[译]DetailsOverviewRowPresenter和FullWidthDetailsOverviewRowPresenter-白红宇

推荐：欢迎关注我创建的Android TV 简书专题，会定期给大家分享一些AndroidTv相关的内容：

本章目的 - DetailsActivity的实现实现了以下功能：

在MainFragment中setOnItemViewClickedListener - onItemClicked回调函数。实现之后，我们可以点击card去详情页。我们将在本章中显示每个电影项目的内容详细信息。

编写DetailsActivity，VideoDetailsFragment和DetailsDescriptionPresenter DetailsActivity通过在MainActivity中card来调用。它显示VideoDetailsFragment，它是显示card内容的布局。

###在MainFragment 中实现点击监听当用户点击某个card时跳转到下一个动作，使用BrowseFragment类中定义的setOnItemViewClickedListener方法（MainFragment类是一个BrowseFragment的子类）。

示例实现如下。这与上一章中介绍的setOnItemViewSelectedListener几乎相同。 MainFragment.java

@Override    public void onActivityCreated(Bundle savedInstanceState) {        ...        setupEventListeners();        picassoBackgroundManager = new PicassoBackgroundManager(getActivity());    }    private void setupEventListeners() {        setOnItemViewSelectedListener(new ItemViewSelectedListener());        setOnItemViewClickedListener(new ItemViewClickedListener());    }    private final class ItemViewClickedListener implements OnItemViewClickedListener {        @Override        public void onItemClicked(Presenter.ViewHolder itemViewHolder, Object item,                                  RowPresenter.ViewHolder rowViewHolder, Row row) {            // each time the item is clicked, code inside here will be executed.            }        }    }复制代码

###DetailsActivity和VideoDetailsFragment - 说明以下是AOSP示例应用程序的图片。

在Android示例应用程序中，我们在VideoDetailsFragment中设置2行。第一行是DetailsOverviewRow，第二行是ListRow（已在MainFragment中解释）。 DetailsOverviewRow显示内容详细信息，其中包括图片中的图片，描述和一些操作设置在左下角。

我们可以准备我们自己的Presenter来指定DetailsOverviewRow的设计布局。我们可以在Leanback支持库中使用2个预先实施的presenters。 1.DetailsOverviewRowPresenter：在上图中显示，但它已经在版本22.2.0中被弃用。 2.FullWidthDetailsOverviewRowPresenter：用于替换DetailsOverviewRowPresenter，在AOSP文档中建议使用此presenter。

接下来，我将尝试介绍这个新的FullWidthDetailsOverviewRowPresenter（你还可以查看DetailsOverviewRowPresenter，请参阅此帖的底部）。它将指定DetailsOverviewRow的设计布局，通常在你的DetailFragment的第一行中使用它来显示项目详细信息。 FullWidthDetailsOverviewRowPresenter包含三部分，即： 1.Logo view：可定制（可选），通过实现DetailsOverViewLogoPresenter 2.Action list view:通过点击可以查看不同的信息，如视频简介，演员表等。 3.详细的说明view：可定制（必须），是 AbstractDetailsDescriptionPresenter 的子类

我们定义了“DetailsDescriptionPresenter”，它继承了Leanback libarary中定义的AbstractDetailsDescriptionPresenter。 AbstractDetailsDescriptionPresenter决定描述视图的设计布局。

###DetailsActivity 和 VideoDetailsFragment – 实现我们继续创建DetailsActivity来显示内容详细信息的UI。该设计在VideoDetailsFragment中指定，它是DetailFragment的子类。

创建DetailsActivity和VideoDetailsFragment以与中介绍的MainActivity和MainFragment相同的方式完成。

####DetailsActivity 创建：New → Activity → BlankActivity

####VideoDetailsFragment 创建：New -> Java Class -> Name: VideoDetailsFragment

首先，修改activity_details.xml，如下所示，只显示VideoDetailsFragment。


    
    复制代码

修改VideoDetailsFragment。我们将这个VideoDetailsFragment作为DetailFragment的子类。 DetailsFragment类是在 leanback support library中用于内容详细信息的UI。在VideoDetailsFragment中，声明的私有成员mFwdorPresenter是FullWidthDetailsOverviewRowPresenter的实例。

请注意，AsyncTask用于在后台线程（“doInBackground”）中执行一些任务，然后在UI线程（“onPostExecute”）中执行一些任务。在这里，我们在后台加载图片图像，并在UI线程中更新UI。

import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.os.AsyncTask;import android.os.Bundle;import android.support.v17.leanback.app.DetailsFragment;import android.support.v17.leanback.widget.Action;import android.support.v17.leanback.widget.ArrayObjectAdapter;import android.support.v17.leanback.widget.ClassPresenterSelector;import android.support.v17.leanback.widget.DetailsOverviewRow;import android.support.v17.leanback.widget.FullWidthDetailsOverviewRowPresenter;import android.support.v17.leanback.widget.HeaderItem;import android.support.v17.leanback.widget.ListRow;import android.support.v17.leanback.widget.ListRowPresenter;import android.support.v17.leanback.widget.SparseArrayObjectAdapter;import android.util.Log;import com.squareup.picasso.Picasso;import java.io.IOException;public class VideoDetailsFragment extends DetailsFragment {    private static final String TAG = VideoDetailsFragment.class.getSimpleName();    private static final int DETAIL_THUMB_WIDTH = 274;    private static final int DETAIL_THUMB_HEIGHT = 274;    private static final String MOVIE = "Movie";    private CustomFullWidthDetailsOverviewRowPresenter mFwdorPresenter;    private PicassoBackgroundManager mPicassoBackgroundManager;    private Movie mSelectedMovie;    private DetailsRowBuilderTask mDetailsRowBuilderTask;    @Override    public void onCreate(Bundle savedInstanceState) {        Log.i(TAG, "onCreate");        super.onCreate(savedInstanceState);        mFwdorPresenter = new CustomFullWidthDetailsOverviewRowPresenter(new DetailsDescriptionPresenter());        mPicassoBackgroundManager = new PicassoBackgroundManager(getActivity());        mSelectedMovie = (Movie)getActivity().getIntent().getSerializableExtra(MOVIE);        mDetailsRowBuilderTask = (DetailsRowBuilderTask) new DetailsRowBuilderTask().execute(mSelectedMovie);        mPicassoBackgroundManager.updateBackgroundWithDelay(mSelectedMovie.getCardImageUrl());;    }    @Override    public void onStop() {        mDetailsRowBuilderTask.cancel(true);        super.onStop();    }    private class DetailsRowBuilderTask extends AsyncTask
    
      {        @Override        protected DetailsOverviewRow doInBackground(Movie... params) {            DetailsOverviewRow row = new DetailsOverviewRow(mSelectedMovie);            try {                Bitmap poster = Picasso.with(getActivity())                        .load(mSelectedMovie.getCardImageUrl())                        .resize(Utils.convertDpToPixel(getActivity().getApplicationContext(), DETAIL_THUMB_WIDTH),                                Utils.convertDpToPixel(getActivity().getApplicationContext(), DETAIL_THUMB_HEIGHT))                        .centerCrop()                        .get();                row.setImageBitmap(getActivity(), poster);            } catch (IOException e) {                Log.w(TAG, e.toString());            }            return row;        }        @Override        protected void onPostExecute(DetailsOverviewRow row) {                    /* 1st row: DetailsOverviewRow */            SparseArrayObjectAdapter sparseArrayObjectAdapter = new SparseArrayObjectAdapter();            for (int i = 0; i<10; i++){                sparseArrayObjectAdapter.set(i, new Action(i, "label1", "label2"));            }            row.setActionsAdapter(sparseArrayObjectAdapter);        /* 2nd row: ListRow */            ArrayObjectAdapter listRowAdapter = new ArrayObjectAdapter(new CardPresenter());            for(int i = 0; i < 10; i++){                Movie movie = new Movie();                if(i%3 == 0) {                    movie.setCardImageUrl("http://heimkehrend.raindrop.jp/kl-hacker/wp-content/uploads/2014/08/DSC02580.jpg");                } else if (i%3 == 1) {                    movie.setCardImageUrl("http://heimkehrend.raindrop.jp/kl-hacker/wp-content/uploads/2014/08/DSC02630.jpg");                } else {                    movie.setCardImageUrl("http://heimkehrend.raindrop.jp/kl-hacker/wp-content/uploads/2014/08/DSC02529.jpg");                }                movie.setTitle("title" + i);                movie.setStudio("studio" + i);                listRowAdapter.add(movie);            }            HeaderItem headerItem = new HeaderItem(0, "Related Videos");            ClassPresenterSelector classPresenterSelector = new ClassPresenterSelector();            mFwdorPresenter.setInitialState(FullWidthDetailsOverviewRowPresenter.STATE_SMALL);            Log.e(TAG, "mFwdorPresenter.getInitialState: " +mFwdorPresenter.getInitialState());            classPresenterSelector.addClassPresenter(DetailsOverviewRow.class, mFwdorPresenter);            classPresenterSelector.addClassPresenter(ListRow.class, new ListRowPresenter());            ArrayObjectAdapter adapter = new ArrayObjectAdapter(classPresenterSelector);            /* 1st row */            adapter.add(row);            /* 2nd row */            adapter.add(new ListRow(headerItem, listRowAdapter));            /* 3rd row */            //adapter.add(new ListRow(headerItem, listRowAdapter));            setAdapter(adapter);        }    }}复制代码

请注意，适配器的构造函数在MainFragment和VideoDetailsFragment之间是不同的。我们只在MainFragment中使用ListRow - ListRowPresenter。在这种情况下，我们可以通过设置Presenter本身来实例化适配器。 MainFragment.java

adapter = new ArrayObjectAdapter(new ListRowPresenter());复制代码

我们正在使用VideoDetails Fragment中的DetailsOverviewRow - FullWidthDetailsOverviewRowPresenter和ListRow - ListRowPresenter。 ClassPresenterSelector定义了这个对应关系，我们可以在适配器的构造函数的参数中使用它。 VideoDetailsFragment.java

ClassPresenterSelector classPresenterSelector = new ClassPresenterSelector();classPresenterSelector.addClassPresenter(DetailsOverviewRow.class, mFwdorPresenter);classPresenterSelector.addClassPresenter(ListRow.class, new ListRowPresenter());adapter = new ArrayObjectAdapter(classPresenterSelector);复制代码

接下来，在Movie类中添加描述成员，可以在Android studio中通过[Alt] + [Insert]实现Getter和Setter方法。此外，使Movie Serializable可以通过意图传递此对象。因为我们通过意图将Movie对象从MainActivity传递给DetailsActivity。

public class Movie implements Serializable {    private static final String TAG = Movie.class.getSimpleName();    static final long serialVersionUID = 727566175075960653L;    private long id;    private String title;    private String studio;    private String description;    private String cardImageUrl;    ...    public String getDescription() {        return description;    }    public void setDescription(String description) {        this.description = description;    }    ...}复制代码

从AOSP样本源代码复制DetailsDescriptionPresenter如下。再次，DetailsDescriptionPresenter扩展了AbstractDetailsDescriptionPresenter，它决定了描述视图的设计布局。

/* * Copyright (C) 2014 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.corochann.androidtvapptutorial;import android.support.v17.leanback.widget.AbstractDetailsDescriptionPresenter;public class DetailsDescriptionPresenter extends AbstractDetailsDescriptionPresenter {    @Override    protected void onBindDescription(ViewHolder viewHolder, Object item) {        Movie movie = (Movie) item;        if (movie != null) {            viewHolder.getTitle().setText(movie.getTitle());            viewHolder.getSubtitle().setText(movie.getStudio());            viewHolder.getBody().setText(movie.getDescription());        }    }}复制代码

CustomFullWidthDetailsOverviewRowPresenter.java

import android.support.v17.leanback.widget.FullWidthDetailsOverviewRowPresenter;import android.support.v17.leanback.widget.Presenter;import android.support.v17.leanback.widget.RowPresenter;public class CustomFullWidthDetailsOverviewRowPresenter extends FullWidthDetailsOverviewRowPresenter {    CustomFullWidthDetailsOverviewRowPresenter(Presenter presenter) {        super(presenter);    }    @Override    protected void onBindRowViewHolder(RowPresenter.ViewHolder holder, Object item) {        super.onBindRowViewHolder(holder, item);        this.setState((ViewHolder) holder, FullWidthDetailsOverviewRowPresenter.STATE_SMALL);    }}复制代码

最后，修改MainFragment以发送intent来启动DetailsActivity。

private void setupEventListeners() {        setOnItemViewSelectedListener(new ItemViewSelectedListener());        setOnItemViewClickedListener(new ItemViewClickedListener());    }    private final class ItemViewClickedListener implements OnItemViewClickedListener {        @Override        public void onItemClicked(Presenter.ViewHolder itemViewHolder, Object item,                                  RowPresenter.ViewHolder rowViewHolder, Row row) {            // each time the item is clicked, code inside here will be executed.            if (item instanceof Movie) {                Movie movie = (Movie) item;                Log.d(TAG, "Item: " + item.toString());                Intent intent = new Intent(getActivity(), DetailsActivity.class);                intent.putExtra(DetailsActivity.MOVIE, movie);                getActivity().startActivity(intent);            }        }    }复制代码

###编译后运行

当用户再次按“下”键时，将出现下一行（此示例中的ListRow）。

源码在. ###编译运行2

如果您对（已经不推荐使用）DetailsOverviewRowPresenter实现感兴趣，请检查上的更新源代码。下一篇：关注微信公众号，定期为你推荐移动开发相关文章。