ViewModel+LiveData最新版1.1.1的实现案例及fragment懒加载
备注：viewmodel+livedata 在1.1.0之后改动较大，ViewModelProvides类抛弃了，需要使用新的方法获取，后面有提到
最新版为1.1.1，
// alternatively, just ViewModel
implementation "android.arch.lifecycle:viewmodel:1.1.1"
//just LiveData
implementation "android.arch.lifecycle:livedata:1.1.1"
annotationProcessor "android.arch.lifecycle:compiler:1.1.1"
//需要使用 java8 特性的
使用这个依赖
// implementation "android.arch.lifecycle:common-java8:1.1.1"
//Lazyfragmen懒加载Fragment的基类，仅仅在用户可见时调用loaddata
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
/**
* A simple {
@link
Fragment} subclass.
*/
public abstract class BaseFragment extends Fragment {
boolean isUiVisible;
boolean isViewCreate;
public BaseFragment() {
// Required empty public constructor
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
isViewCreate = true;
lazyLoad();
}
@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
isUiVisible = isVisibleToUser;
lazyLoad();
}
protected void lazyLoad(){
if (isUiVisible && isViewCreate){
loadData();
}
}
public abstract void loadData();
}
//ViewModel和LiveData 模拟异步请求获取model
import android.arch.lifecycle.LiveData;
import android.arch.lifecycle.MutableLiveData;
import android.arch.lifecycle.ViewModel;
import android.os.AsyncTask;
import android.os.Handler;
import android.os.Message;
import java.util.ArrayList;
import java.util.List;
/**
*
@author
XiongJiaLong
*
@ClassName
MyUserModel
*
@date
2018
年
04
月
25
日
10:32
*/
//自定义的ViewModel，在此类中执行异步任务获取model
public class MyUserModel extends ViewModel {
MutableLiveData> mutableLiveData;
Handler handler = new Handler(){
@Override
public void handleMessage(Message msg) {
//该方法必须要在主线程执行，否则报错
mutableLiveData.setValue(l);
}
};
List l;
public LiveData> getUserModel(){
if (mutableLiveData == null){
mutableLiveData = new MutableLiveData<>();
loadData();
}
return mutableLiveData;
}
void loadData(){
new ThreadCall().start();
}
public void setNewData(User user){
mutableLiveData.getValue().set(0,user);
}
class ThreadCall extends Thread{
@Override
public void run() {
try {
Thread.
sleep
(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
l = new ArrayList<>();
for (int i=0;i<10;i++){
l.add(new User(i+"
姓名
",20+i,150+i));
}
handler.sendEmptyMessage(0);
}
}
}
// MainActivity获取自定义 viewmodel
void initData(){
//使用new的形式获取model 不存在
// viewModelProvider = new ViewModelProvider(this,
// ViewModelProvider.AndroidViewModelFactory.getInstance(getApplication()));
// myUserModel = viewModelProvider.get(MyUserModel.class);
// viewmodel 1.1.0之后正确获取 ViewModel 的姿势
viewModelProvider=ViewModelProvider.AndroidViewModelFactory.
getInstance
(getApplication());
myUserModel = viewModelProvider.create(MyUserModel.class);
}
//给 fragment用来获取viewmodel 将myUserModel 设置为静态的也可以，根据使用范围设置
public MyUserModel getMyUserModel() {
return myUserModel;
}
////懒加载 fragment 的实现及 ViewModel 的调用
public class BlankFragment extends BaseFragment implements View.OnClickListener, Observer> {
String tit;
TextView tv;
Button btn;
MyUserModel userModel;
public static BlankFragment getFragment(String s){
BlankFragment f = new BlankFragment();
Bundle b = new Bundle();
b.putString("content",s);
f.setArguments(b);
return f;
}
public BlankFragment() {
// Required empty public constructor
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
tit = getArguments().getString("content");
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
super.onCreateView(inflater,container,savedInstanceState);
View inflate = inflater.inflate(R.layout.
fragment_blank
, container, false);
tv = inflate.findViewById(R.id.
neiRong
);
btn = inflate.findViewById(R.id.
change_btn
);
btn.setOnClickListener(this);
// 拿到ViewModel 并且设置 data的变化监听，
userModel = MainActivity.
myUserModel
;
userModel.getUserModel().observe(getActivity(),this);
return inflate;
}
@Override
public void loadData() {
getData();
}
void getData(){
if (userModel!=null) {
List value = userModel.getUserModel().getValue();
if (value != null) {
tv.setText(value.get(0).toString());
}
}
}
@Override
public void onClick(View view) {
User user = new User();
user.setAge(100);
user.setHeight(100);
user.setName(this.getClass().getName());
if (userModel!=null)
//改变单个值不会触发 onChanged 方法
userModel.setNewData(user);
}
//
此监听只会在 setValue的时候调用，如果只改变单个的值不调用改方法，但是重新获取值会改变
@Override
public void onChanged(@Nullable List users) {
Log.
e
("====BlandFragment====","=====onChanged======");
List value = userModel.getUserModel().getValue();
tv.setText(value.get(value.size()-1).toString());
}
}
//懒加载fragment
public class TestFragment1 extends BaseFragment implements View.OnClickListener {
TextView t;
MyUserModel userModel;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.
fragment_test_fragment1
, container, false);
t = view.findViewById(R.id.
tv_received
);
t.setOnClickListener(this);
return view;
}
@Override
public void loadData() {
getData();
}
void getData(){
userModel = MainActivity.
myUserModel
;
t.setText(userModel.getUserModel().getValue().get(0).toString());
}
@Override
public void onResume() {
super.onResume();
}
@Override
public void onPause() {
super.onPause();
}
@Override
public void onClick(View view) {
User user = new User();
user.setAge(500);
user.setHeight(500);
user.setName(this.getClass().getName());
List list = new ArrayList<>();
list.add(user);
if (userModel!=null)
//此设置会出发 onChanged 方法回调
userModel.mutableLiveData.setValue(list);
}
}