How to create a custom alert dialogs in an android app?

This example demonstrates how do I make a specific text on TextView bold in android.

Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="https://schemas.android.com/apk/res/android"
   xmlns:tools="https://schemas.android.com/tools"
   android:id="@+id/activity_main"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   tools:context="MainActivity">
   <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/buttonShowCustomDialog"
      android:onClick="exit"
      android:textStyle="normal|bold"
      style="@android:style/Widget.DeviceDefault.Button.Inset"
      android:layout_alignParentBottom="true"
      android:layout_centerHorizontal="true"
      android:layout_marginBottom="131dp"
      android:text="Click"/>
   <TextView
      android:text="CLICK TO VIEW CUSTOM ALERT DIALOG"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_above="@+id/buttonShowCustomDialog"
      android:layout_centerHorizontal="true"
      android:layout_marginBottom="86dp"
      android:id="@+id/textView"
      android:gravity="center"
      android:textStyle="normal|bold"
      android:textSize="18sp" />
</RelativeLayout>

Step 3 – Create a layout resourse file and add the following code in customdialog.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="https://schemas.android.com/apk/res/android"
   xmlns:app="https://schemas.android.com/apk/res-auto"
   xmlns:tools="https://schemas.android.com/tools"
   android:orientation="vertical" android:layout_width="match_parent"
   android:layout_height="match_parent">
   <TextView
      android:text="Alert...!"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/text"
      android:textStyle="normal|bold"
      android:textSize="18sp"
      android:layout_alignParentTop="true"
      android:layout_centerInParent="true"/>
   <ImageButton
      android:layout_width="35dp"
      android:layout_height="35dp"
      app:srcCompat="@drawable/ic_block"
      android:id="@+id/image"
      android:layout_alignParentLeft="true"
      android:layout_alignParentStart="true"
      tools:ignore="ContentDescription,RtlHardcoded" />
   <Button
      android:id="@+id/dialogButtonOK"
      android:layout_width="200dp"
      android:layout_height="wrap_content"
      android:text="Dismiss"
      android:layout_marginTop="23dp"
      android:paddingRight="5dp"
      android:layout_below="@+id/image"
      style="@style/Widget.AppCompat.Button.Colored"
      android:textSize="18sp" />
</RelativeLayout>

Step 3 − Add the following code to src/MainActivity.java

import android.app.Dialog;
import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity{
   final Context context = this;
   private Button button;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
         button = findViewById(R.id.buttonShowCustomDialog);
         button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
               final Dialog dialog = new Dialog(context);
               dialog.setContentView(R.layout.customdialog);
               Button dialogButton = dialog.findViewById(R.id.dialogButtonOK);
               dialogButton.setOnClickListener(new View.OnClickListener() {
               @Override
               public void onClick(View v) {
                  dialog.dismiss();
                  Toast.makeText(getApplicationContext(),"Dismissed..!!",Toast.LENGTH_SHORT).show();
               }
            });
            dialog.show();
         }
      });
   }
}

Step 4 - Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="https://schemas.android.com/apk/res/android"
   package="app.com.sample">
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <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. Select your mobile device as an option and then check your mobile device which will display your default screen –