simple Ruler library response to user's actions give you accurate measurement in millimeter, with Calibration and Dimension measurement for Android, see project on GitHub.

minSdkVersion=15

Library Size just ~ 18 KB.

add this line to build.gradle

dependencies {
    implementation 'com.github.anastr:rulerview:1.1.0'
}

for maven

<dependency>
  <groupId>com.github.anastr</groupId>
  <artifactId>rulerview</artifactId>
  <version>1.1.0</version>
  <type>pom</type>
</dependency>

add RulerView to your Layout.xml.

<com.github.anastr.rulerview.RulerView
        android:id="@+id/rulerView"
        android:layout_width="match_parent"
        android:layout_height="150dp" />

and that's it!!

you can get the length in millimeter simply By

val length = rulerView.getDistance()

you can change the unit using this method

rulerView.unit = RulerUnit.IN // in inch

in android devices, convert pixels to (MM, IN...) is not always accurate.
you need your users help to calibration RulerView for there devices, that's why you should use RulerCalibrationView to do that.

the user can easily slide to match real measurements.

to use that, add RulerCalibrationView to your layout.xml

<com.github.anastr.rulerview.RulerCalibrationView
        android:id="@+id/rulerCalibrationView"
        android:layout_width="match_parent"
        android:layout_height="100dp" />

then you can get the coefficient and save it, then pass it to RulerView

// coefficient is a float number
val myCoefficient = rulerCalibrationView.coefficient
// save it somewhere (SharedPreferences maybe)
saveNumber(myCoefficient)

...

// pass it to your ruler
rulerView.coefficient = myCoefficient

to measure distance between two lines

<com.github.anastr.rulerview.OneDimensionRulerView
        android:id="@+id/oneDimensionRulerView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

// return distance in Unit you have set
val distance = oneDimensionRulerView.getDistance()

• add control on marks color
• text color
• text size
• new TwoDimensionRulerView

Copyright 2016 Anas Altair

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.