Android之Adapter優化

做過Android開發的都知道，Adapter的使用頻率很高。無論是ListView、GridView、Gallery都需要設置Adapter，而且它們的Adapter幾乎一樣，讓我們來看看我們經常用到的Adapter吧,我們可以邊看邊思考到底有多少東西是我們經常需要重複的:

先從構造說起：LayoutInflater重複

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

在說說其他需要重寫的方法：以下3個方法都是重複的寫（無任何技術含量）

@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：無非就是重用View，setTag (ViewHolder),除了ViewHolder的get和set內容不一樣其他都是在重複(傷不起有木有~！)。

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;
}

我們完全可以寫兩個基類把重複的東西抽取出來把代碼優化一下，看一下優化後的代碼吧：（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 簡化後的Adapter
 * @author Chad.Cym
 * @date 2014年8月25日 下午8:22:31
 *
 * @param <T>
 */
public class MyAdapter<T> extends BaseQuickAdapter<T, BaseAdapterHelper> {

    public MyAdapter(Context context, int layoutResId, List<T> 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);
    }

}

優化後只需要設置控件內容即可，不需要重複之前的所有重複代碼了。我們來看看抽取出來的基類：

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.<br>
 * <br>
 * <p/>
 * <b>Usage</b>
 * <p/>
 *
 * <pre>
 * 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();
 * </pre>
 */
public class BaseAdapterHelper {

    /** Views indexed with their IDs */
    private final SparseArray<View> 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<View>();
        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.<br/>
     * 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 <T 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.<br/>
     * It uses Square's Picasso library to download the image asynchronously and
     * put the result into the ImageView.<br/>
     * Picasso manages recycling of views in a ListView.<br/>
     * 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 <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;
    }

}

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.<br/>
 * Using the provided BaseAdapterHelper, your code is minimalist.
 * @param <T> The type of the items in the 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;

    /**
     * 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<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);
            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<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);

}
效果很明顯，簡單多了吧，希望能對大家有幫助。
源碼地址：https://github.com/JoanZapata/base-adapter-helper