BaseActivity.java

package com.patloew.countries.ui.base;

import android.databinding.DataBindingUtil;
import android.databinding.ViewDataBinding;
import android.os.Bundle;
import android.support.annotation.CallSuper;
import android.support.annotation.ColorRes;
import android.support.annotation.DimenRes;
import android.support.annotation.IntegerRes;
import android.support.annotation.LayoutRes;
import android.support.annotation.Nullable;
import android.support.annotation.StringRes;
import android.support.v7.app.AppCompatActivity;

import com.patloew.countries.BR;
import com.patloew.countries.CountriesApp;
import com.patloew.countries.injection.components.ActivityComponent;
import com.patloew.countries.injection.components.DaggerActivityComponent;
import com.patloew.countries.injection.modules.ActivityModule;
import com.patloew.countries.ui.base.view.MvvmView;
import com.patloew.countries.ui.base.viewmodel.MvvmViewModel;
import com.patloew.countries.ui.base.viewmodel.NoOpViewModel;
import com.squareup.leakcanary.RefWatcher;

import javax.inject.Inject;

import io.realm.Realm;

/* Copyright 2016 Patrick Löwenstein
 *
 * 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.
 *
 * -------
 *
 * FILE MODIFIED 2017 Tailored Media GmbH
 * */

/* Base class for Activities when using a view model with data binding.
 * This class provides the binding and the view model to the subclass. The
 * view model is injected and the binding is created when the content view is set.
 * Each subclass therefore has to call the following code in onCreate():
 *    activityComponent().inject(this);
 *    setAndBindContentView(R.layout.my_activity_layout, savedInstanceState);
 *
 * After calling these methods, the binding and the view model is initialized.
 * saveInstanceState() and restoreInstanceState() methods of the view model
 * are automatically called in the appropriate lifecycle events when above calls
 * are made.
 *
 * Your subclass must implement the MvvmView implementation that you use in your
 * view model. */
public abstract class BaseActivity<B extends ViewDataBinding, V extends MvvmViewModel> extends AppCompatActivity {


    // Inject a Realm instance into every Activity, since the instance
    // is cached and reused for a thread (avoids create/destroy overhead)
    @Inject protected Realm realm;

    protected B binding;
    @Inject protected V viewModel;

    @Inject
    RefWatcher refWatcher;

    private ActivityComponent mActivityComponent;

    @Override
    @CallSuper
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        if(viewModel != null) { viewModel.saveInstanceState(outState); }
    }

    @Override
    @CallSuper
    protected void onDestroy() {
        super.onDestroy();
        if(refWatcher != null) {
            refWatcher.watch(mActivityComponent);
            if(viewModel != null) { refWatcher.watch(viewModel); }
        }
        if(viewModel != null) { viewModel.detachView(); }
        binding = null;
        viewModel = null;
        mActivityComponent = null;
        if(realm != null) { realm.close(); }
    }

    protected final ActivityComponent activityComponent() {
        if (mActivityComponent == null) {
            mActivityComponent = DaggerActivityComponent.builder()
                    .activityModule(new ActivityModule(this))
                    .appComponent(CountriesApp.getAppComponent())
                    .build();
        }
        return mActivityComponent;

    }

    /* Sets the content view, creates the binding and attaches the view to the view model */
    protected final void setAndBindContentView(@Nullable Bundle savedInstanceState, @LayoutRes int layoutResID) {
        if(viewModel == null) { throw new IllegalStateException("viewModel must already be set via injection"); }
        binding = DataBindingUtil.setContentView(this, layoutResID);
        binding.setVariable(BR.vm, viewModel);

        try {
            //noinspection unchecked
            viewModel.attachView((MvvmView) this, savedInstanceState);
        } catch(ClassCastException e) {
            if (!(viewModel instanceof NoOpViewModel)) {
                throw new RuntimeException(getClass().getSimpleName() + " must implement MvvmView subclass as declared in " + viewModel.getClass().getSimpleName());
            }
        }
    }

    public int dimen(@DimenRes int resId) {
        return (int) getResources().getDimension(resId);
    }

    public int color(@ColorRes int resId) {
        return getResources().getColor(resId);
    }

    public int integer(@IntegerRes int resId) {
        return getResources().getInteger(resId);
    }

    public String string(@StringRes int resId) {
        return getResources().getString(resId);
    }
}