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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"// ViewModelimplementation "androidx.lifecycle:lifecycle-viewmodel:$lifecycle_version"// LiveDataimplementation "androidx.lifecycle:lifecycle-livedata:$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。