ListTemplate.java
/*
* Copyright 2020 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.car.app.model;
import static androidx.car.app.model.constraints.ActionsConstraints.ACTIONS_CONSTRAINTS_HEADER;
import static androidx.car.app.model.constraints.ActionsConstraints.ACTIONS_CONSTRAINTS_SIMPLE;
import static androidx.car.app.model.constraints.RowListConstraints.ROW_LIST_CONSTRAINTS_FULL_LIST;
import static java.util.Objects.requireNonNull;
import androidx.annotation.Keep;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.car.app.Screen;
import androidx.car.app.utils.CollectionUtils;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Objects;
/**
* A template representing a list of items.
*
* <h4>Template Restrictions</h4>
*
* In regards to template refreshes, as described in {@link Screen#onGetTemplate()}, this
* template is considered a refresh of a previous one if:
*
* <ul>
* <li>The template title has not changed, and
* <li>The previous template is in a loading state (see {@link Builder#setLoading}}, or the
* {@link ItemList} structure between the templates have not changed. This means that if the
* previous template has multiple {@link ItemList} sections, the new template must have the
* same number of sections with the same headers. Further, the number of rows and the string
* contents (title, texts, not counting spans) of each row must not have changed.
* <li>For rows that contain a {@link Toggle}, updates to the title or texts are also allowed if
* the toggle state has changed between the previous and new templates.
* </ul>
*/
public final class ListTemplate implements Template {
@Keep
private final boolean mIsLoading;
@Keep
@Nullable
private final CarText mTitle;
@Keep
@Nullable
private final Action mHeaderAction;
@Keep
@Nullable
private final ItemList mSingleList;
@Keep
private final List<SectionedItemList> mSectionedLists;
@Keep
@Nullable
private final ActionStrip mActionStrip;
/**
* Returns the title of the template or {@code null} if not set.
*
* @see Builder#setTitle(CharSequence)
*/
@Nullable
public CarText getTitle() {
return mTitle;
}
/**
* Returns the {@link Action} that is set to be displayed in the header of the template, or
* {@code null} if not set.
*
* @see Builder#setHeaderAction(Action)
*/
@Nullable
public Action getHeaderAction() {
return mHeaderAction;
}
/**
* Returns the {@link ActionStrip} for this template or {@code null} if not set.
*
* @see Builder#setActionStrip(ActionStrip)
*/
@Nullable
public ActionStrip getActionStrip() {
return mActionStrip;
}
/**
* Returns whether the template is loading.
*
* @see Builder#setLoading(boolean)
*/
public boolean isLoading() {
return mIsLoading;
}
/**
* Returns the {@link ItemList} instance containing the list of items to display or {@code
* null} if one hasn't been set.
*
* @see Builder#setSingleList(ItemList)
*/
@Nullable
public ItemList getSingleList() {
return mSingleList;
}
/**
* Returns the list of {@link SectionedItemList} instances to be displayed in the template.
*
* @see Builder#addSectionedList(SectionedItemList)
*/
@NonNull
public List<SectionedItemList> getSectionedLists() {
return CollectionUtils.emptyIfNull(mSectionedLists);
}
@NonNull
@Override
public String toString() {
return "ListTemplate";
}
@Override
public int hashCode() {
return Objects.hash(mIsLoading, mTitle, mHeaderAction, mSingleList, mSectionedLists,
mActionStrip);
}
@Override
public boolean equals(@Nullable Object other) {
if (this == other) {
return true;
}
if (!(other instanceof ListTemplate)) {
return false;
}
ListTemplate otherTemplate = (ListTemplate) other;
return mIsLoading == otherTemplate.mIsLoading
&& Objects.equals(mTitle, otherTemplate.mTitle)
&& Objects.equals(mHeaderAction, otherTemplate.mHeaderAction)
&& Objects.equals(mSingleList, otherTemplate.mSingleList)
&& Objects.equals(mSectionedLists, otherTemplate.mSectionedLists)
&& Objects.equals(mActionStrip, otherTemplate.mActionStrip);
}
ListTemplate(Builder builder) {
mIsLoading = builder.mIsLoading;
mTitle = builder.mTitle;
mHeaderAction = builder.mHeaderAction;
mSingleList = builder.mSingleList;
mSectionedLists = CollectionUtils.unmodifiableCopy(builder.mSectionedLists);
mActionStrip = builder.mActionStrip;
}
/** Constructs an empty instance, used by serialization code. */
private ListTemplate() {
mIsLoading = false;
mTitle = null;
mHeaderAction = null;
mSingleList = null;
mSectionedLists = Collections.emptyList();
mActionStrip = null;
}
/** A builder of {@link ListTemplate}. */
public static final class Builder {
boolean mIsLoading;
@Nullable
ItemList mSingleList;
final List<SectionedItemList> mSectionedLists = new ArrayList<>();
@Nullable
CarText mTitle;
@Nullable
Action mHeaderAction;
@Nullable
ActionStrip mActionStrip;
boolean mHasSelectableList;
/**
* Sets whether the template is in a loading state.
*
* <p>If set to {@code true}, the UI will display a loading indicator where the list content
* would be otherwise. The caller is expected to call {@link
* androidx.car.app.Screen#invalidate()} and send the new template content
* to the host once the data is ready.
*
* <p>If set to {@code false}, the UI will display the contents of the {@link ItemList}
* instance(s) added via {@link #setSingleList} or {@link #addSectionedList}.
*/
@NonNull
public Builder setLoading(boolean isLoading) {
mIsLoading = isLoading;
return this;
}
/**
* Sets the {@link Action} that will be displayed in the header of the template, or
* {@code null} to not display an action.
*
* <p>Unless set with this method, the template will not have a header action.
*
* <h4>Requirements</h4>
*
* This template only supports either one of {@link Action#APP_ICON} and
* {@link Action#BACK} as a header {@link Action}.
*
* @throws IllegalArgumentException if {@code headerAction} does not meet the template's
* requirements
* @throws NullPointerException if {@code headerAction} is {@code null}
*/
@NonNull
public Builder setHeaderAction(@NonNull Action headerAction) {
ACTIONS_CONSTRAINTS_HEADER.validateOrThrow(
Collections.singletonList(requireNonNull(headerAction)));
mHeaderAction = headerAction;
return this;
}
/**
* Sets the title of the template.
*
* <p>Unless set with this method, the template will not have a title.
*
* <p>Spans are not supported in the input string.
*
* @throws NullPointerException if {@code title} is null
*/
@NonNull
public Builder setTitle(@NonNull CharSequence title) {
mTitle = CarText.create(requireNonNull(title));
return this;
}
/**
* Sets a single {@link ItemList} to show in the template.
*
* <p>Note that this list cannot be mixed with others added via {@link #addSectionedList}
* . If multiple lists were previously added, they will be cleared.
*
* @throws NullPointerException if {@code list} is null
*/
@NonNull
public Builder setSingleList(@NonNull ItemList list) {
mSingleList = requireNonNull(list);
mSectionedLists.clear();
mHasSelectableList = false;
return this;
}
/**
* Adds an {@link SectionedItemList} to display in the template.
*
* <p>Use this method to add multiple lists to the template. Each
* {@link SectionedItemList} will be grouped under its header. These lists cannot be
* mixed with an {@link ItemList} added via {@link #setSingleList}. If a single list was
* previously added, it will be cleared.
*
* <p>If the added {@link SectionedItemList} contains a
* {@link ItemList.OnSelectedListener}, then it cannot be added alongside other
* {@link SectionedItemList}(s).
*
* @throws NullPointerException if {@code list} or {@code header} is {@code null}
* @throws IllegalArgumentException if {@code list} is empty, if {@code list}'s {@link
* ItemList.OnItemVisibilityChangedListener} is set, if
* {@code header} is empty, or if a selectable list is
* added alongside other lists
*/
@NonNull
public Builder addSectionedList(@NonNull SectionedItemList list) {
if (requireNonNull(list).getHeader().toString().length() == 0) {
throw new IllegalArgumentException("Header cannot be empty");
}
ItemList itemList = list.getItemList();
boolean isSelectableList = itemList.getOnSelectedDelegate() != null;
if (mHasSelectableList || (isSelectableList && !mSectionedLists.isEmpty())) {
throw new IllegalArgumentException(
"A selectable list cannot be added alongside any other lists");
}
mHasSelectableList = isSelectableList;
if (itemList.getItems().isEmpty()) {
throw new IllegalArgumentException("List cannot be empty");
}
if (itemList.getOnItemVisibilityChangedDelegate() != null) {
throw new IllegalArgumentException(
"OnItemVisibilityChangedListener in the list is disallowed");
}
mSingleList = null;
mSectionedLists.add(list);
return this;
}
/**
* Sets the {@link ActionStrip} for this template or {@code null} to not display an {@link
* ActionStrip}.
*
* <p>Unless set with this method, the template will not have an action strip.
*
* <h4>Requirements</h4>
*
* This template allows up to 2 {@link Action}s in its {@link ActionStrip}. Of the 2 allowed
* {@link Action}s, one of them can contain a title as set via
* {@link Action.Builder#setTitle}. Otherwise, only {@link Action}s with icons are allowed.
*
* @throws IllegalArgumentException if {@code actionStrip} does not meet the requirements
* @throws NullPointerException if {@code actionStrip} is {@code null}
*/
@NonNull
public Builder setActionStrip(@NonNull ActionStrip actionStrip) {
ACTIONS_CONSTRAINTS_SIMPLE.validateOrThrow(requireNonNull(actionStrip).getActions());
mActionStrip = actionStrip;
return this;
}
/**
* Constructs the template defined by this builder.
*
* <h4>Requirements</h4>
*
* This template allows up to 6 {@link Row}s total in the {@link ItemList}(s). The host will
* ignore any items over that limit. Each {@link Row}s can add up to 2 lines of texts via
* {@link Row.Builder#addText}.
*
* <p>Either a header {@link Action} or the title must be set on the template.
*
* @throws IllegalStateException if the template is in a loading state but there are
* lists added or vice versa, or if the template does
* not have either a title or header {@link Action} set
* @throws IllegalArgumentException if the added {@link ItemList}(s) do not meet the
* template's requirements
*/
@NonNull
public ListTemplate build() {
boolean hasList = mSingleList != null || !mSectionedLists.isEmpty();
if (mIsLoading == hasList) {
throw new IllegalStateException(
"Template is in a loading state but lists are added, or vice versa");
}
if (hasList) {
if (!mSectionedLists.isEmpty()) {
ROW_LIST_CONSTRAINTS_FULL_LIST.validateOrThrow(mSectionedLists);
} else if (mSingleList != null) {
ROW_LIST_CONSTRAINTS_FULL_LIST.validateOrThrow(mSingleList);
}
}
if (CarText.isNullOrEmpty(mTitle) && mHeaderAction == null) {
throw new IllegalStateException("Either the title or header action must be set");
}
return new ListTemplate(this);
}
/** Returns an empty {@link Builder} instance. */
public Builder() {
}
}
}