一.构建者模式

不熟悉构建者设计模式的童靴可以参考下面文章:

菜鸟教程-建造者模式

二.源码分析

2.1.在界面中构建AlertDialog

//构建AlertDialog,sdk版本:28 android.app包下
AlertDialog.Builder builder = new AlertDialog.Builder(this);
   builder.setIcon(R.drawable.ic_launcher_background)
           .setTitle("头部")
           .setMessage("内容")
           .setPositiveButton("确定", new DialogInterface.OnClickListener() {
               @Override
               public void onClick(DialogInterface dialog, int which) {
                   Toast.makeText(MainActivity.this,"点击确定按钮",Toast.LENGTH_SHORT).show();
               }
           })
           .setNegativeButton("取消", new DialogInterface.OnClickListener() {
               @Override
               public void onClick(DialogInterface dialog, int which) {
                   Toast.makeText(MainActivity.this,"点击取消按钮",Toast.LENGTH_SHORT).show();
               }
           })
           .create()
           .show();

2.2.builder创建—->setXxx—->create—->show

//AlertDialog类
public class AlertDialog extends Dialog implements DialogInterface {
    private AlertController mAlert;
    //省略...
    //注意:根据修饰符可知,不能直接new对象
        protected AlertDialog(Context context, @StyleRes int themeResId) {
        this(context, themeResId, true);
    }
        //构造函数
    AlertDialog(Context context, @StyleRes int themeResId, boolean createContextThemeWrapper) {
        super(context, createContextThemeWrapper ? resolveDialogTheme(context, themeResId) : 0,
                createContextThemeWrapper);
        mWindow.alwaysReadCloseOnTouchAttr();
        mAlert = AlertController.create(getContext(), this, getWindow());
    }
    //省略...
    // ************  注意:Builder为AlertDialog的内部类   *******************
    public static class Builder对象,调用构造函数 {
            //问题: final修饰了,还是再被赋值  怎么解释呢?
        private final AlertController.AlertParams P;
        //1.创建Builder对象,调用构造函数
        public Builder(Context context) {
            this(context, resolveDialogTheme(context, ResourceId.ID_NULL));
            }
        public Builder(Context context, int themeResId) {
            P = new AlertController.AlertParams(new ContextThemeWrapper(
                    context, resolveDialogTheme(context, themeResId)));
        }
        //省略...
        //2.调用Builder对象中的setXxx方法
        //设置P中的mTitle属性
        public Builder setTitle(CharSequence title) {
            P.mTitle = title;
            return this;
        }
        //省略setXxx...
        //3.构建AlertDialog, 传递参数
        public AlertDialog create() {
            // Context has already been wrapped with the appropriate theme.
            //4.调用AlertDialog构造函数
            final AlertDialog dialog = new AlertDialog(P.mContext, 0, false);
            //5.调用AlertController类中AlertParams对象的apply方法
            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;
        }
        //省略...
    }
    //省略...
}

2.3.AlertDialog的构造方法和内部类Builder


public class AlertDialog extends Dialog implements DialogInterface {
        //位置二:包含AlertController对象;
    private AlertController mAlert;
        //...
        //位置一:构造方法被protected修饰,故不能直接new(而是通过内部类Builder来构建,后面分析);
    protected AlertDialog(Context context) {
        this(context, 0);
    }
    protected AlertDialog(Context context, boolean cancelable, OnCancelListener cancelListener) {
        this(context, 0);
        setCancelable(cancelable);
        setOnCancelListener(cancelListener);
    }
    protected AlertDialog(Context context, @StyleRes int themeResId) {
        this(context, themeResId, true);
    }
        //构造方法,默认的修饰符,只能在同一个包中访问
    AlertDialog(Context context, @StyleRes int themeResId, boolean createContextThemeWrapper) {
        super(context, createContextThemeWrapper ? resolveDialogTheme(context, themeResId) : 0,
                createContextThemeWrapper);
        mWindow.alwaysReadCloseOnTouchAttr();
        mAlert = AlertController.create(getContext(), this, getWindow());
    }
    //...
    //位置三:内部类Builder
    public static class Builder {
        //位置四:包含AlertController的AlertParams对象
        private final AlertController.AlertParams P;
        public Builder(Context context) {
            this(context, resolveDialogTheme(context, ResourceId.ID_NULL));
        }
        public Builder(Context context, int themeResId) {
            P = new AlertController.AlertParams(new ContextThemeWrapper(
                    context, resolveDialogTheme(context, themeResId)));
        }
    //...
}

2.4.AlertController

public class AlertController {
  //省略...
  public static class AlertParams {
              //省略...
              public AlertParams(Context context) {
            mContext = context;
            mCancelable = true;
            mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        }
        //省略...
         //分析二
         public void apply(AlertController dialog) {
                 //给非空的属性赋值
            //调用setView方法
         }
  }
  //省略...
}

2.5.AlertController的create方法

public class AlertDialog extends Dialog implements DialogInterface {
        //...
        /**
         * Creates an {@link AlertDialog} with the arguments supplied to this
         * builder.
         * <p>
         * Calling this method does not display the dialog. If no additional
         * processing is needed, {@link #show()} may be called instead to both
         * create and display the dialog.
         */
        public AlertDialog create() {
            // Context has already been wrapped with the appropriate theme.
            //创建dialog,查看构造方法 ---> 分析一
            final AlertDialog dialog = new AlertDialog(P.mContext, 0, false);
            //接着调用AlertController.AlertParams P的apply方法(相当于组装步骤) ---> 分析二
            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;
        }
        //...
        AlertDialog(Context context, @StyleRes int themeResId, boolean createContextThemeWrapper) {
        super(context, createContextThemeWrapper ? resolveDialogTheme(context, themeResId) : 0,
                createContextThemeWrapper);
        mWindow.alwaysReadCloseOnTouchAttr();
        //分析一 : AlertDialog中包含mAlert对象,传入参数:上下文,DialogInterface,Window
        mAlert = AlertController.create(getContext(), this, getWindow());
    }
}

2.6.包含关系展示

dialog源码分析.png

AlertDialog —> 包含Builder类;
- AlertDialog构造方法中初始化AlertController对象;
- Builder类中初始化AlertParams对象;
AlertController —> 包含AlertParams类;
Builder同时扮演了抽象的builder、具体的ConcreteBuilder、指挥者Director(直接采用链式调用,省去了Director)的角色，简化了Builder模式的设计;
- AlertDialog(电脑对象)
- AlertDialog.Builder 规范一系列的组装过程
- AlertController 具体的构建器
- AlertController.AlertParams 存放参数,一部分设置参数的功能
show方法在Dialog中查看.

三.打造dialog

根据2.6图中的包含关系可知,我们需要定义两个类,AlertDialog和AlertController,其中AlertDialog类中会定义一个内部类Builder,AlertController会定义一个内部类AlertParams.
生成的AlertDialog对象需要设置的属性,都放在AlertController内部类AlertParams中作为内部类变量,AlertParams中的变量通过Builder中设定setXxx方法来设置.
属性都定义好之后,通过builder中的方法来生成AlertDialog对象.
额外创建一个工具类,打造的对话框一共有三个类.

四.源码

github地址

Android一招半式（杂）

2019-04-08-Builder设计模式构建万能Dialog

一.构建者模式

二.源码分析

2.1.在界面中构建AlertDialog

2.2.builder创建—->setXxx—->create—->show

2.3.AlertDialog的构造方法和内部类Builder

2.4.AlertController

2.5.AlertController的create方法

2.6.包含关系展示

三.打造dialog

四.源码