对base-adapter-helper的简单分析

在微博上看到了这篇Android ListView适配器应该这样写，受益匪浅。
于是根据文章结尾的介绍来到了base-adapter-helper的github，地址：https://github.com/JoanZapata/base-adapter-helper
然后下载看看，我等小菜也来分析分析。
源码包含4个文件：
BaseAdapterHelper.java
BaseQuickAdapter.java
EnhancedQuickAdapter.java
QuickAdapter.java
其中最主要的是前两个。
先看BaseAdapterHelper，第一个文章也写了，这个类是替代viewHolder的，进一步封装优化的产物，包含一些封装好的常用功能，比如imageView图片的加载，文本框修改文本，给控件添加各种事件等等。
先上代码，注释我自己加的：

package com.joanzapata.android;import android.content.Context;import android.graphics.Bitmap;import android.graphics.Paint;import android.graphics.Typeface;import android.graphics.drawable.Drawable;import android.os.Build;import android.text.util.Linkify;import android.util.SparseArray;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.view.animation.AlphaAnimation;import android.widget.*;import com.squareup.picasso.Picasso;import com.squareup.picasso.RequestCreator;public class BaseAdapterHelper {    private final SparseArray<View> views;//类似hashMap ,但是更高效强大    private final Context context;    private int position;    private View convertView;    Object associatedObject;//item的数据 item    protected BaseAdapterHelper(Context context, ViewGroup parent, int layoutId, int position) {        this.context = context;        this.position = position;        this.views = new SparseArray<View>();        convertView = LayoutInflater.from(context)                 .inflate(layoutId, parent, false);        convertView.setTag(this);    }    //  静态方法，根据listview里getView的参数生成BaseAdapterHelper    public static BaseAdapterHelper get(Context context, View convertView, ViewGroup parent, int layoutId) {        return get(context, convertView, parent, layoutId, -1);    }    static BaseAdapterHelper get(Context context, View convertView, ViewGroup parent, int layoutId, int position) {        if (convertView == null) {            return new BaseAdapterHelper(context, parent, layoutId, position);        }        BaseAdapterHelper existingHelper = (BaseAdapterHelper) convertView.getTag();        existingHelper.position = position;        return existingHelper;    }    //  根据id得到控件    public <T extends View> T getView(int viewId) {        return retrieveView(viewId);    }    @SuppressWarnings("unchecked")    protected <T extends View> T retrieveView(int viewId) {        View view = views.get(viewId);        if (view == null) {            view = convertView.findViewById(viewId);            views.put(viewId, view);        }        return (T) view;    }    //  textview 设置文字    public BaseAdapterHelper setText(int viewId, String value) {        TextView view = retrieveView(viewId);        view.setText(value);        return this;    }    //  设置图片    public BaseAdapterHelper setImageResource(int viewId, int imageResId) {        ImageView view = retrieveView(viewId);        view.setImageResource(imageResId);        return this;    }    //  设置颜色    public BaseAdapterHelper setBackgroundColor(int viewId, int color) {        View view = retrieveView(viewId);        view.setBackgroundColor(color);        return this;    }    //  设置背景图片    public BaseAdapterHelper setBackgroundRes(int viewId, int backgroundRes) {        View view = retrieveView(viewId);        view.setBackgroundResource(backgroundRes);        return this;    }    public BaseAdapterHelper setTextColor(int viewId, int textColor) {        TextView view = retrieveView(viewId);        view.setTextColor(textColor);        return this;    }    public BaseAdapterHelper setTextColorRes(int viewId, int textColorRes) {        TextView view = retrieveView(viewId);        view.setTextColor(context.getResources().getColor(textColorRes));        return this;    }    public BaseAdapterHelper setImageDrawable(int viewId, Drawable drawable) {        ImageView view = retrieveView(viewId);        view.setImageDrawable(drawable);        return this;    }    //  设置图片url ，异步下载图片    public BaseAdapterHelper setImageUrl(int viewId, String imageUrl) {        ImageView view = retrieveView(viewId);        Picasso.with(context).load(imageUrl).into(view);        return this;    }    //  requestBuilder是Picasso request builder ，异步加载图片    public BaseAdapterHelper setImageBuilder(int viewId, RequestCreator requestBuilder) {        ImageView view = retrieveView(viewId);        requestBuilder.into(view);        return this;    }    public BaseAdapterHelper setImageBitmap(int viewId, Bitmap bitmap) {        ImageView view = retrieveView(viewId);        view.setImageBitmap(bitmap);        return this;    }    //  设置图片的透明度    public BaseAdapterHelper setAlpha(int viewId, float value) {        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {            retrieveView(viewId).setAlpha(value);        } else {            // Pre-honeycomb hack to set Alpha value            AlphaAnimation alpha = new AlphaAnimation(value, value);            alpha.setDuration(0);            alpha.setFillAfter(true);            retrieveView(viewId).startAnimation(alpha);        }        return this;    }    public BaseAdapterHelper setVisible(int viewId, boolean visible) {        View view = retrieveView(viewId);        view.setVisibility(visible ? View.VISIBLE : View.GONE);        return this;    }    //添加 addLinks    public BaseAdapterHelper linkify(int viewId) {        TextView view = retrieveView(viewId);        Linkify.addLinks(view, Linkify.ALL);        return this;    }    //  文本框字体    public BaseAdapterHelper setTypeface(int viewId, Typeface typeface) {        TextView view = retrieveView(viewId);        view.setTypeface(typeface);        view.setPaintFlags(view.getPaintFlags() | Paint.SUBPIXEL_TEXT_FLAG);        return this;    }    public BaseAdapterHelper setTypeface(Typeface typeface, int... viewIds) {        for (int viewId : viewIds) {            TextView view = retrieveView(viewId);            view.setTypeface(typeface);            view.setPaintFlags(view.getPaintFlags() | Paint.SUBPIXEL_TEXT_FLAG);        }        return this;    }    //  设置进度条    public BaseAdapterHelper setProgress(int viewId, int progress) {        ProgressBar view = retrieveView(viewId);        view.setProgress(progress);        return this;    }    public BaseAdapterHelper setProgress(int viewId, int progress, int max) {        ProgressBar view = retrieveView(viewId);        view.setMax(max);        view.setProgress(progress);        return this;    }    public BaseAdapterHelper setMax(int viewId, int max) {        ProgressBar view = retrieveView(viewId);        view.setMax(max);        return this;    }    public BaseAdapterHelper setRating(int viewId, float rating) {        RatingBar view = retrieveView(viewId);        view.setRating(rating);        return this;    }    public BaseAdapterHelper setRating(int viewId, float rating, int max) {        RatingBar view = retrieveView(viewId);        view.setMax(max);        view.setRating(rating);        return this;    }    //  设置控件的点击事件    public BaseAdapterHelper setOnClickListener(int viewId, View.OnClickListener listener) {        View view = retrieveView(viewId);        view.setOnClickListener(listener);        return this;    }    //  设置控件的onTouch事件    public BaseAdapterHelper setOnTouchListener(int viewId, View.OnTouchListener listener) {        View view = retrieveView(viewId);        view.setOnTouchListener(listener);        return this;    }    public BaseAdapterHelper setOnLongClickListener(int viewId, View.OnLongClickListener listener) {        View view = retrieveView(viewId);        view.setOnLongClickListener(listener);        return this;    }    //  设置控件的tag    public BaseAdapterHelper setTag(int viewId, Object tag) {        View view = retrieveView(viewId);        view.setTag(tag);        return this;    }    public BaseAdapterHelper setTag(int viewId, int key, Object tag) {        View view = retrieveView(viewId);        view.setTag(key, tag);        return this;    }    //  设置选中状态    public BaseAdapterHelper setChecked(int viewId, boolean checked) {        Checkable view = (Checkable) retrieveView(viewId);        view.setChecked(checked);        return this;    }    //  设置adapter    public BaseAdapterHelper setAdapter(int viewId, Adapter adapter) {        AdapterView view = retrieveView(viewId);        view.setAdapter(adapter);        return this;    }    public View getView() {        return convertView;    }    //  得到item的position，如果是-1，则异常    public int getPosition() {        if (position == -1)            throw new IllegalStateException("Use BaseAdapterHelper constructor " +                    "with position if you need to retrieve the position.");        return position;    }    public Object getAssociatedObject() {        return associatedObject;    }    /** Should be called during convert */    public void setAssociatedObject(Object associatedObject) {        this.associatedObject = associatedObject;    }}

构造函数是一些初始化，convertView的加载，views的初始化。
看这个静态方法，static BaseAdapterHelper get(Context context, View convertView, ViewGroup parent, int layoutId, int position)，可以通过类名.的方式生成这个类的实例，传入的convertView是listview的getView方法里的，layoutId即为item的布局文件id。
protected <T extends View> T retrieveView(int viewId)这个方法替代了holderview的作用。
后面的方法都是设置控件的属性或者事件等等，注意associatedObject这个属性是item的data，所以是Object类型。

再看看核心的BaseQuickAdapter。
代码：

package com.joanzapata.android;import android.content.Context;import android.view.Gravity;import android.view.View;import android.view.ViewGroup;import android.widget.BaseAdapter;import android.widget.FrameLayout;import android.widget.ProgressBar;import java.util.ArrayList;import java.util.List;public abstract class BaseQuickAdapter<T, H extends BaseAdapterHelper> extends BaseAdapter {    protected static final String TAG = BaseQuickAdapter.class.getSimpleName();    protected final Context context;    protected final int layoutResId;    protected final List<T> data;    protected boolean displayIndeterminateProgress = false;    public BaseQuickAdapter(Context context, int layoutResId) {        this(context, layoutResId, null);    }    //根据layoutId和data初始化    public BaseQuickAdapter(Context context, int layoutResId, List<T> data) {        this.data = data == null ? new ArrayList<T>() : new ArrayList<T>(data);        this.context = context;        this.layoutResId = layoutResId;    }    //如果Progress显示则加1    @Override    public int getCount() {        int extra = displayIndeterminateProgress ? 1 : 0;        return data.size() + extra;    }    @Override    public T getItem(int position) {        if (position >= data.size()) return null;        return data.get(position);    }    @Override    public long getItemId(int position) {        return position;    }    //  item type的数量，两种，一种是item，都是相同的，另一种是Progress    @Override    public int getViewTypeCount() {        return 2;    }    //  当position超过data数量时，加载progress，是另一种布局    @Override    public int getItemViewType(int position) {        return position >= data.size() ? 1 : 0;    }    @Override    public View getView(int position, View convertView, ViewGroup parent) {        if (getItemViewType(position) == 0) {//普通布局            final H helper = getAdapterHelper(position, convertView, parent);//getAdapterHelper()是一个抽象方法，子类实现，需要提供的参数是layoutID，也就是item的布局            T item = getItem(position);            helper.setAssociatedObject(item);            convert(helper, item);//convert需要之类实现，功能逻辑            return helper.getView();        }        return createIndeterminateProgressView(convertView, parent);//加载progress布局    }    private View createIndeterminateProgressView(View convertView, ViewGroup parent) {        if (convertView == null) {            FrameLayout container = new FrameLayout(context);            container.setForegroundGravity(Gravity.CENTER);            ProgressBar progress = new ProgressBar(context);            container.addView(progress);            convertView = container;        }        return convertView;    }    @Override    public boolean isEnabled(int position) {        return position < data.size();    }    public void add(T elem) {        data.add(elem);        notifyDataSetChanged();    }    public void addAll(List<T> elem) {        data.addAll(elem);        notifyDataSetChanged();    }    public void set(T oldElem, T newElem) {        set(data.indexOf(oldElem), newElem);    }    public void set(int index, T elem) {        data.set(index, elem);        notifyDataSetChanged();    }    public void remove(T elem) {        data.remove(elem);        notifyDataSetChanged();    }    public void remove(int index) {        data.remove(index);        notifyDataSetChanged();    }    public void replaceAll(List<T> elem) {        data.clear();        data.addAll(elem);        notifyDataSetChanged();    }    public boolean contains(T elem) {        return data.contains(elem);    }    /** Clear data list */    public void clear() {        data.clear();        notifyDataSetChanged();    }    public void showIndeterminateProgress(boolean display) {        if (display == displayIndeterminateProgress) return;        displayIndeterminateProgress = display;        notifyDataSetChanged();    }    /**     * Implement this method and use the helper to adapt the view to the given item.     * @param helper A fully initialized helper.     * @param item   The item that needs to be displayed.     */    protected abstract void convert(H helper, T item);    /**     * You can override this method to use a custom BaseAdapterHelper in order to fit your needs     * @param position    The position of the item within the adapter's data set of the item whose view we want.     * @param convertView The old view to reuse, if possible. Note: You should check that this view     *                    is non-null and of an appropriate type before using. If it is not possible to convert     *                    this view to display the correct data, this method can create a new view.     *                    Heterogeneous lists can specify their number of view types, so that this View is     *                    always of the right type (see {@link #getViewTypeCount()} and     *                    {@link #getItemViewType(int)}).     * @param parent      The parent that this view will eventually be attached to     * @return An instance of BaseAdapterHelper     */    protected abstract H getAdapterHelper(int position, View convertView, ViewGroup parent);}

这个类继承了BaseAdapter，是抽象类，抽象方法为protected abstract void convert(H helper, T item);和protected abstract H getAdapterHelper(int position, View convertView, ViewGroup parent);供子类实现，convert是用户需要实现的功能逻辑，getAdapterHelper需要用户提供item的layoutId。这个类设计的是包含两种布局，一种是用户自定义的item布局，另一种是Progress的布局，所以在getCount()返回的是data.size()+1,getViewTypeCount()返回2，区分这两种用getItemViewType()。
看最重要的getView()方法，首先根据getItemViewType()判断类型，为0 就是item布局，通过调用子类的getAdapterHelper()方法得到相应的AdapterHelper进行设置，为1就是Progress，通过new了一个FrameLayout布局实现。在item生成过程中，convert()是最重要的，对于实际的开发，一般用于设置item图片加载、文本框设置文本等等类似逻辑。
大概重要的都说了，代码注释也有。在上面第一个提到的文章里也说了，这个项目不支持item有多个布局，其实我们可以修改，那篇文章里也有，具体的就是增加一个布局数组，在getView()方法中加以判断，比如聊天界面，有发送方和接收方，布局是左右相反的，一个是靠左，另一个靠右，在消息类里肯定有这个属性，是否是自己发送，用这个项目当中来，就是重写getItemViewType()，在getView()中判断和加载。
努力学习和运用开源项目，了解后面的原理和流程，对自己思路和能力都有很大提高，还要继续学习。。