Java tutorial
/** * Wire * Copyright (C) 2016 Wire Swiss GmbH * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. */ package com.waz.zclient.pages.main.conversation.views.image; import android.content.Context; import android.support.annotation.NonNull; import android.support.v4.view.ViewCompat; import android.util.AttributeSet; import android.view.MotionEvent; import android.view.View; import android.view.animation.Interpolator; import android.widget.FrameLayout; import com.waz.zclient.ui.utils.MathUtils; import com.waz.zclient.ui.animation.interpolators.penner.Cubic; public class ImageDragViewContainer extends FrameLayout { private static final float MAX_DISTANCE_SCALE_FACTOR = 1.5f; private static final int MAX_ROTATION = 24; private static final int MIN_ROTATION = 5; private static final float FLING_DURATION_SECONDS = 0.05f; private static final Interpolator DISTANCE_INTERPOLATOR = new Cubic.EaseIn(); private static final float NORMALIZED_FLING_DISTANCE_THRESHOLD = 0.3f; private ImageDragViewHelper dragHelper; private boolean enabled = true; private ImageViewDragCallback imageViewDragCallback; private Callback callback; public ImageDragViewContainer(Context context) { this(context, null); } public ImageDragViewContainer(Context context, AttributeSet attrs) { this(context, attrs, 0); } public ImageDragViewContainer(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); imageViewDragCallback = new ImageViewDragCallback(); } @Override protected void onAttachedToWindow() { super.onAttachedToWindow(); dragHelper = ImageDragViewHelper.create(this, 1.0f, imageViewDragCallback); } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { if (ev == null) { return false; } if (ev.getPointerCount() != 1) { return false; } boolean shouldDrag; try { shouldDrag = dragHelper.shouldInterceptTouchEvent(ev); } catch (Exception e) { return false; } if (ev.getAction() == MotionEvent.ACTION_DOWN) { imageViewDragCallback.startX = ev.getX(); imageViewDragCallback.startY = ev.getY(); imageViewDragCallback.centerX = getLeft() + (getRight() - getLeft()) / 2f; imageViewDragCallback.centerY = getTop() + (getBottom() - getTop()) / 2f; } boolean intercept = enabled && shouldDrag; if (callback != null && intercept) { callback.onStartDrag(); } return intercept; } @Override public boolean onTouchEvent(@NonNull MotionEvent ev) { try { dragHelper.processTouchEvent(ev); } catch (Exception ignored) { } return true; } @Override public void computeScroll() { super.computeScroll(); if (dragHelper.continueSettling(true)) { ViewCompat.postInvalidateOnAnimation(this); } else if (imageViewDragCallback.isFlinging) { imageViewDragCallback.settled(); } } public void setDraggingEnabled(boolean enabled) { this.enabled = enabled; } public void setCallback(Callback callback) { this.callback = callback; } public interface Callback { void onFlingRequested(float left, float top, float rotation, float pivotX, float pivotY); void onDragDistance(float distance); void onStartDrag(); void onEndDrag(); } private class ImageViewDragCallback extends ImageDragViewHelper.Callback { private float lastRotation; public float centerX = 0; public float centerY = 0; public float startX = 0; public float startY = 0; public int x = 0; public int y = 0; private boolean isFlinging; @Override public boolean tryCaptureView(View view, int i) { return true; } @Override public int clampViewPositionVertical(View child, int top, int dy) { return top; } @Override public int getViewVerticalDragRange(View child) { return child.getMeasuredHeight(); } @Override public void onViewReleased(View releasedChild, float xvel, float yvel) { super.onViewReleased(releasedChild, xvel, yvel); float normalizedDistance = getNormalizedDragDistance(); if (normalizedDistance > NORMALIZED_FLING_DISTANCE_THRESHOLD && callback != null) { isFlinging = true; dragHelper.settleCapturedViewAt(releasedChild.getLeft(), (int) (releasedChild.getTop() + (yvel / 1.25f) * FLING_DURATION_SECONDS)); } else { if (callback != null) { callback.onEndDrag(); } dragHelper.settleCapturedViewAt(0, 0); } postInvalidate(); } private float getNormalizedDragDistance() { return (float) MathUtils.clamp(Math.abs(y / (MAX_DISTANCE_SCALE_FACTOR * centerY)), 0, 1); } @Override public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) { super.onViewPositionChanged(changedView, left, top, dx, dy); x += dx; y -= dy; float normalizedDistance = getNormalizedDragDistance(); if (callback != null) { callback.onDragDistance(normalizedDistance); } changedView.setPivotX(startX); changedView.setPivotY(startY); float maxRotation = (float) (MAX_ROTATION * MathUtils.clamp(Math.abs(startX - centerX), MIN_ROTATION / MAX_ROTATION, 1f)); changedView.setRotation(maxRotation * DISTANCE_INTERPOLATOR.getInterpolation(normalizedDistance) * Math.signum(-y) * Math.signum(startX - centerX)); lastRotation = changedView.getRotation(); } public void settled() { isFlinging = false; if (callback != null) { callback.onFlingRequested(x, -y, lastRotation, startX, startY); } } } }