Android設計模式－－建造者模式，android設計模式--

Android設計模式－－建造者模式，android設計模式--

回頭看自己寫的東西，在關於Android自訂控制項時，寫的代碼適用性比較高，但是看上去沒有什麼技術含量，所以在學習設計模式的時候，想想有些東西是否能夠改進，比如說：

自訂Dialog是Android應用必須的，系統的控制項實在是太難看了；

在構建中，完全是，new完對象之後，需要什麼構建什麼，這樣寫沒有問題，可讀性也還行，就是看上去不咋的。

以下是小部分程式碼片段：

package com.example.demo.Builder;/** *  * @author qubian * @data 2015年6月10日 * @email naibbian@163.com * */public class BuilderDialog extends Dialog implements View.OnClickListener {private Context mContext;private View view;private View lineView;private TextView titleTv;private TextView contentTv;private Button sureBtn;private Button cancelBtn;private String sureTitle;private String cancelTitle;private String title;private String content;private boolean sureVisible = true;private boolean cancelVisible = true;private View.OnClickListener sureListener;private View.OnClickListener cancelListener;public BuilderDialog(Context context, String title, String content) {super(context, R.style.base_dialog_style);this.mContext = context;this.title = title;this.content = content;view = LayoutInflater.from(mContext).inflate(R.layout.dialog_normal,null);addContentView(view, Utils.getDialogLayoutParams(mContext));}public void setSureTitle(String title) {sureTitle = title;}public void setCancelTitle(String title) {cancelTitle = title;}public void setCancelVisible(boolean visible) {cancelVisible = visible;}public void setSureListener(View.OnClickListener listener) {if (listener != null) {sureListener = listener;}}public void setCancelListener(View.OnClickListener listener) {}/** * 是否可以返回 *  * @param canBack */public void setCanBack(boolean canBack) {}       //初始化private void initView() {lineView = view.findViewById(R.id.line_view);titleTv = (TextView) view.findViewById(R.id.title_tv);contentTv = (TextView) view.findViewById(R.id.content_tv);contentTv.setText((content.replace("\\r","\r").replace("\\n", "\n")));sureBtn = (Button) view.findViewById(R.id.sure_btn);cancelBtn = (Button) view.findViewById(R.id.cancel_btn);}@Overridepublic void show() {initView();titleTv.setText(title);if (sureVisible) {if (sureListener == null) {sureBtn.setOnClickListener(this);} else {sureBtn.setOnClickListener(sureListener);}if (sureTitle != null) {sureBtn.setText(sureTitle);}} else {sureBtn.setVisibility(View.GONE);}if (cancelVisible) {} else {}super.show();}@Overridepublic void onClick(View v) {if (v.getId() == sureBtn.getId()) {this.cancel();} else if (v.getId() == cancelBtn.getId()) {this.cancel();}}}

使用，和適用都沒問題，並且邏輯也比較簡單，那麼如何最佳化呢？

言歸正傳：

建造者模式

1、定義：

將一個複雜的構建與其表示分離，使得相同的構建有了不同的表示。

2、目的：

建造者模式是講複雜的內部構建封裝在內部，對於其他外部成員來說，只需要傳遞構建者和構建工具，便可以得到所需，不需要關心如何構建，以及內部構建過程。

3、使用：

   3.1、在構建的過程中，允許不同的構建過程，產生不同表示的構建對象；

   3.2、在複雜的對象時，其複雜的構建演算法應當獨立於對象的組成部分，或者是獨立於裝配方式時；

4、一個簡單的demo：

核心：抽象建造者，具體建造者，實體類

package com.example.demo.Builder;import android.util.Log;/** * 建造者模式 * @author qubian * @data 2015年6月10日 * @email naibbian@163.com * */public class Product {Builder mBuilder ;public Builder getBuilder(){if (mBuilder==null) {mBuilder = new ProductBuilder();}return mBuilder;}/** * 抽象建造者 * @author qubian * @data 2015年6月10日 * @email naibbian@163.com * */public interface Builder{public Builder buildPart1();public Builder buildPart2();public Product getProduct();}/** * 具體的建造者 * @author qubian * @data 2015年6月10日 * @email naibbian@163.com * */public class ProductBuilder implements Builder{private static final String TAG= "ProductBuilder";Product mProduct = new Product();@Overridepublic Builder buildPart1() {Log.i(TAG, "buildPart1");return this;}@Overridepublic Builder buildPart2() {Log.i(TAG, "buildPart2");return this;}@Overridepublic Product getProduct() {return mProduct;}}}

使用：

package com.example.demo.Builder;/** *  使用 * @author qubian * @data 2015年6月10日 * @email naibbian@163.com * */public class UseProduct {public void use(){Product p = new Product().getBuilder().buildPart1().buildPart2().getProduct();}}

5、在Android的源碼中，建造者模式，肯定是必不可少的；

其中最為代表的就是AlertDialog,在其構建過程中，便是構建與表示分離。其內部的Builder便是他的構建者。

public class AlertDialog extends Dialog implements DialogInterface {    private AlertController mAlert;        @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        mAlert.installContent();    }    @Override    public boolean onKeyDown(int keyCode, KeyEvent event) {        if (mAlert.onKeyDown(keyCode, event)) return true;        return super.onKeyDown(keyCode, event);    }    @Override    public boolean onKeyUp(int keyCode, KeyEvent event) {        if (mAlert.onKeyUp(keyCode, event)) return true;        return super.onKeyUp(keyCode, event);    }        public static class Builder {        private final AlertController.AlertParams P;        private int mTheme;                /**         * Constructor using a context for this builder and the {@link AlertDialog} it creates.         */        public Builder(Context context) {            this(context, resolveDialogTheme(context, 0));        }        /**         * Set the title displayed in the {@link Dialog}.         *         * @return This Builder object to allow for chaining of calls to set methods         */        public Builder setTitle(CharSequence title) {            P.mTitle = title;            return this;        }                /**         * Set the message to display using the given resource id.         *         * @return This Builder object to allow for chaining of calls to set methods         */        public Builder setMessage(int messageId) {            P.mMessage = P.mContext.getText(messageId);            return this;        }                /**         * Set the message to display.          *         * @return This Builder object to allow for chaining of calls to set methods         */        public Builder setMessage(CharSequence message) {            P.mMessage = message;            return this;        }                /**         * Set the resource id of the {@link Drawable} to be used in the title.         *         * @return This Builder object to allow for chaining of calls to set methods         */        public Builder setIcon(int iconId) {            P.mIconId = iconId;            return this;        }        /**         * Set a listener to be invoked when the positive button of the dialog is pressed.         * @param textId The resource id of the text to display in the positive button         * @param listener The {@link DialogInterface.OnClickListener} to use.         *         * @return This Builder object to allow for chaining of calls to set methods         */        public Builder setPositiveButton(int textId, final OnClickListener listener) {            P.mPositiveButtonText = P.mContext.getText(textId);            P.mPositiveButtonListener = listener;            return this;        }                /**         * Set a listener to be invoked when the positive button of the dialog is pressed.         * @param text The text to display in the positive button         * @param listener The {@link DialogInterface.OnClickListener} to use.         *         * @return This Builder object to allow for chaining of calls to set methods         */        public Builder setPositiveButton(CharSequence text, final OnClickListener listener) {            P.mPositiveButtonText = text;            P.mPositiveButtonListener = listener;            return this;        }                /**         * Set a listener to be invoked when the negative button of the dialog is pressed.         * @param textId The resource id of the text to display in the negative button         * @param listener The {@link DialogInterface.OnClickListener} to use.         *         * @return This Builder object to allow for chaining of calls to set methods         */        public Builder setNegativeButton(int textId, final OnClickListener listener) {            P.mNegativeButtonText = P.mContext.getText(textId);            P.mNegativeButtonListener = listener;            return this;        }                /**         * Set a listener to be invoked when the negative button of the dialog is pressed.         * @param text The text to display in the negative button         * @param listener The {@link DialogInterface.OnClickListener} to use.         *         * @return This Builder object to allow for chaining of calls to set methods         */        public Builder setNegativeButton(CharSequence text, final OnClickListener listener) {            P.mNegativeButtonText = text;            P.mNegativeButtonListener = listener;            return this;        }                /**         * Set a listener to be invoked when the neutral button of the dialog is pressed.         * @param textId The resource id of the text to display in the neutral button         * @param listener The {@link DialogInterface.OnClickListener} to use.         *         * @return This Builder object to allow for chaining of calls to set methods         */        public Builder setNeutralButton(int textId, final OnClickListener listener) {            P.mNeutralButtonText = P.mContext.getText(textId);            P.mNeutralButtonListener = listener;            return this;        }        /**         * Set a custom view to be the contents of the Dialog. If the supplied view is an instance         * of a {@link ListView} the light background will be used.         *         * @param view The view to use as the contents of the Dialog.         *          * @return This Builder object to allow for chaining of calls to set methods         */        public Builder setView(View view) {            P.mView = view;            P.mViewSpacingSpecified = false;            return this;        }        /**         * Creates a {@link AlertDialog} with the arguments supplied to this builder. It does not         * {@link Dialog#show()} the dialog. This allows the user to do any extra processing         * before displaying the dialog. Use {@link #show()} if you don't have any other processing         * to do and want this to be created and displayed.         */        public AlertDialog create() {            final AlertDialog dialog = new AlertDialog(P.mContext, mTheme, false);            P.apply(dialog.mAlert);            dialog.setCancelable(P.mCancelable);            if (P.mCancelable) {                dialog.setCanceledOnTouchOutside(true);            }            dialog.setOnCancelListener(P.mOnCancelListener);            dialog.setOnDismissListener(P.mOnDismissListener);            if (P.mOnKeyListener != null) {                dialog.setOnKeyListener(P.mOnKeyListener);            }            return dialog;        }        /**         * Creates a {@link AlertDialog} with the arguments supplied to this builder and         * {@link Dialog#show()}'s the dialog.         */        public AlertDialog show() {            AlertDialog dialog = create();            dialog.show();            return dialog;        }    }    }

或許是為了其開放性，AlterView也有自己的構建過程，這樣使用AlterView的構建者Builder可以構建視圖，他自己的對象也可以對其本身進行操作。