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Android example source code file (GestureStroke.java)

This example Android source code file (GestureStroke.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" TM.

Java - Android tags/keywords

android, arraylist, drawing, gesturepoint, gesturestroke, graphics, io, ioexception, object, orientedboundingbox, override, paint, path, rectf, touch_tolerance, ui

The GestureStroke.java Android example source code

/*
 * Copyright (C) 2009 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.gesture;

import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.RectF;

import java.io.IOException;
import java.io.DataOutputStream;
import java.io.DataInputStream;
import java.util.ArrayList;

/**
 * A gesture stroke started on a touch down and ended on a touch up. A stroke
 * consists of a sequence of timed points. One or multiple strokes form a gesture.
 */
public class GestureStroke {
    static final float TOUCH_TOLERANCE = 3;

    public final RectF boundingBox;

    public final float length;
    public final float[] points;

    private final long[] timestamps;
    private Path mCachedPath;

    /**
     * A constructor that constructs a gesture stroke from a list of gesture points.
     * 
     * @param points
     */
    public GestureStroke(ArrayList<GesturePoint> points) {
        final int count = points.size();
        final float[] tmpPoints = new float[count * 2];
        final long[] times = new long[count];

        RectF bx = null;
        float len = 0;
        int index = 0;

        for (int i = 0; i < count; i++) {
            final GesturePoint p = points.get(i);
            tmpPoints[i * 2] = p.x;
            tmpPoints[i * 2 + 1] = p.y;
            times[index] = p.timestamp;

            if (bx == null) {
                bx = new RectF();
                bx.top = p.y;
                bx.left = p.x;
                bx.right = p.x;
                bx.bottom = p.y;
                len = 0;
            } else {
                len += Math.sqrt(Math.pow(p.x - tmpPoints[(i - 1) * 2], 2)
                        + Math.pow(p.y - tmpPoints[(i -1 ) * 2 + 1], 2));
                bx.union(p.x, p.y);
            }
            index++;
        }
        
        timestamps = times;
        this.points = tmpPoints;
        boundingBox = bx;
        length = len;
    }

    /**
     * A faster constructor specially for cloning a stroke.
     */
    private GestureStroke(RectF bbx, float len, float[] pts, long[] times) {
        boundingBox = new RectF(bbx.left, bbx.top, bbx.right, bbx.bottom);
        length = len;
        points = pts.clone();
        timestamps = times.clone();
    }
    
    @Override
    public Object clone() {
        return new GestureStroke(boundingBox, length, points, timestamps);
    }
    
    /**
     * Draws the stroke with a given canvas and paint.
     * 
     * @param canvas
     */
    void draw(Canvas canvas, Paint paint) {
        if (mCachedPath == null) {
            makePath();
        }

        canvas.drawPath(mCachedPath, paint);
    }

    public Path getPath() {
        if (mCachedPath == null) {
            makePath();
        }

        return mCachedPath;
    }

    private void makePath() {
        final float[] localPoints = points;
        final int count = localPoints.length;

        Path path = null;

        float mX = 0;
        float mY = 0;

        for (int i = 0; i < count; i += 2) {
            float x = localPoints[i];
            float y = localPoints[i + 1];
            if (path == null) {
                path = new Path();
                path.moveTo(x, y);
                mX = x;
                mY = y;
            } else {
                float dx = Math.abs(x - mX);
                float dy = Math.abs(y - mY);
                if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
                    path.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2);
                    mX = x;
                    mY = y;
                }
            }
        }

        mCachedPath = path;
    }

    /**
     * Converts the stroke to a Path of a given number of points.
     * 
     * @param width the width of the bounding box of the target path
     * @param height the height of the bounding box of the target path
     * @param numSample the number of points needed
     * 
     * @return the path
     */
    public Path toPath(float width, float height, int numSample) {
        final float[] pts = GestureUtils.temporalSampling(this, numSample);
        final RectF rect = boundingBox;

        GestureUtils.translate(pts, -rect.left, -rect.top);
        
        float sx = width / rect.width();
        float sy = height / rect.height();
        float scale = sx > sy ? sy : sx;
        GestureUtils.scale(pts, scale, scale);

        float mX = 0;
        float mY = 0;

        Path path = null;

        final int count = pts.length;

        for (int i = 0; i < count; i += 2) {
            float x = pts[i];
            float y = pts[i + 1];
            if (path == null) {
                path = new Path();
                path.moveTo(x, y);
                mX = x;
                mY = y;
            } else {
                float dx = Math.abs(x - mX);
                float dy = Math.abs(y - mY);
                if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
                    path.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2);
                    mX = x;
                    mY = y;
                }
            }
        }

        return path;
    }

    void serialize(DataOutputStream out) throws IOException {
        final float[] pts = points;
        final long[] times = timestamps;
        final int count = points.length;

        // Write number of points
        out.writeInt(count / 2);

        for (int i = 0; i < count; i += 2) {
            // Write X
            out.writeFloat(pts[i]);
            // Write Y
            out.writeFloat(pts[i + 1]);
            // Write timestamp
            out.writeLong(times[i / 2]);
        }
    }

    static GestureStroke deserialize(DataInputStream in) throws IOException {
        // Number of points
        final int count = in.readInt();

        final ArrayList<GesturePoint> points = new ArrayList(count);
        for (int i = 0; i < count; i++) {
            points.add(GesturePoint.deserialize(in));
        }

        return new GestureStroke(points);
    }    

    /**
     * Invalidates the cached path that is used to render the stroke.
     */
    public void clearPath() {
        if (mCachedPath != null) mCachedPath.rewind();
    }
    
    /**
     * Computes an oriented bounding box of the stroke.
     * 
     * @return OrientedBoundingBox
     */
    public OrientedBoundingBox computeOrientedBoundingBox() {
        return GestureUtils.computeOrientedBoundingBox(points);
    }
}

Other Android examples (source code examples)

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