Android - Alert Dialog

A Dialog is small window that prompts the user to a decision or enter additional information.
Some times in your application, if you wanted to ask the user about taking a decision between yes or no in response of any particular action taken by the user, by remaining in the same activity and without changing the screen, you can use Alert Dialog.
In order to make an alert dialog, you need to make an object of AlertDialogBuilder which an inner class of AlertDialog. Its syntax is given below
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(this);
Now you have to set the positive (yes) or negative (no) button using the object of the AlertDialogBuilder class. Its syntax is
alertDialogBuilder.setPositiveButton(CharSequence text, 
   DialogInterface.OnClickListener listener)
alertDialogBuilder.setNegativeButton(CharSequence text, 
   DialogInterface.OnClickListener listener)
Apart from this , you can use other functions provided by the builder class to customize the alert dialog. These are listed below
setIcon(Drawable icon)
This method set the icon of the alert dialog box.
setCancelable(boolean cancel able)
This method sets the property that the dialog can be cancelled or not
setMessage(CharSequence message)
This method sets the message to be displayed in the alert dialog
setMultiChoiceItems(CharSequence[] items, boolean[] checkedItems, DialogInterface.OnMultiChoiceClickListener listener)
This method sets list of items to be displayed in the dialog as the content. The selected option will be notified by the listener
setOnCancelListener(DialogInterface.OnCancelListener onCancelListener)
This method Sets the callback that will be called if the dialog is cancelled.
setTitle(CharSequence title)
This method set the title to be appear in the dialog
After creating and setting the dialog builder , you will create an alert dialog by calling the create() method of the builder class. Its syntax is
AlertDialog alertDialog = alertDialogBuilder.create();
alertDialog.show();
This will create the alert dialog and will show it on the screen.
Before enter into an example we should need to know dialog fragment.Dialog fragment is a fragment which can show fragment in dialog box
public class DialogFragment extends DialogFragment {
   @Override
   public Dialog onCreateDialog(Bundle savedInstanceState) {
      // Use the Builder class for convenient dialog construction
      AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
      builder.setPositiveButton(R.string.fire, new DialogInterface.OnClickListener() {
         public void onClick(DialogInterface dialog, int id) {
            toast.makeText(this,"enter a text here",Toast.LENTH_SHORT).show();
         }
      })
      .setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
         public void onClick(DialogInterface dialog, int id) {
            finish();
         });
         // Create the AlertDialog object and return it
         return builder.create();
      }
   }
}
It has used to show list of items in a dialog box.For suppose, user need to select a list of items or else need to click a item from multiple list of items.At this situation  we can use list dialog.
public Dialog onCreateDialog(Bundle savedInstanceState) {
   AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
   builder.setTitle(Pick a Color)
   
   .setItems(R.array.colors_array, new DialogInterface.OnClickListener() {
      public void onClick(DialogInterface dialog, int which) {
         // The 'which' argument contains the index position
         // of the selected item
      }
   });
   return builder.create();
}
It has used to add single choice list to Dialog box.We can check or uncheck as per user choice.
public Dialog onCreateDialog(Bundle savedInstanceState) {
   mSelectedItems = new ArrayList();
   AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
   
   builder.setTitle("This is list choice dialog box");
   .setMultiChoiceItems(R.array.toppings, null,
      new DialogInterface.OnMultiChoiceClickListener() {
      @Override
      public void onClick(DialogInterface dialog, int which, boolean isChecked) {
         
         if (isChecked) {
            // If the user checked the item, add it to the selected items
            mSelectedItems.add(which);
         }
         
         else if (mSelectedItems.contains(which)) {
            // Else, if the item is already in the array, remove it 
            mSelectedItems.remove(Integer.valueOf(which));
         }
      }
   })
   
   // Set the action buttons
   .setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
      @Override
      public void onClick(DialogInterface dialog, int id) {
         // User clicked OK, so save the mSelectedItems results somewhere
         // or return them to the component that opened the dialog
         ...
      }
   })
   
   .setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
      @Override
      public void onClick(DialogInterface dialog, int id) {
         ...
      }
   });
   return builder.create();
}
The following example demonstrates the use of AlertDialog in android.
To experiment with this example , you need to run this on an emulator or an actual device.
Here is the modified code of src/MainActivity.java
package com.example.sairamkrishna.myapplication;

import android.app.AlertDialog;
import android.content.DialogInterface;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

public class MainActivity extends ActionBarActivity {
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
   }

   public void open(View view){
      AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(this);
      alertDialogBuilder.setMessage("Are you sure,
         You wanted to make decision");
      alertDialogBuilder.setPositiveButton("yes", 
         new DialogInterface.OnClickListener() {
         @Override
         public void onClick(DialogInterface arg0, int arg1) {
            Toast.makeText(MainActivity.this,"You clicked yes 
               button",Toast.LENGTH_LONG).show();
         }
      });

      alertDialogBuilder.setNegativeButton("No",new DialogInterface.OnClickListener() {
         Override
         public void onClick(DialogInterface dialog, int which) {
            finish();
         }
      });

      AlertDialog alertDialog = alertDialogBuilder.create();
      alertDialog.show();
   }
}
Here is the modified code of res/layout/activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<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" 
   android:paddingLeft="@dimen/activity_horizontal_margin"
   android:paddingRight="@dimen/activity_horizontal_margin"
   android:paddingTop="@dimen/activity_vertical_margin"
   android:paddingBottom="@dimen/activity_vertical_margin" 
   tools:context=".MainActivity">
   
   <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Alert Dialog"
      android:id="@+id/textView"
      android:textSize="35dp"
      android:layout_alignParentTop="true"
      android:layout_centerHorizontal="true" />
      
   <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Tutorialspoint"
      android:id="@+id/textView2"
      android:textColor="#ff3eff0f"
      android:textSize="35dp"
      android:layout_below="@+id/textView"
      android:layout_centerHorizontal="true" />
      
   <ImageView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/imageView"
      android:src="@drawable/abc"
      android:layout_below="@+id/textView2"
      android:layout_alignRight="@+id/textView2"
      android:layout_alignEnd="@+id/textView2"
      android:layout_alignLeft="@+id/textView"
      android:layout_alignStart="@+id/textView" />
   <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="Alert dialog"
      android:id="@+id/button"
      android:layout_below="@+id/imageView"
      android:layout_alignRight="@+id/textView2"
      android:layout_alignEnd="@+id/textView2"
      android:layout_marginTop="42dp"
      android:onClick="open"
      android:layout_alignLeft="@+id/imageView"
      android:layout_alignStart="@+id/imageView" />
      
</RelativeLayout>
Here is  ofStrings.xml
<resources>
    <string name="app_name">My Application</string>
</resources>
Here is the default code of AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.example.sairamkrishna.myapplication" >

   <application
      android:allowBackup="true"
      android:icon="@drawable/ic_launcher"
      android:label="@string/app_name"
      android:theme="@style/AppTheme" >
      
      <activity
         android:name="com.example.sairamkrishna.myapplication.MainActivity"
         android:label="@string/app_name" >
         
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
         
      </activity>
      
   </application>
</manifest>
Let's try to run your  application. I assume you have connected your actual Android Mobile device with your computer. To run the app from Android studio, open one of your project's activity files and click Run  icon from the toolbar. Before starting your application, ]Android studio will display following window to select an option where you want to run your Android application.
Select your  an option and then click on it. For suppose, if you have clicked on yes button, then result would as follows
if you click on no button it will call finish() and it will close your application.

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