Android Dialog Tutorial

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1- Android Dialog

In Android, the Dialog is a small window that appears to reminds the user to make a decision or enter additional information. The dialog does not fill the entire screen, and it usually displays in modal mode, that means the user has to make a decision to close it in order to interact with other parts of the application.
If you want a Dialog, write a class extends from the Dialog class or use its existing subclasses. Please stay away from using the Dialog class directly.

AlertDialog

AlertDialog is a direct subclass of the  Dialog. It consists of a header, content area, and 1, 2 or 3 buttons. It is easy for you to get a dialog box with a few lines of codes.

CharacterPickerDialog

Android CharacterPickerDialog is a dialog box that permits the user to select "accented characters" of a base character. Oftentimes, the CharacterPickerDialog is useful because not all of the phones have the Keyboard Layout that is appropriate for a particular language.

DatePickerDialog & TimePickerDialog

Allows the user to select a date or time.
  • TODO Link!

ProgressDialog

ProgressDialog is a dialog box that shows a progress. Basically, this dialog is unsafe when it appears because it hinders the user from interacting with the application (The progress is not completed). You should consider using the  ProgressBar instead of the  ProgressDialog.
  • TODO Link!

DialogFragment vs Dialog

Dialogs are created and displayed in an Activity, they do not have callback methods to be able to identify the status of the Activity lifecycle, so sometimes your Activity needs to tell the Dialog what to do in different periods of time.
To simplify that, take the situation as an example: Your application is displaying a Dialog filled with data, for some reason the user has not interacted with the device for a certain period of time. If so, the device will go into sleeping state and  onPause() method of the  Activity will be called to pause the app. As soon as the user comes back and re-interacts with the device,  onResume() method of the  Activity will be called to resume the app. Additionally, you need to write codes in onResume() to request the Dialog to refresh the data displaying. Remember that you don't need to do that if the Dialogs are only used to show notifications, or to display the fixed data .
DialogFragment is a Fragment that contains a Dialog. Its  callback methods is self-aware of different states in the lifecycle of the Activity, so DialogFragment can smartly do tasks by itself instead of following the Activity instructions. In addition, Dialogs will be closed if the user rotates the phone screen, while DialogFragment is more user-friendly, it will rotate in accordance with the orientation of the phone screen.
That is the key reason why you should use DialogFragment instead of Dialog.  Obviously, it will make your codes clearer. However, you do not need to worry because using Dialog is really convenient in most cases.
  • TODO Link!

2- Example of Custom Dialog

Example preview:
Now, create a new project on Android Studio:
  • File > New > New Project > Empty Activity
    • Name: CustomDialogExample
    • Package name: org.o7planning.customdialogexample
    • Language: Java
First, let's start off with designing the interface for the dialog:
  • File > New > Android Resource File
    • File name: layout_custom_dialog.xml
    • Resource type: Layout
    • Root element: androidx.constraintlayout.widget.ConstraintLayout
    • Directory name: layout
Then design the Interface of the custom Dialog:
After that, set ID, and Text for the components in the interface:
layout_custom_dialog.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="16dp"
        android:text="Enter Your Name:"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/editText_fullName"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:ems="10"
        android:hint="Name"
        android:inputType="textPersonName"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <Button
        android:id="@+id/button_cancel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Cancel"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/editText_fullName" />

    <Button
        android:id="@+id/button_ok"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="OK"
        app:layout_constraintEnd_toStartOf="@+id/button_cancel"
        app:layout_constraintTop_toBottomOf="@+id/editText_fullName" />
</androidx.constraintlayout.widget.ConstraintLayout>
Finally, create a CustomDialog class extending from the Dialog class:
CustomDialog.java
package org.o7planning.customdialogexample;

import android.app.Activity;
import android.app.Dialog;
import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class CustomDialog extends Dialog {

    interface FullNameListener {
        public void fullNameEntered(String fullName);
    }

    public Context context;

    private EditText editTextFullName;
    private Button buttonOK;
    private Button buttonCancel;

    private CustomDialog.FullNameListener listener;

    public CustomDialog(Context context, CustomDialog.FullNameListener listener) {
        super(context);
        this.context = context;
        this.listener = listener;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.layout_custom_dialog);

        this.editTextFullName = (EditText) findViewById(R.id.editText_fullName);
        this.buttonOK = (Button) findViewById(R.id.button_ok);
        this.buttonCancel  = (Button) findViewById(R.id.button_cancel);

        this.buttonOK .setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                 buttonOKClick();
            }
        });
        this.buttonCancel.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                 buttonCancelClick();
            }
        });
    }

    // User click "OK" button.
    private void buttonOKClick()  {
        String fullName = this.editTextFullName.getText().toString();

        if(fullName== null || fullName.isEmpty())  {
            Toast.makeText(this.context, "Please enter your name", Toast.LENGTH_LONG).show();
            return;
        }
        this.dismiss(); // Close Dialog

        if(this.listener!= null)  {
            this.listener.fullNameEntered(fullName);
        }
    }

    // User click "Cancel" button.
    private void buttonCancelClick()  {
        this.dismiss();
    }
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/button_openDialog"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="32dp"
        android:text="Open Dialog"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
    
</androidx.constraintlayout.widget.ConstraintLayout>
MainActivity.java
package org.o7planning.customdialogexample;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private Button buttonOpenDialog;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        this.buttonOpenDialog = (Button) this.findViewById(R.id.button_openDialog);

        this.buttonOpenDialog.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                buttonOpenDialogClicked();
            }
        });
    }

    private void buttonOpenDialogClicked()  {
        CustomDialog.FullNameListener listener = new CustomDialog.FullNameListener() {
            @Override
            public void fullNameEntered(String fullName) {
                Toast.makeText(MainActivity.this, "Full name: " + fullName, Toast.LENGTH_LONG).show();
            }
        };
        final CustomDialog dialog = new CustomDialog(this, listener);

        dialog.show();
    }
}

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