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Fix the ambient Temperature in Android

I successfully made an app to measure the ambient temperature in Android studio. But the next step doesn't want to work. here's the point:
when I start the app the temperature should be shown in 1 textView (works so far). Then it should stay with this temperature but it changes. I only want to check the temperature once.
when I click on submit it shall do the same with the second textView.
I did this successfully with the time but with the temperature, it won't work. And my second question is, I did a lot of research and it looks like the temperature will always be shown in °c. Can I change that so the people who want it in °F can have it this way?
Code for the temperature without change the value and with the button for getting the temperature on textView2:
MainActivity:
public class MainActivity extends AppCompatActivity implements SensorEventListener {
private TextView textView, textView2;
private Button button;
private SensorManager sensorManager;
private Sensor tempSensor;
private Boolean isTemperatureSensorAvailable;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textView = findViewById(R.id.textView);
textView2 = findViewById(R.id.textView2);
button = findViewById(R.id.button);
sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
if(sensorManager.getDefaultSensor(Sensor.TYPE_AMBIENT_TEMPERATURE) !=null) {
tempSensor = sensorManager.getDefaultSensor(Sensor.TYPE_AMBIENT_TEMPERATURE);
isTemperatureSensorAvailable = true;
}else{
textView.setText("Temperature Sensor is not available");
isTemperatureSensorAvailable = false;
}
}
#Override
public void onSensorChanged(SensorEvent event) {
}
#Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
}
#Override
protected void onResume(){
super.onResume();
if(isTemperatureSensorAvailable){
sensorManager.registerListener(this,tempSensor, SensorManager.SENSOR_DELAY_NORMAL);
}
}
#Override
protected void onPause(){
super.onPause();
if(isTemperatureSensorAvailable){
sensorManager.unregisterListener(this);
}
}
private void update_text_unit()//Run from button
{
boolean toogle = false;
float temperature = 0;
float C_temp = 0;
float F_temp =0;
//Get sensor data
Sensor temp = sensorManager.getDefaultSensor(Sensor.TYPE_AMBIENT_TEMPERATURE);
F_temp = (C_temp * (9/5) +32);//Convert to °F
if(toogle = true) {
textView2.setText("Temp is:" + C_temp + "°C");
toogle = false;
}
else {
textView2.setText("Temp is:" + F_temp + "°F");
toogle = true;
}
}
}
I hope someone can help me going into a better direction.
Thanks for your help.

In the first code you have a section which is on sensor changed so this will run each time causing your issue. In you oncreate all the API to get the temperature once and chuck it to the text view as a string. For °C to °F you will need to convert. I would just do this manually:
(X°C × 9/5) + 32 = result_°F
Where X is the input temperature and result is the output in °F.

Here is an example of the button temp change feature not exactly sure how you read the temp so the line of Sensor.gettemp will probably need to change. Run this from a button push, it will update your text view
private void update_text_unit()//Run from button
{
boolean toogle = false;
float temperature = 0;
float C_temp = 0;
float F_temp =0;
//Get sensor data
C_temp = Sensor.gettemp();
F_temp = (C_temp * (9/5) +32);//Convert to °F
if(toogle = true) {
yourtextview.setText("Temp is:" + C_temp + "°C");
toogle = false;
}
else {
yourtextview.setText("Temp is:" + F_temp + "°F");
toogle = true;
}
}

Set empty edittext value to zero

I have created a simple program to try to figure out how to do this. it has two edit text fields (input type number decimal), a text view and a button. I want the sum of the two input fields to be displayed in the text view when the user hits the button. can someone tell me how to set the value of one edit text field to zero if the user left it blank? I have tried many ways but nothing worked.
Edit: i want to achieve this while keeping the hint of edit text as before (without changing the value to zero like " setText("0"); ".
here's my java code (tell me what to add)
package com.example.android.testedittexttozero;
import...
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void calculate(View v) { //the button
final EditText number1 = (EditText) findViewById(R.id.numberFirst);
EditText number2 = (EditText) findViewById(R.id.numberSecond);
TextView total = (TextView) findViewById(R.id.totalTV);
try {
int a = Integer.parseInt(number1.getText().toString());
int b = Integer.parseInt(number2.getText().toString());
int sum = a + b;
total.setText("" + sum);
} catch (Exception e) {
Toast.makeText(getApplicationContext(), "One or more field is empty", Toast.LENGTH_LONG).show();
}
}
}

Do you know that in java if you dont initialize a variable with a default value, it's default value be 0?
in short:
try {
int a;//by default, it will be 0;
int b = Integer.parseInt(number2.getText().toString());//let it be 2
int sum = a + b;
total.setText("" + sum);//Ans will be 2 only
} catch (Exception e) {
Toast.makeText(getApplicationContext(), "One or more field is empty", Toast.LENGTH_LONG).show();
}
If you don't enter any value in a, it will be set to as 0. Like if you leave a blank, and enter 2 in second edittext, the ans will be two nevertheless..

public void ZeroingEmpytEditText() {
int f= 0; // Zeroing Factor
if (number1.getText().toString().length() > 0) {
a = Integer.parseInt(number1.getText().toString());
} else {
a=f;
}
if (number2.getText().toString().length() > 0) {
b = Integer.parseInt(number2.getText().toString());
} else {
b=f;
}
int sum = a + b ;
total.setText(sum + "");
}

you can set value 0 of edit text in oncreate method.
like,
public class MainActivity extends AppCompatActivity {
EditText number1,number2;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
number1 = (EditText) findViewById(R.id.numberFirst);
number2 = (EditText) findViewById(R.id.numberSecond);
number1.settext("0");
number2.settext("0");
}
public void calculate(View v) { //the button
TextView total = (TextView) findViewById(R.id.totalTV);
try {
int a = Integer.parseInt(number1.getText().toString());
int b = Integer.parseInt(number2.getText().toString());
int sum = a + b;
total.setText("" + sum);
} catch (Exception e) {
Toast.makeText(getApplicationContext(), "One or more field is empty", Toast.LENGTH_LONG).show();
}
}
}
its helpfull for you.

My Calculations are off when Creating a BMI Calculator

Problem: My Calculations are off when I compared the results on my app to the bmi website. THank you so much in advance, also my math is really bad so I apologize in advance.
Here are the results that my app is giving me:
http://www.tiikoni.com/tis/view/?id=8bd04d4
Here are the results based of the BMI Website NIH
http://www.tiikoni.com/tis/view/?id=86d4458
BMIFRAG.java
public class BmiFrag extends Fragment implements View.OnClickListener
{
Button BmiButton;
public static EditText heightFT;
public static EditText heightIn;
public static EditText weightIn;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View myView = inflater.inflate(R.layout.fragment_bmi, container,
false);
BmiButton = (Button) myView.findViewById(R.id.CalculateBmi);
BmiButton.setOnClickListener(this);
return myView;
}
#Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.CalculateBmi:
weightIn = (EditText)
getActivity().findViewById(R.id.ETtweight);
heightIn = (EditText)
getActivity().findViewById(R.id.ETHeightIn);
heightFT = (EditText)
getActivity().findViewById(R.id.ETHeightFT);
final TextView tv4 = (TextView)
getActivity().findViewById(R.id.TFDisplayBmi);
String getWeightIN = weightIn.getText().toString();
String getHeightIN = heightIn.getText().toString();
String getHeightFT = heightFT.getText().toString();
if (TextUtils.isEmpty(getWeightIN)) {
weightIn.setError("Please enter your weight");
weightIn.requestFocus();
return;
}
else if (TextUtils.isEmpty(getHeightIN)) {
heightIn.setError("Please enter your height in Inches");
heightIn.requestFocus();
return;
}
else if (TextUtils.isEmpty(getHeightFT)) {
heightFT.setError("Please enter your height in Feet");
heightFT.requestFocus();
return;
}
else {
float weight = Float.parseFloat(getWeightIN );
float heightIN = Float.parseFloat(getHeightIN) ;
float heightFT = Float.parseFloat(getHeightFT) ;
float bmiValue = calculateBMI(weight,heightIN,heightFT);
String bmiInterpretation = interpretBMI(bmiValue);
tv4.setText(String.valueOf(bmiValue + "-" +
bmiInterpretation));
}
break;
}
}
private float calculateBMI(float weight, float heightIN, float v) {
float bmi= (float) (weight/ (heightIN*v)*4.88);
float total= Math.round(bmi);
return total;
}
private String interpretBMI(float bmiValue) {
if (bmiValue < 16) {
return "Severely underweight";
} else if (bmiValue < 18.5) {
return "Underweight";
} else if (bmiValue < 25) {
return "Normal";
} else if (bmiValue < 30) {
return "Overweight";
} else {
return "Obese";
}
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
}
#Override
public void onDestroy() {
super.onDestroy();
}
#Override
public void onDetach() {
super.onDetach();
}

You don't use the same formula. Try this:
float bmi = weight * 703f / (float)Math.pow(heightIN+12f*v,2);
The formula above can be found here.
I hope it helps.

Input Validation not working android studio

For some reason my input Validation is not working. Every time I put calculate it crashes "app" when it should have an error saying that I need to input height/weight. When I do input the numbers it does calculate. Thanks for the help :). I'm new to android studio .
here is my calculation java file
public class BmiFrag extends Fragment implements View.OnClickListener {
Button BmiButton;
private double weight1=0;
private double height1=0;
public static EditText heightIn;
public static EditText weightIn;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View myView = inflater.inflate(R.layout.fragment_bmi, container, false);
BmiButton = (Button) myView.findViewById(R.id.CalculateBmi);
BmiButton.setOnClickListener(this);
return myView;
}
#Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.CalculateBmi:
weightIn = (EditText)
getActivity().findViewById(R.id.ETtweight);
heightIn = (EditText) getActivity().findViewById(R.id.ETHeight);
final TextView tv4 = (TextView)
getActivity().findViewById(R.id.TFDisplayBmi);
String str1 = weightIn.getText().toString();
String str2 = heightIn.getText().toString();
float weight = Float.parseFloat(str1);
float height = Float.parseFloat(str2) ;
float bmiValue = calculateBMI(weight, height);
String bmiInterpretation = interpretBMI(bmiValue);
tv4.setText(String.valueOf(bmiValue + "-" + bmiInterpretation));
if (TextUtils.isEmpty(str1)) {
weightIn.setError("Please enter your weight");
weightIn.requestFocus();
return;
}
else if (TextUtils.isEmpty(str2)) {
heightIn.setError("Please enter your height");
heightIn.requestFocus();
return;
}
break;
}
}
private float calculateBMI(float weight, float height) {
float bmi= (float) (weight/ (height*height)*4.88);
float total= Math.round(bmi);
return total;
}
private String interpretBMI(float bmiValue) {
if (bmiValue < 16) {
return "Severely underweight";
} else if (bmiValue < 18.5) {
return "Underweight";
} else if (bmiValue < 25) {
return "Normal";
} else if (bmiValue < 30) {
return "Overweight";
} else {
return "Obese";
}
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
}
#Override
public void onDestroy() {
}
#Override
public void onDetach() {
super.onDetach();
}
}

Try to change the code like the following,
if (TextUtils.isEmpty(str1)) {
weightIn.setError("Please enter your weight");
weightIn.requestFocus();
return;
}
else if (TextUtils.isEmpty(str2)) {
heightIn.setError("Please enter your height");
heightIn.requestFocus();
return;
}else{
float weight = Float.parseFloat(str1);
float height = Float.parseFloat(str2) ;
float bmiValue = calculateBMI(weight, height);
String bmiInterpretation = interpretBMI(bmiValue);
tv4.setText(String.valueOf(bmiValue + "-" + bmiInterpretation));
}

if (TextUtils.isEmpty(str1)) {
weightIn.setError("Please enter your weight");
weightIn.requestFocus();
return;
}
if (TextUtils.isEmpty(str2)) {
heightIn.setError("Please enter your height");
heightIn.requestFocus();
return;
}

firstly, sort your indentation and variable names out. Never name a variable str1, str2: always meaningful names. Indentation should always be consistent. This will help out but fixing in the future for readability and speed.
You're doing input validation after you actually input and assign things through
calculateBMI() method
That part of your code reads: Lets take text from text fields, interpret the BMI and then see if the textfields are empty

How Can I put a error msg if there is a blank field on Java?

I am trying to make a unit converter and it seems its working i just need to give them an error if they don't put any number on the first field and other error if they put a number on the second field (so they cant convert it backwards)
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final EditText editCentimeters = (EditText) findViewById(R.id.editCentimeters);
final EditText editInches = (EditText) findViewById(R.id.editInches);
Button buttonConvert = (Button)findViewById(R.id.buttonConvert);
buttonConvert.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
double centimeters = Double.valueOf( editCentimeters.getText().toString());
double inches = centimeters * 0.393700787 ;
editInches.setText(String.valueOf(inches));
}
});
}
}

You can use Toast to give a error message.
But I use EditText.setError() method. So user will be able see exactly which field is responsible for validation problem
Click HERE for a tutorial and Here for another solid tutorial.
This is a sample code (I do not have ADT in here, so forgive me if it needs some correction):
final EditText editCentimeters = (EditText) findViewById(R.id.editCentimeters);
final EditText editInches = (EditText) findViewById(R.id.editInches);
#Override
public void onClick(View arg0) {
boolean isValid = true;
if (editCentimeters.getText().toString().isEmpty())
{
editCentimeters.setError("This input cannot be null");
isValid = false;
}
if (editInches.getText().toString().isEmpty())
{
editInches.setError("This input cannot be null");
isValid = false;
}
if (isValid)
{
double centimeters = Double.valueOf( editCentimeters.getText().toString());
double inches = centimeters * 0.393700787 ;
editInches.setText(String.valueOf(inches));
}
}

use setError() method for this. do somthing like this
buttonConvert.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
if(editCentimeters.getText().toString().equals("")){
editCentimeters.setError("*Field Required");
}else{
double centimeters = Double.valueOf( editCentimeters.getText().toString());
double inches = centimeters * 0.393700787 ;
editInches.setText(String.valueOf(inches));
}
}
});

The Toast class will be suitable for this purpose as:-
if(editText.getText().toString().equals(""))
Toast.makeText(this,"Your Error msg",Toast.LENGTH_LONG).show();
The first argument is the Context of your Activity
Second is the CharSequence
And third is the duration of the Toast.

You must check the value inside each EditText yourself, and notify the user if its empty:
buttonConvert.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
if(!"".equals(editCentimeters.getText().toString())) {
// If the field is not empty, proceed to calculation
double centimeters = Double.valueOf( editCentimeters.getText().toString());
double inches = centimeters * 0.393700787 ;
editInches.setText(String.valueOf(inches));
} else {
// If it's empty, show a message to the user)
editCentimeters.setError("This field can not be empty");
}
}
};

editinches should b a textview so that user can't edit or add any value... Next use should do a check if editcentimeter is empty, if yes you display an error... Can be Alertdialog, toast to show the error message.
if(editcentimeter.isEmpty(){
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(context);
// set title
alertDialogBuilder.setTitle("Missing value");
// set dialog message
alertDialogBuilder
.setMessage("Please enter a value");
// set title
alertDialogBuilder.setTitle("Your Title");
// set dialog message
alertDialogBuilder
.setMessage("Please enter a numbert!")
.setCancelable(false)
.setPositiveButton("Yes",new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,int id) {
dismiss();
}
});
}
}