Develop Reference

Error while trying to execute Sugar database CRUD operation

I (having mediocre developing skills) actually try to use Sugar as a database wrapper for my android project.
Therefore, I was following along the "Getting-Started-Guide" (http://satyan.github.io/sugar/getting-started.html) to get ready as soon as possible.
I created a class for my entities, called DataSet.java :
import com.orm.SugarRecord;
public class DataSet extends SugarRecord{
int someData;
double evenMoreData;
public DataSet(Context ctx){
super(ctx);
}
public DataSet(Context ctx,
int someData,
long evenMoreData) {
super(ctx);
this.someData = someData;
this.evenMoreData = evenMoreData;
}
}
I call the class in the following way:
someGreatClass something;
someMoreGreatCode somemore;
DataSet dataSet = new DataSet(
ctx, // Here Eclipse throws the error
something.method(),
somemore.anothermethod());
DataSet.save();
When I try to build this and to push it onto my device, Eclipse refuses to compile and throws this error:
ctx cannot be resolved to a variable
Considering the fact that I'm relatively new to Android development, the error may be obvious and I hope to get a tip how to solve this.
P.S.: Furthermore, I don't fully get the developer's statement in the getting-started-Note:
Please retain one constructor with Context argument. (This constraint will be removed in subsequent release.)
Thank you very much!
// Edit: Did edit the class name from LocationDataSet to Data set for clarification

First of all, the getting-started-note tells you that you need a constructor with only a context parameter, you did this here so that's ok
public DataSet(Context ctx){
super(ctx);
}
about
ctx cannot be resolved to a variable
I think you don't have a variable called ctx, I don't know if you're familiar with android context? (basically a context is a service or an activity), if you're using this code in an activity or a service, just use the 'this' keyword and not the ctx variable
The code you provide doesn't really show what you're doing, but you showed us the code from 'DataSet', but the error happens with a LocationDataSet? And you're calling save on DataSet?
The save method must be called on an object, not a class.
Also don't forget that sugar needs the special application class in the manifest
UPDATE with example:
Your dataset class (the sugarrecord) should look like this, that's ok in your code as far as I can see
public class DataSet extends SugarRecord<DataSet>{
private String someData;
public DataSet(Context c){
super(c);
}
public DataSet(Context c, String someData){
super(c);
this.someData = someData;
}
}
An activity that uses the record should look like this
public class SomeActivity extends Activity {
public void someMethodThatUsesDataSet(){
// Create a dataset object with some data you want the save and a context
// The context we use here is 'this', this is the current instance of SomeActivity,
// you absolutely need this, I think this is what you're doing wrong,
// you can't use ctx here because that's not a known variable at this point
DataSet example = new DataSet(this, "data you want to save");
// Tell Sugar to save this record in the database
example.save();
}
}

How to use getString() on static String before onCreate()?

I am trying to use getString() to get an String from resources to assign it to an String array before my activity is created:
private static final String[] MenuNames = {
Resources.getSystem().getString(R.string.LCMeterMenu),
Resources.getSystem().getString(R.string.FrecMenu),
Resources.getSystem().getString(R.string.LogicAnalyzerMenu),
"Prueba con achartengine",
Resources.getSystem().getString(R.string.BrazoMenu)
};
When I use Resources.getSystem().getString(R.string.LCMeterMenu), Eclipse doesn't complain but I get an error at runtime:
Caused by: android.content.res.Resources$NotFoundException: String Resource ID #0x7f0a000a
But if I put inside onCreate():
Log.i("StringR", "String: " + getString(R.string.LCMeterMenu));
I get the String but I can't assign it to the final String I defined before. If I use only getString() before onCreate() I get and static error message. How can I use resources before onCreate() for global variables?

You cannot initialize a static final field from resources; the field needs to be initialized at the time the class is initialized and that happens before the application resources have been bound at run time. (By the way, the reason you cannot use Resources.getSystem() is that the Resources object you obtain that way contains only system resources, not any application resources.)
If you need those strings available before the application resources are bound, the only practical thing to do is to put the strings into the code directly. However, the "Android way" would be to organize your code so initialization only needs to happen during (or after) onCreate(). Just initialize the string array in onCreate() and don't worry about making the fields static or final.
If you don't want the string array to be associated with a particular activity, then you can subclass Application and read the array from resources inside the application class's onCreate() method. (You also need to declare your custom application class in the manifest.) However, the docs recommend against such an approach. (Since the array is private, I suspect that it is closely tied to a single activity anyway, so the use of an Application subclass doesn't seem warranted.)
An alternative is to declare a singleton class for your array. The singleton accessor function then needs a Context so it can retrieve the resources if necessary:
public class StringArray {
private static String[] theArray;
public static String[] getArray(Context context) {
if (theArray == null) {
theArray = context.getResources().getStringArray(R.array.my_strings);
}
return theArray;
}
}
(This assumes the string data are defined in a <string-array> resource like #JaiSoni suggested in his answer.) Once again, the member field cannot be declared final.

No, you can't use Resources before onCreate(). You can get the instance of Resources in onCreate() by using getResources() where you can get all the Strings. Also the strings are already declared as static by defining them in the strings.xml.
Pseudo code for accessing the Resources,
Resources res = getResources();
String app_name = res.getString(R.string.app_name);

Another approach could be to initialize the static array with resource identifiers (which are already available as opposed to the resources themselves).
private static final int[] MenuNames = {
R.string.LCMeterMenu,
R.string.FrecMenu,
...
};
This way, you can defer the loading of resources to when they are actually available:
String s = getResources().getString(MenuNames[i]);

The following is a working approach to initialize static final variables in android from XML, such as strings.xml.
Subclass application and provide a "static context"
Register the application class in manifest
Use the static context to initialize your constants
1. MyApplication.java
public abstract class MyApplication extends Application {
private static Context context;
#Override
public void onCreate() {
super.onCreate();
context = getApplicationContext();
}
/**
* Returns a "static" application context. Don't try to create dialogs on
* this, it's not gonna work!
*
* #return
*/
public static Context getContext() {
return context;
}
}
2. AndroidManifest.xml
<application
android:name=".android.application.MyApplication"
<!-- ... -->
</application>
3. Your application code, e.g. Activity
private static final String[] MenuNames = {
getContext().getString(R.string.LCMeterMenu),
getContext().getString(R.string.FrecMenu),
getContext().getString(R.string.LogicAnalyzerMenu),
"Prueba con achartengine",
getContext().getString(R.string.BrazoMenu)
};
protected static Context getContext() {
return MyApplication.getContext();
}
For working examples refer to AbstractApplication and PreferencesServiceSharedPreferences.
Note that this approach also has its downsides:
Apart from being opposed to the "Android way" (as #Ted Hopp suggested in his answer),
it makes testing a bit difficult. That is why the call to MyApplication.getContext() is wrapped in another method. As it is a static method, overriding it in testing code is not simple. But you could use a framework such as Powermock for this purpose.
In addition it is a bit prone to NullPointerExceptions. As soon as the context is null (e.g. in your testing code) the application code crashes. One option to overcome this, is to do the initialization in a constructor, where you could react to getContext()returning null (see example).

Whatever you get by the getString(int resId) will already be a constant for your application. Why do you have to keep it in another final static variable. You can read it like that whenever you want, right?

call static void

How do I call my function?
public static void dial(Activity call)
{
Intent intent = new Intent(Intent.ACTION_DIAL);
call.startActivity(intent);
}
Obviously not with:
dial(); /*Something should be within the brackets*/

You should try
ClassName.dial();
The reason is that static methods belong the class itself, not to an individual instance of it. The call to instance.dial() is legal, but discouraged.

you should use your ClassName.StaticMethod.... to call a static method of a class

You can't pass null. You have to send a context object.
Where is your function located? If it's inside an Activity or the such, simply pass "this" as the parameter.
If it's inside an BroadcastListener, or a Service, just change the parameter to Context and pass "this".

What exaclty is the Problem?
If you've got a class like
public class Test {
public void nonStaticFct() {
staticFct();
}
public static void staticFct() {
//do something
}
}
Works perfectly (even if you should call static functions always by Classname.FctName (Test.staticFct())
I guess the problem here is the missing argument.
[Edit] Obviously I am wrong, according to the Java Code Conventions you may use a Classmethod by simply calling it, without using the classname (even if it seems odd, since I would expect an implicit this.staticFct() - but possibly the Java compiler is smart enough)

R.string.value Help android notification

whats the deal with
CharSequence contentTitle = R.string.value;
Error cannot convert from int to CharSequence. Is there a way around this or am i missing something?
i tried
String s = R.string.value + "";
CharSequence contentTitle = s;
it returns integers values.
Any help?

R.string.value is a call to the static field in the class R, which is auto generated by Eclipse and which does a kind of summary of all your resources. To retrieve the string, you need to use :
CharSequence contentTitle = getString(R.string.value);
If you open the R class you will see that it contains only numbers that are references to the compiled resources of your project.

To retrieve the string, you need to use getString(),
but getString() is a method from Context class.
If you want to use this method outside your Activity class, you should get link to your context first and then call:
String s = mContext.getString(R.string.somestring)

R.string.value returns the reference ID number of the resource 'value'. If you look at your R class it will appear as something like this:
public static final class string {
public static final int value=0x7f040007;
}
I've been experiencing issues with referencing the getString() method. The exact error that Eclipse spits at me is:
The method getString(int) is undefined for the type DatabaseHelper.MainDatabaseHelper
After reading for awhile I've figured out that you must reference your application's context to get access to the getString() method. I was trying to create a private SQLDatabase helper class in a content provider, however, that was not allowing me to reference the getString() method. My solution so far is to do something like this:
private class MainDatabaseHelper extends SQLiteOpenHelper {
MainDatabaseHelper(Context context) {
super(context, context.getString(R.string.createRoutesTable), null, 1);
}
public void onCreate(SQLiteDatabase db) {
db.execSQL((getContext()).getString(R.string.createRoutesTable));
}
}
Notice these two context references:
context.getString()
(getContext()).getString()
I don't know if this is the optimal long-term solution but it seems to work for the moment. Hope this helps.

You could use String s = getResources().getString(R.string.value); also.

how to read value from string.xml in android?

I have written the line:
String Mess = R.string.mess_1 ;
to get string value, but instead of returning string, it is giving me id of type integer. How can I get its string value? I mentioned the string value in the string.xml file.

Try this
String mess = getResources().getString(R.string.mess_1);
UPDATE
String string = getString(R.string.hello);
You can use either getString(int) or getText(int) to retrieve a string. getText(int) will retain any rich text styling applied to the string.
Reference: https://developer.android.com/guide/topics/resources/string-resource.html

In Activity:
this.getString(R.string.resource_name)
If not in activity but have access to context:
context.getString(R.string.resource_name)
application.getString(R.string.resource_name)

I'm using this:
String URL = Resources.getSystem().getString(R.string.mess_1);

By the way, it is also possible to create string arrays in the strings.xml like so:
<string-array name="tabs_names">
<item>My Tab 1</item>
<item>My Tab 2</item>
</string-array>
And then from your Activity you can get the reference like so:
String[] tab_names = getResources().getStringArray(R.array.tab_names);
String tabname1=tab_names[0];//"My Tab 1"

Only for future references.
In the String resources documentation it says:
You can use either getString(int) or getText(int) to retrieve a string. getText(int) will >retain any rich text styling applied to the string.

Solution 1
Context context;
String mess = context.getString(R.string.mess_1)
Solution 2
String mess = getString(R.string.mess_1)

In fragments, you can use
getActivity().getString(R.id.whatever);

If you want to add the string value to a button for example, simple use
android:text="#string/NameOfTheString"
The defined text in strings.xml looks like this:
<string name="NameOfTheString">Test string</string>

Details
Android Studio 3.1.4
Kotlin version: 1.2.60
Task
single line use
minimum code
use suggestions from the compiler
Step 1. Application()
Get link to the context of you application
class MY_APPLICATION_NAME: Application() {
companion object {
private lateinit var instance: MY_APPLICATION_NAME
fun getAppContext(): Context = instance.applicationContext
}
override fun onCreate() {
instance = this
super.onCreate()
}
}
Step 2. Add int extension
inline fun Int.toLocalizedString(): String = MY_APPLICATION_NAME.getAppContext().resources.getString(this)
Usage
strings.xml
<resources>
<!-- ....... -->
<string name="no_internet_connection">No internet connection</string>
<!-- ....... -->
</resources>
Get string value:
val errorMessage = R.string.no_internet_connection.toLocalizedString()
Results

You must reference Context name before using getResources() in Android.
String user=getApplicationContext().getResources().getString(R.string.muser);
OR
Context mcontext=getApplicationContext();
String user=mcontext.getResources().getString(R.string.muser);

You can read directly the value defined into strings.xml:
<resources>
<string name="hello">Hello StackOverflow!</string>
</resources>
and set into a variable:
String mymessage = getString(R.string.hello);
but we can define the string into the view:
<TextView
android:id="#+id/myTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/hello"/>

You can use this code:
getText(R.string.mess_1);
Basically, you need to pass the resource id as a parameter to the getText() method.

If you are in an activity you can use
getResources().getString(R.string.whatever_string_youWant);
If you are not in an Activity
use this :
getApplicationContext.getResource().getString(R.String.Whatever_String_you_want)

while u write R. you are referring to the R.java class created by eclipse, use getResources().getString() and pass the id of the resource from which you are trying to read inside the getString() method.
Example : String[] yourStringArray = getResources().getStringArray(R.array.Your_array);

**
I hope this code is beneficial
**
String user = getResources().getString(R.string.muser);

Update
You can use getString(R.string.some_string_id) in both Activity or Fragment.
You can use Context.getString(R.string.some_string_id) where you don't have direct access to getString() method. Like Dialog.
Problem is where you don't have Context access, like a method in your Util class.
Assume below method without Context.
public void someMethod(){
...
// can't use getResource() or getString() without Context.
}
Now you will pass Context as a parameter in this method and use getString().
public void someMethod(Context context){
...
context.getString(R.string.some_id);
}
What i do is
public void someMethod(){
...
App.getRes().getString(R.string.some_id)
}
What? It is very simple to use anywhere in your app!
So here is a Bonus unique solution by which you can access resources from anywhere like Util class .
import android.app.Application;
import android.content.res.Resources;
public class App extends Application {
private static App mInstance;
private static Resources res;
#Override
public void onCreate() {
super.onCreate();
mInstance = this;
res = getResources();
}
public static App getInstance() {
return mInstance;
}
public static Resources getResourses() {
return res;
}
}
Add name field to your manifest.xml <application tag.
<application
android:name=".App"
...
>
...
</application>
Now you are good to go.

getString(R.string.your_string) get the result

String myString = getResources().getString(R.string.here_your_string_name);
Now your string is copied into myString. I hope it will work for you.

If you are using Jetpack Compose, you can use
stringResource(R.string.yourstring)