未经检查的演员表 <String, String> allPreferences

Question

I have a gradle warning about unchecked cast. The app builds without bugs but I want to clean up any code issues. I saw a similar post here How do I cast from int to generic type Integer?

It is not clear to me how to check the value for the cast.

.../mayday/md/model/SMSSettings.java:56: warning: [unchecked] unchecked cast
        Map<String, String> allPreferences = (Map<String, String>) sharedPreferences.getAll();
                                                                                           ^
  required: Map<String,String>
  found:    Map<String,CAP#1>
  where CAP#1 is a fresh type-variable:
    CAP#1 extends Object from capture of ?

line 56 Map<String, String> allPreferences = (Map<String, String>) sharedPreferences.getAll();

public static SMSSettings retrieve(Context context) {
    SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(context);
    Map<String, String> allPreferences = (Map<String, String>) sharedPreferences.getAll();
    List<String> retrievedPhoneNumbers = retrievePhoneNumbers(allPreferences);
    return new SMSSettings(retrievedPhoneNumbers, allPreferences.get(SMS_MESSAGE));
}

Answer 1

请注意， SharedPreferences 可以包含除字符串之外的其他对象。如果您100％确保SharedPreferences对象中只有Strings，则可以忽略此警告，并在方法中或转换的上方添加@SuppressWarnings("unchecked") 。

Answer 2

getAll returns a Map<String, ?> not a Map<String, String> , where the unbounded wildcard ? , is a short version of <? extends Object> <? extends Object> . If I didn't misunderstood you

 Map<String, ?> allPreferences = sharedPreferences.getAll();

should remove the warning