button ---

        lButton.setOnClickListener(new View.OnClickListener() {

           public void onClick(View v) {

           myText.setText(myInput.getText());

           }

       

        });

        imgv.setOnLongClickListener(new OnLongClickListener() {

                 @Override

                 public boolean onLongClick(View v) {

                          // TODO Auto-generated method stub

                          Toast toast = Toast.makeText(MainActivity.this,

                                            "you clicked ", Toast.LENGTH_SHORT);

                          toast.setGravity(Gravity.TOP ,10,140);

                         

                          toast.show();

                          return true;

                 }

                 });

        imgvv.setOnTouchListener(new View.OnTouchListener() {       

            @Override

            public boolean onTouch(View v, MotionEvent event) {

                switch(event.getAction()) {

                    case MotionEvent.ACTION_DOWN:

                        // PRESSED

                          Toast toast1 = Toast.makeText(MainActivity.this,

                                                    "you pressed ", Toast.LENGTH_SHORT);

                                   toast1.setGravity(Gravity.TOP ,10, 260);

                                   toast1.show();

                        return true; // if you want to handle the touch event

                    case MotionEvent.ACTION_UP:

                        // RELEASED

                          Toast toast2 = Toast.makeText(MainActivity.this,

                                                    "you released ", Toast.LENGTH_SHORT);

                                   toast2.setGravity(Gravity.TOP ,10, 260);

                                   toast2.show();

                        return true; // if you want to handle the touch event

                }

                return false;

            }

        });

    }

    @Override

    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.

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

        return true;

    }

  

   

}

activity_main.Xml

<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:orientation="vertical"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context="com.example.assignmentno6.MainActivity">

 <TableRow

            android:id="@+id/tableRow"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

           >       

         <EditText

              android:hint="@string/reminder"

              android:layout_height="wrap_content"

              android:layout_width="wrap_content"

              android:id="@+id/editText1"

              android:layout_marginLeft="20dip"

              android:layout_marginRight="20dip"

               >                

                               

     </EditText>

       <Button

    android:id="@+id/buttonl"

    android:layout_height="wrap_content"

    android:layout_width="wrap_content"

    android:text="@string/Submit"

    android:layout_marginLeft="10dp">

 </Button>

 </TableRow>

         <TableRow

            android:id="@+id/tableRow1"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

           >

           

     <TextView

         android:id="@+id/textView1"

              android:layout_width="wrap_content"

              android:layout_height="wrap_content"

              android:text="Display Name Here :"

              android:textColor="#000000"

              android:layout_marginLeft="20dip">

                         </TextView>

        </TableRow>

      <TableRow

            android:id="@+id/tableRow2"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

              android:padding="50dip"

              android:layout_gravity="center_horizontal"

            >

    

 <ImageView

        android:id="@+id/image"

        android:contentDescription="@string/content"

        android:layout_width="50dp"

        android:layout_height="50dp"

        android:src="@drawable/ ic_launcher "

        

         />

</TableRow>

    <TableRow

            android:id="@+id/tableRow3"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:padding="50dip"

            android:layout_gravity="center_horizontal">

 <ImageView

        android:id="@+id/image1"

        android:contentDescription="@string/content"

        android:layout_width="50dp"

        android:layout_height="50dp"

        android:src="@drawable/ic_launcher"

         />

 </TableRow>

</TableLayout>

Screen Shots:

Example3 onKey: Create new Project

MainActivity.java

import android.os.Bundle;

import android.view.KeyEvent;

import android.view.View;

import android.view.View.OnKeyListener;

import android.widget.EditText;

import android.widget.Toast;

import android.app.Activity;

public class MainActivity extends Activity implements OnKeyListener {

 private EditText userName;

 private EditText password;

 private String mUserName;

 private String mPassword;

 @Override

 protected void onCreate(Bundle savedInstanceState) {

  super.onCreate(savedInstanceState);

  setContentView(R.layout.activity_main);

  userName = (EditText) findViewById(R.id.txt_name);

  password = (EditText) findViewById(R.id.password);

  // set onkeyListner

  userName.setOnKeyListener(this);

  password.setOnKeyListener(this);

 }

 @Override

 public boolean onKey(View v, int keyCode, KeyEvent event) {

  switch (v.getId()) {

  case R.id.txt_name:

   // keyup and "ENTER"

   if ((event.getAction() == KeyEvent.ACTION_DOWN)

     && (keyCode == KeyEvent.KEYCODE_ENTER)) {

    mUserName = userName.getText().toString();

    if (mUserName.equals("")) {

     Toast.makeText(this, "Enter user name...",

       Toast.LENGTH_SHORT).show();

    } else

     password.requestFocus();

   }

   break;

  case R.id.password:

   // keydown and "ENTER"

   if ((event.getAction() == KeyEvent.ACTION_DOWN)

     && (keyCode == KeyEvent.KEYCODE_ENTER)) {

    mPassword = password.getText().toString();

    if (mPassword.equals(""))

     Toast.makeText(this, "Enter password...",

       Toast.LENGTH_SHORT).show();

    else

     // show Toast Long time

     Toast.makeText(

       this,

       "User name : " + mUserName + "  Password : "

         + mPassword, Toast.LENGTH_LONG).show();

   }

   break;

  }

  return false;

 }

}

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".EditTextKeyListener" >

    <TextView

        android:id="@+id/textView1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="@string/hello_world"

        android:textSize="20sp" />

    <EditText

        android:id="@+id/txt_name"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_below="@+id/textView1"

        android:layout_centerHorizontal="true"

        android:layout_marginTop="48dp"

        android:ems="10"

        android:inputType="textPersonName"

        android:hint="@string/username"

       >

        <requestFocus />

    </EditText>

    <EditText

        android:id="@+id/password"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignRight="@+id/txt_name"

        android:layout_below="@+id/txt_name"

        android:layout_marginTop="24dp"

        android:ems="10"

        android:inputType="textPassword"

        android:hint="@string/psass" />

</RelativeLayout>

ScreenShots:

Example 4 contextmenu: create new project

MainActivity.java

import android.app.Activity;

import android.content.Intent;

import android.net.Uri;

import android.os.Bundle;

import android.view.ContextMenu;

import android.view.ContextMenu.ContextMenuInfo;

import android.view.MenuItem;

import android.view.View;

import android.widget.AdapterView;

import android.widget.AdapterView.OnItemClickListener;

import android.widget.LinearLayout;

import android.widget.ListView;

public class MainActivity extends Activity

{

  

      

            ListView listViewSmartContacts;

            ContactListAdapter  contactListAdapter;

            //ArrayList<String> numberList;

           

            String number;

           

            public ShowSmartContactsActivity()

            {

                /// numberList=new ArrayList<String>();

           

            }

            @Override

            public void onCreate(Bundle savedInstanceState)

            {

                    super.onCreate(savedInstanceState);

                    setContentView(R.layout.show_contacts);

       

                   

                    LinearLayout layoutContacts=(LinearLayout)findViewById(R.id.layoutSmartContacts);

                    int APILevel=android.os.Build.VERSION.SDK_INT ;

                    if(APILevel>=14)

                    {

                        layoutContacts.setBackgroundResource(R.color.Default);

                    }

                   

                    listViewSmartContacts=(ListView)findViewById(R.id.listSmartContacts);

                    //getList();

                    contactListAdapter=new ContactListAdapter(this);

                    listViewSmartContacts.setAdapter(contactListAdapter);

      

                    registerForContextMenu(listViewSmartContacts);

                   

              

            }

           

           

           

           

           

   

           

      

      

           

               

   

            @Override

            public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo)

            {

                    super.onCreateContextMenu(menu, v, menuInfo);

                    menu.setHeaderTitle("Select The Action"); 

                    menu.add(0, v.getId(), 0, "Call"); 

                    menu.add(0, v.getId(), 0, "Send SMS");

    

            }

            @Override 

            public boolean onContextItemSelected(MenuItem item)

            { 

                        AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo)item.getMenuInfo();

                        String number;

              

                        try

                        {

                                number=new ContactListAdapter(this).numberList.get(info.position);

                

               

                

                                if(item.getTitle()=="Call")

                                {

                

                

                                        Intent callIntent = new Intent(Intent.ACTION_CALL);

                                        callIntent.setData(Uri.parse("tel:"+number));

                                        startActivity(callIntent);

                 

                

                

        

                                } 

                                else if(item.getTitle()=="Send SMS")

                                {

                                        Intent smsIntent = new Intent(Intent.ACTION_VIEW);

                                        smsIntent.setType("vnd.android-dir/mms-sms");

                                        smsIntent.putExtra("address", number);

                                        startActivity(smsIntent);

                    

                                } 

                                else

                                {return false;} 

                                return true; 

                        }

                        catch(Exception e)

                        {

                                return true;

                        }

            } 

           

           

    

}

Screen Shots