Builder 模式 (建造者模式)

使用场景:

事例

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();

 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();