Fragment生命周期
Fragment的生命周期可以参考文章:
ViewPager实现首页
首页使用的是ViewPager和Fragment来实现,首页效果图:
但是Fragment的复杂的生命周期就会带来一个问题,比如我们刚打开APP,这个时候我们只想AFragment加载数据,而其他的页面的数据并不加载.但是真实的情况是,当AFragment可见,BFragment的数据也会同时加载.这是因为使用ViewPager是会预加载Fragment的临近的Fragment,虽然临近的Fragment是不可见的但是他的OnResume方法其实已经执行了,如果我们的网络初始化函数 写在onCreateView里面,显然是不合适.下面我们来看一具体的日志信息.
1.刚进入APP:
这个时候,A和B的页面逻辑同时加载完毕,如果在onCreateView里面有网络请求的逻辑,显然这样的效果不是,我们需要的.
2.单击BFragment:
在BFragment可见是,由于之前BFragment的onResume已经执行完毕,所以BFragment不会继续执行他的生命周期,这样时候会预加载CFragment.
4.单击CFragment:
这个时候,在预加载DFragment的时候,也会同时执行AFragment的onDestoryView方法即将Fragment的View被移除.
5.单击DFragment:
由于D Fragment的onResume方法已经执行完毕,所以BFragment的onDestoryView会执行.
6:在次回去单击CFragment:
7:再次回去单击AFragment:
setUserVisibleHint和getUserVisibleHint方法
getUserVisibleHint该方法用于告诉系统，这个Fragment的UI是否是可见.setUserVisibleHint方法是系统的方法,setUserVisibleHint方法是优先于onAttach方法执行的.在该方法内我们可以通过getUserVisibleHint方法获取到当前的Fragment是否可见.如果可见设置isVisible为true.如果不可见设置为false.
代码:
BaseFragment:
public abstract class BaseFragment extends Fragment
{
//当前的Fragment是否可见
protected boolean isVisible ;
@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
Log.i("TAG",this.toString() +" setUserVisibleHint");
if(getUserVisibleHint())
{
isVisible = true;
onVisible();
}
else
{
isVisible = false;
onInVisible();
}
}
/**
* 当Fragment可见时执行的函数
*/
private void onVisible()
{
lazyLoad();
}
/**
* 当Fragment不可见执行的函数
*/
private void onInVisible()
{
}
protected abstract void lazyLoad();
}
MainActivity:
public class MainActivity extends FragmentActivity implements View.OnClickListener{
private List list = new ArrayList<>();
private AFragment aFragment;
private BFragment bFragment;
private CFragment cFragment;
private DFragment dFragment;
private ViewPager mvp;
private LinearLayout merchant_lay;
private LinearLayout order_lay;
private LinearLayout privilege_lay;
private LinearLayout mine_lay;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initFragment();
initView();
MyAdapter adapter = new MyAdapter(this.getSupportFragmentManager(),list);
mvp.setAdapter(adapter);
mvp.setCurrentItem(0);
}
private void initFragment()
{
aFragment = new AFragment();
bFragment = new BFragment();
cFragment = new CFragment();
dFragment = new DFragment();
list.add(aFragment);
list.add(bFragment);
list.add(cFragment);
list.add(dFragment);
}
private void initView()
{
mvp = (ViewPager)this.findViewById(R.id.mvp);
merchant_lay = (LinearLayout)this.findViewById(R.id.merchant_lay);
order_lay = (LinearLayout)this.findViewById(R.id.order_lay);
privilege_lay = (LinearLayout)this.findViewById(R.id.privilege_lay);
mine_lay = (LinearLayout)this.findViewById(R.id.mine_lay);
merchant_lay.setOnClickListener(this);
order_lay.setOnClickListener(this);
privilege_lay.setOnClickListener(this);
mine_lay.setOnClickListener(this);
}
@Override
public void onClick(View v) {
switch (v.getId())
{
case R.id.merchant_lay:
mvp.setCurrentItem(0);
break;
case R.id.order_lay:
mvp.setCurrentItem(1);
break;
case R.id.privilege_lay:
mvp.setCurrentItem(2);
break;
case R.id.mine_lay:
mvp.setCurrentItem(3);
break;
}
}
}
Adapter:
public class MyAdapter extends FragmentPagerAdapter {
private List<Fragment> mList;
public MyAdapter(FragmentManager fm,List<Fragment> list) {
super(fm);
this.mList = list;
}
@Override
public int getCount() {
return mList != null ? mList.size() : 0;
}
@Override
public Fragment getItem(int position) {
return mList != null ? mList.get(position) : null;
}
}
AFragmnet:
public class AFragment extends BaseFragment {
private static final String TAG = AFragment.class.getSimpleName();
//标志是否已经加载完毕
private boolean isPrepared;
//是否已经加载过一次，第二次则不加载。
private boolean mHasLoadedOnce = false;
@Override
public void onAttach(Context context) {
Log.i(“TAG”, TAG + ” onAttach”);
super.onAttach(context);
}
@Override
public void onCreate(Bundle savedInstanceState) {
Log.i("TAG", TAG + " onCreate");
super.onCreate(savedInstanceState);
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
Log.i("TAG", TAG + " onCreateView");
View view = inflater.inflate(R.layout.fragment_a,container,false);
isPrepared = true;
lazyLoad();
return view;
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
Log.i("TAG", TAG + " onActivityCreated");
super.onActivityCreated(savedInstanceState);
}
@Override
public void onStart() {
Log.i("TAG", TAG + " onStart");
super.onStart();
}
@Override
public void onResume() {
Log.i("TAG", TAG + " onResume");
super.onResume();
}
@Override
public void onStop() {
Log.i("TAG", TAG + " onStop");
super.onStop();
}
@Override
public void onPause() {
Log.i("TAG", TAG + " onPause");
super.onPause();
}
@Override
public void onDestroyView() {
Log.i("TAG", TAG + " onDestroyView");
super.onDestroyView();
}
@Override
public void onDestroy() {
Log.i("TAG", TAG + " onDestroy");
super.onDestroy();
}
@Override
public void onDetach() {
Log.i("TAG", TAG + " onDetach");
super.onDetach();
}
@Override
protected void lazyLoad()
{
Log.i("TAG", TAG +" lazy" + isPrepared + " " + isVisible + " " + mHasLoadedOnce);
if (!isPrepared || !isVisible || mHasLoadedOnce) {
return;
}
mHasLoadedOnce = true;
}
}
ViewPager的不可滑动设置
public class MyViewPager extends ViewPager {
private boolean isCanScroll = false;
public MyViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
// TODO Auto-generated constructor stub
}
public void setScanScroll(boolean isCanScroll) {
this.isCanScroll = isCanScroll;
}
@Override
public void scrollTo(int x, int y) {
super.scrollTo(x, y);
}
@Override
public boolean onInterceptTouchEvent(MotionEvent arg0) {
if (isCanScroll) {
return super.onInterceptTouchEvent(arg0);
} else {
return false;
}
}
@Override
public boolean onTouchEvent(MotionEvent arg0) {
if (isCanScroll) {
return super.onTouchEvent(arg0);
} else {
return false;
}
}
}
布局文件:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<RelativeLayout
android:id="@+id/main_activity_layout"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_weight="1"
android:background="#CE112D"
android:gravity="center_vertical"
android:orientation="vertical" >
<com.example.dengquan.lazyloadmodule.viewpager.MyViewPager
android:id="@+id/mvp"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="@android:color/white"
android:layout_above="@+id/bottomView">
</com.example.dengquan.lazyloadmodule.viewpager.MyViewPager>
<include
android:id="@id/bottomView"
layout="@layout/bottom_view"
android:layout_width="match_parent"
android:layout_height="50dp"
android:layout_alignParentBottom="true"/>
</RelativeLayout>
</LinearLayout>补充
如果想更新某个Fragment可以通过广播来更新,或者(EventBus,otto).
参考文献:
http://www.jcodecraeer.com/a/anzhuokaifa/androidkaifa/2014/1021/1813.html
代码下载地址:
