Android 仿今日头条的开源项目

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2017-02-23
原文链接:www.weyye.me

起因

看到众多大神纷纷有了自己的开源项目,于是自己琢磨着也想做一个开源项目来学习下,因为每次无聊必刷的app就是今日头条,评论简直比内容都精彩,所以我打算仿今日头条来练练手,期间也曾放弃过,也遇到很多坑,拿出来跟大家分享一下。该项目使用的是MVP+RxJava+Retrofit。喜欢的记得给个Star,当作是给我的鼓励和动力吧。

源码链接

github.com/yewei02538/…

无图言屌

第三方库

技术要点

  • 主要是一些第三方库的使用
  • 首页顶部导航使用的hongyang大神的ColorTrackView然后做了一下封装来实现滑动渐变效果
  • 多种Item布局展示->BaseRecyclerViewAdapterHelper
  • 日夜间模式切换->MultipleTheme
  • 个人中心 自定义ScrollView实现下拉图片放大
  • 新闻详情我采用的是RecyclerView添加头的方式添加WebView(当然是Adapter里面添加),加载页面成功之后获取评论信息,点击评论图标滑动至评论第一条,这里我是调用recyclerView.smoothScrollToPosition(1);
  • 视频播放我使用的是JieCaoVideoPlayer,一群大牛封装的代码,底层实际使用ijkplayer,视频源均使用非正常手段获取,视频源地址分析请看我的另一篇博客 手撸一个今日头条视频下载器

问题1

在使用MultipleTheme的时候唯一的缺陷就是需要在布局里面大量使用到自定义控件,这对于我们的项目而言,布局看着很冗余,也有点恶心。。我有时候就在想,那我可不可以写原生控件,然后在特定的时机来个偷梁换柱换成我们的自定义控件呢?(比如我们布局写RelativeLayout—转换成MyRelativeLayout),似乎好像是可以的。

思路1

当时想到一个最简单最快实现的方法,也就是替换,我在布局里面写原生控件,然后在用工具全局替换成我们的自定义控件,但是假如我们换了包名,那就需要重新替换,这无疑是不易扩展的,所以这个方法放弃掉

思路2

不知道大家有木有发现就是,我们在布局里面写上ButtonImageViewTextView等这些控件的时候,在5.0以上运行的时候实际变成了AppCompatButtonAppCompatImageViewAppCompatTextView(debug或者打印对象就可以看到实际的类型),在当我们运行的时候就这样悄无声息的给替换了,那系统又是怎么做到的?那只要找到它的实现方法,我们的问题不就迎刃而解了吗?

于是我找到系统替换的代码(以下代码全部基于Api23)

AppCompatViewInflater.java

public final View createView(View parent, final String name, @NonNull Context context,        @NonNull AttributeSet attrs, boolean inheritContext,        boolean readAndroidTheme, boolean readAppTheme, boolean wrapContext) {    final Context originalContext = context;    // We can emulate Lollipop's android:theme attribute propagating down the view hierarchy    // by using the parent's context    if (inheritContext && parent != null) {        context = parent.getContext();    }    if (readAndroidTheme || readAppTheme) {        // We then apply the theme on the context, if specified        context = themifyContext(context, attrs, readAndroidTheme, readAppTheme);    }    if (wrapContext) {        context = TintContextWrapper.wrap(context);    }    View view = null;    // We need to 'inject' our tint aware Views in place of the standard framework versions    switch (name) {        case "TextView":            view = new AppCompatTextView(context, attrs);            break;        case "ImageView":            view = new AppCompatImageView(context, attrs);            break;        case "Button":            view = new AppCompatButton(context, attrs);            break;        case "EditText":            view = new AppCompatEditText(context, attrs);            break;        case "Spinner":            view = new AppCompatSpinner(context, attrs);            break;        case "ImageButton":            view = new AppCompatImageButton(context, attrs);            break;        case "CheckBox":            view = new AppCompatCheckBox(context, attrs);            break;        case "RadioButton":            view = new AppCompatRadioButton(context, attrs);            break;        case "CheckedTextView":            view = new AppCompatCheckedTextView(context, attrs);            break;        case "AutoCompleteTextView":            view = new AppCompatAutoCompleteTextView(context, attrs);            break;        case "MultiAutoCompleteTextView":            view = new AppCompatMultiAutoCompleteTextView(context, attrs);            break;        case "RatingBar":            view = new AppCompatRatingBar(context, attrs);            break;        case "SeekBar":            view = new AppCompatSeekBar(context, attrs);            break;    }    if (view == null && originalContext != context) {        // If the original context does not equal our themed context, then we need to manually        // inflate it using the name so that android:theme takes effect.        view = createViewFromTag(context, name, attrs);    }    if (view != null) {        // If we have created a view, check it's android:onClick        checkOnClickListener(view, attrs);    }    return view;}

当我们在xml写的那些布局映射成对象的时候,都会调用到这里来转换成对应的AppCompat。

偷梁换柱的关键点我们找到了,那如何找到这个入口呢?

其实当我们加载布局的时候最终都会用LayoutInflater来加载,所以我打算从这里入手,看源码我发现有一个接口可以利用->Factory,这个接口有一个方法

public interface Factory {    /**     * Hook you can supply that is called when inflating from a LayoutInflater.     * You can use this to customize the tag names available in your XML     * layout files.     *      * <p>     * Note that it is good practice to prefix these custom names with your     * package (i.e., com.coolcompany.apps) to avoid conflicts with system     * names.     *      * @param name Tag name to be inflated.     * @param context The context the view is being created in.     * @param attrs Inflation attributes as specified in XML file.     *      * @return View Newly created view. Return null for the default     *         behavior.     */    public View onCreateView(String name, Context context, AttributeSet attrs);}

果然功夫不负有心人,如果我们实现了这个接口,最终加载布局的时候那么就会调用onCreateView在这里面来实现偷梁换柱替换成我们的自定义控件

ok,入口和关键代码都找到了,剩下的就是撸代码了

public class SkinFactory implements LayoutInflaterFactory {    private AppCompatActivity mActivity;    public SkinFactory(AppCompatActivity activity) {        mActivity = activity;    }    @Override    public View onCreateView(View parent, String name, Context context, AttributeSet attrs) {        View view = null;		//是否需要替换成自定义View        boolean isColorUi = attrs.getAttributeBooleanValue("http://schemas.android.com/apk/res-auto", "isColorUi", false);        if (!isColorUi) return delegateCreateView(parent, name, context, attrs);        switch (name) {            case "TextView":                view = new ColorTextView(context, attrs);                break;            case "ImageView":                view = new ColorImageView(context, attrs);                Logger.i("ImageView 转换成"+view.getClass().getSimpleName());                break;            case "RelativeLayout":                view = new ColorRelativeLayout(context, attrs);                break;            case "LinearLayout":                view = new ColorLinearLayout(context, attrs);                break;            case "View":                view = new ColorView(context, attrs);                break;        }        if (view == null) {            view = delegateCreateView(parent, name, context, attrs);        }        return view;    }    private View delegateCreateView(View parent, String name, Context context, AttributeSet attrs) {        AppCompatDelegate delegate = mActivity.getDelegate();        return delegate.createView(parent, name, context, attrs);    }}

这里isColorUi做了一个标示,因为有的是不需要转换的,如果不转换,直接走系统的创建View流程

关键代码写好了,下面是入口

BaseActivity.java

   protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);LayoutInflaterCompat.setFactory(layoutInflater, new SkinFactory(this));}

原本以为这样就完美的解决了,没想到又引出了下一个问题

Caused by: java.lang.IllegalStateException: A factory has already been set on this LayoutInflater        at android.view.LayoutInflater.setFactory2(LayoutInflater.java:317)        at android.support.v4.view.LayoutInflaterCompatLollipop.setFactory(LayoutInflaterCompatLollipop.java:28)        at android.support.v4.view.LayoutInflaterCompat$LayoutInflaterCompatImplV21.setFactory(LayoutInflaterCompat.java:55)        at android.support.v4.view.LayoutInflaterCompat.setFactory(LayoutInflaterCompat.java:85)        at me.weyye.todaynews.base.BaseActivity.setLayoutInflaterFactory(BaseActivity.java:70)        at me.weyye.todaynews.base.BaseActivity.onCreate(BaseActivity.java:60)        at android.app.Activity.performCreate(Activity.java:6910)        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123)        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2746)        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2864)         at android.app.ActivityThread.-wrap12(ActivityThread.java)         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1567)

于是找到这个方法

public void setFactory(Factory factory) {        if (mFactorySet) {            throw new IllegalStateException("A factory has already been set on this LayoutInflater");        }        if (factory == null) {            throw new NullPointerException("Given factory can not be null");        }        mFactorySet = true;        if (mFactory == null) {            mFactory = factory;        } else {            mFactory = new FactoryMerger(factory, null, mFactory, mFactory2);        }    }

mFactorySet=true的时候就会抛出这个错误,可是我并没有去set,那么可能是系统set了,对,没错,不然它怎么转换成AppCompat呢。

那么我只需要用反射把mFactorySet改成false就可以了

于是乎我修改了下原来的代码

BaseActivity.java

@Overrideprotected void onCreate(Bundle savedInstanceState) {	super.onCreate(savedInstanceState);	setLayoutInflaterFactory();}   public void setLayoutInflaterFactory() {       LayoutInflater layoutInflater = getLayoutInflater();       try {           Field mFactorySet = LayoutInflater.class.getDeclaredField("mFactorySet");           mFactorySet.setAccessible(true);           mFactorySet.set(layoutInflater, false);           LayoutInflaterCompat.setFactory(layoutInflater, new SkinFactory(this));       } catch (Exception e) {           e.printStackTrace();       }   }

先利用反射改成false然后在设置上去,这样就不会报错了

问题2

好吧,几经周折终于完成了日夜间切换,但是当我滑动新闻列表的时候,又一个问题出来了…

当点击切换成夜间主题后,列表滑动后有的还是白天的主题,这很明显是RecyclerView复用的问题,我的思路是当点击切换主题后清除掉复用的View,这样就不会出现这种问题。怎么清除呢?好像RecyclerView没有直接给我们方法,所以我得去源码好好看看,发现RecyclerView里面有个内部类Recycler用来管理复用和回收的类,而且有clear方法,

public final class Recycler {	...	/**    * Clear scrap views out of this recycler. Detached views contained within a    * recycled view pool will remain.    */    public void clear() {        mAttachedScrap.clear();        recycleAndClearCachedViews();    }	...}

看代码好像是我所需要的,于是找到这个类对应的变量mRecycler,可惜的是private并且没有get方法,那就只好反射咯~

RecyclerView recyclerView = (RecyclerView) rootView;try {    Field mRecyclerField = RecyclerView.class.getDeclaredField("mRecycler");    mRecyclerField.setAccessible(true);    Method clearMethod = RecyclerView.Recycler.class.getDeclaredMethod("clear");    clearMethod.setAccessible(true);    clearMethod.invoke(mRecyclerField.get(recyclerView));} catch (Exception e) {    e.printStackTrace();}

ok,成功解决!

未完待续…

TODO

  • 加入未写界面以及功能
  • 逻辑代码的整理

参考

Android 源码系列之<四>从源码的角度深入理解LayoutInflater.Factory之主题切换(上)

声明

这个属于个人开发作品,仅做学习交流使用,如用到实际项目还需多考虑其他因素如并发等,请多多斟酌。诸位勿传播于非技术人员,拒绝用于商业用途,数据均属于非正常渠道获取,原作公司拥有所有权利。

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