| /* |
| * 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 android.view.animation; |
| |
| import android.content.Context; |
| import android.content.res.TypedArray; |
| import android.graphics.Path; |
| import android.util.AttributeSet; |
| import android.view.InflateException; |
| |
| /** |
| * An interpolator that can traverse a Path that extends from <code>Point</code> |
| * <code>(0, 0)</code> to <code>(1, 1)</code>. The x coordinate along the <code>Path</code> |
| * is the input value and the output is the y coordinate of the line at that point. |
| * This means that the Path must conform to a function <code>y = f(x)</code>. |
| * |
| * <p>The <code>Path</code> must not have gaps in the x direction and must not |
| * loop back on itself such that there can be two points sharing the same x coordinate. |
| * It is alright to have a disjoint line in the vertical direction:</p> |
| * <p><blockquote><pre> |
| * Path path = new Path(); |
| * path.lineTo(0.25f, 0.25f); |
| * path.moveTo(0.25f, 0.5f); |
| * path.lineTo(1f, 1f); |
| * </pre></blockquote></p> |
| */ |
| public class PathInterpolator implements Interpolator { |
| |
| // This governs how accurate the approximation of the Path is. |
| private static final float PRECISION = 0.002f; |
| |
| private float[] mX; // x coordinates in the line |
| |
| private float[] mY; // y coordinates in the line |
| |
| /** |
| * Create an interpolator for an arbitrary <code>Path</code>. The <code>Path</code> |
| * must begin at <code>(0, 0)</code> and end at <code>(1, 1)</code>. |
| * |
| * @param path The <code>Path</code> to use to make the line representing the interpolator. |
| */ |
| public PathInterpolator(Path path) { |
| initPath(path); |
| } |
| |
| /** |
| * Create an interpolator for a quadratic Bezier curve. The end points |
| * <code>(0, 0)</code> and <code>(1, 1)</code> are assumed. |
| * |
| * @param controlX The x coordinate of the quadratic Bezier control point. |
| * @param controlY The y coordinate of the quadratic Bezier control point. |
| */ |
| public PathInterpolator(float controlX, float controlY) { |
| initQuad(controlX, controlY); |
| } |
| |
| /** |
| * Create an interpolator for a cubic Bezier curve. The end points |
| * <code>(0, 0)</code> and <code>(1, 1)</code> are assumed. |
| * |
| * @param controlX1 The x coordinate of the first control point of the cubic Bezier. |
| * @param controlY1 The y coordinate of the first control point of the cubic Bezier. |
| * @param controlX2 The x coordinate of the second control point of the cubic Bezier. |
| * @param controlY2 The y coordinate of the second control point of the cubic Bezier. |
| */ |
| public PathInterpolator(float controlX1, float controlY1, float controlX2, float controlY2) { |
| initCubic(controlX1, controlY1, controlX2, controlY2); |
| } |
| |
| public PathInterpolator(Context context, AttributeSet attrs) { |
| TypedArray a = context.obtainStyledAttributes(attrs, |
| com.android.internal.R.styleable.PathInterpolator); |
| if (!a.hasValue(com.android.internal.R.styleable.PathInterpolator_controlX1)) { |
| throw new InflateException("pathInterpolator requires the controlX1 attribute"); |
| } else if (!a.hasValue(com.android.internal.R.styleable.PathInterpolator_controlY1)) { |
| throw new InflateException("pathInterpolator requires the controlY1 attribute"); |
| } |
| float x1 = a.getFloat(com.android.internal.R.styleable.PathInterpolator_controlX1, 0); |
| float y1 = a.getFloat(com.android.internal.R.styleable.PathInterpolator_controlY1, 0); |
| |
| boolean hasX2 = a.hasValue(com.android.internal.R.styleable.PathInterpolator_controlX2); |
| boolean hasY2 = a.hasValue(com.android.internal.R.styleable.PathInterpolator_controlY2); |
| |
| if (hasX2 != hasY2) { |
| throw new InflateException( |
| "pathInterpolator requires both controlX2 and controlY2 for cubic Beziers."); |
| } |
| |
| if (!hasX2) { |
| initQuad(x1, y1); |
| } else { |
| float x2 = a.getFloat(com.android.internal.R.styleable.PathInterpolator_controlX2, 0); |
| float y2 = a.getFloat(com.android.internal.R.styleable.PathInterpolator_controlY2, 0); |
| initCubic(x1, y1, x2, y2); |
| } |
| |
| a.recycle(); |
| } |
| |
| private void initQuad(float controlX, float controlY) { |
| Path path = new Path(); |
| path.moveTo(0, 0); |
| path.quadTo(controlX, controlY, 1f, 1f); |
| initPath(path); |
| } |
| |
| private void initCubic(float x1, float y1, float x2, float y2) { |
| Path path = new Path(); |
| path.moveTo(0, 0); |
| path.cubicTo(x1, y1, x2, y2, 1f, 1f); |
| initPath(path); |
| } |
| |
| private void initPath(Path path) { |
| float[] pointComponents = path.approximate(PRECISION); |
| |
| int numPoints = pointComponents.length / 3; |
| if (pointComponents[1] != 0 || pointComponents[2] != 0 |
| || pointComponents[pointComponents.length - 2] != 1 |
| || pointComponents[pointComponents.length - 1] != 1) { |
| throw new IllegalArgumentException("The Path must start at (0,0) and end at (1,1)"); |
| } |
| |
| mX = new float[numPoints]; |
| mY = new float[numPoints]; |
| float prevX = 0; |
| float prevFraction = 0; |
| int componentIndex = 0; |
| for (int i = 0; i < numPoints; i++) { |
| float fraction = pointComponents[componentIndex++]; |
| float x = pointComponents[componentIndex++]; |
| float y = pointComponents[componentIndex++]; |
| if (fraction == prevFraction && x != prevX) { |
| throw new IllegalArgumentException( |
| "The Path cannot have discontinuity in the X axis."); |
| } |
| if (x < prevX) { |
| throw new IllegalArgumentException("The Path cannot loop back on itself."); |
| } |
| mX[i] = x; |
| mY[i] = y; |
| prevX = x; |
| prevFraction = fraction; |
| } |
| } |
| |
| /** |
| * Using the line in the Path in this interpolator that can be described as |
| * <code>y = f(x)</code>, finds the y coordinate of the line given <code>t</code> |
| * as the x coordinate. Values less than 0 will always return 0 and values greater |
| * than 1 will always return 1. |
| * |
| * @param t Treated as the x coordinate along the line. |
| * @return The y coordinate of the Path along the line where x = <code>t</code>. |
| * @see Interpolator#getInterpolation(float) |
| */ |
| @Override |
| public float getInterpolation(float t) { |
| if (t <= 0) { |
| return 0; |
| } else if (t >= 1) { |
| return 1; |
| } |
| // Do a binary search for the correct x to interpolate between. |
| int startIndex = 0; |
| int endIndex = mX.length - 1; |
| |
| while (endIndex - startIndex > 1) { |
| int midIndex = (startIndex + endIndex) / 2; |
| if (t < mX[midIndex]) { |
| endIndex = midIndex; |
| } else { |
| startIndex = midIndex; |
| } |
| } |
| |
| float xRange = mX[endIndex] - mX[startIndex]; |
| if (xRange == 0) { |
| return mY[startIndex]; |
| } |
| |
| float tInRange = t - mX[startIndex]; |
| float fraction = tInRange / xRange; |
| |
| float startY = mY[startIndex]; |
| float endY = mY[endIndex]; |
| return startY + (fraction * (endY - startY)); |
| } |
| |
| } |