Android Button – Remove Shadow and Border from Button with Image on it

We can remove the border and shadows from a button by adding the following style code in your activity_main.xml file. Or what ever your XML file is.


Code for button. We are setting an image as the background.


Comparison of buttons. One on the left still has the shadow on it

Difference between border and borderless buttons

More info here

Getting Android WiFi state in Kotlin

In Kotlin you can request if the WiFi adapter is on or off with the following code
This changes the text on a textbox, replace with your textbox.

wifiManager = this.applicationContext.getSystemService(Context.WIFI_SERVICE) as WifiManager
textBox.text = "WiFi State = ${wifiManager.wifiState}"

The important part is


It will return a number from 0-4 which indicates if it is on or off.

0 = WiFi is being disabled
1 = WiFi Disabled
2 = WiFi is being enabled
3 = WiFi is Enabled
4 = Error

Kotlin, Launching Settings Activity is Showing Main Activity

The problem is that the code in SettingsActivity is not tied to the settings_activity.xml file. So it is using the activity_main.xml instead. It does in fact switch activities, the header at the top shows that it is in the Settings, but it shows the same information on the Main Activity. Problem showed up after copying and pasting code.

Check the following line under the initial onCreate function

override fun onCreate(savedInstanceState: Bundle?) {
        setContentView(R.layout.activity_main)  // <-- Should be R.layout.settings_activity

The setContentView line should reflect the Layout XML file under res -> layout -> settings_activity.xml

You need to use a Theme.AppCompat theme (or descendant) with this activity.

You need to use a Theme.AppCompat theme (or descendant) with this activity.

Looks like if you get the above error resolved by adding the following to the Android Manifest file.


Kotlin – Buttons and TextViews

Set Text for text view

val textBoxVar: TextView = findViewById(
textBoxVar.text = "Hello World!"

Button clicked – do something

val buttonVar: Button = findViewById(
buttonVar.setOnClickListener {
    buttonVar.text = "Button Pushed..."  //Change text on button


Toast notification

val text = "Hello World! This is a toast message!"
val duration = Toast.LENGTH_SHORT
val toast = Toast.makeText(applicationContext, text, duration)

Using Seeed Studio O2 Sensor Arduino Without Grove Breakout board

The Seeed Studio O2 sensor is a nice Oxygen sensor. It works up to 25% Oxygen concentration and is easy to use in an Arduino project.

Wiring Up the O2 Sensor to Arduino

If you look on the back of the sensor there are only 3 wires used. VCC, GND, and a SIG. The NC pin is “Not Connected”

Wire the
GND -> Arduino ground
VCC -> Arduino 3.3V (Looks like it may also accept 5V)
SIG -> A5 (Analog 5)

Code to read O2 Sensor

Copy and paste the following code into the Arduino IDE

// Grove - Gas Sensor(O2) test code
// Note:
// 1. It need about about 5-10 minutes to preheat the sensor
// 2. modify VRefer if needed

const float VRefer = 3.3;       // voltage of adc reference

const int pinAdc   = A5;

void setup() 
    // put your setup code here, to run once:
    Serial.println("Grove - Gas Sensor Test Code...");

void loop() 
    // put your main code here, to run repeatedly:
    float Vout =0;
    Serial.print("Vout =");

    Vout = readO2Vout();
    Serial.print(" V, Concentration of O2 is ");

float readO2Vout()
    long sum = 0;
    for(int i=0; i<32; i++)
        sum += analogRead(pinAdc);
    sum >>= 5;
    float MeasuredVout = sum * (VRefer / 1023.0);
    return MeasuredVout;

float readConcentration()
    // Vout samples are with reference to 3.3V
    float MeasuredVout = readO2Vout();
    //float Concentration = FmultiMap(MeasuredVout, VoutArray,O2ConArray, 6);
    //when its output voltage is 2.0V,
    float Concentration = MeasuredVout * 0.21 / 2.0;
    float Concentration_Percentage=Concentration*100;
    return Concentration_Percentage;

Upload and Launch the Serial Monitor
Tools -> Serial Monitor
Ctrl + Shift + M

Bash Loop Examples

For i in 1-100 do

Basically count to 100 and perform an operation each time i increases.

for ((i=1; i<=100;i++))
  echo $i

for loop 1 liner

for ((i=1; i<=100;i++)) do echo $i ; done

While true (Execute forever)

Handy if you just want a script to run and repeat the same thing over and over again. Doesn't stop till you kill it.

while true
  echo "Repeat till infinity"
  sleep 1

While command is true

The following will execute the loop as long as the command in the () returns true. Once it returns false, it'll stop the loop

while (fping | grep alive); 
  echo alive
  sleep 1

Bash array example

array=(one two three)
echo "Printing first object in array."  #Replace 0 with the place number of the array item
echo ${array[0]}

echo ""

echo "Whole array"
echo ${array[*]} 

echo "" 

echo "Array indexes" 
echo ${!array[*]}


Printing first object in array. 

Whole array
one two three

Array indexes
0 1 2

Clamp rotation of camera in Unity

Some notes and issues when trying to clamp the rotation of a camera in Unity. All the code was put on a script assigned to a controller that controlled the camera view. Used the Simple Touch Controller from the asset store.

Problem trying to clamp EulerAngles

It appears that the following code does not work as EulerAngles expects a value from 0-365.

transform.localEulerAngles = new Vector3(Mathf.Clamp(transform.localEulerAngles.x - rightController.GetTouchPosition.y * Time.deltaTime * speedContinuousLook, 0f , 20f ),transform.localEulerAngles.y + rightController.GetTouchPosition.x * Time.deltaTime * speedContinuousLook, 0f);

Extra debug info

Debug.Log("Rotation = " + transform.localEulerAngles.ToString());

Code to clamp rotation

You have to do some math to take the value from 0-365, then translate it to -90 – 90 so it can be clamped properly

// Put these with the rest of your public variables.  These should show up in the Unity Inspector and allow you to modify the values
public float speedProgressiveLook;
public float clampXRotationUp;
//  The following lines allow the script to Clamp the camera X rotation and should go in the Update function

float playerRotation = transform.localEulerAngles.x - rightController.GetTouchPosition.y * Time.deltaTime * speedContinuousLook; 

if (playerRotation > 180)        {             
    playerRotation = playerRotation - 360 ;  // Sets our working numbers between -180 - 180  
playerRotation = Mathf.Clamp(playerRotation, clampXRotationDown, clampXRotationUp);

Vector3 newRotation;
newRotation.x = playerRotation;
newRotation.y = transform.localEulerAngles.y + rightController.GetTouchPosition.x * Time.deltaTime * speedContinuousLook;
newRotation.z = 0;

transform.localEulerAngles = newRotation;

The following links were helpful.