DropDownListView.java revision 8375d639986529969ea5e118de548d29db16ec97
1/* 2 * Copyright (C) 2015 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17package android.widget; 18 19 20import com.android.internal.widget.AutoScrollHelper.AbsListViewAutoScroller; 21 22import android.animation.Animator; 23import android.animation.AnimatorListenerAdapter; 24import android.animation.ObjectAnimator; 25import android.content.Context; 26import android.graphics.drawable.Drawable; 27import android.util.IntProperty; 28import android.view.MotionEvent; 29import android.view.View; 30import android.view.animation.AccelerateDecelerateInterpolator; 31import android.widget.TextView; 32import android.widget.ListView; 33 34 35/** 36 * Wrapper class for a ListView. This wrapper can hijack the focus to 37 * make sure the list uses the appropriate drawables and states when 38 * displayed on screen within a drop down. The focus is never actually 39 * passed to the drop down in this mode; the list only looks focused. 40 * 41 * @hide 42 */ 43public class DropDownListView extends ListView { 44 /** Duration in milliseconds of the drag-to-open click animation. */ 45 private static final long CLICK_ANIM_DURATION = 150; 46 47 /** Target alpha value for drag-to-open click animation. */ 48 private static final int CLICK_ANIM_ALPHA = 0x80; 49 50 /** Wrapper around Drawable's <code>alpha</code> property. */ 51 private static final IntProperty<Drawable> DRAWABLE_ALPHA = 52 new IntProperty<Drawable>("alpha") { 53 @Override 54 public void setValue(Drawable object, int value) { 55 object.setAlpha(value); 56 } 57 58 @Override 59 public Integer get(Drawable object) { 60 return object.getAlpha(); 61 } 62 }; 63 64 /* 65 * WARNING: This is a workaround for a touch mode issue. 66 * 67 * Touch mode is propagated lazily to windows. This causes problems in 68 * the following scenario: 69 * - Type something in the AutoCompleteTextView and get some results 70 * - Move down with the d-pad to select an item in the list 71 * - Move up with the d-pad until the selection disappears 72 * - Type more text in the AutoCompleteTextView *using the soft keyboard* 73 * and get new results; you are now in touch mode 74 * - The selection comes back on the first item in the list, even though 75 * the list is supposed to be in touch mode 76 * 77 * Using the soft keyboard triggers the touch mode change but that change 78 * is propagated to our window only after the first list layout, therefore 79 * after the list attempts to resurrect the selection. 80 * 81 * The trick to work around this issue is to pretend the list is in touch 82 * mode when we know that the selection should not appear, that is when 83 * we know the user moved the selection away from the list. 84 * 85 * This boolean is set to true whenever we explicitly hide the list's 86 * selection and reset to false whenever we know the user moved the 87 * selection back to the list. 88 * 89 * When this boolean is true, isInTouchMode() returns true, otherwise it 90 * returns super.isInTouchMode(). 91 */ 92 private boolean mListSelectionHidden; 93 94 /** 95 * True if this wrapper should fake focus. 96 */ 97 private boolean mHijackFocus; 98 99 /** Whether to force drawing of the pressed state selector. */ 100 private boolean mDrawsInPressedState; 101 102 /** Current drag-to-open click animation, if any. */ 103 private Animator mClickAnimation; 104 105 /** Helper for drag-to-open auto scrolling. */ 106 private AbsListViewAutoScroller mScrollHelper; 107 108 /** 109 * Creates a new list view wrapper. 110 * 111 * @param context this view's context 112 */ 113 public DropDownListView(Context context, boolean hijackFocus) { 114 this(context, hijackFocus, com.android.internal.R.attr.dropDownListViewStyle); 115 } 116 117 /** 118 * Creates a new list view wrapper. 119 * 120 * @param context this view's context 121 */ 122 public DropDownListView(Context context, boolean hijackFocus, int defStyleAttr) { 123 super(context, null, defStyleAttr); 124 mHijackFocus = hijackFocus; 125 // TODO: Add an API to control this 126 setCacheColorHint(0); // Transparent, since the background drawable could be anything. 127 } 128 129 @Override 130 protected boolean shouldShowSelector() { 131 View selectedView = getSelectedView(); 132 return selectedView != null && selectedView.isEnabled() || super.shouldShowSelector(); 133 } 134 135 @Override 136 public boolean onHoverEvent(MotionEvent ev) { 137 final int action = ev.getActionMasked(); 138 if (action == MotionEvent.ACTION_HOVER_ENTER 139 || action == MotionEvent.ACTION_HOVER_MOVE) { 140 final int position = pointToPosition((int) ev.getX(), (int) ev.getY()); 141 if (position != INVALID_POSITION && position != mSelectedPosition) { 142 final View hoveredItem = getChildAt(position - getFirstVisiblePosition()); 143 if (hoveredItem.isEnabled()) { 144 // Force a focus so that the proper selector state gets used when we update. 145 requestFocus(); 146 147 positionSelector(position, hoveredItem); 148 setSelectedPositionInt(position); 149 setNextSelectedPositionInt(position); 150 } 151 updateSelectorState(); 152 } 153 } else { 154 // Do not cancel the selected position if the selection is visible by other reasons. 155 if (!super.shouldShowSelector()) { 156 setSelectedPositionInt(INVALID_POSITION); 157 } 158 } 159 return super.onHoverEvent(ev); 160 } 161 162 /** 163 * Handles forwarded events. 164 * 165 * @param activePointerId id of the pointer that activated forwarding 166 * @return whether the event was handled 167 */ 168 public boolean onForwardedEvent(MotionEvent event, int activePointerId) { 169 boolean handledEvent = true; 170 boolean clearPressedItem = false; 171 172 final int actionMasked = event.getActionMasked(); 173 switch (actionMasked) { 174 case MotionEvent.ACTION_CANCEL: 175 handledEvent = false; 176 break; 177 case MotionEvent.ACTION_UP: 178 handledEvent = false; 179 // $FALL-THROUGH$ 180 case MotionEvent.ACTION_MOVE: 181 final int activeIndex = event.findPointerIndex(activePointerId); 182 if (activeIndex < 0) { 183 handledEvent = false; 184 break; 185 } 186 187 final int x = (int) event.getX(activeIndex); 188 final int y = (int) event.getY(activeIndex); 189 final int position = pointToPosition(x, y); 190 if (position == INVALID_POSITION) { 191 clearPressedItem = true; 192 break; 193 } 194 195 final View child = getChildAt(position - getFirstVisiblePosition()); 196 setPressedItem(child, position, x, y); 197 handledEvent = true; 198 199 if (actionMasked == MotionEvent.ACTION_UP) { 200 clickPressedItem(child, position); 201 } 202 break; 203 } 204 205 // Failure to handle the event cancels forwarding. 206 if (!handledEvent || clearPressedItem) { 207 clearPressedItem(); 208 } 209 210 // Manage automatic scrolling. 211 if (handledEvent) { 212 if (mScrollHelper == null) { 213 mScrollHelper = new AbsListViewAutoScroller(this); 214 } 215 mScrollHelper.setEnabled(true); 216 mScrollHelper.onTouch(this, event); 217 } else if (mScrollHelper != null) { 218 mScrollHelper.setEnabled(false); 219 } 220 221 return handledEvent; 222 } 223 224 /** 225 * Sets whether the list selection is hidden, as part of a workaround for a touch mode issue 226 * (see the declaration for mListSelectionHidden). 227 * @param listSelectionHidden 228 */ 229 public void setListSelectionHidden(boolean listSelectionHidden) { 230 this.mListSelectionHidden = listSelectionHidden; 231 } 232 233 /** 234 * Starts an alpha animation on the selector. When the animation ends, 235 * the list performs a click on the item. 236 */ 237 private void clickPressedItem(final View child, final int position) { 238 final long id = getItemIdAtPosition(position); 239 final Animator anim = ObjectAnimator.ofInt( 240 mSelector, DRAWABLE_ALPHA, 0xFF, CLICK_ANIM_ALPHA, 0xFF); 241 anim.setDuration(CLICK_ANIM_DURATION); 242 anim.setInterpolator(new AccelerateDecelerateInterpolator()); 243 anim.addListener(new AnimatorListenerAdapter() { 244 @Override 245 public void onAnimationEnd(Animator animation) { 246 performItemClick(child, position, id); 247 } 248 }); 249 anim.start(); 250 251 if (mClickAnimation != null) { 252 mClickAnimation.cancel(); 253 } 254 mClickAnimation = anim; 255 } 256 257 private void clearPressedItem() { 258 mDrawsInPressedState = false; 259 setPressed(false); 260 updateSelectorState(); 261 262 final View motionView = getChildAt(mMotionPosition - mFirstPosition); 263 if (motionView != null) { 264 motionView.setPressed(false); 265 } 266 267 if (mClickAnimation != null) { 268 mClickAnimation.cancel(); 269 mClickAnimation = null; 270 } 271 } 272 273 private void setPressedItem(View child, int position, float x, float y) { 274 mDrawsInPressedState = true; 275 276 // Ordering is essential. First, update the container's pressed state. 277 drawableHotspotChanged(x, y); 278 if (!isPressed()) { 279 setPressed(true); 280 } 281 282 // Next, run layout if we need to stabilize child positions. 283 if (mDataChanged) { 284 layoutChildren(); 285 } 286 287 // Manage the pressed view based on motion position. This allows us to 288 // play nicely with actual touch and scroll events. 289 final View motionView = getChildAt(mMotionPosition - mFirstPosition); 290 if (motionView != null && motionView != child && motionView.isPressed()) { 291 motionView.setPressed(false); 292 } 293 mMotionPosition = position; 294 295 // Offset for child coordinates. 296 final float childX = x - child.getLeft(); 297 final float childY = y - child.getTop(); 298 child.drawableHotspotChanged(childX, childY); 299 if (!child.isPressed()) { 300 child.setPressed(true); 301 } 302 303 // Ensure that keyboard focus starts from the last touched position. 304 setSelectedPositionInt(position); 305 positionSelectorLikeTouch(position, child, x, y); 306 307 // Refresh the drawable state to reflect the new pressed state, 308 // which will also update the selector state. 309 refreshDrawableState(); 310 311 if (mClickAnimation != null) { 312 mClickAnimation.cancel(); 313 mClickAnimation = null; 314 } 315 } 316 317 @Override 318 boolean touchModeDrawsInPressedState() { 319 return mDrawsInPressedState || super.touchModeDrawsInPressedState(); 320 } 321 322 /** 323 * Avoids jarring scrolling effect by ensuring that list elements 324 * made of a text view fit on a single line. 325 * 326 * @param position the item index in the list to get a view for 327 * @return the view for the specified item 328 */ 329 @Override 330 View obtainView(int position, boolean[] isScrap) { 331 View view = super.obtainView(position, isScrap); 332 333 if (view instanceof TextView) { 334 ((TextView) view).setHorizontallyScrolling(true); 335 } 336 337 return view; 338 } 339 340 @Override 341 public boolean isInTouchMode() { 342 // WARNING: Please read the comment where mListSelectionHidden is declared 343 return (mHijackFocus && mListSelectionHidden) || super.isInTouchMode(); 344 } 345 346 /** 347 * Returns the focus state in the drop down. 348 * 349 * @return true always if hijacking focus 350 */ 351 @Override 352 public boolean hasWindowFocus() { 353 return mHijackFocus || super.hasWindowFocus(); 354 } 355 356 /** 357 * Returns the focus state in the drop down. 358 * 359 * @return true always if hijacking focus 360 */ 361 @Override 362 public boolean isFocused() { 363 return mHijackFocus || super.isFocused(); 364 } 365 366 /** 367 * Returns the focus state in the drop down. 368 * 369 * @return true always if hijacking focus 370 */ 371 @Override 372 public boolean hasFocus() { 373 return mHijackFocus || super.hasFocus(); 374 } 375}