官方解释：保存UI数据的类，会在配置变更（如手机屏幕的旋转）后继续存在。
view Model不应持有context，否则在Activity销毁后View Model仍然持有Activity的context，造成内存泄漏；可以继承AndroidViewModel，或者选择application context
1.建立data类
public class Time {
private MutableLiveData<Integer> seconds = new MutableLiveData<>();
public MutableLiveData<Integer> getSeconds() {
return seconds;
}
}2.继承View Model
public class TestViewModel extends ViewModel {
private Time time;
public TestViewModel(){
time = new Time();
// 修改liveData包装的数据，主线程用setValue，其他线程PostValue
time.getSeconds().setValue(0);
}
public Time getLiveData(){
return time;
}
}3.observe数据
private TestViewModel vm;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
vm = new TestViewModel();
vm.getLiveData().getSeconds().observe(this, new Observer<Integer>() {
@Override
public void onChanged(Integer integer) {
EditText ed = findViewById(R.id.ed);
ed.setText(""+integer);
}
});1.build.gradle添加
buildFeatures {
viewBinding true
}
根视图和所有有ID的视图都会根据xml文件名称，生成对应的Binding类
2. 在Activity中使用view Binding
ActivityMainBinding binding = ActivityMainBinding.inflate(getLayoutInflater()); View view = binding.getRoot(); setContentView(view);
如果找不到Binding类，可能是名字错了，顺序再调一下可能就对了
在Fragment中使用view Binding
@Override
public View onCreateView (LayoutInflater inflater,
ViewGroup container,
Bundle savedInstanceState) {
ActivityMainBinding binding = ResultProfileBinding.inflate(inflater, container, false);
View view = binding.getRoot();
return view;
}由于fragment的生命周期更长，所以务必在destroy解除绑定
@Override
public void onDestroyView() {
super.onDestroyView();
binding = null;
}
