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panwj edited this page Jun 13, 2017
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在设计模式中对Builder模式的定义是用于构建复杂对象的一种模式，所构建的对象往往需要多步初始化或赋值才能完成。
1、当创建复杂对象的算法应该独立于该对象的组成部分以及它们的装配方式时。 2、当构造过程必须允许被构造的对象有不同的表示时。
public class DoDoContact {
private final int age;
private final int safeID;
private final String name;
private final String address;
public int getAge() {
return age;
}
public int getSafeID() {
return safeID;
}
public String getName() {
return name;
}
public String getAddress() {
return address;
}
public static class Builder {
private int age = 0;
private int safeID = 0;
private String name = null;
private String address = null;
// 构建的步骤
public Builder(String name) {
this.name = name;
}
public Builder age(int val) {
age = val;
return this;
}
public Builder safeID(int val) {
safeID = val;
return this;
}
public Builder address(String val) {
address = val;
return this;
}
public DoDoContact build() { // 构建，返回一个新对象
return new DoDoContact(this);
}
}
private DoDoContact(Builder b) {
age = b.age;
safeID = b.safeID;
name = b.name;
address = b.address;
}
}
客户端的调用：
DoDoContact ddc = new DoDoContact.Builder("Ace").age(10)
.address("beijing").build();在android api里也给我们提供了很多好用的builder模式，例如android.support.v7.app.AlertDialog
public static class Builder {
private final AlertController.AlertParams P;
private final int mTheme;
/**
* Creates a builder for an alert dialog that uses the default alert
* dialog theme.
* <p>
* The default alert dialog theme is defined by
* {@link android.R.attr#alertDialogTheme} within the parent
* {@code context}'s theme.
*
* @param context the parent context
*/
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;
}
/**
* Returns a {@link Context} with the appropriate theme for dialogs created by this Builder.
* Applications should use this Context for obtaining LayoutInflaters for inflating views
* that will be used in the resulting dialogs, as it will cause views to be inflated with
* the correct theme.
*
* @return A Context for built Dialogs.
*/
@NonNull
public Context getContext() {
return P.mContext;
}
/**
* Set the title using the given resource id.
*
* @return This Builder object to allow for chaining of calls to set methods
*/
public Builder setTitle(@StringRes int titleId) {
P.mTitle = P.mContext.getText(titleId);
return this;
}
/**
* 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;
}
public Builder setCustomTitle(View customTitleView) {
P.mCustomTitleView = customTitleView;
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(@StringRes 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.
* <p>
* Takes precedence over values set using {@link #setIcon(Drawable)}.
*
* @return This Builder object to allow for chaining of calls to set methods
*/
public Builder setIcon(@DrawableRes int iconId) {
P.mIconId = iconId;
return this;
}
/**
* Set the {@link Drawable} to be used in the title.
* <p>
* <strong>Note:</strong> To ensure consistent styling, the drawable
* should be inflated or constructed using the alert dialog's themed
* context obtained via {@link #getContext()}.
*
* @return this Builder object to allow for chaining of calls to set
* methods
*/
public Builder setIcon(Drawable icon) {
P.mIcon = icon;
return this;
}
/**
* Set an icon as supplied by a theme attribute. e.g.
* {@link android.R.attr#alertDialogIcon}.
* <p>
* Takes precedence over values set using {@link #setIcon(int)} or
* {@link #setIcon(Drawable)}.
*
* @param attrId ID of a theme attribute that points to a drawable resource.
*/
public Builder setIconAttribute(@AttrRes int attrId) {
TypedValue out = new TypedValue();
P.mContext.getTheme().resolveAttribute(attrId, out, true);
P.mIconId = out.resourceId;
return this;
}
public Builder setPositiveButton(@StringRes 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;
}
public Builder setNegativeButton(@StringRes int textId, final OnClickListener listener) {
P.mNegativeButtonText = P.mContext.getText(textId);
P.mNegativeButtonListener = listener;
return this;
}
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(@StringRes int textId, final OnClickListener listener) {
P.mNeutralButtonText = P.mContext.getText(textId);
P.mNeutralButtonListener = listener;
return this;
}
/**
* Set a listener to be invoked when the neutral button of the dialog is pressed.
* @param text 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(CharSequence text, final OnClickListener listener) {
P.mNeutralButtonText = text;
P.mNeutralButtonListener = listener;
return this;
}
public Builder setCancelable(boolean cancelable) {
P.mCancelable = cancelable;
return this;
}
public Builder setOnCancelListener(OnCancelListener onCancelListener) {
P.mOnCancelListener = onCancelListener;
return this;
}
public Builder setOnDismissListener(OnDismissListener onDismissListener) {
P.mOnDismissListener = onDismissListener;
return this;
}
public Builder setOnKeyListener(OnKeyListener onKeyListener) {
P.mOnKeyListener = onKeyListener;
return this;
}
public Builder setItems(@ArrayRes int itemsId, final OnClickListener listener) {
P.mItems = P.mContext.getResources().getTextArray(itemsId);
P.mOnClickListener = listener;
return this;
}
public Builder setItems(CharSequence[] items, final OnClickListener listener) {
P.mItems = items;
P.mOnClickListener = listener;
return this;
}
public Builder setAdapter(final ListAdapter adapter, final OnClickListener listener) {
P.mAdapter = adapter;
P.mOnClickListener = listener;
return this;
}
/**
* Set a list of items, which are supplied by the given {@link Cursor}, to be
* displayed in the dialog as the content, you will be notified of the
* selected item via the supplied listener.
*
* @param cursor The {@link Cursor} to supply the list of items
* @param listener The listener that will be called when an item is clicked.
* @param labelColumn The column name on the cursor containing the string to display
* in the label.
*
* @return This Builder object to allow for chaining of calls to set methods
*/
public Builder setCursor(final Cursor cursor, final OnClickListener listener,
String labelColumn) {
P.mCursor = cursor;
P.mLabelColumn = labelColumn;
P.mOnClickListener = listener;
return this;
}
public Builder setMultiChoiceItems(@ArrayRes int itemsId, boolean[] checkedItems,
final OnMultiChoiceClickListener listener) {
P.mItems = P.mContext.getResources().getTextArray(itemsId);
P.mOnCheckboxClickListener = listener;
P.mCheckedItems = checkedItems;
P.mIsMultiChoice = true;
return this;
}
public Builder setMultiChoiceItems(CharSequence[] items, boolean[] checkedItems,
final OnMultiChoiceClickListener listener) {
P.mItems = items;
P.mOnCheckboxClickListener = listener;
P.mCheckedItems = checkedItems;
P.mIsMultiChoice = true;
return this;
}
public Builder setMultiChoiceItems(Cursor cursor, String isCheckedColumn, String labelColumn,
final OnMultiChoiceClickListener listener) {
P.mCursor = cursor;
P.mOnCheckboxClickListener = listener;
P.mIsCheckedColumn = isCheckedColumn;
P.mLabelColumn = labelColumn;
P.mIsMultiChoice = true;
return this;
}
public Builder setSingleChoiceItems(@ArrayRes int itemsId, int checkedItem,
final OnClickListener listener) {
P.mItems = P.mContext.getResources().getTextArray(itemsId);
P.mOnClickListener = listener;
P.mCheckedItem = checkedItem;
P.mIsSingleChoice = true;
return this;
}
public Builder setSingleChoiceItems(Cursor cursor, int checkedItem, String labelColumn,
final OnClickListener listener) {
P.mCursor = cursor;
P.mOnClickListener = listener;
P.mCheckedItem = checkedItem;
P.mLabelColumn = labelColumn;
P.mIsSingleChoice = true;
return this;
}
public Builder setSingleChoiceItems(CharSequence[] items, int checkedItem, final OnClickListener listener) {
P.mItems = items;
P.mOnClickListener = listener;
P.mCheckedItem = checkedItem;
P.mIsSingleChoice = true;
return this;
}
public Builder setSingleChoiceItems(ListAdapter adapter, int checkedItem, final OnClickListener listener) {
P.mAdapter = adapter;
P.mOnClickListener = listener;
P.mCheckedItem = checkedItem;
P.mIsSingleChoice = true;
return this;
}
public Builder setOnItemSelectedListener(final AdapterView.OnItemSelectedListener listener) {
P.mOnItemSelectedListener = listener;
return this;
}
public Builder setView(int layoutResId) {
P.mView = null;
P.mViewLayoutResId = layoutResId;
P.mViewSpacingSpecified = false;
return this;
}
public Builder setView(View view) {
P.mView = view;
P.mViewLayoutResId = 0;
P.mViewSpacingSpecified = false;
return this;
}
@RestrictTo(GROUP_ID)
@Deprecated
public Builder setView(View view, int viewSpacingLeft, int viewSpacingTop,
int viewSpacingRight, int viewSpacingBottom) {
P.mView = view;
P.mViewLayoutResId = 0;
P.mViewSpacingSpecified = true;
P.mViewSpacingLeft = viewSpacingLeft;
P.mViewSpacingTop = viewSpacingTop;
P.mViewSpacingRight = viewSpacingRight;
P.mViewSpacingBottom = viewSpacingBottom;
return this;
}
@Deprecated
public Builder setInverseBackgroundForced(boolean useInverseBackground) {
P.mForceInverseBackground = useInverseBackground;
return this;
}
/**
* @hide
*/
@RestrictTo(GROUP_ID)
public Builder setRecycleOnMeasureEnabled(boolean enabled) {
P.mRecycleOnMeasure = enabled;
return this;
}
/**
* 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() {
// We can't use Dialog's 3-arg constructor with the createThemeContextWrapper param,
// so we always have to re-set the theme
final AlertDialog dialog = new AlertDialog(P.mContext, mTheme);
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 an {@link AlertDialog} with the arguments supplied to this
* builder and immediately displays the dialog.
* <p>
* Calling this method is functionally identical to:
* <pre>
* AlertDialog dialog = builder.create();
* dialog.show();
* </pre>
*/
public AlertDialog show() {
final AlertDialog dialog = create();
dialog.show();
return dialog;
}
}
AlertDialog dialog = new AlertDialog.Builder(this)
.setView(view)
.create();优点 ： 1,客户端代码的可用性和可读性得到了大大提高，调用起来非常直观。 2,单个builder构建多个对象时Builder参数可在创建期间进行调整，还可以根据对象不同而进行改变，Builder模式特别适合那些属性个数很多的类
缺点 ： 1,增加代码量。尽管客户端的代码可读性明显改善，但随之而来的客户端代码变得更加冗长，而且会增加一个builder类代码。