毕业设计-基于Java的Android app：Music Player设计与实现

/* * Copyright (C) 2013 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 com.susion.boring.base.view.swipebacklayout; import android.content.Context; import android.support.v4.view.MotionEventCompat; import android.support.v4.view.VelocityTrackerCompat; import android.support.v4.view.ViewCompat; import android.support.v4.widget.ScrollerCompat; import android.view.MotionEvent; import android.view.VelocityTracker; import android.view.View; import android.view.ViewConfiguration; import android.view.ViewGroup; import android.view.animation.Interpolator; import java.util.Arrays; /** * ViewDragHelper is a utility class for writing custom ViewGroups. It offers a * number of useful operations and state tracking for allowing a user to drag * and reposition views within their parent ViewGroup. */ public class ViewDragHelper { private static final String TAG = "ViewDragHelper"; /** * A null/invalid pointer ID. */ public static final int INVALID_POINTER = -1; /** * A view is not currently being dragged or animating as a result of a * fling/snap. */ public static final int STATE_IDLE = 0; /** * A view is currently being dragged. The position is currently changing as * a result of user input or simulated user input. */ public static final int STATE_DRAGGING = 1; /** * A view is currently settling into place as a result of a fling or * predefined non-interactive motion. */ public static final int STATE_SETTLING = 2; /** * Edge flag indicating that the left edge should be affected. */ public static final int EDGE_LEFT = 1 << 0; /** * Edge flag indicating that the right edge should be affected. */ public static final int EDGE_RIGHT = 1 << 1; /** * Edge flag indicating that the top edge should be affected. */ public static final int EDGE_TOP = 1 << 2; /** * Edge flag indicating that the bottom edge should be affected. */ public static final int EDGE_BOTTOM = 1 << 3; /** * Edge flag set indicating all edges should be affected. */ public static final int EDGE_ALL = EDGE_LEFT | EDGE_TOP | EDGE_RIGHT | EDGE_BOTTOM; /** * Indicates that a check should occur along the horizontal axis */ public static final int DIRECTION_HORIZONTAL = 1 << 0; /** * Indicates that a check should occur along the vertical axis */ public static final int DIRECTION_VERTICAL = 1 << 1; /** * Indicates that a check should occur along all axes */ public static final int DIRECTION_ALL = DIRECTION_HORIZONTAL | DIRECTION_VERTICAL; public static final int EDGE_SIZE = 20; // dp private static final int BASE_SETTLE_DURATION = 256; // ms private static final int MAX_SETTLE_DURATION = 600; // ms // Current drag state; idle, dragging or settling private int mDragState; // Distance to travel before a drag may begin private int mTouchSlop; // Last known position/pointer tracking private int mActivePointerId = INVALID_POINTER; private float[] mInitialMotionX; private float[] mInitialMotionY; private float[] mLastMotionX; private float[] mLastMotionY; private int[] mInitialEdgeTouched; private int[] mEdgeDragsInProgress; private int[] mEdgeDragsLocked; private int mPointersDown; private VelocityTracker mVelocityTracker; private float mMaxVelocity; private float mMinVelocity; private int mEdgeSize; private int mTrackingEdges; private ScrollerCompat mScroller; private final Callback mCallback; private View mCapturedView; private boolean mReleaseInProgress; private final ViewGroup mParentView; /** * A Callback is used as a communication channel with the ViewDragHelper * back to the parent view using it. <code>on*</code>methods are invoked on * siginficant events and several accessor methods are expected to provide * the ViewDragHelper with more information about the state of the parent * view upon request. The callback also makes decisions governing the range * and draggability of child views. */ public static abstract class Callback { /** * Called when the drag state changes. See the <code>STATE_*</code> * constants for more information. * * @param state The new drag state * @see #STATE_IDLE * @see #STATE_DRAGGING * @see #STATE_SETTLING */ public void onViewDragStateChanged(int state) { } /** * Called when the captured view's position changes as the result of a * drag or settle. * * @param changedView View whose position changed * @param left New X coordinate of the left edge of the view * @param top New Y coordinate of the top edge of the view * @param dx Change in X position from the last call * @param dy Change in Y position from the last call */ public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) { } /** * Called when a child view is captured for dragging or settling. The ID * of the pointer currently dragging the captured view is supplied. If * activePointerId is identified as {@link #INVALID_POINTER} the capture * is programmatic instead of pointer-initiated. * * @param capturedChild Child view that was captured * @param activePointerId Pointer id tracking the child capture */ public void onViewCaptured(View capturedChild, int activePointerId) { } /** * Called when the child view is no longer being actively dragged. The * fling velocity is also supplied, if relevant. The velocity values may * be clamped to system minimums or maximums. * <p> * Calling code may decide to fling or otherwise release the view to let * it settle into place. It should do so using * {@link #settleCapturedViewAt(int, int)} or * {@link #flingCapturedView(int, int, int, int)}. If the Callback * invokes one of these methods, the ViewDragHelper will enter * {@link #STATE_SETTLING} and the view capture will not fully end until * it comes to a complete stop. If neither of these methods is invoked * before <code>onViewReleased</code> returns, the view will stop in * place and the ViewDragHelper will return to {@link #STATE_IDLE}. * </p> * * @param releasedChild The captured child view now being released * @param xvel X velocity of the pointer as it left the screen in pixels * per second. * @param yvel Y velocity of the pointer as it left the screen in pixels * per second. */ public void onViewReleased(View releasedChild, float xvel, float yvel) { } /** * Called when one of the subscribed edges in the parent view has been * touched by the user while no child view is currently captured. * * @param edgeFlags A combination of edge flags describing the edge(s) * currently touched