Alert And Toast

Alert: It is a type of dialog box.

Toast: It is a message that holds on screen for a while<milliseconds>.

Code for Alert and Toast
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class AlertandtoastActivity extends Activity {
    Button b;
// it is used for create for create an alert  that is by clicking on it. a dialog box i.e an alert will display on screen
   
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        b =(Button)findViewById(R.id.button1);
       
    }
    public void show(View V)
// just right click on button in layout and on properties just select onclick and set show or any name on it.
    {
        AlertDialog.Builder ob = new AlertDialog.Builder(this);
//Alerdialog.builder is used to create an alert.
        ob.setMessage("is ur entry is correct");
//setmessage just set your message
        ob.setNeutralButton("yes", new DialogInterface.OnClickListener() {
       
            @Override
            public void onClick(DialogInterface dialog, int which) {
                // TODO Auto-generated method stub
                Toast.makeText(AlertandtoastActivity.this, "ur correct", 5000).show();
//5000 means 5k milliseconds is used to hold a message on screen
            }
        });ob.setPositiveButton("no", new DialogInterface.OnClickListener() {
           
            @Override
            public void onClick(DialogInterface dialog, int which) {
                // TODO Auto-generated method stub
                Toast.makeText(getBaseContext(), "plz re eneter", 7000).show();
//instead of getbasecontext we can use alerttoastactivity.this
            }
        });
        ob.show();
    }
} 

xml file

<?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:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/hello" />

    <LinearLayout
        android:id="@+id/linearLayout1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <TextView
            android:id="@+id/textView1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="0.11"
            android:text="username" />



        <EditText
            android:id="@+id/editText1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="0.38"
            android:inputType="textEmailAddress" >

            <requestFocus />
        </EditText>

    </LinearLayout>



    <LinearLayout
        android:id="@+id/linearLayout2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <TextView
            android:id="@+id/textView2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="0.08"
            android:text="PAssword" />









        <EditText
            android:id="@+id/editText2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="0.26"
            android:inputType="textPassword" />

    </LinearLayout>



    <LinearLayout
        android:id="@+id/linearLayout3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" >

    </LinearLayout>





    <Button
        android:id="@+id/button1"
        android:layout_width="166dp"
        android:layout_height="34dp"
        android:onClick="show"
        android:text="LOGIN" />

</LinearLayout>