java 只有在可见并完成初始化时才会丢弃数据的片段。

Posted 2021-05-08

public abstract class LazyFragmentBase extend Fragment {
    protected boolean isVisible;
      
      
    @Override
    public void setUserVisibleHint(boolean isVisibleToUser) {
        super.setUserVisibleHint(isVisibleToUser);
      
        if(getUserVisibleHint()) {
            isVisible = true;
            onVisible();
        } else {
            isVisible = false;
            onInvisible();
        }
    }
      
    protected void onVisible() {
        lazyLoad();
    }
    
    protected void onInvisible() {
        // no-op  
    }
    
    protected abstract void lazyLoad();
}

public class LazyFragment extends LazyFragmentBase {
    private boolean isPrepared;    // 标志位, 标志已经初始化完成
    
    
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_open_result, container, false);
        
        // 初始化 view 的各控件
        isPrepared = true;
        lazyLoad();
        
        return view;
    }
    
    @Override
    protected void lazyLoad() {
        if (!isPrepared || !isVisible) {
            return;
        }
        
        //填充各控件的数据
    }
}