Fragment懒加载
用于viewpager+fragment布局
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.widget.FrameLayout;
/**
* <h1>懒加载Fragment</h1> 只有创建并显示的时候才会调用onCreateViewLazy方法<br>
* <br>
* <p>
* 懒加载的原理onCreateView的时候Fragment有可能没有显示出来。<br>
* 但是调用到setUserVisibleHint(boolean isVisibleToUser),isVisibleToUser =
* true的时候就说明有显示出来<br>
* 但是要考虑onCreateView和setUserVisibleHint的先后问题所以才有了下面的代码
* <p>
* 注意：<br>
* 《1》原先的Fragment的回调方法名字后面要加个Lazy，比如Fragment的onCreateView方法， 就写成onCreateViewLazy <br>
* 《2》使用该LazyFragment会导致多一层布局深度
* <p>
* LuckyJayce
*/
public class LazyFragment extends BaseFragment {
private boolean isInit = false;
private Bundle savedInstanceState;
public static final String INTENT_BOOLEAN_LAZYLOAD = "intent_boolean_lazyLoad";
private boolean isLazyLoad = true;
private FrameLayout layout;
@Deprecated
protected final void onCreateView(Bundle savedInstanceState) {
super.onCreateView(savedInstanceState);
this.savedInstanceState = savedInstanceState;
Bundle bundle = getArguments();
if (bundle != null) {
isLazyLoad = bundle.getBoolean(INTENT_BOOLEAN_LAZYLOAD, isLazyLoad);
}
//为什么不直接getUserVisibleHint();而是通过自己存isVisibleToUserState变量判断
//因为v4的25的版本 已经调用 setUserVisibleHint(true)，结果到这里getUserVisibleHint是false
// （ps:看了FragmentManager源码Fragment被重新创建有直接赋值isVisibleToUser不知道是不是那里和之前v4有改动的地方）
//所以我默认VISIBLE_STATE_NOTSET，之前没有调用setUserVisibleHint方法，就用系统的getUserVisibleHint，否则就用setUserVisibleHint后保存的值
//总之就是调用了setUserVisibleHint 就使用setUserVisibleHint的值
boolean isVisibleToUser;
if (isVisibleToUserState == VISIBLE_STATE_NOTSET) {
isVisibleToUser = getUserVisibleHint();
} else {
isVisibleToUser = isVisibleToUserState == VISIBLE_STATE_VISIABLE;
}
if (isLazyLoad) {
if (isVisibleToUser && !isInit) {
isInit = true;
onCreateViewLazy(savedInstanceState);
} else {
LayoutInflater layoutInflater = inflater;
if (layoutInflater == null) {
layoutInflater = LayoutInflater.from(getApplicationContext());
}
layout = new FrameLayout(layoutInflater.getContext());
View view = getPreviewLayout(layoutInflater, layout);
if (view != null) {
layout.addView(view);
}
layout.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
super.setContentView(layout);
}
} else {
isInit = true;
onCreateViewLazy(savedInstanceState);
}
}
private int isVisibleToUserState = VISIBLE_STATE_NOTSET;
//未设置值
private static final int VISIBLE_STATE_NOTSET = -1;
//可见
private static final int VISIBLE_STATE_VISIABLE = 1;
//不可见
private static final int VISIBLE_STATE_GONE = 0;
@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
isVisibleToUserState = isVisibleToUser ? VISIBLE_STATE_VISIABLE : VISIBLE_STATE_GONE;
if (isVisibleToUser && !isInit && getContentView() != null) {
isInit = true;
onCreateViewLazy(savedInstanceState);
onResumeLazy();
}
if (isInit && getContentView() != null) {
if (isVisibleToUser) {
isStart = true;
onFragmentStartLazy();
} else {
isStart = false;
onFragmentStopLazy();
}
}
}
protected View getPreviewLayout(LayoutInflater inflater, ViewGroup container) {
return null;
}
@Deprecated
@Override
public final void onStart() {
super.onStart();
if (isInit && !isStart && getUserVisibleHint()) {
isStart = true;
onFragmentStartLazy();
}
}
@Deprecated
@Override
public final void onStop() {
super.onStop();
if (isInit && isStart && getUserVisibleHint()) {
isStart = false;
onFragmentStopLazy();
}
}
private boolean isStart = false;
protected void onFragmentStartLazy() {
}
protected void onFragmentStopLazy() {
}
protected void onCreateViewLazy(Bundle savedInstanceState) {
}
protected void onResumeLazy() {
}
protected void onPauseLazy() {
}
protected void onDestroyViewLazy() {
}
@Override
public void setContentView(int layoutResID) {
if (isLazyLoad && getContentView() != null && getContentView().getParent() != null) {
layout.removeAllViews();
View view = inflater.inflate(layoutResID, layout, false);
layout.addView(view);
} else {
super.setContentView(layoutResID);
}
}
@Override
public void setContentView(View view) {
if (isLazyLoad && getContentView() != null && getContentView().getParent() != null) {
layout.removeAllViews();
layout.addView(view);
} else {
super.setContentView(view);
}
}
@Override
@Deprecated
public final void onResume() {
super.onResume();
if (isInit) {
onResumeLazy();
}
}
@Override
@Deprecated
public final void onPause() {
super.onPause();
if (isInit) {
onPauseLazy();
}
}
@Override
@Deprecated
public final void onDestroyView() {
super.onDestroyView();
if (isInit) {
onDestroyViewLazy();
}
isInit = false;
}
}
import java.lang.reflect.Field;
import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class BaseFragment extends Fragment {
protected LayoutInflater inflater;
private View contentView;
private Context context;
private ViewGroup container;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
context = getActivity().getApplicationContext();
}
@Override
public final View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
this.inflater = inflater;
this.container = container;
onCreateView(savedInstanceState);
if (contentView == null)
return super.onCreateView(inflater, container, savedInstanceState);
return contentView;
}
protected void onCreateView(Bundle savedInstanceState) {
}
@Override
public void onDestroyView() {
super.onDestroyView();
contentView = null;
container = null;
inflater = null;
}
public Context getApplicationContext() {
return context;
}
public void setContentView(int layoutResID) {
setContentView((ViewGroup) inflater.inflate(layoutResID, container, false));
}
public void setContentView(View view) {
contentView = view;
}
public View getContentView() {
return contentView;
}
public View findViewById(int id) {
if (contentView != null)
return contentView.findViewById(id);
return null;
}
// http://stackoverflow.com/questions/15207305/getting-the-error-java-lang-illegalstateexception-activity-has-been-destroyed
@Override
public void onDetach() {
super.onDetach();
try {
Field childFragmentManager = Fragment.class.getDeclaredField("mChildFragmentManager");
childFragmentManager.setAccessible(true);
childFragmentManager.set(this, null);
} catch (NoSuchFieldException e) {
throw new RuntimeException(e);
} catch (IllegalAccessException e) {
throw new RuntimeException(e);
}
}
}
使用方法
public class ListFragment extends LazyFragment {
@Override
protected void onCreateViewLazy(Bundle savedInstanceState) {
super.onCreateViewLazy(savedInstanceState);
// 在这里进行初始化控件 findViewById
}
@Override
protected void onResumeLazy() {
super.onResumeLazy();
// 在这里加载数据
}
@Override
protected void onDestroyViewLazy() {
super.onDestroyViewLazy();
// 在这里进行对象的释放
}
}