I know what a static variable in java and I know when to use it. But I see often appear in the android source code, the parameter private static final String TAG = "MyActivity" Do we really need this variable is kept in memory? I want to know why we use it in this way?
Related
I can store them in res/strings
<resources>
<string name="str1">app</string>
</resources>
And I can store them in static const
public static final string str1 = "app"
Which one is better?
I mean that which one will use more memory and which one will make package larger.
If you have to change some text in your app's view, then you don't have to find where you have written that text. You simply go to the strings.xml in res folder and can change the string. For that reason, the first option will always be the better option.
If you want a string that will be used as a key in your app then you can store it in a static constant variable. Like: If you want to pass data through intent or in any other way, at that time you have to pass a key. That key will be a string and can be stored in a static constant variable.
it's really depend if you treat strings as constants or not.
If you string are constants (e.g. string that will be sent as key of intent) then you can either create some Constants class or define it as a constant in your activity/fragment class. If those string are texts that will be displayed on your application UI then they should be defined as resources in your application.
BTW all the resources string can be localized to different languages
If you need more info or examples please let me know.
The package size:
I believe that "Ran Hassid"'s comment describes well about the package size.
Memory usage:
Just create an android apk file with some static final strings and then decompile it. You will see that the variable has no initial value in the compiled version and the value is replaced in all references!
For example check this sample from my decompiled apk which is also obfusicated by proguard:
public static String f10850f;
...
...
...
hashMap.put(C1554f.m14687a("\u0014]SCVQ^V"), str);
here is the actual code I have written:
public static String packageName="\u0014]SCVQ^V";
...
...
...
hashMap.put(EncryptorClass.decrypt(packageName), str);
In this case, the static final String variable in my written code has value of "\u0014]SCVQ^V" but it is not used in run-time and just copy/pasted in related pieces of code.
So using static final String variables needs no memory because variable has no initial value.
Have a look at android docs about using static final variables
Also take a look at this post regarding memory of variables with no value
Overally, I use static final variables and string resources for different purposes like code encryption, language support and whether I want to access the variable using a Context or not.
I'm trying to declare all constants used by my application in a separate constants class. I'd like to declare the application path but can't figure out how to do it in a static way.
How do I replace the "this" to something that will let me get the path?
public static final String DL_PATH = this.getApplicationContext().getFilesDir().getAbsolutePath() + "/";
How do I replace the "this" to something that will let me get the path?
You don't. There is nothing that you can use for this.
You are welcome to assign the value to DL_PATH from onCreate() of a custom Application. Or, delete DL_PATH entirely and just call getFilesDir() as needed from your various components (e.g., Activity, Service).
My question is very simple ! I have seen several applications that define database name(or table name) as a static variable !
why ?
like :
private static final String DATABASE_NAME = "database" ;
can I define it as a final variable ?
Possibly this way you want to say that your DATABASE_NAME is not part of every instance of your class, but a part of the class itself. That would mean that each time you declare an instance of your class, each of those classes won't have a copy of that attribute but they will share that attribute instead.
Quite logic, this is meant to be a static field so why make an instance of it? And yes, it should be a final variable, as it is unlike it will change at execution time.
For convenience. The DB name never changes while the app is running or between instances of the same class - it can only change between app versions. This way if you change the name of your database you won't have to search for it in the entire app - just modify the DATABASE_NAME variable.
I need a solution for the really common but important issue that i am thinking of.
I have created application in which i have hard coded my server address in /res/values/strings.xml file. Suppose if my server address changes run-time due to some reasons, then i have to make changes in the file and then i have to recompile it.
So is there any way that i put my server address out of my application.. So we do not have to recomplie the application. Instead of it, it will read new server address from out side and resume its normal work...
Any type of related suggestions,links,blogs appreciated..
While I am making apps in Android , I mostly create a Utility class e.g. Constants.java , Utils.java etc. In these classes, I put all the constant numerical and String values like this:
public static String ip="74.117.153.111";
public static final String LOGIN_TOKEN_URL = "http://"+ ip + "/api/getLoginToken";
public static final String USERNAME_PARAM = "username";
public static final String PASSWORD_FIELD_EMPTY_ERROR = "Please enter password";
public static final int GRID_ICON_COUNT = 4;
public static final String FACEBOOK_KEY = "16411636362877862";
These are some type of constants which we generally use here and there. So I put them into a different dedicated class. So now when I need their value somewhere, I get it like this:
params.put(Constants.USERNAME_PARAM, username);
fbRocket = new FBRocket(this, Constants.APP_NAME,Constants.FACEBOOK_KEY);
The benefit of this approach is that if I have to change a value later on which is being used at lot of places , then I don't have to change it everywhere. I will just change the value in Constants.java and this change will replicate in the whole app.
Utils.showErrorMessage(this, Constants.PASSWORD_FIELD_EMPTY_ERROR, Constants.TOAST_VISIBLE_SHORT);
I got the answer by reading this blog.
Which says you should use shard preferences with the activity extending PreferenceActivity.
Here you can set your server address and all the dynamic stuff that will change by the time. So that you will not have to recompile the apk. Just change the settings in shared preferences.
Read this important bog that all app developer wants to know it..
Is there a way to have an global settings variable for an android application, which is accessable as well from any help java classes without giving them context?!
I try to explain what I mean.
I have an application version as string value in strings.xml
I can get its value from every android activity, but not from help java classes withought giving context
What I do now, is saving it in a static variable of my first activity, but it seems, that sometimes it will be erased and set to null.
May be I do something wrong?!
Sorry for newbie question.
And thank you in advance,
Mur
P.s.
I wrote a small tutorial for this topic, to show the solution.
A variable declared as public, static, and final will be visible to all of your classes and never get erased.
public static final String VERSION = "1.2.3.4";
You could make a public static variable in your application class that you fill with the value from strings.xml in the onCreate method. The application class is a singleton and will be the last thing that is killed as part of your app so it will always be there and if you make it public static there will be only one instance.
I'm guessing that you have a JAVA class for some common utility functions. You get the value of your string using a context in your Activity/Service and then pass in that value to the JAVA class function as a parameter.