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      1 /*
      2  * Copyright (C) 2010 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 
     17 package com.android.launcher3;
     18 
     19 import android.content.Context;
     20 import android.util.AttributeSet;
     21 import android.view.MotionEvent;
     22 import android.view.View;
     23 
     24 
     25 /* Class that does most of the work of enabling dragging items out of a PagedView by performing a
     26  * vertical drag. Used by both CustomizePagedView and AllAppsPagedView.
     27  * Subclasses must do the following:
     28  *   * call setDragSlopeThreshold after making an instance of the PagedViewWithDraggableItems
     29  *   * call child.setOnLongClickListener(this) and child.setOnTouchListener(this) on all children
     30  *       (good place to do it is in syncPageItems)
     31  *   * override beginDragging(View) (but be careful to call super.beginDragging(View)
     32  *
     33  */
     34 public abstract class PagedViewWithDraggableItems extends PagedView
     35     implements View.OnLongClickListener, View.OnTouchListener {
     36     private View mLastTouchedItem;
     37     private boolean mIsDragging;
     38     private boolean mIsDragEnabled;
     39     private float mDragSlopeThreshold;
     40     private Launcher mLauncher;
     41 
     42     public PagedViewWithDraggableItems(Context context) {
     43         this(context, null);
     44     }
     45 
     46     public PagedViewWithDraggableItems(Context context, AttributeSet attrs) {
     47         this(context, attrs, 0);
     48     }
     49 
     50     public PagedViewWithDraggableItems(Context context, AttributeSet attrs, int defStyle) {
     51         super(context, attrs, defStyle);
     52         mLauncher = (Launcher) context;
     53     }
     54 
     55     protected boolean beginDragging(View v) {
     56         boolean wasDragging = mIsDragging;
     57         mIsDragging = true;
     58         return !wasDragging;
     59     }
     60 
     61     protected void cancelDragging() {
     62         mIsDragging = false;
     63         mLastTouchedItem = null;
     64         mIsDragEnabled = false;
     65     }
     66 
     67     private void handleTouchEvent(MotionEvent ev) {
     68         final int action = ev.getAction();
     69         switch (action & MotionEvent.ACTION_MASK) {
     70             case MotionEvent.ACTION_DOWN:
     71                 cancelDragging();
     72                 mIsDragEnabled = true;
     73                 break;
     74             case MotionEvent.ACTION_MOVE:
     75                 if (mTouchState != TOUCH_STATE_SCROLLING && !mIsDragging && mIsDragEnabled) {
     76                     determineDraggingStart(ev);
     77                 }
     78                 break;
     79         }
     80     }
     81 
     82     @Override
     83     public boolean onInterceptTouchEvent(MotionEvent ev) {
     84         handleTouchEvent(ev);
     85         return super.onInterceptTouchEvent(ev);
     86     }
     87 
     88     @Override
     89     public boolean onTouchEvent(MotionEvent ev) {
     90         handleTouchEvent(ev);
     91         return super.onTouchEvent(ev);
     92     }
     93 
     94     @Override
     95     public boolean onTouch(View v, MotionEvent event) {
     96         mLastTouchedItem = v;
     97         mIsDragEnabled = true;
     98         return false;
     99     }
    100 
    101     @Override
    102     public boolean onLongClick(View v) {
    103         // Return early if this is not initiated from a touch
    104         if (!v.isInTouchMode()) return false;
    105         // Return early if we are still animating the pages
    106         if (mNextPage != INVALID_PAGE) return false;
    107         // When we have exited all apps or are in transition, disregard long clicks
    108         if (!mLauncher.isAllAppsVisible() ||
    109                 mLauncher.getWorkspace().isSwitchingState()) return false;
    110         // Return if global dragging is not enabled
    111         if (!mLauncher.isDraggingEnabled()) return false;
    112 
    113         return beginDragging(v);
    114     }
    115 
    116     /*
    117      * Determines if we should change the touch state to start scrolling after the
    118      * user moves their touch point too far.
    119      */
    120     protected void determineScrollingStart(MotionEvent ev) {
    121         if (!mIsDragging) super.determineScrollingStart(ev);
    122     }
    123 
    124     /*
    125      * Determines if we should change the touch state to start dragging after the
    126      * user moves their touch point far enough.
    127      */
    128     protected void determineDraggingStart(MotionEvent ev) {
    129         /*
    130          * Locally do absolute value. mLastMotionX is set to the y value
    131          * of the down event.
    132          */
    133         final int pointerIndex = ev.findPointerIndex(mActivePointerId);
    134         final float x = ev.getX(pointerIndex);
    135         final float y = ev.getY(pointerIndex);
    136         final int xDiff = (int) Math.abs(x - mLastMotionX);
    137         final int yDiff = (int) Math.abs(y - mLastMotionY);
    138 
    139         final int touchSlop = mTouchSlop;
    140         boolean yMoved = yDiff > touchSlop;
    141         boolean isUpwardMotion = (yDiff / (float) xDiff) > mDragSlopeThreshold;
    142 
    143         if (isUpwardMotion && yMoved && mLastTouchedItem != null) {
    144             // Drag if the user moved far enough along the Y axis
    145             beginDragging(mLastTouchedItem);
    146 
    147             // Cancel any pending long press
    148             if (mAllowLongPress) {
    149                 mAllowLongPress = false;
    150                 // Try canceling the long press. It could also have been scheduled
    151                 // by a distant descendant, so use the mAllowLongPress flag to block
    152                 // everything
    153                 final View currentPage = getPageAt(mCurrentPage);
    154                 if (currentPage != null) {
    155                     currentPage.cancelLongPress();
    156                 }
    157             }
    158         }
    159     }
    160 
    161     public void setDragSlopeThreshold(float dragSlopeThreshold) {
    162         mDragSlopeThreshold = dragSlopeThreshold;
    163     }
    164 
    165     @Override
    166     protected void onDetachedFromWindow() {
    167         cancelDragging();
    168         super.onDetachedFromWindow();
    169     }
    170 }
    171