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 Android教程網 >> Android技術 >> 關於Android編程 >> Android基類設計方法詳解

Android基類設計方法詳解

編輯：關於Android編程

1 為什麼要設計基類

為什麼要給程序設計基類呢？主要是出於2個原因，一是方便代碼編寫，減少重復代碼和冗余邏輯，優化代碼；二是優化程序架構，降低耦合度，方便拓展、修改。

ok，編寫代碼是程序員的第一步，那麼第二步就是要編寫高質量的代碼，代碼能實現功能是一方面，寫的優美則是另一方面，這也是我們所有攻城獅們應該追求的境界。

2 設計基類的基本思路

那麼，哪些東西我們需要抽象到基類中呢？

2.1 重復的代碼：如果一個邏輯是大多數子類都需要使用的

2.2 臭而長的代碼：典型的findviewbyid、Toast

2.3 需要修改原生行為的：要改變某控件的樣式

2.4 為子類創建標准流程模板：模板設計模式

2.5 常用的方法：轉換dip、px

3 常用基類的設計實例

3.1 BaseActivity
public abstract class BaseActivity extends Activity {

	protected int mScreenWidth;
	protected int mScreenHeight;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);

		// 公共屬性
		DisplayMetrics metric = new DisplayMetrics();
		getWindowManager().getDefaultDisplay().getMetrics(metric);
		mScreenWidth = metric.widthPixels;
		mScreenHeight = metric.heightPixels;

		// 定制流程
		setContentView();
		initViews();
		initListeners();
		initData();
	}

	Toast mToast;

	public abstract void setContentView();

	public abstract void initViews();

	public abstract void initListeners();

	public abstract void initData();

	// 常用方法
	public void ShowToast(String text) {
		if (!TextUtils.isEmpty(text)) {
			if (mToast == null) {
				mToast = Toast.makeText(getApplicationContext(), text,
						Toast.LENGTH_SHORT);
			} else {
				mToast.setText(text);
			}
			mToast.show();
		}
	}

	// 常用方法
	public int getStateBar() {
		Rect frame = new Rect();
		getWindow().getDecorView().getWindowVisibleDisplayFrame(frame);
		int statusBarHeight = frame.top;
		return statusBarHeight;
	}

	// 常用方法
	public static int dip2px(Context context, float dipValue) {
		float scale = context.getResources().getDisplayMetrics().density;
		return (int) (scale * dipValue + 0.5f);
	}
}

3.2 BaseAdapter
/**
 * 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.annotation.TargetApi;
import android.content.Context;
import android.graphics.Bitmap;
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.ImageView;
import android.widget.ProgressBar;
import android.widget.RatingBar;
import android.widget.TextView;

import com.squareup.picasso.Picasso;
import com.squareup.picasso.RequestCreator;

/**
 * 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();
 * 

 */
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public class BaseAdapterHelper {

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

    private final Context context;

    private int position;

    private View convertView;

    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);
        }
        return (BaseAdapterHelper) convertView.getTag();
    }

    /**
     * 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  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 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);
        Picasso.with(context).load(imageUrl).into(view);
        return this;
    }

    /**
     * Will download an image from a URL and put it in an ImageView.

     * @param viewId         The view id.
     * @param requestBuilder The Picasso request builder. (e.g. Picasso.with(context).load(imageUrl))
     * @return The BaseAdapterHelper for chaining.
     */
    public BaseAdapterHelper setImageBuilder(int viewId, RequestCreator requestBuilder) {
        ImageView view = retrieveView(viewId);
        requestBuilder.into(view);
        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 */
    public BaseAdapterHelper setTypeface(int viewId, Typeface typeface) {
        TextView view = retrieveView(viewId);
        view.setTypeface(typeface);
        return this;
    }

    /** Apply the typeface to all the given viewIds */
    public BaseAdapterHelper setTypeface(Typeface typeface, int... viewIds) {
        for (int viewId : viewIds) {
            TextView view = retrieveView(viewId);
            view.setTypeface(typeface);
        }
        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.setProgress(progress);
        view.setMax(max);
        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.setRating(rating);
        view.setMax(max);
        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 retrieveView(int viewId) {
        View view = views.get(viewId);
        if (view == null) {
            view = convertView.findViewById(viewId);
            views.put(viewId, view);
        }
        return (T) view;
    }

}

如何使用呢：
/**
 * 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 BaseQuickAdapter 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 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);

}

最後再看下我們在設置adapter的時候如何使用：
/**
 * 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 java.util.List;

import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import static com.bmob.lostfound.adapter.BaseAdapterHelper.get;

/**
 * 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 QuickAdapter extends BaseQuickAdapter {

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

    /**
     * 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 QuickAdapter(Context context, int layoutResId, List data) {
        super(context,layoutResId,data);
    }

	protected BaseAdapterHelper getAdapterHelper(int position, View convertView, ViewGroup parent) {
		return get(context, convertView, parent, layoutResId, position);
	}

}

是不算少寫很多代碼，也許有人會說你寫前面那麼多代碼，比你後面少寫的還要多。確實，但是你忽略了一點就是上面的基類是通用的，也就是說，你一句話不用改就可以在其他項目中用了，你的程序員生涯就再也不用寫那麼多adapter了。
以上，關於Android基類設計方法就到這裡















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