Java tutorial
/* * The MIT License (MIT) * * Copyright (c) 2015 XiNGRZ <xxx@oxo.ooo> * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in all * copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE * SOFTWARE. */ package com.isanechek.beardycast.ui.widget; import android.content.Context; import android.support.annotation.IntDef; import android.support.annotation.NonNull; import android.support.annotation.Nullable; import android.support.v4.view.ViewCompat; import android.support.v4.widget.ViewDragHelper; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.View; import android.view.ViewConfiguration; import android.widget.FrameLayout; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; public class PullBackLayout extends FrameLayout { /** * Flag indicated pulling up is allowed * * @see #setDirection(int) */ public static final int DIRECTION_UP = 1; /** * Flag indicated pulling down is allowed * * @see #setDirection(int) */ public static final int DIRECTION_DOWN = 1 << 1; private final ViewDragHelper dragger; private final int minimumFlingVelocity; @Direction private int direction = DIRECTION_UP | DIRECTION_DOWN; @Nullable private Callback callback; public PullBackLayout(Context context) { this(context, null); } public PullBackLayout(Context context, AttributeSet attrs) { this(context, attrs, 0); } public PullBackLayout(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); dragger = ViewDragHelper.create(this, 1f / 8f, new ViewDragCallback()); minimumFlingVelocity = ViewConfiguration.get(context).getScaledMinimumFlingVelocity(); } /** * @return Allowed pulling direction */ @Direction public int getDirection() { return direction; } /** * Sets pulling directions allowed * * @param direction Directions allowed * @see #DIRECTION_UP * @see #DIRECTION_DOWN */ public void setDirection(@Direction int direction) { this.direction = direction; } public void setCallback(@Nullable Callback callback) { this.callback = callback; } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { try { return dragger.shouldInterceptTouchEvent(ev); } catch (Exception e) { return false; } } @Override public boolean onTouchEvent(@NonNull MotionEvent event) { try { dragger.processTouchEvent(event); return true; } catch (Exception e) { return false; } } @Override public void computeScroll() { if (dragger.continueSettling(true)) { ViewCompat.postInvalidateOnAnimation(this); } } private void onPullStart() { if (callback != null) { callback.onPullStart(); } } private void onPull(@Direction int direction, float progress) { if (callback != null) { callback.onPull(direction, progress); } } private void onPullCancel(@Direction int direction) { if (callback != null) { callback.onPullCancel(direction); } } private void onPullComplete(@Direction int direction) { if (callback != null) { callback.onPullComplete(direction); } } private void reset() { dragger.settleCapturedViewAt(0, 0); invalidate(); } @Retention(RetentionPolicy.SOURCE) @IntDef(value = { DIRECTION_UP, DIRECTION_DOWN }, flag = true) public @interface Direction { } public interface Callback { void onPullStart(); void onPull(@Direction int direction, float progress); void onPullCancel(@Direction int direction); void onPullComplete(@Direction int direction); } private class ViewDragCallback extends ViewDragHelper.Callback { @Override public boolean tryCaptureView(View child, int pointerId) { return true; } @Override public int clampViewPositionHorizontal(View child, int left, int dx) { return 0; } @Override public int clampViewPositionVertical(View child, int top, int dy) { if ((direction & (DIRECTION_UP | DIRECTION_DOWN)) != 0) { return top; } else if ((direction & DIRECTION_UP) != 0) { return Math.min(0, top); } else if ((direction & DIRECTION_DOWN) != 0) { return Math.max(0, top); } else { return 0; } } @Override public int getViewHorizontalDragRange(View child) { return 0; } @Override public int getViewVerticalDragRange(View child) { if (direction == 0) { return 0; } else if ((direction & (DIRECTION_UP | DIRECTION_DOWN)) != 0) { return getHeight() * 2; } else { return getHeight(); } } @Override public void onViewCaptured(View capturedChild, int activePointerId) { onPullStart(); } @Override public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) { if (top > 0) { onPull(DIRECTION_DOWN, (float) top / (float) getHeight()); } else if (top < 0) { onPull(DIRECTION_UP, (float) -top / (float) getHeight()); } } @Override public void onViewReleased(View releasedChild, float xvel, float yvel) { int top = releasedChild.getTop(); int slop = Math.abs(yvel) > minimumFlingVelocity ? getHeight() / 6 : getHeight() / 3; if (top > 0) { if (top > slop) { onPullComplete(DIRECTION_DOWN); } else { onPullCancel(DIRECTION_DOWN); reset(); } } else if (top < 0) { if (top < -slop) { onPullComplete(DIRECTION_UP); } else { onPullCancel(DIRECTION_UP); reset(); } } } } }