Android Image Dialog/Popup

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();
}

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);
    }
});

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>