What Does Ellipsize Mean in Android?

In my experience, Ellipsis works only if the below two attributes are set.

android:ellipsize="end"
android:singleLine="true"

for the width of TextView, wrap_content or match_parent should both be good.

android:ellipsize added in API Level 1. An ellipsis is three periods in a row. (...) .

In your .xml

 <TextView
       ....
       android:text="Hi I am Amiyo, you can see how to ellipse works."
       android:ellipsize = "end" />

At this point, the ellipsis will not display yet as a TextView is set to automatically expand on default when new text is entered. You will need to limit TextView in some way. Do this, you can use either add to your TextView a scrollHorizontally, minLines, or maxLines to have the ellipsis display.

To make the ellipse:

    at the end: this is how it would.   
    use: android:ellipsize = "end"

And

 in the middle:
 use: android:ellipsize = "middle"

And

 at the start:
 use: android:ellipsize = "start"

And

 to have no ellipse
 use: android:ellipsize = "none"

Note Please :

Do not use android:singeLine = "true", it is deprecated.
android:maxLines = "1" will not display the three dots (...)
android:lines = "1" will not display the three dots (...)

For more details you can visit here

An ellipsis is three periods in a row...

The TextView will use an ellipsis when it cannot expand to show all of its text. The attribute ellipsized sets the position of the three dots if it is necessary.

Text:

 This is my first android application and
 I am trying to make a funny game,
 It seems android is really very easy to play.

Suppose above is your text and if you are using ellipsize's start attribute it will seen like this

This is my first android application and
...t seems android is really very easy to play.

with end attribute

 This is my first android application and
 I am trying to make a funny game,...

Here is an example on how ellipsize works without using deprecated android:singleLine="true" in a ConstraintLayout:

<TextView
   android:layout_width="0dp"
   android:layout_height="wrap_content"
   android:textSize="13sp"
   android:ellipsize="end"
   android:maxLines="2"
   app:layout_constraintEnd_toEndOf="parent"
   app:layout_constraintStart_toStartOf="parent"
   tools:text="long long long long long long text text text" />

remember if you have a text that is supposed to be in a single line, then change the maxLines to 1.

Note: your text must be larger than the container box for the following to marquee:

 android:ellipsize="marquee"    

Set this property to EditText. Ellipsize is working with disable EditText

android:lines="1"
android:scrollHorizontally="true"
android:ellipsize="end"
android:singleLine="true"
android:editable="false"

or setKeyListener(null);

Use ellipsize when you have fixed width, then it will automatically truncate the text & show the ellipsis at end,

it Won't work if you set layout_width as wrap_content & match_parent.

android:width="40dp"
android:ellipsize="end"
android:singleLine="true"