Android进阶系列之源码分析AlertDialog建造者模式
*本篇文章已授权微信公众号 hongyangAndroid （鸿洋）独家发布
建造者模式之前也写了一篇学习笔记，不过那只是很简单的运用，要去看源码，要去看源码还是得在撸一遍设计模式才行啊。不能怂就是干。
建造者模式，在于分工明确，一个抽象建造者，一个指挥者，一个具体的建造者，当然还需要具体的产品。那么我们以一个软件产品为例。技术主管就是抽象建造者，他和产品经理沟通，知道要做一个什么样的产品。而程序猿就是苦逼的体力劳动者，技术主管说咋做你就咋做。而指挥者就是公司的产品经理，负责和用户沟通，了解客户的需求。
那么基本的套路有了，开始撸一个简单的例子出来。
public class Product {
public static final int ANDROID = 0;
public static final int IOS = 1;
private String appName;
private String appFuction;
private int appSystem;
public String getAppName() {
return appName;
}
public void setAppName(String appName) {
this.appName = appName;
}
public String getAppFuction() {
return appFuction;
}
public void setAppFuction(String appFuction) {
this.appFuction = appFuction;
}
public int getAppSystem() {
return appSystem;
}
public void setAppSystem(int appSystem) {
this.appSystem = appSystem;
}
}
/**
* 技术主管
* Created by Administrator on 2016/12/29.
*/
public abstract class TechManager {
public abstract TechManager setAppName(@NonNull String appName);
public abstract TechManager setAppFuction(@NonNull String appFuction);
public abstract TechManager setAppSystem(@AppSystem int appSystem);
public abstract Product build();
}/**
*程序猿。IOS和ANDROID，后台都会的全栈选手
* Created by Administrator on 2016/12/29.
*/
public class Progremer extends TechManager{
private Product product;
private InnerProduct innerProduct = new InnerProduct();
@Override
public TechManager setAppName(@NonNull String appName) {
innerProduct.setAppName(appName);
return this;
}
@Override
public TechManager setAppFuction(@NonNull String appFuction) {
innerProduct.setAppFuction(appFuction);
return this;
}
@Override
public TechManager setAppSystem(@AppSystem int appSystem) {
innerProduct.setAppSystem(appSystem);
return this;
}
private class InnerProduct{
private String appName;
private String appFuction;
private int appSystem;
public String getAppName() {
return appName;
}
public void setAppName(String appName) {
this.appName = appName;
}
public String getAppFuction() {
return appFuction;
}
public void setAppFuction(String appFuction) {
this.appFuction = appFuction;
}
public int getAppSystem() {
return appSystem;
}
public void setAppSystem(int appSystem) {
this.appSystem = appSystem;
}
}
@Override
public Product build() {
product = new Product();
product.setAppName(innerProduct.getAppName());
product.setAppFuction(innerProduct.getAppFuction());
product.setAppSystem(innerProduct.getAppSystem());
return product;
}
}
/**
* 产品经理
* Created by Administrator on 2016/12/29.
*/
public class ProductManager {
public static Product create(@AppSystem int system){
return new Progremer().setAppSystem(system).setAppName("探探").setAppFuction("划一划，找妹子。").build();
}
}
在客户类里，只需要持有产品经理类之后，就可以得到产品了。
public class Client {
public void main(String[] args){
//客户：我需要一个可以摇一摇找妹子的软件
//产品经理：分析得出那就做一个探探吧
//技术主管：appName:探探 系统：ios,android 功能：摇一摇，找妹子
Product android = ProductManager.create(Product.ANDROID);
Product ios = ProductManager.create(Product.IOS);
}
}
public class Client {
public void main(String[] args){
//客户：我需要一个可以摇一摇找妹子的软件
//产品经理：分析得出那就做一个探探吧
//技术主管：appName:探探 系统：ios,android 功能：摇一摇，找妹子
Product android = ProductManager.create(Product.ANDROID);
Product ios = ProductManager.create(Product.IOS);
//程序猿觉得太累了，工资又少，干的最多。最后决定自己出去单干。
Progremer niubiProgremer = new Progremer();
Product androidBest = niubiProgremer.setAppName("探探").setAppSystem(Product.ANDROID).setAppFuction("摇一摇，找妹子").build();
Product iosBest = niubiProgremer.setAppName("探探").setAppSystem(Product.IOS).setAppFuction("摇一摇，找妹子").build();
}
}Android源码这里我给个百度云的连接，大家需要的自行下载。链接：http://pan.baidu.com/s/1nv8prJj 密码：5mfz
只用AlertDialog的时候，都知道。
AlertDialog.Builder builder = new AlertDialog.Builder(this);
public static class Builder {
private final AlertController.AlertParams P;
private final int mTheme;
public Builder(@NonNull Context context) {
this(context, resolveDialogTheme(context, 0));
}
public Builder(@NonNull Context context, @StyleRes int themeResId) {
P = new AlertController.AlertParams(new ContextThemeWrapper(
context, resolveDialogTheme(context, themeResId)));
mTheme = themeResId;
}
@NonNull
public Context getContext() {
return P.mContext;
}
public Builder setTitle(@StringRes int titleId) {
P.mTitle = P.mContext.getText(titleId);
return this;
}
public Builder setTitle(CharSequence title) {
P.mTitle = title;
return this;
}
........
public Builder setPositiveButton(@StringRes int textId, final OnClickListener listener) {
P.mPositiveButtonText = P.mContext.getText(textId);
P.mPositiveButtonListener = listener;
return this;
}
public AlertDialog create() {
final AlertDialog dialog = new AlertDialog(P.mContext, mTheme);
P.apply(dialog.mAlert);//这里调用了apply真正创建了需要显示的dialog，也就是说之前的设置都是以P做一个数据缓存
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;
}
public AlertDialog show() {
final AlertDialog dialog = create();
dialog.show();
return dialog;
}
}
public static class AlertParams {
public final Context mContext;
public final LayoutInflater mInflater;
public int mIconId = 0;
public Drawable mIcon;
public int mIconAttrId = 0;
public CharSequence mTitle;
public View mCustomTitleView;
public CharSequence mMessage;
public CharSequence mPositiveButtonText;
........
public AlertParams(Context context) {
mContext = context;
mCancelable = true;
mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public void apply(AlertController dialog) {//传入一个dialog，获取AlertParams缓存的数据。
if (mCustomTitleView != null) {
dialog.setCustomTitle(mCustomTitleView);
} else {
if (mTitle != null) {
dialog.setTitle(mTitle);
}
if (mIcon != null) {
dialog.setIcon(mIcon);
}
if (mIconId != 0) {
dialog.setIcon(mIconId);
}
if (mIconAttrId != 0) {
dialog.setIcon(dialog.getIconAttributeResId(mIconAttrId));
}
}
if (mMessage != null) {
dialog.setMessage(mMessage);
}
if (mPositiveButtonText != null) {
dialog.setButton(DialogInterface.BUTTON_POSITIVE, mPositiveButtonText,
mPositiveButtonListener, null);
}
if (mNegativeButtonText != null) {
dialog.setButton(DialogInterface.BUTTON_NEGATIVE, mNegativeButtonText,
mNegativeButtonListener, null);
}
if (mNeutralButtonText != null) {
dialog.setButton(DialogInterface.BUTTON_NEUTRAL, mNeutralButtonText,
mNeutralButtonListener, null);
}
// For a list, the client can either supply an array of items or an
// adapter or a cursor
if ((mItems != null) || (mCursor != null) || (mAdapter != null)) {
createListView(dialog);
}
if (mView != null) {
if (mViewSpacingSpecified) {
dialog.setView(mView, mViewSpacingLeft, mViewSpacingTop, mViewSpacingRight,
mViewSpacingBottom);
} else {
dialog.setView(mView);
}
} else if (mViewLayoutResId != 0) {
dialog.setView(mViewLayoutResId);
}
/*
dialog.setCancelable(mCancelable);
dialog.setOnCancelListener(mOnCancelListener);
if (mOnKeyListener != null) {
dialog.setOnKeyListener(mOnKeyListener);
}
*/
}
......
}这里最主要的方法时apply()，在这里AlertParams 的所有属性转给了一个AlertController dialog。那么我们看看AlertController 是什么。
class AlertController {
private final Context mContext;
final AppCompatDialog mDialog;
private final Window mWindow;
private CharSequence mTitle;
private CharSequence mMessage;
ListView mListView;
private View mView;
private int mViewLayoutResId;
private int mViewSpacingLeft;
private int mViewSpacingTop;
private int mViewSpacingRight;
private int mViewSpacingBottom;
private boolean mViewSpacingSpecified = false;
Button mButtonPositive;
private CharSequence mButtonPositiveText;
Message mButtonPositiveMessage;
Button mButtonNegative;
private CharSequence mButtonNegativeText;
Message mButtonNegativeMessage;
Button mButtonNeutral;
private CharSequence mButtonNeutralText;
Message mButtonNeutralMessage;
NestedScrollView mScrollView;
private int mIconId = 0;
private Drawable mIcon;
private ImageView mIconView;
private TextView mTitleView;
private TextView mMessageView;
private View mCustomTitleView;
ListAdapter mAdapter;
int mCheckedItem = -1;
private int mAlertDialogLayout;
private int mButtonPanelSideLayout;
int mListLayout;
int mMultiChoiceItemLayout;
int mSingleChoiceItemLayout;
int mListItemLayout;
private int mButtonPanelLayoutHint = AlertDialog.LAYOUT_HINT_NONE;
Handler mHandler;
..........
}那么AlertDialog在建造者模式中担任的是指挥者，Bilder就是具体的建造者。采用了链式调用。AlertController是产品，而AlertController.AlertParams是产品的缓存。比如我调用了两次setTitle()，在缓存时后一次会覆盖前一次，这样就解决了开发者冲动调用的问题。最后不论是调用Builder的show方法，还是调用调用AlertDialog的show方法。都是允许的。
比如：
new AlertDialog.Builder(this).setTitle("标题").setIcon(R.mipmap.ic_launcher).setMessage("测试").show();这样是可以的，最后调用的是Builder的show方法，在Builder的show方法中，调用了AlertDialog的create()得到缓存数据的AlertDialog进行显示。
new AlertDialog.Builder(this).setTitle("标题").setIcon(R.mipmap.ic_launcher).setMessage("测试").create().show();这样也是可以的，手动调用create()方法，之后在调用AlertDialog的show方法进行显示。
那么这样呢？
new AlertDialog.Builder(this).setTitle("标题").setIcon(R.mipmap.ic_launcher).setMessage("测试").show().show();第一个show是builder的show，里面创建了AlertDialog并且调用了AlertDialog的show方法。那么第二个show也是AlertDialog的show方法，会重复调用么？答案肯定是不可能的。看看Dialog的show方法源码、
public void show() {
if (mShowing) {
if (mDecor != null) {
if (mWindow.hasFeature(Window.FEATURE_ACTION_BAR)) {
mWindow.invalidatePanelMenu(Window.FEATURE_ACTION_BAR);
}
mDecor.setVisibility(View.VISIBLE);
}
return;
}
.....
try {
mWindowManager.addView(mDecor, l);
mShowing = true;
sendShowMessage();
} finally {
}
}在调用底层的show方法时，会先进行一次判断，第一次show之后mShowing已经设为true。那么第二次调用时，判断到已经显示，就不会再次调用绘制逻辑（省略号部分）。
那么建造者模式就到这儿了，源码的博大精深真是令人向往。