Question

将View Model实例传递给自定义视图有多安全？会导致内存泄漏吗？从布局中删除视图时，应该将实例设置为null吗？

我也尝试过将View Model实例与数据绑定一起传递，但是代码无法编译。您可以在文章底部看到该示例如何实现数据绑定的示例。

这是创建视图模型并将其传递到自定义视图的方式：

  public class MainActivity extends AppCompatActivity {

     private MainViewModel mViewModel;

     private MainActivityBinding mBinding;

       @Override
       protected void onCreate(@Nullable Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         mBinding = DataBindingUtil.setContentView(this, R.layout.activity_main);

         // Pass the application instance, not the activity context
         mViewModel = new MainViewModel(getApplication());

         createViews();
     }

     private void createViews() {
         // other UI stuff
         // ....

         addViewWithNames();
     }

     // Called only at activity onCreate()
     private void addViewWithNames() {
         // Inflate the custom view
         CustomView view = (CustomView) LayoutInflater.from(this).inflate(R.layout.layout_view_names, mBinding.mainLayoutContainer);

         // THIS IS WHERE THE VIEW MODEL IS PASSED TO THE VIEW
         view.setViewModel(mViewModel);

         // Add the view to the bottom of the page
         mBinding.linearLayoutBottom.addView(view);
     }

     // As you can see, there are a couple of different Custom Views, not a single one.
     // The Views are getting changed once an action is made in the app
     private void addViewWithScores() {
         // Inflate the custom view
         CustomView view = (CustomView) LayoutInflater.from(this).inflate(R.layout.layout_name_scores, mBinding.mainLayoutContainer);

         view.setViewModel(mViewModel);
         mBinding.linearLayoutBottom.addView(view);
     }

     // Random event that can happen
     private void onMoveToPage() {

         // Is this safe? Will the View Model removed from the Custom View? Will it keep a reference?
         mBinding.linearLayoutBottm.removeAllViews();
     }
  }

下面是带有视图模型实例的自定义视图：

private class CustomView extends RelativeLayout {

    private MainViewModel mViewModel;

    public CustomView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    public void setViewModel(MainViewModel viewModel) {
        mViewModel = viewModel;
    }

    // Should I set to null once the View is detached?
    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        mViewModel = null;
    }
}

这是我尝试通过数据绑定传递视图模型的方法，但是在视图膨胀时失败：

<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">

<data>

    <variable
        name="viewModel"
        type="de.nmnm.pager.GameViewModel" />
</data>

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <!-- OTHER VIEWS ... -->

    <de.nmnm.pager.CustomView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:setViewModel="@{viewModel}" />

    <!-- OTHER VIEWS ... -->

</LinearLayout>

使用上述数据绑定，项目将编译，创建生成的类，但是当布局膨胀（在活动的onCreate()时，应用崩溃）。

为自定义视图传递View Model实例是否安全？

0 个答案: