Some basic information for enum and IntDef/StringDef:
use enum in adnroid is not efficient ,so we use IntDef/StringDef to replace it
How to use IntDef/StringDef:
Annotation explain:
Enumerated Annotations explain:
Now ,show how to use IntDef replace the Enum
if we have a function
input(int i)
it only can accpet the below number
public static final int LOCATION_STATUS_OK = 0;
public static final int LOCATION_STATUS_SERVER_DOWN = 1;
public static final int LOCATION_STATUS_SERVER_INVALID = 2;
public static final int LOCATION_STATUS_UNKNOWN = 3;
how can we limite the function only accept the above:
Method1:,we can use enum
enum State {
LOCATION_STATUS_OK, LOCATION_STATUS_SERVER_DOWN, LOCATION_STATUS_SERVER_INVALID,LOCATION_STATUS_UNKNOWN
}
void input(State s){
//do something
}
However, enum in android is not efficient ,we will not use it
Method2:use int
public static final int LOCATION_STATUS_OK = 0;
public static final int LOCATION_STATUS_SERVER_DOWN = 1;
public static final int LOCATION_STATUS_SERVER_INVALID = 2;
public static final int LOCATION_STATUS_UNKNOWN = 3;
void input(int state){
//do something
}
however, we can’t not limited user only input the above number,we need to write more function to prevent the use input other number
Method3:
use IntDef
@IntDef(flag = true, value = {LOCATION_STATUS_OK, LOCATION_STATUS_SERVER_DOWN,LOCATION_STATUS_SERVER_INVALID,LOCATION_STATUS_UNKNOWN})
@Retention(RetentionPolicy.SOURCE)
public @interface State {}
public static final int LOCATION_STATUS_OK = 0;
public static final int LOCATION_STATUS_SERVER_DOWN = 1;
public static final int LOCATION_STATUS_SERVER_INVALID = 2;
public static final int LOCATION_STATUS_UNKNOWN = 3;
void input(@Stateint state){
//do something
}
Some information of RetentionPolicy
RetentionPolicy.SOURCE: Discard during the compile. These annotations don't make any sense after the compile has completed, so they aren't written to the bytecode.
Example: @Override, @SuppressWarnings
RetentionPolicy.CLASS: Discard during class load. Useful when doing bytecode-level post-processing. Somewhat surprisingly, this is the default.
RetentionPolicy.RUNTIME: Do not discard. The annotation should be available for reflection at runtime. Example: @Deprecated
example to use
step1:define the state code
@IntDef(flag = true, value = {LOCATION_STATUS_OK, LOCATION_STATUS_SERVER_DOWN, LOCATION_STATUS_SERVER_INVALID, LOCATION_STATUS_UNKNOWN})
@Retention(RetentionPolicy.SOURCE)
public @interface LocationStates {
}
public static final int LOCATION_STATUS_OK = 0;
public static final int LOCATION_STATUS_SERVER_DOWN = 1;
public static final int LOCATION_STATUS_SERVER_INVALID = 2;
public static final int LOCATION_STATUS_UNKNOWN = 3;
step2,define the function to save the state by sharedPreference
private void setLocationState(@LocationStates int locationstate){
SharedPreferences sp = mContext.getSharedPreferences(mContext.getString(R.string.pref_location_state_key), Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sp.edit();
editor.putInt(mContext.getString(R.string.pref_location_state_key), locationstate);
editor.commit();
}
step3 call the function on different location in the app
