Java tutorial
/* * 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.carlrice.reader.view; import android.content.Context; import android.content.res.Resources; import android.content.res.TypedArray; import android.graphics.Canvas; import android.support.v4.view.ViewCompat; import android.util.AttributeSet; import android.util.DisplayMetrics; import android.view.MotionEvent; import android.view.View; import android.view.ViewConfiguration; import android.view.ViewGroup; import android.view.animation.AccelerateInterpolator; import android.view.animation.Animation; import android.view.animation.Animation.AnimationListener; import android.view.animation.DecelerateInterpolator; import android.view.animation.Transformation; import android.widget.AbsListView; /** * The SwipeRefreshLayout should be used whenever the user can refresh the * contents of a view via a vertical swipe gesture. The activity that * instantiates this view should add an OnRefreshListener to be notified * whenever the swipe to refresh gesture is completed. The SwipeRefreshLayout * will notify the listener each and every time the gesture is completed again; * the listener is responsible for correctly determining when to actually * initiate a refresh of its content. If the listener determines there should * not be a refresh, it must call setRefreshing(false) to cancel any visual * indication of a refresh. If an activity wishes to show just the progress * animation, it should call setRefreshing(true). To disable the gesture and progress * animation, call setEnabled(false) on the view. * <p/> * <p> This layout should be made the parent of the view that will be refreshed as a * result of the gesture and can only support one direct child. This view will * also be made the target of the gesture and will be forced to match both the * width and the height supplied in this layout. The SwipeRefreshLayout does not * provide accessibility events; instead, a menu item must be provided to allow * refresh of the content wherever this gesture is used.</p> */ public class SwipeRefreshLayout extends ViewGroup { private static final long RETURN_TO_ORIGINAL_POSITION_TIMEOUT = 300; private static final float ACCELERATE_INTERPOLATION_FACTOR = 1.5f; private static final float DECELERATE_INTERPOLATION_FACTOR = 2f; private static final float PROGRESS_BAR_HEIGHT = 4; private static final float MAX_SWIPE_DISTANCE_FACTOR = .6f; private static final int REFRESH_TRIGGER_DISTANCE = 120; private static final int[] LAYOUT_ATTRS = new int[] { android.R.attr.enabled }; private final DecelerateInterpolator mDecelerateInterpolator; private final AccelerateInterpolator mAccelerateInterpolator; private SwipeProgressBar mProgressBar; //the thing that shows progress is going private View mTarget; //the content that gets pulled down private int mOriginalOffsetTop; private OnRefreshListener mListener; private MotionEvent mDownEvent; private int mFrom; private final Animation mAnimateToStartPosition = new Animation() { @Override public void applyTransformation(float interpolatedTime, Transformation t) { int targetTop = 0; if (mFrom != mOriginalOffsetTop) { targetTop = (mFrom + (int) ((mOriginalOffsetTop - mFrom) * interpolatedTime)); } int offset = targetTop - mTarget.getTop(); final int currentTop = mTarget.getTop(); if (offset + currentTop < 0) { offset = 0 - currentTop; } setTargetOffsetTopAndBottom(offset); } }; private boolean mRefreshing = false; private int mTouchSlop; private float mDistanceToTriggerSync = -1; private float mPrevY; private int mMediumAnimationDuration; private float mFromPercentage = 0; private Animation mShrinkTrigger = new Animation() { @Override public void applyTransformation(float interpolatedTime, Transformation t) { float percent = mFromPercentage + ((0 - mFromPercentage) * interpolatedTime); mProgressBar.setTriggerPercentage(percent); } }; private float mCurrPercentage = 0; private final AnimationListener mShrinkAnimationListener = new BaseAnimationListener() { @Override public void onAnimationEnd(Animation animation) { mCurrPercentage = 0; } }; private int mProgressBarHeight; private int mCurrentTargetOffsetTop; private final AnimationListener mReturnToStartPositionListener = new BaseAnimationListener() { @Override public void onAnimationEnd(Animation animation) { // Once the target content has returned to its start position, reset // the target offset to 0 mCurrentTargetOffsetTop = 0; } }; // Target is returning to its start offset because it was cancelled or a // refresh was triggered. private boolean mReturningToStart; private final Runnable mReturnToStartPosition = new Runnable() { @Override public void run() { mReturningToStart = true; animateOffsetToStartPosition(mCurrentTargetOffsetTop + getPaddingTop(), mReturnToStartPositionListener); } }; // Cancel the refresh gesture and animate everything back to its original state. private final Runnable mCancel = new Runnable() { @Override public void run() { mReturningToStart = true; // Timeout fired since the user last moved their finger; animate the // trigger to 0 and put the target back at its original position if (mProgressBar != null) { mFromPercentage = mCurrPercentage; mShrinkTrigger.setDuration(mMediumAnimationDuration); mShrinkTrigger.setAnimationListener(mShrinkAnimationListener); mShrinkTrigger.reset(); mShrinkTrigger.setInterpolator(mDecelerateInterpolator); startAnimation(mShrinkTrigger); } animateOffsetToStartPosition(mCurrentTargetOffsetTop + getPaddingTop(), mReturnToStartPositionListener); } }; /** * Simple constructor to use when creating a SwipeRefreshLayout from code. * * @param context */ public SwipeRefreshLayout(Context context) { this(context, null); } /** * Constructor that is called when inflating SwipeRefreshLayout from XML. * * @param context * @param attrs */ public SwipeRefreshLayout(Context context, AttributeSet attrs) { super(context, attrs); mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop(); mMediumAnimationDuration = getResources().getInteger(android.R.integer.config_mediumAnimTime); setWillNotDraw(false); mProgressBar = new SwipeProgressBar(this); final DisplayMetrics metrics = getResources().getDisplayMetrics(); mProgressBarHeight = (int) (metrics.density * PROGRESS_BAR_HEIGHT); mDecelerateInterpolator = new DecelerateInterpolator(DECELERATE_INTERPOLATION_FACTOR); mAccelerateInterpolator = new AccelerateInterpolator(ACCELERATE_INTERPOLATION_FACTOR); final TypedArray a = context.obtainStyledAttributes(attrs, LAYOUT_ATTRS); setEnabled(a.getBoolean(0, true)); a.recycle(); } @Override public void onAttachedToWindow() { super.onAttachedToWindow(); removeCallbacks(mCancel); removeCallbacks(mReturnToStartPosition); } @Override public void onDetachedFromWindow() { super.onDetachedFromWindow(); removeCallbacks(mReturnToStartPosition); removeCallbacks(mCancel); } private void animateOffsetToStartPosition(int from, AnimationListener listener) { mFrom = from; mAnimateToStartPosition.reset(); mAnimateToStartPosition.setDuration(mMediumAnimationDuration); mAnimateToStartPosition.setAnimationListener(listener); mAnimateToStartPosition.setInterpolator(mDecelerateInterpolator); mTarget.startAnimation(mAnimateToStartPosition); } /** * Set the listener to be notified when a refresh is triggered via the swipe * gesture. */ public void setOnRefreshListener(OnRefreshListener listener) { mListener = listener; } private void setTriggerPercentage(float percent) { if (percent == 0f) { // No-op. A null trigger means it's uninitialized, and setting it to zero-percent // means we're trying to reset state, so there's nothing to reset in this case. mCurrPercentage = 0; return; } mCurrPercentage = percent; mProgressBar.setTriggerPercentage(percent); } /** * Set the four colors used in the progress animation. The first color will * also be the color of the bar that grows in response to a user swipe * gesture. * * @param colorRes1 Color resource. * @param colorRes2 Color resource. * @param colorRes3 Color resource. * @param colorRes4 Color resource. */ public void setColorScheme(int colorRes1, int colorRes2, int colorRes3, int colorRes4) { ensureTarget(); final Resources res = getResources(); final int color1 = res.getColor(colorRes1); final int color2 = res.getColor(colorRes2); final int color3 = res.getColor(colorRes3); final int color4 = res.getColor(colorRes4); mProgressBar.setColorScheme(color1, color2, color3, color4); } /** * @return Whether the SwipeRefreshWidget is actively showing refresh * progress. */ public boolean isRefreshing() { return mRefreshing; } /** * Notify the widget that refresh state has changed. Do not call this when * refresh is triggered by a swipe gesture. * * @param refreshing Whether or not the view should show refresh progress. */ public void setRefreshing(boolean refreshing) { if (mRefreshing != refreshing) { ensureTarget(); mCurrPercentage = 0; mRefreshing = refreshing; if (mRefreshing) { mProgressBar.start(); } else { mProgressBar.stop(); } } } private void ensureTarget() { // Don't bother getting the parent height if the parent hasn't been laid out yet. if (mTarget == null) { if (getChildCount() > 1 && !isInEditMode()) { throw new IllegalStateException("SwipeRefreshLayout can host only one direct child"); } mTarget = getChildAt(0); mOriginalOffsetTop = mTarget.getTop() + getPaddingTop(); } if (mDistanceToTriggerSync == -1) { if (getParent() != null && ((View) getParent()).getHeight() > 0) { final DisplayMetrics metrics = getResources().getDisplayMetrics(); mDistanceToTriggerSync = (int) Math.min( ((View) getParent()).getHeight() * MAX_SWIPE_DISTANCE_FACTOR, REFRESH_TRIGGER_DISTANCE * metrics.density); } } } @Override public void draw(Canvas canvas) { super.draw(canvas); mProgressBar.draw(canvas); } @Override protected void onLayout(boolean changed, int left, int top, int right, int bottom) { final int width = getMeasuredWidth(); final int height = getMeasuredHeight(); mProgressBar.setBounds(0, 0, width, mProgressBarHeight); if (getChildCount() == 0) { return; } final View child = getChildAt(0); final int childLeft = getPaddingLeft(); final int childTop = mCurrentTargetOffsetTop + getPaddingTop(); final int childWidth = width - getPaddingLeft() - getPaddingRight(); final int childHeight = height - getPaddingTop() - getPaddingBottom(); child.layout(childLeft, childTop, childLeft + childWidth, childTop + childHeight); } @Override public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); if (getChildCount() > 1 && !isInEditMode()) { throw new IllegalStateException("SwipeRefreshLayout can host only one direct child"); } if (getChildCount() > 0) { getChildAt(0).measure( MeasureSpec.makeMeasureSpec(getMeasuredWidth() - getPaddingLeft() - getPaddingRight(), MeasureSpec.EXACTLY), MeasureSpec.makeMeasureSpec(getMeasuredHeight() - getPaddingTop() - getPaddingBottom(), MeasureSpec.EXACTLY)); } } /** * @return Whether it is possible for the child view of this layout to * scroll up. Override this if the child view is a custom view. */ public boolean canChildScrollUp() { if (android.os.Build.VERSION.SDK_INT < 14) { if (mTarget instanceof AbsListView) { final AbsListView absListView = (AbsListView) mTarget; return absListView.getChildCount() > 0 && (absListView.getFirstVisiblePosition() > 0 || absListView.getChildAt(0).getTop() < absListView.getPaddingTop()); } else { return mTarget.getScrollY() > 0; } } else { return ViewCompat.canScrollVertically(mTarget, -1); } } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { ensureTarget(); boolean handled = false; if (mReturningToStart && ev.getAction() == MotionEvent.ACTION_DOWN) { mReturningToStart = false; } if (isEnabled() && !mReturningToStart && !canChildScrollUp()) { handled = onTouchEvent(ev); } return !handled ? super.onInterceptTouchEvent(ev) : true; } @Override public void requestDisallowInterceptTouchEvent(boolean b) { // Nope. } @Override public boolean onTouchEvent(MotionEvent event) { final int action = event.getAction(); boolean handled = false; switch (action) { case MotionEvent.ACTION_DOWN: mCurrPercentage = 0; mDownEvent = MotionEvent.obtain(event); mPrevY = mDownEvent.getY(); break; case MotionEvent.ACTION_MOVE: if (mDownEvent != null && !mReturningToStart) { final float eventY = event.getY(); float yDiff = eventY - mDownEvent.getY(); if (yDiff > mTouchSlop) { // User velocity passed min velocity; trigger a refresh if (yDiff > mDistanceToTriggerSync) { // User movement passed distance; trigger a refresh startRefresh(); handled = true; break; } else { // Just track the user's movement setTriggerPercentage( mAccelerateInterpolator.getInterpolation(yDiff / mDistanceToTriggerSync)); float offsetTop = yDiff; if (mPrevY > eventY) { offsetTop = yDiff - mTouchSlop; } updateContentOffsetTop((int) (offsetTop)); if (mPrevY > eventY && (mTarget.getTop() < mTouchSlop)) { // If the user puts the view back at the top, we // don't need to. This shouldn't be considered // cancelling the gesture as the user can restart from the top. removeCallbacks(mCancel); } else { updatePositionTimeout(); } mPrevY = event.getY(); handled = true; } } } break; case MotionEvent.ACTION_UP: case MotionEvent.ACTION_CANCEL: if (mDownEvent != null) { mDownEvent.recycle(); mDownEvent = null; } break; } return handled; } private void startRefresh() { removeCallbacks(mCancel); mReturnToStartPosition.run(); setRefreshing(true); mListener.onRefresh(); } private void updateContentOffsetTop(int targetTop) { final int currentTop = mTarget.getTop(); if (targetTop > mDistanceToTriggerSync) { targetTop = (int) mDistanceToTriggerSync; } else if (targetTop < 0) { targetTop = 0; } setTargetOffsetTopAndBottom(targetTop - currentTop); } private void setTargetOffsetTopAndBottom(int offset) { mTarget.offsetTopAndBottom(offset); mCurrentTargetOffsetTop = mTarget.getTop(); } private void updatePositionTimeout() { removeCallbacks(mCancel); postDelayed(mCancel, RETURN_TO_ORIGINAL_POSITION_TIMEOUT); } /** * Classes that wish to be notified when the swipe gesture correctly * triggers a refresh should implement this interface. */ public interface OnRefreshListener { public void onRefresh(); } /** * Simple AnimationListener to avoid having to implement unneeded methods in * AnimationListeners. */ private class BaseAnimationListener implements AnimationListener { @Override public void onAnimationStart(Animation animation) { } @Override public void onAnimationEnd(Animation animation) { } @Override public void onAnimationRepeat(Animation animation) { } } }