Develop Reference

DialogFragment: constant height of the central view

I have a DialogFragment which consists of three parts, from up to down: the title, the central view which displays all the contents, and the bottom pane which holds the PositiveButton "OK":
public Dialog onCreateDialog(Bundle savedInstanceState)
{
FragmentActivity act = getActivity();
LayoutInflater inflater = act.getLayoutInflater();
AlertDialog.Builder builder = new AlertDialog.Builder(act);
// TITLE:
TextView title = (TextView) inflater.inflate(R.layout.dialog_title, null);
title.setText(R.string.updates);
builder.setCustomTitle(title);
// CENTRAL VIEW:
View view = inflater.inflate(R.layout.dialog_updates, null);
// ... customize it ...
builder.setView(view);
// POSITIVE BUTTON:
builder.setPositiveButton( R.string.ok, new DialogInterface.OnClickListener()
{
#Override
public void onClick(DialogInterface dialog, int which)
{
// something
}
});
}
The stuff that's shown by the central view is downloaded from the web. Initially, when a user pops up the dialog, the View shows just the "Downloading..." message:
When we get an answer, we create a ScrollView and keep adding vertically scrollable Panes to it like so:
(image above shows three such panes added so far)
The result is that the height of the dialog keeps changing, which is visually unpleasant.
So I really want to keep the height of the whole Dialog constant, let's say pinned to 3/4 of the height of the screen. Let's do it then:
public void onResume()
{
super.onResume();
Window window = getDialog().getWindow();
Context context = getContext();
if( window!=null && context!=null )
{
DisplayMetrics metrics = context.getResources().getDisplayMetrics();
final float height= metrics.heightPixels;
WindowManager.LayoutParams params = window.getAttributes();
params.width = WindowManager.LayoutParams.WRAP_CONTENT;
params.height = (int)(0.75f*height);
window.setAttributes(params);
}
}
Result:
This does kind of work, as you can see though - it works by enlarging the lower pane with the 'OK' button, rather than the central View.
How to fix this?
EDIT: here's my dialog_title.xml:
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:textSize="20sp"
android:gravity="center"
android:padding="10dp"/>

One workaround for this issue is to use ConstrainedLayout for your whole dialog like this:
fragment_dialog layout:
<?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"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<TextView
android:id="#+id/title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:padding="10dp"
android:text="Updates"
android:textSize="20sp"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="#+id/central_view"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:text="Downloading"
app:layout_constrainedHeight="true"
app:layout_constraintBottom_toTopOf="#id/positive_action"
app:layout_constraintHeight_percent="0.8"
app:layout_constraintTop_toBottomOf="#id/title" />
<androidx.appcompat.widget.AppCompatButton
android:id="#+id/positive_action"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="end"
android:layout_margin="8dp"
android:text="OK"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
You can change the percentage of your central view with app:layout_constraintHeight_percent="0.8"
DialogFragment class:
public class LoadingDialog extends DialogFragment {
#NonNull
#Override
public Dialog onCreateDialog(#Nullable Bundle savedInstanceState) {
FragmentActivity act = getActivity();
LayoutInflater inflater = act.getLayoutInflater();
View view = inflater.inflate(R.layout.fragment_dialog, null);
AlertDialog.Builder builder = new AlertDialog.Builder(act).setView(view);
// POSITIVE BUTTON:
view.findViewById(R.id.positive_action).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//something
}
});
return builder.create();
}
#Override
public void onResume() {
super.onResume();
getDialog().getWindow().setLayout(
ViewGroup.LayoutParams.MATCH_PARENT,
ViewGroup.LayoutParams.WRAP_CONTENT
);
}
}
And you will get this result:

how to make custom layout for alertdialog wrap content

I have created a custom layout with 3 buttons for alertdialog which is working fine. I am trying to make the layout so that width and height layout will be only wrap its content i.e. no extra width/height but I am unable to do so. Can you help me on this please?
Here is my custom layout for alertdialog:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:background="#00ffffff"
>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:background="#drawable/rectangle_menu"
>
<ImageButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/wowButtonId"
android:layout_marginLeft="5dp"
android:src="#drawable/love_icon"
android:background="#drawable/round_button_for_round_menu_like_button"
android:layout_gravity="center"
/>
<ImageButton
android:layout_width="40dp"
android:layout_height="35dp"
android:id="#+id/blehButtonId"
android:layout_marginLeft="5dp"
android:src="#drawable/bleh"
android:background="#drawable/round_button_for_round_menu_like_button"
android:layout_gravity="center"
/>
<ImageButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/dislikeButtonId"
android:layout_marginLeft="5dp"
android:src="#drawable/dislike_icon"
android:background="#drawable/round_button_for_round_menu_like_button"
android:layout_gravity="center"
/>
</LinearLayout>
</LinearLayout>
alertDialog implement in adapter code:
AlertDialog.Builder builder=new AlertDialog.Builder(context);
AlertDialog alertDialog=builder.create();
View view1=LayoutInflater.from(context).inflate(R.layout.layout_for_long_like_button_option,null);
ImageButton wow=(ImageButton) view1.findViewById(R.id.wowButtonId);
ImageButton disLike=(ImageButton) view1.findViewById(R.id.dislikeButtonId);
ImageButton bleh=(ImageButton) view1.findViewById(R.id.blehButtonId);
wow.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Toast.makeText(context,"wow",Toast.LENGTH_SHORT).show();
}
});
disLike.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Toast.makeText(context,"dislike",Toast.LENGTH_SHORT).show();
}
});
bleh.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Toast.makeText(context,"bleh",Toast.LENGTH_SHORT).show();
}
});
alertDialog.setView(view1);
alertDialog.show();

try this on your class file where you inflate your alert dialog...
WindowManager.LayoutParams lp = new WindowManager.LayoutParams();
Window window = alertDialog.getWindow();
lp.copyFrom(window.getAttributes());
//This makes the dialog take up the full width
lp.width = WindowManager.LayoutParams.WRAP_CONTENT;
lp.height = WindowManager.LayoutParams.WRAP_CONTENT;
window.setAttributes(lp);

Summary: Use RelativeLayout tag at the root in your custom layout
I had two alert dialogs in the application I was writing. One of them did not wrap content, while the other did. The one with the LinearLayout tag at its root, was expanding a tad more in height, than the space its contents really occupied.
I tried setting the width and height properties to wrap_content on the LinearLayout but to no avail.
The one with the RelativeLayout tightly wrapped its contents. The code structure to achieve this would look like:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
>
<!-- More widgets -->
</LinearLayout>
</RelativeLayout>
Although care must be taken, that the inner LinearLayout should still specify wrap_content. You can of course specify match_parent if your intention is to present an elongated dialog, the intentions for doing so, which I would leave it to the developer.
Android Studio still warns me that The LinearLayout layout or its RelativeLayout parent is useless. I do not consider this a solution to the problem, rather it's just a fix. And, I should mention that I've always had these layout problems working with Android. This, I feel, is a more saner approach as it keeps the code modifications down to the layout.

You can use below code for set layout and show dialog
public void showDialog() {
LayoutInflater li = LayoutInflater.from(MainActivity.this);
View promptsView = li.inflate(R.layout.layout_for_long_like_button_option, null);
final TextView txtOk = (TextView) promptsView.findViewById(R.id.txtOk);
final TextView txtCancel = (TextView) promptsView.findViewById(R.id.txtCancel);
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(BaseActivity.this);
alertDialogBuilder.setView(promptsView);
final AlertDialog alertDialog = alertDialogBuilder.create();
alertDialog.getWindow().setBackgroundDrawable(new ColorDrawable(android.graphics.Color.TRANSPARENT));
txtOk.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
alertDialog.dismiss();
}
});
txtCancel.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
alertDialog.dismiss();
}
});
alertDialog.show();
}

You can try setting the width of the inflated view directly when the dialog is shown and therefore has a window
val dialog = AlertDialog.Builder(context)
.setView(myView)
.create()
dialog.setOnShowListener {
dialog.window?.setLayout(
myView.width,
ViewGroup.LayoutParams.WRAP_CONTENT
)
}

Dialog custom layout not stretching properly

Im creating a custom Dialog.
But it is showing extra space around.
Code:
private void showPushAlert(Context context, String message, int layoutID) {
// custom dialog
final Dialog dialog = new Dialog(context);
dialog.setContentView(layoutID);
TextView tvPushMessage = (TextView) dialog.findViewById(R.id.tvAlertMessage);
tvPushMessage.setText(message);
Button btnPushOk = (Button) dialog.findViewById(R.id.btnAlertOk);
btnPushOk.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View view) {
dialog.dismiss();
}
});
dialog.show();
}
Layout:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="275dp"
android:layout_height="wrap_content"
android:background="#drawable/background_round_rectangle"
android:orientation="vertical"
android:padding="#dimen/activity_vertical_margin">
<TextView
android:id="#+id/tvAlertMessage"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:text="Message"
android:textAppearance="?android:attr/textAppearanceMedium"
android:textColor="#color/black" />;
<Button
android:id="#+id/btnAlertOk"
android:layout_width="65dp"
android:layout_height="30dp"
android:layout_below="#id/tvAlertMessage"
android:layout_centerHorizontal="true"
android:layout_marginTop="20dp"
android:background="#drawable/btn_use"
android:text="#string/ok"
android:textColor="#color/white" />
</RelativeLayout>
I also tried inflater:
final Dialog dialog = new Dialog(context);
View view = getLayoutInflater().inflate(layoutID, null);
dialog.setContentView(view);
But not the perfect result. Jut the width stretched.
I wanted to keep simple, so used just Dialog, instead of AlertDialog, or Dialog fragment.

Not sure why that was happening..
Used https://stackoverflow.com/a/6922903/4510869
to do this after dialog.show()
WindowManager.LayoutParams lp = new WindowManager.LayoutParams();
lp.copyFrom(dialog.getWindow().getAttributes());
lp.width = 500;
dialog.getWindow().setAttributes(lp);
This showed the custom width, but the top space was still visible.
Had to change to AlertDialog.Builder + the above snippet (AlertDialog also showed top space) to finally get the result.

Styling titleDivider in Dialog

I am wondering how it is possible to get rid of (or change color) titleDivider in Dialog. It is a blue line below dialog title shown on honeycomb+ devices.
I guess this is relevant piece of layout from SDK, but since there is no style attribute I dont know how to style it. If i try with findViewById there is no android.R.id.titleDivider
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:fitsSystemWindows="true">
<TextView android:id="#android:id/title" style="?android:attr/windowTitleStyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:minHeight="#android:dimen/alert_dialog_title_height"
android:paddingLeft="16dip"
android:paddingRight="16dip"
android:gravity="center_vertical|left" />
<View android:id="#+id/titleDivider"
android:layout_width="match_parent"
android:layout_height="2dip"
android:background="#android:color/holo_blue_light" />
<FrameLayout
android:layout_width="match_parent" android:layout_height="wrap_content"
android:layout_weight="1"
android:orientation="vertical"
android:foreground="?android:attr/windowContentOverlay">
<FrameLayout android:id="#android:id/content"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</FrameLayout>
</LinearLayout>
I have tried to override dialogTitleDecorLayout which is only reference to dialog_title_holo.xml in my theme.xml, but without success. Error is:
error: Error: No resource found that matches the given name: attr
'dialogTitleDecorLayout'.

To get a reference to titleDivider of AlertDialog to change its color:
int divierId = dialog.getContext().getResources()
.getIdentifier("android:id/titleDivider", null, null);
View divider = dialog.findViewById(divierId);
divider.setBackgroundColor(getResources().getColor(R.color.creamcolor));

You need to implement
myDialog = builder.create();
myDialog.setOnShowListener(new OnShowListenerMultiple());
//----------------------------
//Function to change the color of title and divider of AlertDialog
public static class OnShowListenerMultiple implements DialogInterface.OnShowListener {
#Override
public void onShow( DialogInterface dialog ) {
if( !(dialog instanceof Dialog) )
return;
Dialog d = ((Dialog) dialog);
final Resources resources = d.getContext().getResources();
final int color = AppUtility.getColor( resources, R.color.defaultColor );
try {
int titleId = resources.getIdentifier( "android:id/alertTitle", null, null );
TextView titleView = d.findViewById( titleId );
titleView.setTextColor( color );
}
catch( Exception e ) {
Log.e( "XXXXXX", "alertTitle could not change color" );
}
try {
int divierId = resources.getIdentifier( "android:id/titleDivider", null, null );
View divider = d.findViewById( divierId );
divider.setBackgroundColor( color );
}
catch( Exception e ) {
Log.e( "XXXXXX", "titleDivider could not change color" );
}
}
}

I solved the issue by using DialogFragment.STYLE_NO_TITLE theme and then faking title bar in dialog layout.

Here is how I resolved that (thanks to http://joerg-richter.fuyosoft.com/?p=181 ):
MyDialogBuilder.class
public class MyDialogBuilder extends android.app.AlertDialog.Builder {
public MyDialogBuilder(Context context) {
super(context);
}
#NonNull
#Override
public android.app.AlertDialog create() {
final android.app.AlertDialog alertDialog = super.create();
alertDialog.setOnShowListener(new DialogInterface.OnShowListener() {
#Override
public void onShow(DialogInterface dialog) {
int titleDividerId = getContext().getResources()
.getIdentifier("titleDivider", "id", "android");
View titleDivider = alertDialog.findViewById(titleDividerId);
if (titleDivider != null) {
titleDivider.setBackgroundColor(getContext().getResources()
.getColor(R.color.alert_dialog_divider));
}
}
});
return alertDialog;
}
}

use
<View android:id="#+id/titleDivider"
android:layout_width="match_parent"
android:layout_height="2dip"
android:background=#CC3232 />

Before write dialog.show(), write:
int divierId = dialog.getContext().getResources().getIdentifier("android:id/titleDivider", null, null);
View divider = dialog.findViewById(divierId);
if(divider!=null){
divider.setBackgroundColor(getResources().getColor(R.color.transparent));}
In colors.xml:
<color name="transparent">#00000000</color>

If you don't want to use Default style, don't use AlertDialog. You could go with Activity(with your custom layout) with Dialog Theme.
<activity android:theme="#android:style/Theme.Dialog">

This one is tested on some 4.x devices:
TextView title = (TextView)getWindow().getDecorView().findViewById(android.R.id.title);
((ViewGroup)title.getParent()).getChildAt(1).setVisibility(View.GONE);

Your idea was correct. However, dialogTitleDecorLayout you were looking for is a private resource, so you can't access it in a normal way. But you still can access it using * syntax:
<item name="*android:dialogTitleDecorLayout">#layout/dialog_title</item>
Adding this to my own style and simply copying dialog_title.xml to my app and changing it slightly solved the problem in my case.

Do you watchthis and there is a pcecial library for that, you can watch it there. And the last link will solve you problem

you can make a custom dialog like this:
Dialog dialog = new Dialog(this);
dialog.setContentView(R.layout.custom_dialog);
Button okay = (Button) dialog.findViewById(R.id.button1);
okay.setOnClickListener(new OnClickListener() {
public void onClick(View arg0) {
// do your work
}
});
Set a custom title in layout don't use android
dialog.setTitle();
and your custom_dialog.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:android1="http://schemas.android.com/apk/res/android"
android:id="#+id/layout_root"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:padding="10dp">
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#ffffff"
android:textSize="40sp"
android:text="Hello"/>
<Button
android:id="#+id/button1"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:layout_marginLeft="150dp"
android:text="OK" />
</RelativeLayout>

"Removing the blue line" if I guess correctly means dropping the border between the title of the dialog and it's body. That border come from the Holo theme, so it's not possible to drop it without using your custom layout.
Create a file named custom-dialog.xml with the following content (it's just an example..modify it as you want):
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/general_dialog_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<ImageView
android:id="#+id/dialogTopImage"
android:layout_width="fill_parent"
android:layout_height="0dp"
android:layout_weight="0.12"
android:padding="10dp" />
<LinearLayout
android:id="#+id/dialogLine"
android:layout_width="fill_parent"
android:layout_height="3dp"
android:background="#drawable/green_btn"
android:orientation="vertical" />
<TextView
android:id="#+id/dialogText"
android:layout_width="fill_parent"
android:layout_height="0dp"
android:layout_weight="0.32"
android:padding="5dp"
android:text=""
/>
<LinearLayout
android:id="#+id/general_dialog_layout"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_gravity="center"
android:layout_marginBottom="5dp"
android:layout_weight="0.11"
android:gravity="center"
android:orientation="horizontal" >
<Button
android:id="#+id/dialogButton"
android:layout_width="100dp"
android:textSize="8pt"
android:layout_height="wrap_content"
android:layout_marginRight="10dp"
android:background="#drawable/green_btn"
android:gravity="center"
android:text="Ok" />
</LinearLayout>
As you see I'm using resources and stuff that won't be in your project, but you can remove them safely. The result in my case is more or less the following one, with an image at top that I'll programatically set in the code.
To create the dialog then use something like:
private Dialog createAndShowCustomDialog(String message, Boolean positive, Drawable d, View.OnClickListener cl, String text1) {
final Dialog dialog = new Dialog(this);
dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
dialog.setContentView(R.layout.general_dialog_layout);
// BIND
ImageView image = (ImageView) dialog.findViewById(R.id.dialogTopImage);
TextView text = (TextView) dialog.findViewById(R.id.dialogText);
Button button = (Button) dialog.findViewById(R.id.dialogButton);
LinearLayout line = (LinearLayout) dialog.findViewById(R.id.dialogLine);
// SET WIDTH AND HEIGHT
DisplayMetrics displaymetrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
int width = (int) (displaymetrics.widthPixels * 0.85);
int height = (int) (displaymetrics.heightPixels * 0.60);
WindowManager.LayoutParams params = getWindow().getAttributes();
params.width = width;
dialog.getWindow().setLayout(width, height);
// SET TEXTS
text.setText(message);
button.setText(text1);
// SET IMAGE
if (d == null) {
image.setImageDrawable(getResources().getDrawable(R.drawable.font_error_red));
} else {
image.setImageDrawable(d);
}
// SET ACTION
if (cl == null) {
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
dialog.dismiss();
}
});
} else {
button.setOnClickListener(cl);
}
// SHOW
dialog.show();
return dialog;
}

These is no way hiding it by control brotha.. I've had the same problem. only thing you can do is create your own CustomDialog
Here is a sample App
Download and have look at the design pattern, then it will be easy
Here is one Tutorial About making Custom Dialog
Important part is after creating the DialogObject don't set the Title by setTitle()
create TextView inside your CustomLayout and call it from findViewByID() and set your title

In colors.xml:
<color name="transparent">#00000000</color>
In dialog:
int divierId = dialog.getContext().getResources().getIdentifier("android:id/titleDivider",null, null);
View divider = d.findViewById(divierId);
divider.setBackgroundColor(getResources().getColor(R.color.transparent));

In order to hide the default blue line completely (assuming you're in DialogFragment):
Dialog dialog = getDialog();
if (dialog != null) {
final int dividerId = dialog.getContext().getResources()
.getIdentifier("android:id/titleDivider", null, null);
View divider = dialog.findViewById(dividerId);
if (divider != null) {
divider.setBackground(null);
}
}

Android Image Dialog/Popup

Is it possible to have just an image popup/come-up in an Android application? It's similar to an overriding the normal view of an AlertDialog so that it contains just an image and nothing else.
SOLUTION: I was able to find an answer thanks to #blessenm's help. Masking an activity as a dialog seems to be the ideal way. The following is the code that I have used. This dialog styled activity can be invoked as needed by the application the same way a new activity would be started
ImageDialog.java
public class ImageDialog extends Activity {
private ImageView mDialog;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.your_dialog_layout);
mDialog = (ImageView)findViewById(R.id.your_image);
mDialog.setClickable(true);
//finish the activity (dismiss the image dialog) if the user clicks
//anywhere on the image
mDialog.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
finish();
}
});
}
}
your_dialog_layout.xml
<?xml version="1.0" encoding="UTF-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/image_dialog_root"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#android:color/transparent"
android:gravity = "center">
<ImageView
android:id="#+id/your_image"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src = "#drawable/your_image_drawable"/>
</FrameLayout>
It is crucial that you set the following style for the activity to accomplish this:
styles.xml
<style name="myDialogTheme" parent="#android:style/Theme.Dialog">
<item name="android:windowNoTitle">true</item>
<item name="android:windowFrame">#null</item>
<item name="android:background">#android:color/transparent</item>
<item name="android:windowBackground">#android:color/transparent</item>
<item name="android:windowIsFloating">true</item>
<item name="android:backgroundDimEnabled">false</item>
<item name="android:windowContentOverlay">#null</item>
</style>
The final step is to declare this style for the activity in the manifest as follows:
<activity android:name=".ImageDialog" android:theme="#style/myDialogTheme" />

No xml:
public void showImage() {
Dialog builder = new Dialog(this);
builder.requestWindowFeature(Window.FEATURE_NO_TITLE);
builder.getWindow().setBackgroundDrawable(
new ColorDrawable(android.graphics.Color.TRANSPARENT));
builder.setOnDismissListener(new DialogInterface.OnDismissListener() {
#Override
public void onDismiss(DialogInterface dialogInterface) {
//nothing;
}
});
ImageView imageView = new ImageView(this);
imageView.setImageURI(imageUri);
builder.addContentView(imageView, new RelativeLayout.LayoutParams(
ViewGroup.LayoutParams.MATCH_PARENT,
ViewGroup.LayoutParams.MATCH_PARENT));
builder.show();
}

If you just want to use a normal dialog something like this should work
Dialog settingsDialog = new Dialog(this);
settingsDialog.getWindow().requestFeature(Window.FEATURE_NO_TITLE);
settingsDialog.setContentView(getLayoutInflater().inflate(R.layout.image_layout
, null));
settingsDialog.show();
image_layout.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content" android:layout_height="wrap_content"
android:orientation="vertical">
<ImageView android:layout_width="wrap_content"
android:layout_height="wrap_content" android:src="YOUR IMAGE"/>
<Button android:layout_width="wrap_content" android:layout_height="wrap_content"
android:text="OK" android:onClick="dismissListener"/>
</LinearLayout>

Try the following:
It has image zoom_in/zoom_out as well.
Step 1:
Add compile 'com.github.chrisbanes.photoview:library:1.2.4' to your build.gradle
Step 2:
Add the following xml
custom_fullimage_dialoge.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/layout_root" android:orientation="horizontal"
android:layout_width="fill_parent" android:layout_height="fill_parent"
android:padding="10dp">
<ImageView android:id="#+id/fullimage" android:layout_width="fill_parent"
android:layout_height="fill_parent">
</ImageView>
<TextView android:id="#+id/custom_fullimage_placename"
android:layout_width="wrap_content" android:layout_height="fill_parent"
android:textColor="#FFF">
</TextView>
</LinearLayout>
Step 3:
private void loadPhoto(ImageView imageView, int width, int height) {
final Dialog dialog = new Dialog(this);
dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
dialog.getWindow().setBackgroundDrawable(new ColorDrawable(android.graphics.Color.TRANSPARENT));
//dialog.setContentView(R.layout.custom_fullimage_dialog);
LayoutInflater inflater = (LayoutInflater) this.getSystemService(LAYOUT_INFLATER_SERVICE);
View layout = inflater.inflate(R.layout.custom_fullimage_dialog,
(ViewGroup) findViewById(R.id.layout_root));
ImageView image = (ImageView) layout.findViewById(R.id.fullimage);
image.setImageDrawable(imageView.getDrawable());
image.getLayoutParams().height = height;
image.getLayoutParams().width = width;
mAttacher = new PhotoViewAttacher(image);
image.requestLayout();
dialog.setContentView(layout);
dialog.show();
}
Step 4:
user_Image.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Display display = getWindowManager().getDefaultDisplay();
int width = display.getWidth();
int height = display.getHeight();
loadPhoto(user_Image,width,height);
}
});

You can do it easily by create a Dialog Fragment in Kotlin:
BigImageDialog.kt
class BigImageDialog():DialogFragment() {
private var imageUrl = ""
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
arguments?.let {
imageUrl = arguments.getString("url")
}
}
override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View {
val v = inflater!!.inflate(R.layout.dialog_big_image, container, false)
this.dialog.window.requestFeature(Window.FEATURE_NO_TITLE)
Picasso.get().load(imageUrl).into(v.bigImageView)
return v
}
override fun onStart() {
super.onStart()
val dialog = dialog
if (dialog != null) {
dialog.window.setLayout(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT)
}
}
companion object {
#JvmStatic
fun newInstance(imageUrl: String) =
BigImageDialog().apply {
arguments = Bundle().apply {
putString("url", imageUrl)
}
}
}
}
dialog_big_image.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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">
<ImageView
android:id="#+id/bigImageView"
android:layout_width="0dp"
android:layout_height="0dp"
android:scaleType="centerCrop"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>
Opening Dialog:
"smallImageView".setOnClickListener { BigImageDialog.newInstance("image url").show(fragmentManager,"") }

There is a couple ways you can do this. But, if you're looking to have your image appear to be floating above your existing activity, you may want to use an activity with android:theme="#style/Theme.Transparent" defined in the manifest. Then, design your layout to just have a single ImageView positioned in the center of the screen. The user will have to push the back button to get out of this, but it sounds like that's what you want.
If you want it to look like an actual dialog, you can always use a dialog styled activity as well using Theme.Dialog. OR, you could just use a dialog and customize it.

The more flexible and recommended way is use DialogFragment. If you want to support versions before 3.0 you can use compatibility library