android.app.Fragment#getId ( )源码实例Demo

private String getStateId() {
    if (stateId != null) {
        return stateId;
    }

    Fragment parentFragment = getParentFragment();
    stateId = parentFragment.getTag();
    if (stateId == null) {
        int id = parentFragment.getId();
        if (id > 0) {
            stateId = Integer.toString(id);
        }
    }

    if (stateId == null) {
        throw new IllegalStateException("Fragment dose not have a valid id");
    }
    
    return stateId;
}
 

@Override
public int getId(Fragment fragment) {
  return fragment.getId();
}
 

public static boolean isAdded(Fragment fragment) {
    // FIXME
    return fragment.isAdded() || fragment.getTag() != null || fragment.getId() != 0;
}
 

@Override
public int getId(Fragment fragment) {
  return fragment.getId();
}