AndroidJava创建ViewModel新api

背景

项目使用Java，创建ViewModel发现之前旧api不管用了。不要问为什么项目还要用Java，别问。老项目不让升级。

ViewModel创建新方式

新方式是因为依赖新版本库，其实用旧版本库就回到旧方式了。 依赖：

def lifecycle_version = "2.5.0" // ViewModel implementation "androidx.lifecycle:lifecycle-viewmodel:$lifecycle_version" // LiveData implementation "androidx.lifecycle:lifecycle-livedata:$lifecycle_version" // Lifecycles only (without ViewModel or LiveData) implementation "androidx.lifecycle:lifecycle-runtime:$lifecycle_version"

从2.4开始换新方式，当然传递参数更容易了。

public class LauncherViewModel extends ViewModel { private static final String TAG = "LauncherViewModel"; public static final ViewModelInitializer<LauncherViewModel> initializer = new ViewModelInitializer<>( LauncherViewModel.class, creationExtras -> { return new LauncherViewModel(); } ); }

传递参数的案例： 也可以参考传递参数，变得简单了

public class MyViewModel extends ViewModel { public MyViewModel( MyRepository myRepository, SavedStateHandle savedStateHandle ) { /* Init ViewModel here */ } static final ViewModelInitializer<MyViewModel> initializer = new ViewModelInitializer<>( MyViewModel.class, creationExtras -> { MyApplication app = (MyApplication) creationExtras.get(APPLICATION_KEY); assert app != null; SavedStateHandle savedStateHandle = createSavedStateHandle(creationExtras); return new MyViewModel(app.getMyRepository(), savedStateHandle); } ); }

初始化：

MyViewModel myViewModel = new ViewModelProvider( this, ViewModelProvider.Factory.from(MyViewModel.initializer) ).get(MyViewModel.class);

没错，就是这样，比之前多了2个参数。