This is really doing my head in, I have been following these instructions but it won't work. Step three is causing me trouble. I'm note sure exactly what needs to be added where. It says;
"In the onCreate() method of your app instance, save your context (e.g. this) to a static >field named app and create a static method that returns this field, e.g. getApp():"
But I only have this at the top of my main java file:
protected static final String App = null;
The error I get is on this line, it says "The method getContext() is undefined for the type String":
String[] items = App.getContext().getResources().getStringArray(testholderint);
I figure the issues is with not following step three, and was wondering what exactly I need to add.
Once I've got this rectified my project is basically finished...
I think this line
protected static final String App = null;
shouldn't appear at all. The link you provided tells you to create a subclass of your application, like
public class App extends Application { ... }
In this subclass you should put the onCreate() and getContext() methods indicated in the code provided at that link. After doing so your last line (String[] items...) should work just fine.
Related
I know, there is a way to see which functions are called in log-cat is to write a log message on top for every function like this
#Override
protected void onDestroy() {
super.onDestroy();
Log.d("myTag","onDestroy function is called!");
// some logic
}
But it becomes irritating when you have more function.
So, I wonder if there is a way to see which functions are called in adb-logcat without writing log messages for every function.
I hope they can be fetched from somewhere in the stack but I couldn't find it.
You can try Hugo. In that case you have to annotate your methods with #DebugLog only. Then Hugo will generate logs for you (and will print out arguments and return value!). Example from GitHub:
#DebugLog
public String getName(String first, String last) {
SystemClock.sleep(15); // Don't ever really do this!
return first + " " + last;
}
And log output:
V/Example: ⇢ getName(first="Jake", last="Wharton")
V/Example: ⇠ getName [16ms] = "Jake Wharton"
Instead of printing log in every function. I (or most of the people) would suggest you to put debug.
To use debug first create breakpoints inside every function you want to check. To apply breakpoints simply left click in the area to the left of your code (refer image the pink circle represents a break-point).
Then to use Debug you have to press this button after successfully running your application.
As soon as the first method is called your application will pause at the break-point, then you can use F8 (or F6 if you are using eclipse settings) to move to next line, to move to next break-point you can press F9(or F8 if you are using eclipse settings). this way to can check all the functions being called.
This break-point method is really helpful if you just want to make sure that a particular function is being called.
Other than this if you still insist to know the details of all the functions you can store the stacktrace.
final StackTraceElement[] trace = new Throwable().getStackTrace())
StackTraceElement STrace = trace[1];
String className = STrace.getMethodName();
I've followed Google docs and created an inner class to popup a dialog in my android app.
I've been running it fine in eclipse for a while, unbeknownst to me there was an error that came up when I imported the app into android studio to start using the stable release. I was getting the "Fragment inner class should be static" error upon trying to build.
OK so I understand now after researching that this is a bad thing, but when I change it to static, I now have a bunch of references to (a) global variables , and (b) "MainActivity.class" , that are now errors.
So inside this DialogFragment inner class, how do I access my globals, or pass them in, and how do I reference MainActivity.class ?
Eg:
final EditText input = new EditText(MainActivity.this);
for (NewsEvent ne : filteredList) { //filteredList is global List of objects
...
I am calling the dialog in the onOptionsItemSelected like this:
AlertDialogFragment alert = new AlertDialogFragment();
alert.show(this.getFragmentManager(), "Alerts");
To send a Data to the DialogFragment use static newInstance(params) method.
Put the Data in a Intent and on the onCreate() method get your Data from the Intent.
Check this example from the Android dev
I'm fairly new to Java & Android, so I have little idea what I am doing.
My test program successfully creates view objects, so now I am trying to organize my code.
I want to make a separate class to manage my GUI, but it always fails.
Basic info about my gui class:
package horc.gui;
...
public class GUI{
private Context context;
From my main activity, I constructed that gui class with the app context.
gui=new GUI(getApplicationContext()); // gui is a var of type GUI, & this sets the context of the class
The problem is when I make/modify a view object that is in the class from outside, it throws an exception.
My main activity...
package horc.test;
...
GUI gui;
LinearLayout test=gui.newLinear("ff", "v"); // <-- this sets fill parent for width/height
// & vertical orientation of the vertical layout.
// Doesnt work for the reason stated above.
// I cannot manage any view objects from a separate class.
gui.lastText.setText("##########"); // <-- a variable in the class to hold the view object I am manipulating
setContentView(t);
...calls this class function:
public TextView newText(String text){
TextView test=new TextView(context);
lastLinear.addView(test);
return test;
}
I tested this similar body within the main activity & it worked fine. It only fails when I do anything from outside that gui class.
Is there a common issue that people run into when managing view objects in separate classes? I have absolutely no idea what I am doing at this point. Coming from C++, java seems like a nutty language. I cannot plan things the way I would in C++.
instead of
gui=new GUI(getApplicationContext());
try
gui=new GUI(MyActivity.this);
Please put your activity name instead of MyActivity
Everything I've read about Intents talks about using them to push data, or to start one Activity from another Activity. I want to pull data from an Activity that's already running.
The Tab Layout tutorial at http://developer.android.com/resources/tutorials/views/hello-tabwidget.html illustrates what I want to do. (My app is doing some engineering calculations instead, but the tutorial code provides a good analogy to my app.) The tutorial creates an app with three tabs, and each tab hosts a separate activity.
To expand on the example in the tutorial, suppose I select an artist in the Artists tab/activity. I want to be able to select the Albums tab/activity and have it display all the albums featuring that artist.
It seems to me that I need to use an Intent to do this. All of the tutorials I've found assume that I would create a "See albums" Button in the Artists tab/activity, and that pressing the Button would execute an Intent that starts the Albums activity and passes artistName.
I DO NOT want to create that Button. Real estate on the Artists layout is precious, and I have a perfectly good Albums tab, AND the HelloTabWidget activity already contains an intent to create the Albums tab.
Besides, a user will want to skip back and forth between Album and Artist in order to change artist selections, and the tabs are a perfectly good way to do this. There's no need to complicate the UI with another button.
So how can I have the Albums activity PULL artistName from the Artists activity when the Albums tab is selected (or the Albums layout is displayed), rather than have the Artists activity START Albums and PUSH the artistName?
Equivalents I can think of from other programming worlds:
Global variables. Discouraged in Android devt, right? And if they do exist, what are they called?
A getter, like artistName = Artists.getArtistName(); . I get the feeling that it's not that easy.
Writing to, and reading from, a file - that is, mass storage or non-volatile memory. I don't need the artistName value to be permanent. It will be reset to null every time the user launches the application.
So how is it done in the Android world? Do I use an Intent - and if so, how?
Global variables were the right answer.
I thought Java discouraged their use, but a couple of links that appeared in the "Related" links on the right margin of this window mentioned them directly. One was "Android: How to declare global variables?" and the other was "how to pass value betweeen two tab in android". Both pointed to the Application Class as the place to define global variables and methods. Armed with this new knowledge, I found an article called "Android Application Class" on the Xoriant blog that expanded on the StackOverflow answers.
It's best to review those three links first. I need to add some tips to what those authors have said.
Your Application class has to be in its own separate file. (That might be a "duh" to some people, but not to everybody.) Here's a good framework for an example called Something.java:
public class Something extends Application {
// Put application wide (global) variables here
// Constants are final, so they don't have to be private
// But other variables should be declared private;
// use getters/setters to access them
public final boolean FEET = false;
public final boolean METERS = true;
private boolean units = FEET;
#Override
public void onCreate() {
super.onCreate();
// Put any application wide (global) initialization here
}
// Put application wide (global) methods here
public boolean getUnits() {
return units;
}
public void setUnits(boolean whichOne) {
units = whichOne;
}
}
I'm using Eclipse with the ADT plug-in, in Windows XP. Eclipse doesn't always behave properly if you edit XML code directly, so it's best to open AndroidManifest.xml, then select the Application tab and enter your application name in the Name field. You don't need to put a dot or period in front of the name. Just type in the name of your class, like "Globals" or "MyApplication" or whatever. (Note that this is the default application in your Manifest. You don't have to create a separate <application></application> tag.
This step may not be necessary on an actual Android device, but it was necessary for the emulator: you need to use the getApplicationContext() command in every onCreate() and every method that will be accessing the global variables and methods. I tried to put it outside of onCreate() with the rest of my activity wide variables, and it didn't work. Putting it inside every method seems wasteful, but both the emulator and the Android device work fine with it that way. Here's a sample showing how I used it:
public void fooBar() {
// Access to global variables and methods
final Something s = (Something)getApplicationContext();
// ...
// This next line demonstrates both a global method and a global variable
if (s.getUnits() == s.FEET) {
// do something with feet
} else {
// do something with meters instead
}
// ...
}
Those were the only hiccups I encountered. The three references that I have listed, taken together, are otherwise pretty complete.
So far i've been writing my Android app just by typing names in to methods. I am now sorting this out, going through and putting these into string.xml instead and referencing the string using:
txt.setText(this.getString(R.string.string_name));
However, when trying to use this in a static context (in public static void), it does not work and gives an error.
Does anyone have any pointers of how to overcome this? I am fairly new to Java/Android programming and this is the first time I have come across this problem. Any help is much appreciated.
Extra code:
public static void ShowCatAddedAlert(Context con)
{
AlertDialog.Builder builder=new AlertDialog.Builder(con);
builder.setTitle("Add new Category");
builder.setIcon(android.R.drawable.ic_dialog_info);
DialogListner listner=new DialogListner();
builder.setMessage("Category Added successfully");
builder.setPositiveButton("ok", listner);
AlertDialog diag=builder.create();
diag.show();
}
Assuming that txt is a TextView, then you can just do txt.setText(R.string.string_name). You can usually reference to a string by it's resource id rather than getting it explicitly. More on that http://developer.android.com/guide/topics/resources/string-resource.html
String resources, as all resources, are resolved from the application from a Context instance (usually that's an Activity instance or the Application instance). In a static context, you don't have any instances unless you pass them in to your static methods.
One way or another, you need to do something in a non static context. Either you keep a copy of the Resources object around and pass it to your static methods, or you pass a Context instance around that is capable of resolving your resources, or you have a static Resources object that gets set at some point before your static methods get called.
That being said, you might want to revisit whether or not you absolutely need these methods to be static.