Java tutorial
/* * Copyright (C) 2015 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.amitupadhyay.aboutexample.util; import android.content.res.TypedArray; import android.graphics.Bitmap; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Point; import android.graphics.Rect; import android.graphics.RectF; import android.graphics.Typeface; import android.os.Build; import android.support.annotation.FloatRange; import android.support.v4.text.TextDirectionHeuristicsCompat; import android.support.v4.view.GravityCompat; import android.support.v4.view.ViewCompat; import android.text.TextPaint; import android.text.TextUtils; import android.view.Gravity; import android.view.View; import android.view.animation.Interpolator; import com.amitupadhyay.aboutexample.R; /** * Adapted from design support lib. */ public final class CollapsingTextHelper { // Pre-JB-MR2 doesn't support HW accelerated canvas scaled text so we will workaround it // by using our own texture private static final boolean USE_SCALING_TEXTURE = Build.VERSION.SDK_INT < 18; private static final boolean DEBUG_DRAW = false; private static final Paint DEBUG_DRAW_PAINT; static { DEBUG_DRAW_PAINT = DEBUG_DRAW ? new Paint() : null; if (DEBUG_DRAW_PAINT != null) { DEBUG_DRAW_PAINT.setAntiAlias(true); DEBUG_DRAW_PAINT.setColor(Color.MAGENTA); } } private final View mView; private final Rect mExpandedBounds; private final Rect mCollapsedBounds; private final RectF mCurrentBounds; private final TextPaint mTextPaint; private boolean mDrawTitle; private float mExpandedFraction; private int mExpandedTextGravity = Gravity.CENTER_VERTICAL; private int mCollapsedTextGravity = Gravity.CENTER_VERTICAL; private float mExpandedTextSize = 15; private float mCollapsedTextSize = 15; private int mExpandedTextColor; private int mCollapsedTextColor; private float mExpandedDrawY; private float mCollapsedDrawY; private float mExpandedDrawX; private float mCollapsedDrawX; private float mCurrentDrawX; private float mCurrentDrawY; private CharSequence mText; private CharSequence mTextToDraw; private boolean mIsRtl; private boolean mUseTexture; private Bitmap mExpandedTitleTexture; private Paint mTexturePaint; private float mTextureAscent; private float mTextureDescent; private float mScale; private float mCurrentTextSize; private boolean mBoundsChanged; private Interpolator mPositionInterpolator; private Interpolator mTextSizeInterpolator; public CollapsingTextHelper(View view) { mView = view; mTextPaint = new TextPaint(); mTextPaint.setAntiAlias(true); mCollapsedBounds = new Rect(); mExpandedBounds = new Rect(); mCurrentBounds = new RectF(); } /** * Set the value indicating the current scroll value. This decides how much of the * background will be displayed, as well as the title metrics/positioning. * <p/> * A value of {@code 0.0} indicates that the layout is fully expanded. * A value of {@code 1.0} indicates that the layout is fully collapsed. */ public void setExpansionFraction(@FloatRange(from = 0f, to = 1f) float fraction) { fraction = MathUtils.constrain(fraction, 0f, 1f); if (fraction != mExpandedFraction) { mExpandedFraction = fraction; calculateCurrentOffsets(); } } public float getExpansionFraction() { return mExpandedFraction; } public void draw(Canvas canvas) { final int saveCount = canvas.save(); if (mTextToDraw != null && mDrawTitle) { float x = mCurrentDrawX; float y = mCurrentDrawY; final boolean drawTexture = mUseTexture && mExpandedTitleTexture != null; final float ascent; final float descent; // Update the TextPaint to the current text size mTextPaint.setTextSize(mCurrentTextSize); if (drawTexture) { ascent = mTextureAscent * mScale; descent = mTextureDescent * mScale; } else { ascent = mTextPaint.ascent() * mScale; descent = mTextPaint.descent() * mScale; } if (DEBUG_DRAW) { // Just a debug tool, which drawn a Magneta rect in the text bounds canvas.drawRect(mCurrentBounds.left, y + ascent, mCurrentBounds.right, y + descent, DEBUG_DRAW_PAINT); } if (drawTexture) { y += ascent; } if (mScale != 1f) { canvas.scale(mScale, mScale, x, y); } if (drawTexture) { // If we should use a texture, draw it instead of text canvas.drawBitmap(mExpandedTitleTexture, x, y, mTexturePaint); } else { canvas.drawText(mTextToDraw, 0, mTextToDraw.length(), x, y, mTextPaint); } } canvas.restoreToCount(saveCount); } /** * Set the title to display * * @param text */ public void setText(CharSequence text) { if (text == null || !text.equals(mText)) { mText = text; mTextToDraw = null; clearTexture(); recalculate(); } } public CharSequence getText() { return mText; } public void setTextSizeInterpolator(Interpolator interpolator) { mTextSizeInterpolator = interpolator; recalculate(); } public void setPositionInterpolator(Interpolator interpolator) { mPositionInterpolator = interpolator; recalculate(); } public void setExpandedBounds(int left, int top, int right, int bottom) { if (!rectEquals(mExpandedBounds, left, top, right, bottom)) { mExpandedBounds.set(left, top, right, bottom); mBoundsChanged = true; onBoundsChanged(); } } public Rect getExpandedBounds() { return mExpandedBounds; } public Point getTextTopLeft() { return new Point((int) mCurrentBounds.left, (int) (mCurrentBounds.bottom + mTextPaint.ascent())); } public void setCollapsedBounds(int left, int top, int right, int bottom) { if (!rectEquals(mCollapsedBounds, left, top, right, bottom)) { mCollapsedBounds.set(left, top, right, bottom); mBoundsChanged = true; onBoundsChanged(); } } public int getExpandedTextGravity() { return mExpandedTextGravity; } public void setExpandedTextGravity(int gravity) { if (mExpandedTextGravity != gravity) { mExpandedTextGravity = gravity; recalculate(); } } public int getCollapsedTextGravity() { return mCollapsedTextGravity; } public void setCollapsedTextGravity(int gravity) { if (mCollapsedTextGravity != gravity) { mCollapsedTextGravity = gravity; recalculate(); } } public void setCollapsedTextAppearance(int resId) { TypedArray a = mView.getContext().obtainStyledAttributes(resId, R.styleable.TextAppearance); if (a.hasValue(R.styleable.TextAppearance_android_textColor)) { mCollapsedTextColor = a.getColor(R.styleable.TextAppearance_android_textColor, mCollapsedTextColor); } if (a.hasValue(R.styleable.TextAppearance_android_textSize)) { mCollapsedTextSize = a.getDimensionPixelSize(R.styleable.TextAppearance_android_textSize, (int) mCollapsedTextSize); } a.recycle(); recalculate(); } public void setExpandedTextAppearance(int resId) { TypedArray a = mView.getContext().obtainStyledAttributes(resId, R.styleable.TextAppearance); if (a.hasValue(R.styleable.TextAppearance_android_textColor)) { mExpandedTextColor = a.getColor(R.styleable.TextAppearance_android_textColor, mExpandedTextColor); } if (a.hasValue(R.styleable.TextAppearance_android_textSize)) { mExpandedTextSize = a.getDimensionPixelSize(R.styleable.TextAppearance_android_textSize, (int) mExpandedTextSize); } a.recycle(); recalculate(); } public Typeface getTypeface() { return mTextPaint.getTypeface(); } public void setTypeface(Typeface typeface) { if (typeface == null) { typeface = Typeface.DEFAULT; } if (mTextPaint.getTypeface() != typeface) { mTextPaint.setTypeface(typeface); recalculate(); } } public float getCollapsedTextSize() { return mCollapsedTextSize; } public void setCollapsedTextSize(float textSize) { if (mCollapsedTextSize != textSize) { mCollapsedTextSize = textSize; recalculate(); } } public float getExpandedTextSize() { return mExpandedTextSize; } public void setExpandedTextSize(float textSize) { if (mExpandedTextSize != textSize) { mExpandedTextSize = textSize; recalculate(); } } public int getExpandedTextColor() { return mExpandedTextColor; } public void setExpandedTextColor(int textColor) { if (mExpandedTextColor != textColor) { mExpandedTextColor = textColor; recalculate(); } } public int getCollapsedTextColor() { return mCollapsedTextColor; } public void setCollapsedTextColor(int textColor) { if (mCollapsedTextColor != textColor) { mCollapsedTextColor = textColor; recalculate(); } } public float getCurrentTextSize() { return mCurrentTextSize; } private static float lerp(float startValue, float endValue, float fraction, Interpolator interpolator) { if (interpolator != null) { fraction = interpolator.getInterpolation(fraction); } return AnimUtils.lerp(startValue, endValue, fraction); } private static boolean rectEquals(Rect r, int left, int top, int right, int bottom) { return !(r.left != left || r.top != top || r.right != right || r.bottom != bottom); } private void onBoundsChanged() { mDrawTitle = mCollapsedBounds.width() > 0 && mCollapsedBounds.height() > 0 && mExpandedBounds.width() > 0 && mExpandedBounds.height() > 0; } private void calculateCurrentOffsets() { final float fraction = mExpandedFraction; interpolateBounds(fraction); mCurrentDrawX = lerp(mExpandedDrawX, mCollapsedDrawX, fraction, mPositionInterpolator); mCurrentDrawY = lerp(mExpandedDrawY, mCollapsedDrawY, fraction, mPositionInterpolator); setInterpolatedTextSize(lerp(mExpandedTextSize, mCollapsedTextSize, fraction, mTextSizeInterpolator)); if (mCollapsedTextColor != mExpandedTextColor) { // If the collapsed and expanded text colors are different, blend them based on the // fraction mTextPaint.setColor(blendColors(mExpandedTextColor, mCollapsedTextColor, fraction)); } else { mTextPaint.setColor(mCollapsedTextColor); } ViewCompat.postInvalidateOnAnimation(mView); } private void calculateBaseOffsets() { // We then calculate the collapsed text size, using the same logic mTextPaint.setTextSize(mCollapsedTextSize); float width = mTextToDraw != null ? mTextPaint.measureText(mTextToDraw, 0, mTextToDraw.length()) : 0; final int collapsedAbsGravity = GravityCompat.getAbsoluteGravity(mCollapsedTextGravity, mIsRtl ? ViewCompat.LAYOUT_DIRECTION_RTL : ViewCompat.LAYOUT_DIRECTION_LTR); switch (collapsedAbsGravity & Gravity.VERTICAL_GRAVITY_MASK) { case Gravity.BOTTOM: mCollapsedDrawY = mCollapsedBounds.bottom; break; case Gravity.TOP: mCollapsedDrawY = mCollapsedBounds.top - mTextPaint.ascent(); break; case Gravity.CENTER_VERTICAL: default: float textHeight = mTextPaint.descent() - mTextPaint.ascent(); float textOffset = (textHeight / 2) - mTextPaint.descent(); mCollapsedDrawY = mCollapsedBounds.centerY() + textOffset; break; } switch (collapsedAbsGravity & Gravity.HORIZONTAL_GRAVITY_MASK) { case Gravity.CENTER_HORIZONTAL: mCollapsedDrawX = mCollapsedBounds.centerX() - (width / 2); break; case Gravity.RIGHT: mCollapsedDrawX = mCollapsedBounds.right - width; break; case Gravity.LEFT: default: mCollapsedDrawX = mCollapsedBounds.left; break; } mTextPaint.setTextSize(mExpandedTextSize); width = mTextToDraw != null ? mTextPaint.measureText(mTextToDraw, 0, mTextToDraw.length()) : 0; final int expandedAbsGravity = GravityCompat.getAbsoluteGravity(mExpandedTextGravity, mIsRtl ? ViewCompat.LAYOUT_DIRECTION_RTL : ViewCompat.LAYOUT_DIRECTION_LTR); switch (expandedAbsGravity & Gravity.VERTICAL_GRAVITY_MASK) { case Gravity.BOTTOM: mExpandedDrawY = mExpandedBounds.bottom; break; case Gravity.TOP: mExpandedDrawY = mExpandedBounds.top - mTextPaint.ascent(); break; case Gravity.CENTER_VERTICAL: default: float textHeight = mTextPaint.descent() - mTextPaint.ascent(); float textOffset = (textHeight / 2) - mTextPaint.descent(); mExpandedDrawY = mExpandedBounds.centerY() + textOffset; break; } switch (expandedAbsGravity & Gravity.HORIZONTAL_GRAVITY_MASK) { case Gravity.CENTER_HORIZONTAL: mExpandedDrawX = mExpandedBounds.centerX() - (width / 2); break; case Gravity.RIGHT: mExpandedDrawX = mExpandedBounds.right - width; break; case Gravity.LEFT: default: mExpandedDrawX = mExpandedBounds.left; break; } // The bounds have changed so we need to clear the texture clearTexture(); } private void interpolateBounds(float fraction) { mCurrentBounds.left = lerp(mExpandedBounds.left, mCollapsedBounds.left, fraction, mPositionInterpolator); mCurrentBounds.top = lerp(mExpandedDrawY, mCollapsedDrawY, fraction, mPositionInterpolator); mCurrentBounds.right = lerp(mExpandedBounds.right, mCollapsedBounds.right, fraction, mPositionInterpolator); mCurrentBounds.bottom = lerp(mExpandedBounds.bottom, mCollapsedBounds.bottom, fraction, mPositionInterpolator); } private boolean calculateIsRtl(CharSequence text) { final boolean defaultIsRtl = ViewCompat.getLayoutDirection(mView) == ViewCompat.LAYOUT_DIRECTION_RTL; return (defaultIsRtl ? TextDirectionHeuristicsCompat.FIRSTSTRONG_RTL : TextDirectionHeuristicsCompat.FIRSTSTRONG_LTR).isRtl(text, 0, text.length()); } private void setInterpolatedTextSize(final float textSize) { if (mText == null) return; final float availableWidth; final float newTextSize; boolean updateDrawText = false; if (isClose(textSize, mCollapsedTextSize)) { availableWidth = mCollapsedBounds.width(); newTextSize = mCollapsedTextSize; mScale = 1f; } else { availableWidth = mExpandedBounds.width(); newTextSize = mExpandedTextSize; if (isClose(textSize, mExpandedTextSize)) { // If we're close to the expanded text size, snap to it and use a scale of 1 mScale = 1f; } else { // Else, we'll scale down from the expanded text size mScale = textSize / mExpandedTextSize; } } if (availableWidth > 0) { updateDrawText = (mCurrentTextSize != newTextSize) || mBoundsChanged; mCurrentTextSize = newTextSize; mBoundsChanged = false; } if (mTextToDraw == null || updateDrawText) { mTextPaint.setTextSize(mCurrentTextSize); // If we don't currently have text to draw, or the text size has changed, ellipsize... final CharSequence title = TextUtils.ellipsize(mText, mTextPaint, availableWidth, TextUtils.TruncateAt.END); if (mTextToDraw == null || !mTextToDraw.equals(title)) { mTextToDraw = title; } mIsRtl = calculateIsRtl(mTextToDraw); } // Use our texture if the scale isn't 1.0 mUseTexture = USE_SCALING_TEXTURE && mScale != 1f; if (mUseTexture) { // Make sure we have an expanded texture if needed ensureExpandedTexture(); } ViewCompat.postInvalidateOnAnimation(mView); } private void ensureExpandedTexture() { if (mExpandedTitleTexture != null || mExpandedBounds.isEmpty() || TextUtils.isEmpty(mTextToDraw)) { return; } mTextPaint.setTextSize(mExpandedTextSize); mTextPaint.setColor(mExpandedTextColor); mTextureAscent = mTextPaint.ascent(); mTextureDescent = mTextPaint.descent(); final int w = Math.round(mTextPaint.measureText(mTextToDraw, 0, mTextToDraw.length())); final int h = Math.round(mTextureDescent - mTextureAscent); if (w <= 0 && h <= 0) { return; // If the width or height are 0, return } mExpandedTitleTexture = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888); Canvas c = new Canvas(mExpandedTitleTexture); c.drawText(mTextToDraw, 0, mTextToDraw.length(), 0, h - mTextPaint.descent(), mTextPaint); if (mTexturePaint == null) { // Make sure we have a paint mTexturePaint = new Paint(Paint.ANTI_ALIAS_FLAG | Paint.FILTER_BITMAP_FLAG); } } private void recalculate() { if (mView.getHeight() > 0 && mView.getWidth() > 0) { // If we've already been laid out, calculate everything now otherwise we'll wait // until a layout calculateBaseOffsets(); calculateCurrentOffsets(); } } private void clearTexture() { if (mExpandedTitleTexture != null) { mExpandedTitleTexture.recycle(); mExpandedTitleTexture = null; } } /** * Returns true if {@code value} is 'close' to it's closest decimal value. Close is currently * defined as it's difference being < 0.001. */ private static boolean isClose(float value, float targetValue) { return Math.abs(value - targetValue) < 0.001f; } /** * Blend {@code color1} and {@code color2} using the given ratio. * * @param ratio of which to blend. 0.0 will return {@code color1}, 0.5 will give an even blend, * 1.0 will return {@code color2}. */ private static int blendColors(int color1, int color2, float ratio) { final float inverseRatio = 1f - ratio; float a = (Color.alpha(color1) * inverseRatio) + (Color.alpha(color2) * ratio); float r = (Color.red(color1) * inverseRatio) + (Color.red(color2) * ratio); float g = (Color.green(color1) * inverseRatio) + (Color.green(color2) * ratio); float b = (Color.blue(color1) * inverseRatio) + (Color.blue(color2) * ratio); return Color.argb((int) a, (int) r, (int) g, (int) b); } }