src/android/src/com/google/android/inputmethod/japanese/DependencyFactory.java

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package org.mozc.android.inputmethod.japanese;

import org.mozc.android.inputmethod.japanese.model.SymbolCandidateStorage.SymbolHistoryStorage;
import org.mozc.android.inputmethod.japanese.preference.MozcFragmentPreferenceActivity;
import org.mozc.android.inputmethod.japanese.ui.MenuDialog.MenuDialogListener;
import org.mozc.android.inputmethod.japanese.util.ImeSwitcherFactory.ImeSwitcher;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Optional;
import com.google.common.base.Preconditions;

import android.app.Activity;
import android.content.Context;
import android.os.Build;

/**
 * Factory class for dependency.
 *
 * Here "Depenency" is for "Dependency Injection".
 * Dependency is resolved on runtime.
 * For example preference activity is dependent on the API level.
 * Previously the same thing is done by string resources (create instances by reflection).
 * But it is hard to test and sometime cause crash bugs which are found after external launch.
 */
public class DependencyFactory {


  /**
   * Dependencies.
   */
  public interface Dependency {

    /**
     * Creates a ViewManager.
     */
    public ViewManagerInterface createViewManager(
        Context context,
        ViewEventListener listener,
        SymbolHistoryStorage symbolHistoryStorage,
        ImeSwitcher imeSwitcher,
        MenuDialogListener menuDialogListener);

    /**
     * Returns a class for preference activity.
     */
    public Class<? extends Activity> getPreferenceActivityClass();

    public boolean isWelcomeActivityPreferrable();
  }

  /**
   * Dependency for standard (with fragment) UI.
   */
  @VisibleForTesting
  static final Dependency TOUCH_FRAGMENT_PREF = new Dependency() {

    @Override
    public ViewManagerInterface createViewManager(Context context, ViewEventListener listener,
        SymbolHistoryStorage symbolHistoryStorage, ImeSwitcher imeSwitcher,
        MenuDialogListener menuDialogListener) {
      return new ViewManager(
          Preconditions.checkNotNull(context),
          Preconditions.checkNotNull(listener),
          Preconditions.checkNotNull(symbolHistoryStorage),
          Preconditions.checkNotNull(imeSwitcher),
          Preconditions.checkNotNull(menuDialogListener));
    }

    @Override
    public Class<? extends Activity> getPreferenceActivityClass() {
      return MozcFragmentPreferenceActivity.class;
    }

    @Override
    public boolean isWelcomeActivityPreferrable() {
      return true;
    }
  };


  // For testing
  private static Optional<Dependency> dependencyForTesting = Optional.absent();

  @VisibleForTesting
  public static void setDependency(Optional<Dependency> dependency) {
    Preconditions.checkNotNull(dependency);
    dependencyForTesting = dependency;
  }

  public static Dependency getDependency(Context context) {
    Preconditions.checkNotNull(context);
    if (dependencyForTesting.isPresent()) {
      return dependencyForTesting.get();
    }
    return TOUCH_FRAGMENT_PREF;
  }

  private DependencyFactory() {}
}