对base-adapter-helper的简单分析
长孙深
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。。
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