samples/SupportLeanbackJank/src/com/google/android/leanbackjank/presenter/HeaderItemPresenter.java

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * 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 com.google.android.leanbackjank.presenter;

import android.content.Context;
import android.graphics.drawable.Drawable;
import android.support.v17.leanback.widget.HeaderItem;
import android.support.v17.leanback.widget.ListRow;
import android.support.v17.leanback.widget.Presenter;
import android.support.v17.leanback.widget.RowHeaderPresenter;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import com.google.android.leanbackjank.R;

public class HeaderItemPresenter extends RowHeaderPresenter {
    private float mUnselectedAlpha;

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup viewGroup) {
        mUnselectedAlpha = viewGroup.getResources()
                .getFraction(R.fraction.lb_browse_header_unselect_alpha, 1, 1);
        LayoutInflater inflater = (LayoutInflater) viewGroup.getContext()
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        View view = inflater.inflate(R.layout.header_item, null);
        view.setAlpha(mUnselectedAlpha); // Initialize icons to be at half-opacity.

        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(Presenter.ViewHolder viewHolder, Object item) {
        HeaderItem headerItem = ((ListRow) item).getHeaderItem();
        View rootView = viewHolder.view;
        rootView.setFocusable(true);

        ImageView iconView = (ImageView) rootView.findViewById(R.id.header_icon);
        Drawable icon = rootView.getResources().getDrawable(R.drawable.android_header, null);
        iconView.setImageDrawable(icon);

        TextView label = (TextView) rootView.findViewById(R.id.header_label);
        label.setText(headerItem.getName());
    }

    @Override
    public void onUnbindViewHolder(Presenter.ViewHolder viewHolder) {
        // no op
    }

    // TODO: This is a temporary fix. Remove me when leanback onCreateViewHolder no longer sets the
    // mUnselectAlpha, and also assumes the xml inflation will return a RowHeaderView.
    @Override
    protected void onSelectLevelChanged(RowHeaderPresenter.ViewHolder holder) {
        holder.view.setAlpha(
                mUnselectedAlpha + holder.getSelectLevel() * (1.0f - mUnselectedAlpha));
    }
}