在微博上看到了这篇Android ListView适配器应该这样写，受益匪浅。
于是依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。
源代码包括4个文件：
BaseAdapterHelper.java
BaseQuickAdapter.java
EnhancedQuickAdapter.java
QuickAdapter.java
其中最基本的是前两个。
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，包括一些封装好的经常使用功能，比方imageView图片的载入，文本框改动文本，给控件加入各种事件等等。
先上代码，凝视我自己加的：
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;
private final Context context;
private int position;
private View convertView;
Object associatedObject;
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);
}
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;
}
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;
}
public BaseAdapterHelper setText(int viewId, String value) {
TextView view = retrieveView(viewId);
view.setText(value);
return this;
}
public BaseAdapterHelper setImageResource(int viewId, int imageResId) {
ImageView view = retrieveView(viewId);
view.setImageResource(imageResId);
return this;
}
public BaseAdapterHelper setBackgroundColor(int viewId, int color) {
View view = retrieveView(viewId);
view.setBackgroundColor(color);
return this;
}
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;
}
public BaseAdapterHelper setImageUrl(int viewId, String imageUrl) {
ImageView view = retrieveView(viewId);
Picasso.with(context).load(imageUrl).into(view);
return this;
}
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;
}
public BaseAdapterHelper setAlpha(int viewId, float value) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
retrieveView(viewId).setAlpha(value);
} else {
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; } public BaseAdapterHelper linkify(int viewId) { TextView view = retrieveView(viewId); Linkify.addLinks(view, Linkify.ALL); return this; } 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; } 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; } public BaseAdapterHelper setOnClickListener(int viewId, View.OnClickListener listener) { View view = retrieveView(viewId); view.setOnClickListener(listener); return this; } 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; } 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; } public BaseAdapterHelper setChecked(int viewId, boolean checked) { Checkable view = (Checkable) retrieveView(viewId); view.setChecked(checked); return this; } public BaseAdapterHelper setAdapter(int viewId, Adapter adapter) { AdapterView view = retrieveView(viewId); view.setAdapter(adapter); return this; } public View getView() { return convertView; } 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的载入。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)，能够通过类名.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)这种方法替代了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);
}
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;
}
@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; } @Override public int getViewTypeCount() { return 2; } @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) { final H helper = getAdapterHelper(position, convertView, parent); T item = getItem(position); helper.setAssociatedObject(item); convert(helper, item); return helper.getView(); } return createIndeterminateProgressView(convertView, parent); } 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); } public void clear() { data.clear(); notifyDataSetChanged(); } public void showIndeterminateProgress(boolean display) { if (display == displayIndeterminateProgress) return; displayIndeterminateProgress = display; notifyDataSetChanged(); } protected abstract void convert(H helper, T item); 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是用户须要实现的功能逻辑，getAdapterHelper须要用户提供item的layoutId。
这个类设计的是包括两种布局，一种是用户自己定义的item布局，还有一种是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，首先依据getItemViewType()推断类型，为0 就是item布局，通过调用子类的getAdapterHelper()方法得到对应的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图片载入、文本框设置文本等等相似逻辑。
大概重要的都说了，代码凝视也有。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，事实上我们能够改动，那篇文章里也有，详细的就是添加一个布局数组，在getView()方法中加以推断，比方聊天界面，有发送方和接收方。布局是左右相反的，一个是靠左。还有一个靠右，在消息类里肯定有这个属性，是否是自己发送。用这个项目其中来。就是重写getItemViewType()，在getView()中推断和载入。
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非常大提高，还要继续学习。
。
本文转自mfrbuaa博客园博客，原文链接：http://www.cnblogs.com/mfrbuaa/p/5173994.html，如需转载请自行联系原作者
