懒加载

自定义一个 LazyLoadFragment 基类，利用 setUserVisibleHint 和 生命周期方法，通过对 Fragment 状态判断，进行数据加载，并将数据加载的接口提供开放出去，供子类使用。然后在子类 Fragment 中实现 requestData 方法即可。这里添加了一个 isDataLoaded 变量，目的是避免重复加载数据。考虑到有时候需要刷新数据的问题，便提供了一个用于强制刷新的参数判断。

public abstract class LazyLoadFragment extends BaseFragment {
protected boolean isViewInitiated;
protected boolean isDataLoaded;
@Override
public void onCreate(Bundle savedInstanceState) {
	super.onCreate(savedInstanceState);
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
	super.onActivityCreated(savedInstanceState);
	isViewInitiated = true;
	prepareRequestData();
}
@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
	super.setUserVisibleHint(isVisibleToUser);
	prepareRequestData();
}
public abstract void requestData();
public boolean prepareRequestData() {
return prepareRequestData(false);
}
public boolean prepareRequestData(boolean forceUpdate) {
	if (getUserVisibleHint() && isViewInitiated && (!isDataLoaded || forceUpdate)) {
		requestData();
		isDataLoaded = true;
		return true;
		}
		return false;
	}
}