Square Flow + Mortar 平板电脑示例

Question

我一直在尝试使用 Flow 和 Mortor 作为我们 Android 应用的替代架构。我一直在开发一个应用程序，该应用程序目前只有一个手机布局，但我想知道如果你想为平板电脑设置不同的布局，流和砂浆架构如何工作。主细节可能是最简单的例子，但显然还有其他例子。

我有一些想法，但我想知道广场开发人员可能已经围绕这个主题想到了什么。

Answer 1

我们仍在为此制定规范的答案，但基本思想是让资源系统更改您在哪种情况下显示的视图。因此，您的活动将其内容视图设置为 R.layout.root_view。该布局的平板电脑版本（我们将其放在res/layout-sw600dp 中）可以绑定到不同的视图，这可能会注入不同的演示者，等等。

对于需要做出运行时决定的情况，请在 values/bools .xml 中定义一个布尔资源

<?xml version="1.0" encoding="utf-8"?>
<resources>
  <bool name="show_tablet_ui">false</bool>
</resources>

和values-sw600dp/bools.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
  <bool name="show_tablet_ui">true</bool>
</resources>

通过 dagger 将其暴露给应用程序的其余部分。使用这个绑定注解：

/**
 * Whether we should show a tablet UI.
 */
@Retention(RUNTIME) @Qualifier
public @interface ShowTabletUi {
  int ID = R.bool.show_tablet_ui;
}

还有一个提供者方法，例如：

/** 
 * Singleton because there's no reason to read it from resources again, 
 * it won't change. 
 */
@Provides @ShowTabletUi @Singleton boolean showTabletUi(Resources resources) {
  return resources.getBoolean(ShowTabletUi.ID);
}

但是等等还有更多！假设您想要一个单一的屏幕/蓝图定义，为不同的外形尺寸制造不同的模块。我们已经开始使用注释方案来简化这种事情。我们没有让我们的屏幕类都实现BluePrint，而是开始使用一些注释来声明它们的接口类。在这个世界中，屏幕可以选择性地选择用于平板电脑或移动设备的模块。

@Layout(R.layout.some_view) @WithModuleFactory(SomeScreen.ModuleFactory.class)
public class SomeScreen {
  public static class ModuleFactory extends ResponsiveModuleFactory<HomeScreen> {
  @Override protected Object createTabletModule(HomeScreen screen) {
    return new TabletModule();
  }

  @Override protected Object createMobileModule(HomeScreen screen) {
    return new MobileModule();
  }
}

魔法，对吧？这是幕后的东西。首先，ModuleFactory 是一个静态类，可以访问屏幕和资源，并输出一个匕首模块。

public abstract class ModuleFactory<T> {
  final Blueprint createBlueprint(final Resources resources, final MortarScreen screen) {
    return new Blueprint() {
      @Override public String getMortarScopeName() {
        return screen.getName();
      }

      @Override public Object getDaggerModule() {
        return ModuleFactory.this.createDaggerModule(resources, (T) screen);
      }
    };
  }

  protected abstract Object createDaggerModule(Resources resources, T screen);
}

我们的 trixie ResponsiveModuleFactory 子类看起来像这样。 （还记得ShowTabletUi.java 是如何将资源 id 定义为常量的吗？这就是原因。）

public abstract class ResponsiveModuleFactory<T> extends ModuleFactory<T> {

  @Override protected final Object createDaggerModule(Resources resources, T screen) {
    boolean showTabletUi = resources.getBoolean(ShowTabletUi.ID);
    return showTabletUi ? createTabletModule(screen) : createMobileModule(screen);
  }

  protected abstract Object createTabletModule(T screen);

  protected abstract Object createMobileModule(T screen);
}

为了完成这一切，我们有一个 ScreenScoper 类（如下）。在 Mortar 示例代码中，您将让 ScreenConductor 使用其中之一来创建和销毁作用域。迟早（我希望很快）迫击炮和/或其样本将被更新以包含这些东西。

package mortar;

import android.content.Context;
import android.content.res.Resources;
import com.squareup.util.Objects;
import dagger.Module;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.util.LinkedHashMap;
import java.util.Map;

import static java.lang.String.format;

/**
 * Creates {@link MortarScope}s for screens that may be annotated with {@link WithModuleFactory},
 * {@link WithModule} or {@link Module}.
 */
public class ScreenScoper {
  private static final ModuleFactory NO_FACTORY = new ModuleFactory() {
    @Override protected Object createDaggerModule(Resources resources, Object screen) {
      throw new UnsupportedOperationException();
    }
  };

  private final Map<Class, ModuleFactory> moduleFactoryCache = new LinkedHashMap<>();

  public MortarScope getScreenScope(Context context, final MortarScreen screen) {
    MortarScope parentScope = Mortar.getScope(context);
    return getScreenScope(context.getResources(), parentScope, screen);
  }

  /**
   * Finds or creates the scope for the given screen, honoring its optoinal {@link
   * WithModuleFactory} or {@link WithModule} annotation. Note the scopes are also created
   * for unannotated screens.
   */
  public MortarScope getScreenScope(Resources resources, MortarScope parentScope,
      final MortarScreen screen) {
    ModuleFactory moduleFactory = getModuleFactory(screen);
    MortarScope childScope;
    if (moduleFactory != NO_FACTORY) {
      Blueprint blueprint = moduleFactory.createBlueprint(resources, screen);
      childScope = parentScope.requireChild(blueprint);
    } else {
      // We need every screen to have a scope, so that anything it injects is scoped.  We need
      // this even if the screen doesn't declare a module, because Dagger allows injection of
      // objects that are annotated even if they don't appear in a module.
      Blueprint blueprint = new Blueprint() {
        @Override public String getMortarScopeName() {
          return screen.getName();
        }

        @Override public Object getDaggerModule() {
          return null;
        }
      };
      childScope = parentScope.requireChild(blueprint);
    }
    return childScope;
  }

  private ModuleFactory getModuleFactory(MortarScreen screen) {
    Class<?> screenType = Objects.getClass(screen);
    ModuleFactory moduleFactory = moduleFactoryCache.get(screenType);

    if (moduleFactory != null) return moduleFactory;

    WithModule withModule = screenType.getAnnotation(WithModule.class);
    if (withModule != null) {
      Class<?> moduleClass = withModule.value();

      Constructor<?>[] constructors = moduleClass.getDeclaredConstructors();

      if (constructors.length != 1) {
        throw new IllegalArgumentException(
            format("Module %s for screen %s should have exactly one public constructor",
                moduleClass.getName(), screen.getName()));
      }

      Constructor constructor = constructors[0];

      Class[] parameters = constructor.getParameterTypes();

      if (parameters.length > 1) {
        throw new IllegalArgumentException(
            format("Module %s for screen %s should have 0 or 1 parameter", moduleClass.getName(),
                screen.getName()));
      }

      Class screenParameter;
      if (parameters.length == 1) {
        screenParameter = parameters[0];
        if (!screenParameter.isInstance(screen)) {
          throw new IllegalArgumentException(format("Module %s for screen %s should have a "
                  + "constructor parameter that is a super class of %s", moduleClass.getName(),
              screen.getName(), screen.getClass().getName()));
        }
      } else {
        screenParameter = null;
      }

      try {
        if (screenParameter == null) {
          moduleFactory = new NoArgsFactory(constructor);
        } else {
          moduleFactory = new SingleArgFactory(constructor);
        }
      } catch (Exception e) {
        throw new RuntimeException(
            format("Failed to instantiate module %s for screen %s", moduleClass.getName(),
                screen.getName()), e);
      }
    }

    if (moduleFactory == null) {
      WithModuleFactory withModuleFactory = screenType.getAnnotation(WithModuleFactory.class);
      if (withModuleFactory != null) {
        Class<? extends ModuleFactory> mfClass = withModuleFactory.value();

        try {
          moduleFactory = mfClass.newInstance();
        } catch (Exception e) {
          throw new RuntimeException(format("Failed to instantiate module factory %s for screen %s",
              withModuleFactory.value().getName(), screen.getName()), e);
        }
      }
    }

    if (moduleFactory == null) moduleFactory = NO_FACTORY;

    moduleFactoryCache.put(screenType, moduleFactory);

    return moduleFactory;
  }

  private static class NoArgsFactory extends ModuleFactory<Object> {
    final Constructor moduleConstructor;

    private NoArgsFactory(Constructor moduleConstructor) {
      this.moduleConstructor = moduleConstructor;
    }

    @Override protected Object createDaggerModule(Resources resources, Object ignored) {
      try {
        return moduleConstructor.newInstance();
      } catch (InstantiationException | IllegalAccessException | InvocationTargetException e) {
        throw new RuntimeException(e);
      }
    }
  }

  private static class SingleArgFactory extends ModuleFactory {
    final Constructor moduleConstructor;

    public SingleArgFactory(Constructor moduleConstructor) {
      this.moduleConstructor = moduleConstructor;
    }

    @Override protected Object createDaggerModule(Resources resources, Object screen) {
      try {
        return moduleConstructor.newInstance(screen);
      } catch (InstantiationException | IllegalAccessException | InvocationTargetException e) {
        throw new RuntimeException(e);
      }
    }
  }
}