Q:

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" />

A:

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();
}

A:

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>

A:

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);
    }
});

