// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
package org.chromium.components.browser_ui.widget.selectable_list;
import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnLongClickListener;
import android.view.View.OnTouchListener;
import android.view.accessibility.AccessibilityNodeInfo;
import android.widget.Checkable;
import androidx.annotation.Nullable;
import org.chromium.components.browser_ui.widget.selectable_list.SelectionDelegate.SelectionObserver;
import org.chromium.ui.widget.ViewLookupCachingFrameLayout;
import java.util.List;
/**
* Provides a generic base class for representing an item that can be selected. When selected, the
* view will be updated to indicate that it is selected. The exact UI changes for selection state
* should be provided by the implementing class.
*
* A selection is initially established via long-press. If a selection is already established,
* clicking on the item will toggle its selection.
*
* @param <E> The type of the item associated with this SelectableItemViewBase.
*/
public abstract class SelectableItemViewBase<E> extends ViewLookupCachingFrameLayout
implements Checkable,
OnClickListener,
OnLongClickListener,
OnTouchListener,
SelectionObserver<E> {
// Heuristic value used to rule out long clicks preceded by long horizontal move. A long click
// is ignored if finger was moved horizontally more than this threshold.
private static final float LONG_CLICK_SLIDE_THRESHOLD_PX = 100.f;
private @Nullable SelectionDelegate<E> mSelectionDelegate;
private E mItem;
private @Nullable Boolean mIsChecked;
// Controls whether selection should happen during onLongClick.
private boolean mSelectOnLongClick = true;
// X position of touch events to detect the amount of horizontal movement between touch down
// and the position where long click is triggered.
private float mAnchorX;
private float mCurrentX;
/** Constructor for inflating from XML. */
public SelectableItemViewBase(Context context, AttributeSet attrs) {
super(context, attrs);
setOnTouchListener(this);
setOnClickListener(this);
setOnLongClickListener(this);
setAccessibilityDelegate(
new AccessibilityDelegate() {
@Override
public void onInitializeAccessibilityNodeInfo(
View host, AccessibilityNodeInfo info) {
super.onInitializeAccessibilityNodeInfo(host, info);
// Announce checked state if selection mode is on. The actual read out from
// talkback is "checked/unchecked, {content description of this view.}"
boolean checkable =
mSelectionDelegate != null
&& mSelectionDelegate.isSelectionEnabled()
&& mItem != null;
info.setCheckable(checkable);
info.setChecked(isChecked());
}
});
}
/** Destroys and cleans up itself. */
public void destroy() {
if (mSelectionDelegate != null) {
mSelectionDelegate.removeObserver(this);
}
}
/**
* Sets the SelectionDelegate and registers this object as an observer.
*
* @param delegate The SelectionDelegate that will inform this item of selection changes.
*/
public void setSelectionDelegate(@Nullable SelectionDelegate<E> delegate) {
if (mSelectionDelegate != delegate) {
if (mSelectionDelegate != null) mSelectionDelegate.removeObserver(this);
mSelectionDelegate = delegate;
if (mSelectionDelegate != null) mSelectionDelegate.addObserver(this);
}
}
/**
* Controls whether selection happens during onLongClick or onClick.
* @param selectOnLongClick True if selection should happen on longClick, false if selection
* should happen on click instead.
*/
public void setSelectionOnLongClick(boolean selectOnLongClick) {
mSelectOnLongClick = selectOnLongClick;
}
/**
* @param item The item associated with this SelectableItemViewBase.
*/
public void setItem(E item) {
if (mSelectionDelegate == null) return;
mItem = item;
setChecked(mSelectionDelegate.isItemSelected(item));
}
/** @return The item associated with this SelectableItemViewBase. */
public E getItem() {
return mItem;
}
/**
* @return Whether we are currently in selection mode.
*/
protected boolean isSelectionModeActive() {
if (mSelectionDelegate == null) return false;
return mSelectionDelegate.isSelectionEnabled();
}
/**
* Toggles the selection state for a given item.
*
* @param item The given item.
* @return Whether the item was in selected state after the toggle.
*/
protected boolean toggleSelectionForItem(E item) {
if (mSelectionDelegate == null) return false;
return mSelectionDelegate.toggleSelectionForItem(item);
}
/**
* Update the view based on whether this item is selected.
*
* @param animate Whether to animate the selection state changing if applicable.
*/
protected void updateView(boolean animate) {}
/** Called when a click event happens that doesn't result in a selection. */
protected abstract void handleNonSelectionClick();
// View implementation.
@Override
protected void onAttachedToWindow() {
super.onAttachedToWindow();
if (mSelectionDelegate != null) {
setChecked(mSelectionDelegate.isItemSelected(mItem));
}
}
@Override
protected void onDetachedFromWindow() {
super.onDetachedFromWindow();
if (mSelectionDelegate != null) {
resetCheckedState();
}
}
// OnTouchListener implementation.
@Override
public final boolean onTouch(View view, MotionEvent event) {
int action = event.getActionMasked();
if (action == MotionEvent.ACTION_DOWN) {
// mCurrentX needs init here as well, since we might not get ACTION_MOVE
// for a simple click turning into a long click when selection mode is on.
mAnchorX = mCurrentX = event.getX();
} else if (action == MotionEvent.ACTION_MOVE) {
mCurrentX = event.getX();
}
return false;
}
// OnClickListener implementation.
@Override
public void onClick(View view) {
assert view == this;
if (mSelectionDelegate == null) return;
if (!mSelectOnLongClick) {
handleSelection();
return;
}
if (isSelectionModeActive()) {
onLongClick(view);
} else {
handleNonSelectionClick();
}
}
// OnLongClickListener implementation.
@Override
public boolean onLongClick(View view) {
assert view == this;
if (mSelectionDelegate == null) return false;
if (Math.abs(mCurrentX - mAnchorX) < LONG_CLICK_SLIDE_THRESHOLD_PX) handleSelection();
return true;
}
// Checkable implementations.
@Override
public boolean isChecked() {
return mIsChecked != null && mIsChecked;
}
@Override
public void toggle() {
// TODO: Shouldn't this toggle the selection delegate as well??
if (mSelectionDelegate == null) return;
setChecked(!isChecked());
}
/**
* Sets whether the item is checked. Note that if the views to be updated run animations, you
* should override {@link #updateView(boolean)} to get the correct animation state instead of
* overriding this method to update the views.
* @param checked Whether the item is checked.
*/
@Override
public void setChecked(boolean checked) {
if (mIsChecked != null && checked == mIsChecked) return;
// We shouldn't run the animation when mIsChecked is first initialized to the correct state.
final boolean animate = mIsChecked != null;
mIsChecked = checked;
updateView(animate);
}
// SelectionObserver implementation.
@Override
public void onSelectionStateChange(List<E> selectedItems) {
if (mSelectionDelegate == null) return;
setChecked(mSelectionDelegate.isItemSelected(mItem));
}
// Private methods.
/** Resets the checked state to be uninitialized. */
private void resetCheckedState() {
setChecked(false);
mIsChecked = null;
}
private void handleSelection() {
boolean checked = toggleSelectionForItem(mItem);
setChecked(checked);
}
}
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