/
NavigatingViewModel.java
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/
NavigatingViewModel.java
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/*
* Copyright 2016 Andrei Zaiats.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.github.azaiats.androidmvvm.navigation.common;
import android.support.annotation.Nullable;
import io.github.azaiats.androidmvvm.core.common.BaseViewModel;
/**
* ViewModel with navigation
* <p>
* ViewModel has no direct reference to context. So it can't starts new {@link android.app.Activity}
* or replace {@link android.app.Fragment} via {@link android.app.FragmentManager}.
* This work can be delegated to external navigator.
*
* @param <T> the type of {@link Navigator}
* @author Andrei Zaiats
* @since 0.1.1
*/
public abstract class NavigatingViewModel<T extends Navigator> extends BaseViewModel {
@Nullable protected T navigator;
@Nullable protected NavigationCommand<T> pendingCommand;
/**
* Setter for navigator
* @param navigator {@link Navigator} for this ViewModel
*/
public void setNavigator(@Nullable T navigator) {
this.navigator = navigator;
if (navigator != null && pendingCommand != null) {
pendingCommand.execute(navigator);
pendingCommand = null;
}
}
/**
* Executes command if {@link Navigator} is attached.
* Otherwise command will be saved and executed on {@link Navigator} attach.
*
* @param navigationCommand command for {@link Navigator}
*/
public void executeNavigationCommand(NavigationCommand<T> navigationCommand) {
if (navigationCommand == null) {
return;
}
T vmNavigator = navigator;
if (vmNavigator == null) {
pendingCommand = navigationCommand;
} else {
navigationCommand.execute(vmNavigator);
}
}
}