Android之Adapter优化

做过Android开发的都知道，Adapter的使用频率很高。无论是ListView、GridView、Gallery都需要设置Adapter，而且它们的Adapter几乎一样，让我们来看看我们经常用到的Adapter吧,我们可以边看边思考到底有多少东西是我们经常需要重复的:

先从构造说起：LayoutInflater重复

 public MyAdapter1(Context context, int resId, List data) {
         mData = data;
         mContext = context;
         mInflater = (LayoutInflater) context
                 .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
         mLayoutResId = resId;
     }

在说说其他需要重写的方法：以下3个方法都是重复的写（无任何技术含量）

 @Override
     public int getCount() {
         return mData.size();
     }

     @Override
     public Object getItem(int arg0) {
         return mData.get(arg0);
     }

     @Override
     public long getItemId(int arg0) {
         return arg0;
     }

在看看最重要的getView方法：无非就是重用View，setTag (ViewHolder),除了ViewHolder的get和set内容不一样其他都是在重复(伤不起有木有~！)。

 public View getView(int position, View view, ViewGroup viewgroup) {
     if (view == null) {
         mHolder = new ViewHolder();
         view = mInflater.inflate(mLayoutResId, null);
         mHolder.tvText = (TextView) view.findViewById(android.R.id.text1);
         view.setTag(mHolder);
     } else {
         mHolder = (ViewHolder) view.getTag();
     }
     mHolder.tvText.setText(mData.get(position).toString());
     return view;
 }

 static class ViewHolder {
     TextView tvText;
 }

我们完全可以写两个基类把重复的东西抽取出来把代码优化一下，看一下优化后的代码吧：（在git看到的）

 package com.cym.chadtestdemo;

 import java.util.List;

 import android.content.Context;
 import android.view.View;
 import android.view.ViewGroup;

 import com.chronocloud.lib.base.BaseAdapterHelper;
 import com.chronocloud.lib.base.BaseQuickAdapter;

 /**
  *
  * @ClassName: MyAdapter
  * @Description: TODO 简化后的Adapter
  * @author Chad.Cym
  * @date 2014年8月25日 下午8:22:31
  *
  * @param
  */
 public class MyAdapter extends BaseQuickAdapter {

     public MyAdapter(Context context, int layoutResId, List data) {
         super(context, layoutResId, data);
     }

     @Override
     protected void convert(BaseAdapterHelper helper, T item) {
         helper.setText(android.R.id.text1, item.toString());
     }

     @Override
     protected BaseAdapterHelper getAdapterHelper(int position,
             View convertView, ViewGroup parent) {

         return BaseAdapterHelper.get(context, convertView, parent, layoutResId);
     }

 }

优化后只需要设置控件内容即可，不需要重复之前的所有重复代码了。我们来看看抽取出来的基类：

 package com.chronocloud.lib.base;

 /**
  *
  * 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.
  */

 import com.nostra13.universalimageloader.core.DisplayImageOptions;
 import com.nostra13.universalimageloader.core.ImageLoader;

 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.Adapter;
 import android.widget.AdapterView;
 import android.widget.Checkable;
 import android.widget.CompoundButton;
 import android.widget.ImageView;
 import android.widget.ProgressBar;
 import android.widget.RatingBar;
 import android.widget.TextView;

 /**
  * Allows an abstraction of the ViewHolder pattern.
  *
  *
  * Usage
  *
  *
  *
  * return BaseAdapterHelper.get(context, convertView, parent, R.layout.item)
  *      .setText(R.id.tvName, contact.getName())
  *      .setText(R.id.tvEmails, contact.getEmails().toString())
  *      .setText(R.id.tvNumbers, contact.getNumbers().toString()).getView();
  *
  */
 public class BaseAdapterHelper {

     /** Views indexed with their IDs */
     private final SparseArray views;

     private final Context context;

     private int position;

     private View convertView;

     /**
      * Package private field to retain the associated user object and detect a
      * change
      */
     Object associatedObject;

     private BaseAdapterHelper(Context context, ViewGroup parent, int layoutId,
             int position) {
         this.context = context;
         this.position = position;
         this.views = new SparseArray();
         convertView = LayoutInflater.from(context) //
                 .inflate(layoutId, parent, false);
         convertView.setTag(this);
     }

     /**
      * This method is the only entry point to get a BaseAdapterHelper.
      *
      * @param context
      *            The current context.
      * @param convertView
      *            The convertView arg passed to the getView() method.
      * @param parent
      *            The parent arg passed to the getView() method.
      * @return A BaseAdapterHelper instance.
      */
     public static BaseAdapterHelper get(Context context, View convertView,
             ViewGroup parent, int layoutId) {
         return get(context, convertView, parent, layoutId, -1);
     }

     /** This method is package private and should only be used by QuickAdapter. */
     static BaseAdapterHelper get(Context context, View convertView,
             ViewGroup parent, int layoutId, int position) {
         if (convertView == null) {
             return new BaseAdapterHelper(context, parent, layoutId, position);
         }

         // Retrieve the existing helper and update its position
         BaseAdapterHelper existingHelper = (BaseAdapterHelper) convertView
                 .getTag();
         existingHelper.position = position;
         return existingHelper;
     }

     /**
      * This method allows you to retrieve a view and perform custom operations
      * on it, not covered by the BaseAdapterHelper.
      * If you think it's a common use case, please consider creating a new issue
      * at https://github.com/JoanZapata/base-adapter-helper/issues.
      *
      * @param viewId
      *            The id of the view you want to retrieve.
      */
     public extends View> T getView(int viewId) {
         return retrieveView(viewId);
     }

     /**
      * Will set the text of a TextView.
      *
      * @param viewId
      *            The view id.
      * @param value
      *            The text to put in the text view.
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setText(int viewId, String value) {
         TextView view = retrieveView(viewId);
         view.setText(value);
         return this;
     }

     /**
      * Will set the image of an ImageView from a resource id.
      *
      * @param viewId
      *            The view id.
      * @param imageResId
      *            The image resource id.
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setImageResource(int viewId, int imageResId) {
         ImageView view = retrieveView(viewId);
         view.setImageResource(imageResId);
         return this;
     }

     /**
      * Will set background color of a view.
      *
      * @param viewId
      *            The view id.
      * @param color
      *            A color, not a resource id.
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setBackgroundColor(int viewId, int color) {
         View view = retrieveView(viewId);
         view.setBackgroundColor(color);
         return this;
     }

     /**
      * Will set background of a view.
      *
      * @param viewId
      *            The view id.
      * @param backgroundRes
      *            A resource to use as a background.
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setBackgroundRes(int viewId, int backgroundRes) {
         View view = retrieveView(viewId);
         view.setBackgroundResource(backgroundRes);
         return this;
     }

     /**
      * Will set text color of a TextView.
      *
      * @param viewId
      *            The view id.
      * @param textColor
      *            The text color (not a resource id).
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setTextColor(int viewId, int textColor) {
         TextView view = retrieveView(viewId);
         view.setTextColor(textColor);
         return this;
     }

     /**
      * Will set text color of a TextView.
      *
      * @param viewId
      *            The view id.
      * @param textColorRes
      *            The text color resource id.
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setTextColorRes(int viewId, int textColorRes) {
         TextView view = retrieveView(viewId);
         view.setTextColor(context.getResources().getColor(textColorRes));
         return this;
     }

     /**
      * Will set the image of an ImageView from a drawable.
      *
      * @param viewId
      *            The view id.
      * @param drawable
      *            The image drawable.
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setImageDrawable(int viewId, Drawable drawable) {
         ImageView view = retrieveView(viewId);
         view.setImageDrawable(drawable);
         return this;
     }

     /**
      * Will download an image from a URL and put it in an ImageView.
      * It uses Square's Picasso library to download the image asynchronously and
      * put the result into the ImageView.
      * Picasso manages recycling of views in a ListView.
      * If you need more control over the Picasso settings, use
      * {BaseAdapterHelper#setImageBuilder}.
      *
      * @param viewId
      *            The view id.
      * @param imageUrl
      *            The image URL.
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setImageUrl(int viewId, String imageUrl) {
         ImageView view = retrieveView(viewId);
         ImageLoader.getInstance().displayImage(imageUrl, view);
         return this;
     }

     public BaseAdapterHelper setImageUrl(int viewId, String imageUrl,
             DisplayImageOptions options) {
         ImageView view = retrieveView(viewId);
         ImageLoader.getInstance().displayImage(imageUrl, view, options);
         return this;
     }

     /**
      * Add an action to set the image of an image view. Can be called multiple
      * times.
      */
     public BaseAdapterHelper setImageBitmap(int viewId, Bitmap bitmap) {
         ImageView view = retrieveView(viewId);
         view.setImageBitmap(bitmap);
         return this;
     }

     /**
      * Add an action to set the alpha of a view. Can be called multiple times.
      * Alpha between 0-1.
      */
     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;
     }

     /**
      * Set a view visibility to VISIBLE (true) or GONE (false).
      *
      * @param viewId
      *            The view id.
      * @param visible
      *            True for VISIBLE, false for GONE.
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setVisible(int viewId, boolean visible) {
         View view = retrieveView(viewId);
         view.setVisibility(visible ? View.VISIBLE : View.GONE);
         return this;
     }

     /**
      * Add links into a TextView.
      *
      * @param viewId
      *            The id of the TextView to linkify.
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper linkify(int viewId) {
         TextView view = retrieveView(viewId);
         Linkify.addLinks(view, Linkify.ALL);
         return this;
     }

     /** Apply the typeface to the given viewId, and enable subpixel rendering. */
     public BaseAdapterHelper setTypeface(int viewId, Typeface typeface) {
         TextView view = retrieveView(viewId);
         view.setTypeface(typeface);
         view.setPaintFlags(view.getPaintFlags() | Paint.SUBPIXEL_TEXT_FLAG);
         return this;
     }

     /**
      * Apply the typeface to all the given viewIds, and enable subpixel
      * rendering.
      */
     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;
     }

     /**
      * Sets the progress of a ProgressBar.
      *
      * @param viewId
      *            The view id.
      * @param progress
      *            The progress.
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setProgress(int viewId, int progress) {
         ProgressBar view = retrieveView(viewId);
         view.setProgress(progress);
         return this;
     }

     /**
      * Sets the progress and max of a ProgressBar.
      *
      * @param viewId
      *            The view id.
      * @param progress
      *            The progress.
      * @param max
      *            The max value of a ProgressBar.
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setProgress(int viewId, int progress, int max) {
         ProgressBar view = retrieveView(viewId);
         view.setMax(max);
         view.setProgress(progress);
         return this;
     }

     /**
      * Sets the range of a ProgressBar to 0...max.
      *
      * @param viewId
      *            The view id.
      * @param max
      *            The max value of a ProgressBar.
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setMax(int viewId, int max) {
         ProgressBar view = retrieveView(viewId);
         view.setMax(max);
         return this;
     }

     /**
      * Sets the rating (the number of stars filled) of a RatingBar.
      *
      * @param viewId
      *            The view id.
      * @param rating
      *            The rating.
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setRating(int viewId, float rating) {
         RatingBar view = retrieveView(viewId);
         view.setRating(rating);
         return this;
     }

     /**
      * Sets the rating (the number of stars filled) and max of a RatingBar.
      *
      * @param viewId
      *            The view id.
      * @param rating
      *            The rating.
      * @param max
      *            The range of the RatingBar to 0...max.
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setRating(int viewId, float rating, int max) {
         RatingBar view = retrieveView(viewId);
         view.setMax(max);
         view.setRating(rating);
         return this;
     }

     /**
      * Sets the on click listener of the view.
      *
      * @param viewId
      *            The view id.
      * @param listener
      *            The on click listener;
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setOnClickListener(int viewId,
             View.OnClickListener listener) {
         View view = retrieveView(viewId);
         view.setOnClickListener(listener);
         return this;
     }

     /**
      * Sets the on touch listener of the view.
      *
      * @param viewId
      *            The view id.
      * @param listener
      *            The on touch listener;
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setOnTouchListener(int viewId,
             View.OnTouchListener listener) {
         View view = retrieveView(viewId);
         view.setOnTouchListener(listener);
         return this;
     }

     /**
      * Sets the on long click listener of the view.
      *
      * @param viewId
      *            The view id.
      * @param listener
      *            The on long click listener;
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setOnLongClickListener(int viewId,
             View.OnLongClickListener listener) {
         View view = retrieveView(viewId);
         view.setOnLongClickListener(listener);
         return this;
     }

     /**
      * Sets the tag of the view.
      *
      * @param viewId
      *            The view id.
      * @param tag
      *            The tag;
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setTag(int viewId, Object tag) {
         View view = retrieveView(viewId);
         view.setTag(tag);
         return this;
     }

     /**
      * Sets the tag of the view.
      *
      * @param viewId
      *            The view id.
      * @param key
      *            The key of tag;
      * @param tag
      *            The tag;
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setTag(int viewId, int key, Object tag) {
         View view = retrieveView(viewId);
         view.setTag(key, tag);
         return this;
     }

     /**
      * Sets the checked status of a checkable.
      *
      * @param viewId
      *            The view id.
      * @param checked
      *            The checked status;
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setChecked(int viewId, boolean checked) {
         Checkable view = (Checkable) retrieveView(viewId);
         view.setChecked(checked);
         return this;
     }

     /**
      * Sets the adapter of a adapter view.
      *
      * @param viewId
      *            The view id.
      * @param adapter
      *            The adapter;
      * @return The BaseAdapterHelper for chaining.
      */
     public BaseAdapterHelper setAdapter(int viewId, Adapter adapter) {
         AdapterView view = retrieveView(viewId);
         view.setAdapter(adapter);
         return this;
     }

     /** Retrieve the convertView */
     public View getView() {
         return convertView;
     }

     /**
      * Retrieve the overall position of the data in the list.
      *
      * @throws IllegalArgumentException
      *             If the position hasn't been set at the construction of the
      *             this helper.
      */
     public int getPosition() {
         if (position == -1)
             throw new IllegalStateException(
                     "Use BaseAdapterHelper constructor "
                             + "with position if you need to retrieve the position.");
         return position;
     }

     @SuppressWarnings("unchecked")
     private 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;
     }

 }

 package com.chronocloud.lib.base;


 /**
  * Copyright 2013 Joan Zapata
  *
  * 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.
  */

 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;

 /**
  * Abstraction class of a BaseAdapter in which you only need
  * to provide the convert() implementation.
  * Using the provided BaseAdapterHelper, your code is minimalist.
  * @param  The type of the items in the list.
  */
 public abstract class BaseQuickAdapterextends BaseAdapterHelper> extends BaseAdapter {

     protected static final String TAG = BaseQuickAdapter.class.getSimpleName();

     protected final Context context;

     protected final int layoutResId;

     protected final List data;

     protected boolean displayIndeterminateProgress = false;

     /**
      * Create a QuickAdapter.
      * @param context     The context.
      * @param layoutResId The layout resource id of each item.
      */
     public BaseQuickAdapter(Context context, int layoutResId) {
         this(context, layoutResId, null);
     }

     /**
      * Same as QuickAdapter#QuickAdapter(Context,int) but with
      * some initialization data.
      * @param context     The context.
      * @param layoutResId The layout resource id of each item.
      * @param data        A new list is created out of this one to avoid mutable list
      */
     public BaseQuickAdapter(Context context, int layoutResId, List data) {
         this.data = data == null ? new ArrayList() : new ArrayList(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);
             convert(helper, getItem(position));
             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 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 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);

 }

效果很明显，简单多了吧，希望能对大家有帮助。

源码地址：https://github.com/JoanZapata/base-adapter-helper