I came across the code here. Can someone explain to what is Menu.First and why +1? I couldn't find it in the Android developer document.
private static final int MENU_ADD = Menu.FIRST;
private static final int MENU_LIST = MENU.FIRST + 1;
private static final int MENU_REFRESH = MENU.FIRST + 2;
private static final int MENU_LOGIN = MENU.FIRST + 3;
In the context of the accepted answer referenced in your comments, the poster is simply using these values as id's for dynamically added menu items so that clicks can be registered in inOptionsItemSelected().
For example, say you wanted to add a new button to your menu dynamically that turned the screen blue, you might create a constant value called MENU_TURN_SCREEN_BLUE. This would store an arbitrary number which you can later use as an id. For example (keeping in mind Menu.FIRST = 1:
private static final int MENU_TURN_SCREEN_BLUE = Menu.FIRST + 60;
or
private static final int MENU_TURN_SCREEN_BLUE = 69084;
Are both valid. Now, when you add a new item to a menu with the add() method, you can use this value:
menu.add(0, TURN_SCREEN_BLUE, 0, "Press To Turn Screen Blue");
You could of course just write the number in directly, but constant are helpful (amongst other reasons) for avoiding bugs in your code that arise from accidentally typing in the wrong number.
Keep in mind though that there are other ways to generate unique id's - see this question for details.
Refer this documentation
FIRST Refers to
First value for group and item identifier integers.
It is a constant value
Constant Value: 1 (0x00000001)
Refer this link
Related
I'm trying to build a profile for the Tasker app that responds to the BATTERY_CHANGED broadcast intent and I saw one of the Extras called Online that appears to correspond with the specific charger type or condition, but I can't seem to find a proper list of potential values for this Extra. At best, I've found a few of the values, such as 1 being None, 4 is USB, 10 is Wireless, 100 is Fast Wireless. Others I have just guessed at, such as 6 being a QuickCharge 2.0 or 3.0 type charger and 19 being a Power Delivery charger, but otherwise I can't be sure.
Is there any official documentation for this Extra in Android P?
There's surprisingly little documentation about the online extra!
I found this list which seems to be from a decompiled Samsung Pay app, weirdly enough:
public static final int BATTERY_ONLINE_FAST_WIRELESS_CHARGER = 100;
public static final int BATTERY_ONLINE_INCOMPATIBLE_CHARGER = 0;
public static final int BATTERY_ONLINE_NONE = 1;
public static final int BATTERY_ONLINE_POGO = 23;
public static final int BATTERY_ONLINE_TA = 3;
public static final int BATTERY_ONLINE_USB = 4;
public static final int BATTERY_ONLINE_WATER_IN_CONNECTOR = 101;
public static final int BATTERY_ONLINE_WIRELESS_CHARGER = 10;
The values seem to match with almost all of yours, I do find it very odd that seems to be no other record of them (from a quick Google).
Despite the android.os package of the linked file, perhaps it's not part of the OS / has been changed / has a different name. Maybe a Samsung-specific feature?
I use SignalStength to get the quality of the signal, before sending sms:
signalStrength.getLevel()
I then wanted to compare the integer with a static constant in SignalStength:
if (signalStrengthLevel == SignalStrength.SIGNAL_STRENGTH_POOR) {
//...
}
But it doesn't compile in Android Studio. I realized that for some reason, these constants are marked as hidden in the source code:
/** #hide */
public static final int SIGNAL_STRENGTH_POOR
= TelephonyProtoEnums.SIGNAL_STRENGTH_POOR; // = 1
Which forces me to copy/paste these constants in one of my own classes...
I then wonder if anyone knows the reason why the developers decided to mark these constants as hidden?
In the documentation of the TelephonyManager, we can find getSignalStrength() method, which returns SignalStrength type, which has getLevel() method. In the documentation of getLevel() method, we can read the following information about returned integer value:
a single integer from 0 to 4 representing the general signal quality.
This may take into account many different radio technology inputs. 0
represents very poor signal strength while 4 represents a very strong
signal strength.
Taking that into consideration, I'd solve that in the following way:
create static values like:
private final static int VERY_POOR_SIGNAL = 0;
private final static int POOR_SIGNAL = 1;
private final static int MEDIUM_SIGNAL = 2;
private final static int STRONG_SIGNAL = 3;
private final static int VERY_STRONG_SIGNAL = 4;
and use this values to compare them with the integer value returned by:
telephonyManager.getSignalStrength().getLevel()
The word /** #hide */ just informs that the API is not accessible from SDK. I think it might be for security reasons.
Check this post
How do you add 3 or more complications in your watch face? Does the name of the complication ids matter? I know how to have 2 complications,https://codelabs.developers.google.com/codelabs/adding-complications-to-your-android-wear-watch-face/index.html#0, but not 3 or 4.
Is this correct?:
private static final int LEFT_DIAL_COMPLICATION = 0;
private static final int RIGHT_DIAL_COMPLICATION = 1;
private static final int BOTTOM_DIAL_COMPLICATION = 2;
public static final int[] COMPLICATION_IDS = {LEFT_DIAL_COMPLICATION, RIGHT_DIAL_COMPLICATION, BOTTOM_DIAL_COMPLICATION};
Or do I have to change that code? I haven't found any documentations on 3 complications or more.
Thanks for any answer!
(Posted solution on behalf of the OP).
The name wasn't the problem, it was a name-array.
My program reads data from socket and now I want to display that data in a textbox. I splitted the data into seperate variables and here is my code:
final int aData = 0;
final int aData = 0;
final int cData = 0;
final String[] separated = data.split(":");
if ((separated.length == 3) && (data.contains(":")))
{
aData = Integer.parseInt(separated[0]);
bData = Integer.parseInt(separated[1]);
cData = Integer.parseInt(separated[2]);
}
handler.post(new Runnable() {
public void run() {
txtDebug.setText("a: "+aData + " b: "+bData + " c: " + cData);
}
});
it doesn't allow me to run the program and shows me following error:
"The final local variable aData cannot be assigned. It must be blank and not using a compound assignment". Any help to solve the problem would be highly appreciated.
You're assigning aData twice. I assume you meant to have aData, bData and cData but you have two lots of aData and one cData.
Besides that problem, you also assign 0 to each of these variables when you declare them. You then try to assign new values in the if block. You can only assign to a final variable once.
The final reserved work means that your variable might be initialized/assigned just once. Since you're assigning final int aData = 0;, it means it won't be able to assign it again. This has its benefits (for instance, if you're sure you just want your variable be assigned for once, you should declare it as final - even this will help a little to the compiler), but its for sure a behavior you're not looking for. Simply remove final from your variables.
Since you have used the keyword 'final' on the variables aData, bData and cData, they can no longer be reassigned new values elsewhere within the program. They take the value 0 and remain that way. Remove the modifier 'final' if you want to change them.
just looking through the source for renderscript.
I think I spotted a mistake, on line 36
private static final boolean LOG_ENABLED = DEBUG ? Config.LOGD : Config.LOGV;
Think that needs to be a double == but don't have enough coding experience to be sure.
No, I don't think it is a bug. It's setting LOG_ENABLED to either LOGD or LOGV depending on the value of DEBUG.
The relevant bit is:
public class RenderScript {
static final String LOG_TAG = "libRS_jni";
private static final boolean DEBUG = false;
#SuppressWarnings({"UnusedDeclaration", "deprecation"})
private static final boolean LOG_ENABLED = DEBUG ? Config.LOGD : Config.LOGV;
and that last line is conceptually equivalent to:
private static final boolean LOG_ENABLED;
if (DEBUG)
LOG_ENABLED = Config.LOGD;
else
LOG_ENABLED = Config.LOGV;
In fact,
private static final boolean LOG_ENABLED == DEBUG ? Config.LOGD : Config.LOGV;
doesn't actually make sense since it means:
private static final boolean ((LOG_ENABLED == DEBUG)
? Config.LOGD
: Config.LOGV);
which doesn't have a variable name being declared at all, just a value that should be assigned to something.
It's just a simple bit of confusion about how ternary operators work in Java. You're doing something like:
int i;
boolean b;
int n1=2;
int n2=3;
i = b ? n1 : n2;
where b can be an expression evaluating to true or false. I used to use parenthesis around the first element to make this clear, although I just looked through some of my code and I seem to have stopped doing that now!