So, I am messing around with java/android programming and right now I am trying to make a really basic calculator. I am hung up on this issue though. This is the code I have right now for getting the number thats in the textview and making it an int
CharSequence value1 = getText(R.id.textView);
int num1 = Integer.parseInt(value1.toString());
And from what I can tell it is the second line that is causing the error, but im not sure why it is doing that. It is compiling fine, but when it tries to run this part of the program it crashes my app. And the only thing thats in the textview is numbers
Any advice?
I can also provide more of my code if necessary
You can read on the usage of TextView.
How to declare it:
TextView tv;
Initialize it:
tv = (TextView) findViewById(R.id.textView);
or:
tv = new TextView(MyActivity.this);
or, if you are inflating a layout,
tv = (TextView) inflatedView.findViewById(R.id.textView);
To set a string to tv, use tv.setText(some_string) or tv.setText("this_string"). If you need to set an integer value, use tv.setText("" + 5) as setText() is an overloaded method that can handle string and int arguments.
To get a value from tv use tv.getText().
Always check if the parser can handle the possible values that textView.getText().toString() can supply. A NumberFormatException is thrown if you try to parse an empty string(""). Or, if you try to parse ..
String tvValue = tv.getText().toString();
if (!tvValue.equals("") && !tvValue.equals(......)) {
int num1 = Integer.parseInt(tvValue);
}
TextView tv = (TextView)findviewbyID(R.id.textView);
int num = Integer.valueOf(tv.getText().toString());
Here is the kotlin version :
var value = textview.text.toString().toIntOrNull() ?: 0
TextView tv = (TextView)findviewbyID(R.id.textView);
String text = tv.getText().toString();
int n;
if(text.matches("\\d+")) //check if only digits. Could also be text.matches("[0-9]+")
{
n = Integer.parseInt(text);
}
else
{
System.out.println("not a valid number");
}
this code actually works better:
//this code to increment the value in the text view by 1
TextView quantityTextView = (TextView)findViewById(R.id.quantity_text_view);
CharSequence v1=quantityTextView.getText();
int q=Integer.parseInt(v1.toString());
q+=1;
quantityTextView.setText(q +"");
//I hope u like this
Related
I'm creating a simple app that calculates BMI and I'm struggling with one small problem. I have 2 edit text fields, which are allowed to type numbers only. The point is when one of the text fields are empty the app is to generate a toast message and display nothing. I wrote an if statement to check if an edit text is empty and if not just to calculate further.
All would work fine, but I needed to put return statement and Android Studio suggested me writing "return 0;" so did I.
This is the code responsible for calculations:
/// parse input value from edittext field into double type
private double weight() {
EditText weightInput = (EditText) findViewById(R.id.weight_input);
String sWeightInput = weightInput.getEditableText().toString();
if (sWeightInput.matches("")){
Toast.makeText(this, R.string.noweight, Toast.LENGTH_SHORT).show();
} else {
String weight = sWeightInput;
double weightTyped = Double.parseDouble(weight);
return weightTyped;
}
return 0;
}
private double heigh() {
EditText heightInput = (EditText) findViewById(R.id.height_input);
String sHightInput = heightInput.getEditableText().toString();
if (sHightInput.matches("")){
Toast.makeText(this, R.string.noheight, Toast.LENGTH_SHORT).show();
} else {
String height = sHightInput;
double heightTyped = Double.parseDouble(height);
heightTyped = heightTyped / 100;
heightTyped = heightTyped * heightTyped;
return heightTyped;
}
return 0;
}
//make calculations and return the output value
public void makeCalculations(View view){
double result = weight() / heigh();
String message = String.valueOf(result);
TextView bmiSummaryTextView = (TextView) findViewById(R.id.bmi_calculation);
bmiSummaryTextView.setText(message);
}
This is the interface of the app.
To sum up, all I want to do is to display nothing instead of NaN (not a number).
Return a non-primitive Double rather than a double, and you will be able to use null as a value. Be sure to check for this value though, or you'll run into a NullPointerException.
Alternatively, you could look into using optionals, but since you're using Android you might need an external library for that (unless your minimum SDK version is high enough, then you can use Java 8's Optional).
The problem is probably if in your calculation weight() / height height is 0 it outputs NaN because it is infinity.
Also put your return 0; after Toast.makeText() in the condition. AS grumbles because you are not returning a value in the if branch.
if (sHightInput.matches("")){
Toast.makeText(this, R.string.noheight, Toast.LENGTH_SHORT).show();
return 0;
}
Maybe this will help you also to avoid dividing by zero.
public void makeCalculations(View view) {
String message = "Invalid input!";
if (weight() > 0 && height() > 0) {
double result = weight() / heigh();
String message = String.valueOf(result);
}
TextView bmiSummaryTextView = (TextView) findViewById(R.id.bmi_calculation);
bmiSummaryTextView.setText(message);
}
Can someone tell me, why my app keep getting crashed. Cannot find solution for this and why its happening when TextField is empty
public void contanges(View v){
TextView wynik = (TextView)findViewById(R.id.wynik);
double b = Double.parseDouble(wynik.getText().toString());
if(wynik.getText().length() == 0 ){
wynik.setText("Bad opperand!");
}else if(b % 180 ==0){
wynik.setText("Bad opperand!");
}else {
BigDecimal a = new BigDecimal(wynik.getText().toString());
BigDecimal result = new BigDecimal("0");
result = new BigDecimal(1 / Math.tan(Math.toRadians(a.doubleValue())));
wynik.setText(result.toString());
}
}
Don't check for 0 length. Instead use TextTextUtils.isEmpty(). This way, you can check if the TextView actually has text to parse before you parse it.
TextView wynik = (TextView)findViewById(R.id.wynik);
if (TextUtils.isEmpty(wynik.toString().trim())) {
// Do your stuff here
}
Your error is in this line :
Double.parseDouble(wynik.getText().toString());
You are trying to parse an empty string to double which is not valid.
Add this line before that
if(wynik.getText().length() > 0){
Double.parseDouble(wynik.getText().toString());
}
Also it depends what you are passing as a textview value because if it is not been able to parse than also it will throw an exception
Try passing a double value to edittext when not empty.
New Android/Java coder. Trying to replicate in Android app a project I built in MS-Access.
I have a layout with similar named TextViews, like text10, text12, etc. In MS-Access I can dynamically build those names with collection referencing:
For X = 10 To 15
Me.Controls("text" & X) = Null
Next
There is no array required. So looking for structure in java that can accomplish the same functionality.
I want to dynamically set background color of multiple TextView based on two inputs. One is to build TextView reference and the other is a state indicator that will determine color.
Here is one procedure calling setSubColor:
public void Clear(MenuItem mi) {
puz.setText("");
sol.setText("");
for (int i=0; i<26; i++) {
setSubColor(aryA[i].charAt(0), 0);
What I have so far for setSubColor:
public void setSubColor (char c, int i) {
TextView v = (TextView) >>>dynamically reference v using name built with ("tv" + c)
if (i == 0) {v.setBackgroundColor(Color.TRANSPARENT);}
else {v.setBackgroundColor(Color.YELLOW);}
You can get the res id from the res name at runtime. So if your textview had name "text1", you could get the integer id by using:
int id = getResources().getIdentifier("text1", "string", getPackageName());
TextView view = findViewById(id);
But do so only as a last resort, it's error prone, slow and somewhat of an anti pattern.
EDIT by OP: No matter what the name argument is always returns 0 but marked as answer because it led to the following code that works exactly as I want, anti-pattern or not.
TextView v = (TextView) findViewById(getResources().getIdentifier("tv" + c, "id", getPackageName()));
Instead of the TextView Id field use its Tag field.
String tag = (String)textView.getTag() and textView.setTag(Object tag) with tag instanceof String
then you can find the TextView by Tag
I'm working on a android app that send and recieves data. In the app i have a button an a few texviews. When i press the button then data (two chars) will be send. And an the data that has been send will be shown in two tekst views.
I did the same with two integers and that worked now i want to do the same with bytes and chars and that failes.
The logcat gives the following error:
10-28 09:27:19.338: E/AndroidRuntime(13138): android.content.res.Resources$NotFoundException: String resource ID #0x0
Beloww is the onClick lisener code:
#Override
public void onClick(View v) {
// Control value
ArrayOutput[0] = 'B';
ArrayOutput[1] = 'B';
//Creating TextView Variable
TextView text = (TextView) findViewById(R.id.tv);
//Creating TextView Variable
TextView statustext = (TextView) findViewById(R.id.status);
//Sets the new text to TextView (runtime click event)
text.setText("You Have click the button");
// Convert string to bytes
ArrayOutput[0] = ArrayRecieved[0];
ArrayOutput[1] = ArrayRecieved[1];
final char Byte1 = (char) ArrayOutput[0];
final char Byte2 = (char) ArrayOutput[1];
final TextView Xtext = (TextView) findViewById(R.id.xtext);
final TextView Ytext = (TextView) findViewById(R.id.ytext);
Ytext.setText(Byte1);
Xtext.setText(Byte2);
try
{
statustext.setText("Sending....");
server.send(ArrayOutput);
statustext.setText("Sending succes");
}
catch (IOException e)
{
statustext.setText("Sending failed");
Log.e("microbridge", "problem sending TCP message", e);
}
}
});
Does anybody have a sugestion what the problem might be? Any suggestions is welcome! if i need to supply more information please say so.
Update
Thanks you all for your suggestions! For the onclick function it works! I tried to do the same for the recieve function. This event handler funnction is called when there is data avalable.
When i use the setText function it crashes my ap after a few cycles, in this function i have three settext operations. only the first one is called (then the app crashes). When i change the ordere of these operations then still only the first one is called. Could it be that the app displays the first settext operation but crashes? I use dummy data, so when the eventhandler function is called the actual recieved data is not used, but still the app crashes after the first operation. Does anybody have a sugestion?
On the other side data is send every second.
Below is the onRecieve (event handler)function:
#Override
public void onReceive(com.example.communicationmodulebase.Client client, byte[] data)
{
Log.e(TAG, "In handler!");
//Control value
ArrayRecieved[0] = 'C';
ArrayRecieved[1] = 'B';
if (data.length < 2){
return;
}
// Set data that has been recieved in array
//ArrayRecieved[0] = data[0];
//ArrayRecieved[1] = data[1];
char Byte1 = (char) ArrayRecieved[0] ;
char Byte2 = (char) ArrayRecieved[1] ;
TextView Xtext = (TextView) findViewById(R.id.xtext);
TextView Ytext = (TextView) findViewById(R.id.ytext);
Xtext.setText(""+Byte2);
Ytext.setText(""+Byte1);
TextView textRecvStatus = (TextView) findViewById(R.id.RecvStatusText);
textRecvStatus.setText("In handler!");
}
});
TextView has two methods like
TextView.setText(CharSequence) and TextView.setText(int).
1) first method directly assigns a text to TextView which is passed as CharSequence (can be String,StringBuffer,Spannable...)
2) second methods searches for the String resource that you define in Resources with ID passed as parameter.
and you are passing char as parameter. this char is type casted into int and invokes it as TextView.setText(int) and searches for the Resource String with that int ID whose value is not defined in Resources.
type cast char as String like String.valueOf(char) and try once...
The signature for the method you are using takes a CharSequence, hence sequence of characters. Using setText(someEmptyString + Byte1), you create a sequence of characters from the concatenation of someEmptyString (which you would define as "") and Byte1.
set with some change like
Ytext.setText(""+Byte1);
setText() expects string or resource id (int). If you want to display numeric value, you need to convert it to string, i.e.:
setText(String.valueOf(someInt));
Try out as below:
Ytext.setText(""+Byte1);
Xtext.setText(""+Byte2);
I have the following setup. In my xml i have a bunch of image views. I am trying to show only one of them depending on the number set in preferences and the day of week. This must be really easy but i can't find out the correct way to pass variable into findViewByID. Here is code snippet:
String groupName = "R.id."+prefs.getString("groupListKey", "<unset>")+"_"+(Calendar.getInstance().get(Calendar.DAY_OF_WEEK));
ImageView image = (ImageView) findViewById(groupName);
findViewById() expects you to pass it an integer that represents a resource identifier. You are trying to pass it a string
Your best bet would be to have a conditional statement that evaluates your day of week and returns you the proper ID rather than doing it the way you are
int resourceId = 0;
switch (Calendar.getInstance().get(Calendar.DAY_OF_WEEK)) {
case Calendar.SUNDAY:
resourceId = R.id.sundayView;
break;
case Calendar.MONDAY:
resourceId = R.id.mondayView;
break;
...etc
}
ImageView image = (ImageView) findViewById(resourceId);
findViewById receives an int as an argument, which is one of the generated in the R.id class.
You can have an array with your ids:
int[] imagesIds = new int[] { R.id.image1, ... R.id.image7 };
And then determine the index based on your conditions:
int imageIndex = ...
ImageView image = (ImageView) findViewById(imagesIds[imageIndex]);