I have been having a problem with a Boolean in an if statement all day and it is really starting to irritate me now!! I have looked at other Android threads on here and the solutions just don't seem t work.
My code started off like this:
public class MainActivity extends Activity
{
public static boolean isSignedIn = false;
public final static String USERNAME_MESSAGE = "com.example.libnoise.MESSAGE";
Button btnSignIn;
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btnSignIn = (Button) findViewById(R.id.btnSignIn);
Intent intent = getIntent();
String message = intent.getStringExtra(PlayZone.USERNAME_MESSAGE);
if(isSignedIn == false))
{
btnSignIn.setText("SignIn");
}
else
{
btnSignIn.setText(message);
}
}
Then I had a thought that made it's not like other languages and I only need one "=" sign so I had it as this:
if(isSignedIn = false)
{
btnSignIn.setText("SignIn");
}
else
{
btnSignIn.setText(message);
}
That didn't work and that's when I started looking online, after finding a previous thread on here changed it to the following:
if("false".equals(isSignedIn))
{
btnSignIn.setText("SignIn");
}
else
{
btnSignIn.setText(message);
}
Now that doesn't look right to me in the first place but hoped it would work and it didn't.
As this is the MainActivity it loads first however since I added all this, the app crashes before it will even load when I take out the if statement it work as expected.
Any ideas?
This
if (isSignedIn == false)
is perfectly correct. (You could also write if (!isSignedIn), but that's just a matter of style.)
Note that, since you never change the value of isSignedIn (at least not in the code you have shown us), it will always be false.
i think you can simply use
if(!isSignedIn)
{
btnSignIn.setText("SignIn");
}
else
{
btnSignIn.setText(message);
}
the way you followed is also correct i didn't find any mistake in except you are using extra bracket in condition if(isSignedIn == false))
If statements with boolean are same how you do it in Java, == is the right way to compare
The problem in your code is extra bracket
if (isSignedIn == false))
Just to deviate from the question, but point out what is possibly your problem, your null pointer could be because you are accessing a UI object that may well not be ready to have it's text set yet.
While some API versions cope fine with what you're doing, I've found many device/API combos simply aren't ready to have anything changed from what's in the xml until onStart. The general guidance is to load data in onCreate, but not start doing anything until onStart.
Related
I have a ITextViewer object and from that the StyledText widget in which Eclipse displays code. I want to hihglight one single line that is defined by the line number. Therefore I added a LineBackgroundListener to the StyledText object an wrote the following code:
private class HighlightLine implements LineBackgroundListener {
#Override
public void lineGetBackground(LineBackgroundEvent event) {
if (lineToHighlight != -1) {
int line = ((StyledText) event.widget).getLineAtOffset(event.lineOffset);
if (line == lineToHighlight) {
event.lineBackground = styledText.getSelectionBackground();
} else if (line == previousLineToHighlight) {
event.lineBackground = styledText.getBackground();
}
styledText.redraw();
styledText.update();
}
}
}
This work more or less fine, but the problem is, it very much slows down Eclipse. It's probably the case because it has to update the Widget very often and that's not optimal. However, I couldn't think of another way to to it after a lot of trials. Any idea?
You don't need these (expensive) calls:
styledText.redraw();
styledText.update();
lineGetBackground is called during the draw line operation so it does not need a redraw or update.
Note: If the StyledText control has any StyleRange ranges they may override the background.
I have two activities; the first activity starts the second one with some data passed through the intent.
Intent i = new Intent(this,BActivity.class);
i.putExtra("identify", "c2f");
startActivityForResult(i, 1);
In the second activity, I want to make some TextViews/EditTexts visible (which are initially set to invisible) based on the information passed from the first activity.
Here's the code for that:
tv1 = (TextView)findViewById(R.id.textView2);
tv2 = (TextView)findViewById(R.id.textView3);
et1 = (EditText)findViewById(R.id.editText1);
et2 = (EditText)findViewById(R.id.editText2);
button = (Button)findViewById(R.id.send_result);
Bundle extras = getIntent().getExtras();
String identifier = extras.getString("identify");
if(identifier == "c2f")
{
tv1.setVisibility(0);
tv1.setText("Celcius");
et1.setVisibility(0);
}
else if(identifier == "f2c")
{
tv1.setVisibility(0);
tv1.setText("Fahrenheit");
et1.setVisibility(0);
}
else if(identifier == "currency")
{
tv1.setVisibility(0);
tv1.setText("Amount");
tv2.setVisibility(0);
tv2.setText("Conv. Rate");
et1.setVisibility(0);
et2.setVisibility(0);
}
Now when the second activity starts, none of these TextViews or EditTexts seem to get visible!
identifier (string) holds the correct value passed from first activity and it even goes into the if conditions, but it doesn't make any view visible.
Am I making any mistake in trying to make these views visible?
Use .equals instead of == to string comparison. You can also use the variable after the quoted string to avoid nullpointer. And you can use TextView.VISIBLE, it's a constant to get it visible.
if("c2f".equals(identifier))
{
tv1.setVisibility(TextView.VISIBLE);
tv1.setText("Celcius");
et1.setVisibility(TextView.VISIBLE);
}
Simply use the View's constants for this.
your_view.setVisibility(View.VISIBLE);
This will make your View visible.
your_view.setVisibility(View.INVISIBLE);
This will make it invisible but still with the layout visible (basically, the space where it goes remains untouched)
your_view.setVisibility(View.GONE);
This will make your View disappear, like it never existed!
As pointed by giacomoni, please use equals for String comparison. Here is a link to explain why.
http://javarevisited.blogspot.in/2012/03/how-to-compare-two-string-in-java.html
Also, try using the standard View.VISIBLE etc constants for showing and hiding views. They are much more easy to use and understand. Happy coding. :)
I've just started learning to use Robotium for testing my app. I have written a test case that resets a list of stats, and then checks if the values are equal to 0. The code is below:
public void testClearStats() {
solo.clickOnButton("Clear Stats");
solo.clickOnButton("Yes");
TextView views = (TextView) solo.getView(R.id.textViewsNum);
TextView prompts = (TextView) solo.getView(R.id.textPromptsNum);
TextView completions = (TextView) solo.getView(R.id.textCompleteNum);
assertEquals("0", views.getText().toString());
assertEquals("0", prompts.getText().toString());
assertEquals("0", completions.getText().toString());
}
The test was failing when it shouldn't because it was checking the values of the TextViews before their results were reset. To get around this, I added this line:
solo.waitForActivity(solo.getCurrentActivity().toString());
With this statement the test passes but it seems to take an unnecessary long time to complete. I was wondering if there was a better/correct way of way doing this, or is this the best way of doing it?
Thanks
You will have to wait on something, what you choose will depend on your application and without looking at it i cannot answer what will be the best thing to wait for.
What visual indicators do you have for the reset to occur? do you have a new activity open? Is there text telling it has complete? if it is literally just the three textfields. if it is then you might manage to use solo.waitfortext("0") although the better way will be to use the new concept of conditions and use the solo.waitForCondition(method) (the condition will probably be to wait for the text to be 0, but you would have put the condition into one place and then if you later find a better way then you only have to change it once).
public class WaitForReset implements Condition
{
public boolean isSatisfied()
{
TextView views = (TextView) solo.getView(R.id.textViewsNum);
TextView prompts = (TextView) solo.getView(R.id.textPromptsNum);
TextView completions = (TextView) solo.getView(R.id.textCompleteNum);
if(isViewZero(views) && isViewZero(prompts) && isViewZero(completions))
{
return true
}
else
{
return false;
}
}
private isViewZero(TextView textView)
{
if((textView!=null) && (textView.getText().toString() ==0))
{
return true;
}
else
{
return false;
}
}
}
You can then assert on the value of the waitforcondition being true!
You can always use waitForActivity and choose a specific timeout.solo.waitForActivity(YourActivity.class, timeout);
So I'm trying to create an activity that passes some values into another activity and then, depending on those values, chooses one of several different layouts.
I know that the values are passed through fine, but it won't display the layout (or any layout, it just stays on the previous screen). My code is:
public class ContactDisplay extends GetContact {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Bundle extras = getIntent().getExtras();
String nameChosen = extras.getString("nameSpinner");
String addressChosen = extras.getString("addressSpinner");
if((nameChosen == "Michael") && (addressChosen == "Michaels Address")){
setContentView(R.layout.contact1_layout);
}
}
}
I've only set it up to with one of the layouts so far, but it should work if Michael and Michaels Address are chosen. Does anyone have any idea where I'm going wrong?
Use this code instead:
if((transportItemChosen.equals("Michael")) && (locationItemChosen.equals("Michaels Address"))){
setContentView(R.layout.contact1_layout);
}
In Java you want to use the equals() function when comparing strings not the == operator.
The first thought is that I would try to not use hard coded values for extras because you can misspell something and it is very easy to get stuck ... if that is not the problem then try to make some logs and see what exactly you receive in transportItemChosen and locationItemChosen
EDIT:
And yes, to compare two Objects you have to use equals() method not the == operator.
i'm trying to access an EditText from an onClick() method within an onClickListener implementation for a button. here's the code:
transmit.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
//data validation
///////////////////////
boolean valid = true;
if(((EditText)findViewById(R.id.drv_in)).getText().toString() == "") {
TX_FAIL_TEXT = "Missing Driver ID!";
showDialog(DIALOG_FAIL);
TX_FAIL_TEXT = "Transmission Failed!"; //reset the dialog fail text to default
valid = false;
}
Log.e("smsDRVERR",((EditText)findViewById(R.id.drv_in)).getText().toString());
//begin transmission
///////////////////////
if(valid) {
showDialog(DIALOG_TX_PROGRESS);
Thread t = new Thread(txRunnable);
t.start();
} else {
//do things if needed
}
}
});
the Log.e is never called (does not show up in logcat). and the program executes as if the conditional statement doesn't exist. how do i reference layout items properly in an onClick implementation? i've also tried the following line:
Log.e("smsDRVERR",((EditText)smsActivity.this.findViewById(R.id.drv_in)).getText().toString());
which was alluded to in this question i found on SO:
Inside OnClickListener I cannot access a lot of things - how to approach?
but it does not solve the problem. i'm missing something that i need to reference these items within this inner class, or maybe i have my syntax a bit jarbled. any help is appreciated.
You are not comparing your String correctly.
if(((EditText)findViewById(R.id.drv_in)).getText().toString() == "") {
is checking if the objects are equal, whereas you want to check if the values are equal. You should be using:
if(((EditText)findViewById(R.id.drv_in)).getText().toString().equals("")) {
Personally, I'd assign the value returned by getText to a String variable, rather than calling getText multiple times:
String myEditTextValue = (EditText)findViewById(R.id.drv_in)).getText().toString();
...
if ("".equals(myEditTextValue)) {
First, is your onClick method being called? Second, don't use == to do string comparisons; use .equals(). (Strings that are equal are not necessarily the same object, which is what == tests.)