1 /* 2 * Copyright (C) 2014 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.example.android.elevationdrag; 18 19 import android.content.Context; 20 import android.support.v4.widget.ViewDragHelper; 21 import android.util.AttributeSet; 22 import android.view.MotionEvent; 23 import android.view.View; 24 import android.widget.FrameLayout; 25 26 import java.util.ArrayList; 27 import java.util.List; 28 29 /** 30 * A {@link FrameLayout} that allows the user to drag and reposition child views. 31 */ 32 public class DragFrameLayout extends FrameLayout { 33 34 /** 35 * The list of {@link View}s that will be draggable. 36 */ 37 private List<View> mDragViews; 38 39 /** 40 * The {@link DragFrameLayoutController} that will be notify on drag. 41 */ 42 private DragFrameLayoutController mDragFrameLayoutController; 43 44 private ViewDragHelper mDragHelper; 45 DragFrameLayout(Context context)46 public DragFrameLayout(Context context) { 47 this(context, null, 0, 0); 48 } 49 DragFrameLayout(Context context, AttributeSet attrs)50 public DragFrameLayout(Context context, AttributeSet attrs) { 51 this(context, attrs, 0, 0); 52 } 53 DragFrameLayout(Context context, AttributeSet attrs, int defStyleAttr)54 public DragFrameLayout(Context context, AttributeSet attrs, int defStyleAttr) { 55 this(context, attrs, defStyleAttr, 0); 56 } 57 DragFrameLayout(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes)58 public DragFrameLayout(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) { 59 super(context, attrs, defStyleAttr, defStyleRes); 60 mDragViews = new ArrayList<View>(); 61 62 /** 63 * Create the {@link ViewDragHelper} and set its callback. 64 */ 65 mDragHelper = ViewDragHelper.create(this, 1.0f, new ViewDragHelper.Callback() { 66 @Override 67 public boolean tryCaptureView(View child, int pointerId) { 68 return mDragViews.contains(child); 69 } 70 71 @Override 72 public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) { 73 super.onViewPositionChanged(changedView, left, top, dx, dy); 74 } 75 76 @Override 77 public int clampViewPositionHorizontal(View child, int left, int dx) { 78 return left; 79 } 80 81 @Override 82 public int clampViewPositionVertical(View child, int top, int dy) { 83 return top; 84 } 85 86 @Override 87 public void onViewCaptured(View capturedChild, int activePointerId) { 88 super.onViewCaptured(capturedChild, activePointerId); 89 if (mDragFrameLayoutController != null) { 90 mDragFrameLayoutController.onDragDrop(true); 91 } 92 } 93 94 @Override 95 public void onViewReleased(View releasedChild, float xvel, float yvel) { 96 super.onViewReleased(releasedChild, xvel, yvel); 97 if (mDragFrameLayoutController != null) { 98 mDragFrameLayoutController.onDragDrop(false); 99 } 100 } 101 }); 102 } 103 104 @Override onInterceptTouchEvent(MotionEvent ev)105 public boolean onInterceptTouchEvent(MotionEvent ev) { 106 final int action = ev.getActionMasked(); 107 if (action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_UP) { 108 mDragHelper.cancel(); 109 return false; 110 } 111 return mDragHelper.shouldInterceptTouchEvent(ev); 112 } 113 114 @Override onTouchEvent(MotionEvent ev)115 public boolean onTouchEvent(MotionEvent ev) { 116 mDragHelper.processTouchEvent(ev); 117 return true; 118 } 119 120 /** 121 * Adds a new {@link View} to the list of views that are draggable within the container. 122 * @param dragView the {@link View} to make draggable 123 */ addDragView(View dragView)124 public void addDragView(View dragView) { 125 mDragViews.add(dragView); 126 } 127 128 /** 129 * Sets the {@link DragFrameLayoutController} that will receive the drag events. 130 * @param dragFrameLayoutController a {@link DragFrameLayoutController} 131 */ setDragFrameController(DragFrameLayoutController dragFrameLayoutController)132 public void setDragFrameController(DragFrameLayoutController dragFrameLayoutController) { 133 mDragFrameLayoutController = dragFrameLayoutController; 134 } 135 136 /** 137 * A controller that will receive the drag events. 138 */ 139 public interface DragFrameLayoutController { 140 onDragDrop(boolean captured)141 public void onDragDrop(boolean captured); 142 } 143 } 144