懒加载fragment

LazyFragment.java

public abstract class LazyFragment extends BaseFragment {

    private boolean isPrepared;
    private boolean isFirstResume = true;
    private boolean isFirstVisible = true;
    private boolean isFirstInvisible = true;

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        initPrepare();
    }

    @Override
    public void onResume() {
        super.onResume();
        if (isFirstResume) {
            isFirstResume = false;
            return;
        }
        if (getUserVisibleHint()) {
            onInvisible();
        }
    }

    @Override
    public void onPause() {
        super.onPause();
        if (getUserVisibleHint()) {
            onInvisible();
        }
    }

    @Override
    public void setUserVisibleHint(boolean isVisibleToUser) {
        super.setUserVisibleHint(isVisibleToUser);
        if (isVisibleToUser) {
            if (isFirstVisible) {
                isFirstVisible = false;
                initPrepare();
            } else {
                onVisible();
            }
        } else {
            if (isFirstInvisible) {
                isFirstInvisible = false;
                onFirstInvisible();
            } else {
                onInvisible();
            }
        }
    }

    public synchronized void initPrepare() {
        if (isPrepared) {
            onFirstVisible();
        } else {
            isPrepared = true;
        }
    }

    protected abstract void onFirstVisible();

    protected abstract void onFirstInvisible();

    protected abstract void onVisible();

    protected abstract void onInvisible();

}