Develop Reference

I can't see my logs in Android Studio logcat

Here's a simple app, I'm trying to create logs in the printToLogs method.
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.v("Log0","test");
}
public void printToLogs(View view){
TextView menuTextView1 = findViewById(R.id.menu_item_1);
TextView menuTextView2 = findViewById(R.id.menu_item_2);
TextView menuTextView3 = findViewById(R.id.menu_item_3);
String item1 = (String) menuTextView1.getText();
String item2 = (String) menuTextView2.getText();
String item3 = (String) menuTextView3.getText();
Log.v("Log1",item1);
Log.v("Log2",item2);
Log.v("Log3",item3);
}
but logs with the tags Log1, Log2, Log3 are not shown at all in the logcat, what does show up is the Log0 in the onCreate method, but the other ones in printToLogs never show up when I search for them at all. I attempted re-installing the app and restarting logging. That didn't work.
The menu items are: Mango sorbet, Blueberry pie, Chocolate lava cake. And yes, I tried searching for them, and they are not in the logcat either.

If this is your actual code, you aren't even calling printToLogs in the onCreate method. You should be more diligent before posting something simple like this.

Barring a serious runtime environment issue, this problem should be fairly easy to solve.
It seems as if the printToLogs(View view) method is to be executed in response to the user clicking a button. If so, try including the following line in your activity_main.xml if you haven't already:
android:onClick="printToLogs"
This will bind the button on the UI with the printToLogs(View view) method.
If, on the other hand, printToLogs(View view) is intended to be a standalone method (i.e. one that should execute regardless of user input) it should not accept a View as an argument. For your purposes, its parameter list should be completely empty. In other words, the method signature should read:
public void printToLogs()
Also, it should be called within the onCreate(Bundle savedInstances) method. Add the following to the onCreate(Bundle savedInstances) method:
printToLogs();
This will initiate the execution of the method as soon as the app begins to run.
Make sure the logcat filter is set to "Verbose" when testing like so: (img is link since apparently I need 10 rep. to embed images into answers directly)
logcat filter

heyy add your method/function name in your button by using property section or just android:onClick in your xml file and then it will be solved

TextView setText Cannot resolve type

Im using Android Studio, trying set text to Text View but every time i do this
TextView test = (TextView) findViewById(R.id.testView);
test.setText("fds");
on Android Studio i see Cannot resolve symbol 'setText'.
Can someone tell me what im doing wrong?

setText() will accept String which you have passed, so there is no issue in that.
One possible reason for this might be you have not written your code inside onCreate() or onCreateView().
If it is Activity you need to use these lines after setContentView() in onCreate().
If it is Fragment you need to use these lines after inflating your view in onCreateView().
Second reason, you might be having one more test variable of different type like String or something else

Buttons using onClickListener

am new to android
I have seen many examples on creating buttons, but i just can't get what does each line mean :(
take the following piece of code as an ex.
connect = (Button) findViewById(R.id.button_connect)
connect.setOnClickListener(connectListener)
private OnClickListener connectListener = new OnClickListener() {
public void onClick(View v) {
Log.i("CONNECT PRESSED", "press")
// ....
// ....
// ....
};
what i know is that the first line Defines a button, but wht is findViewbyId?
i know the second line
but then when defining the listener, what's the log.i?
nd r "connect pressed" and "press" just labels for the button? f so why there r two for a single button...

You should have an additional Button connect; before those lines.
connect = (Button) findViewById(R.id.button_connect) // findViewById() in layman term it means, finding view by id. Which also means finding the view(button/textview/edittext) by ID(value you stated in your main.xml for the view. e.e. android:id=#+id/"")
connect.setOnClickListener(connectListener) //listens to a click when clicked
private OnClickListener connectListener = new OnClickListener() { //if button of android:id="button_connect" is clicked, Do this method.
public void onClick(View v) {
Log.i("CONNECT PRESSED", "press") //prints message in your logcat
// ....
// ....
// ....
};
If you still don't understand what does findViewById(), just think of it this way. View is man. Id is name. So in the end you are finding the man by name("Whatever this is")

In Android you normally define the layout of an Activity in an XML file. Each View element in a layout that you want to interact with in code needs an id. In you example the layout XML file needs to have a button with the id button_connect.
In the onCreate() method of an Activity you normally call setContentView() and pass it the layout you want to use in this Activity. E.g. setContentView(R.layout.my_layout); where your layout file's name is my_layout.xml.
The setContentView() method builds up the defined layout as objects and with findViewById(R.id.button_connect) you get a reference to a Button object from this layout whose id is button_connect.
Log.i() is simply logs the message "press" under the tag "CONNECT PRESSED" in the log cat.

It seem to be you didn't read basic things about android app development. Android Developers website providing information to learn android app development with good examples and tutorials. You are asking very basic things by just copying the code from tutorials.
Actually its not the right place for this kind of questions. First do practice by reading tutorials around the web.
Coming to your doubts regarding code you posted here, those are very basic things.
findViewById() finds a View by field Id, which is declared in XML layout file as below
Log.i() is LogCat info message displayed in your logcat window when debugging is enabled in your app.

in your example you probably have defined an xml layout file as the style of your activity with setContentView(R.layout.myXMLLayout);
If not, findViewById(R.id.button_connect) will fail.
R.id.button_connect refers to an id created in your xml layout.
There has to be a line android:id="#+id/button_connect" in a < Button > tag.
findViewById finds this Button (which is more genereally a view, which is why you have to cast it to a Button with the (Button) before findViewById(...) ). You then refer to exactly the button you've put in your xml.
Log.i("CONNECT PRESSED","press"); isn't necessary at all. It's just logging the press of the button and displays it in the log cat. It can be removed without any further impact. This is for debugging only and should be removed for any final (public) versions of your code.

android setBackgroundColor in runtime and other general confusion help?

i have a row of buttins created like this
i want to change the background colour at runtime in code.
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
LinearLayout track1 = (LinearLayout)findViewById(R.id.my_toggle_container);
for (int i = 0; i<32; i++) {
ToggleButton tgl = new ToggleButton(this);
tgl.setId(i);
...
track1.addView(tgl);
this names the id of the togglebuttons 1, 2, 3... (i presume?)
i have an int variable called 'xBtn' that changes 1, 2,..
this is how i get a reference to the button using xBtn
String buttonID = ""+xBtn;
int resID = getResources().getIdentifier(buttonID, "id", "com.thing");
//find the button
ToggleButton tb = (ToggleButton) findViewById(resID);
//change its colour
tb.setBackgroundColor(Color.BLUE);
it crashes on the setBackgroundColor line.
it may be obvious to someone whats wrong and thats what im hoping
any help would be totaly ace ta
thanks
main.xml
<LinearLayout android:layout_width="wrap_content" android:layout_height="match_parent" android:id="#+id/my_toggle_container" android:orientation="vertical">

The id of your togglebuttons is gonna be a number from 1 to 32... However, trying to find the toggle button by id will return null because simply instantiating a new toggle button and giving an id wont help you. findViewById looks in the parent view for a child view with the specified id. If you havent added that toggle button with that id to the view, then findViewById will return null. I am 99.99% sure even without looking at the log, that it crashes because you are calling setBackgroundColor on a null object.
In other words, the id that you set a view to is only relevant once the view is actually added to a parent view. In your case you are probably trying to add these toggle buttons to your main content view, in which case you need grab hold of that view that you used for setContentView and call addView on that view and pass in each new toggle button. Note that this will probably not look right unless you also specify layoutparams for the togglebuttons.
EDIT
If thats your entire main.xml, then you've got other issues. Post the full xml file. In any event, you still are going to have to do what I've said, which is to grab hold of the view or a child view of that view and then add the toggle buttons to it via addView (after giving the togglebuttons their proper ids). Once the button has been added, then you can find it. Note though that if you're gonna add the toggle buttons to a child view of your main view, then you'll likely have to grab hold of that child view and call findViewById on THAT.
For example, you can do a nested call like this. findViewById(1) <--- gets you the LinearLayout or whatever inside of your main content view, then once you have that you can call addView on it. So LinearLayout ll = (LinearLayout)findViewById(someNumber); ll.addView(tb);

Try to use the method setTag() , and then you can get all your ToggleButton by using : findViewByTag();

Perhaps tb is null? Could you check that out?

To expand on what LuxuryMode said... What gets an ID INTO your java is inflating it via setContentView and setting it as content. That's why it's ok to have overlapping (duplicate) IDs in different layouts. You can have #+id/submit_button in layout1.xml and in layout2.xml and the Activity will get you the object via findViewById(R.id.submit_button) based on which one you have loaded into setContentView() at any given moment.
So, we're all guessing that you're probably not setting the content view and hoping that the code will find your object in your non inflated XML, which it won't. Which would lead (as everyone has guessed) to you now dealing with a null object, which you obviously can't set a background color on.
I know it gets confusing cause you have the XML RIGHT THERE!!! But the reality is that the xml isn't "alive". It's just stuff for you to look at until you have tasked the Application with inflating it and converting all of it into Android objects of some kind. A lot of the time this is done mostly transparently to you, so, it's easy to forget that none of these things really exist.

It's very likely that tb is null, because findViewById() didn't go as you expected.
You can verify this by surrounding the erroneous line with try.. catch block:
try {
tb.setBackgroundColor(Color.BLUE);
} catch (Exception e){
}
and watch for the message of e. It's likely to be null pointer exception.
In fact, I think you should not use getResources().getIdentifier(buttonID, "id", "com.thing") in the first place. It seems to me that all these resources are continuously numbered in R file, thus you should simply get the first id (as an integer), and then increment on that.
That is, you should do things like:
// The following code is not tested; I just wrote it here on SO.
for (int resID = R.id.button1; resID <= 32; resID++) {
ToggleButton tb = (ToggleButton) findViewById(resID);
tb.setBackgroundColor(Color.BLUE);
}
this should make all 32 buttons blue.

XML scope in Android

Is there anywhere that I can find documentation on the scope of the XML files? I have an app I am currently working on and have been struggling with getting a feature to work and it seems that the problem I am having is that I am trying to access an element in an XML file that must be out of scope. To simplify the layout, my project has main.xml, sub.xml, main.java, and sub.java files in it. As you can probably guess, main.java works with main.xml and sub.java is working with the elements in sub.xml. Here's where the issue comes in, I have a TextView element that is created in main.xml that I would like to modify the text in, but the action that would trigger it will occur in sub.java. I can't figure out how to change it from sub.java, and I can't figure out how to move the element into sub.xml. The code I am using is pretty simple:
TextView titleText = (TextView) findViewById(R.id.myTitle);
titleText.setText(filePath);
I get a FC every time I run the app, but if I move the code into main.java, it runs flawlessly. If anyone can offer any ideas, or point me in the direction of some documentation that would explain what java files can access what elements in which xml files, that would be awesome! Sorry for the novel, but I'm just struggling to get the point across. Thanks.

try like this Bryan in Main.xml file it works with no issue...........Declare first & then Initialize it...
public class Main extends Activity {
static TextView tv;
static Button submit;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
tv = (TextView) findViewById(R.id.header_text1);
}
}

Activity.findViewById(int) only works if that view is in the activity's layout. So no, you can't refer to a view in main.xml because that layout doesn't apply to sub.
Do you have any TextViews in sub.xml called myTitle?

You can access the the textview of main.java(main.xml) in submain.java as follows
In main.java write the following code
static TextView titleText = (TextView) findViewById(R.id.myTitle);
titleText.setText(filePath);
and u can access this submain.java as
Main.titleText.setText(filePath);