Android example source code file (Gesture.java)

This example Android source code file (Gesture.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, atomicinteger, bitmap, bitmap_rendering_dither, canvas, datainputstream, dataoutputstream, drawing, error, gesture, gesture_id_base, graphics, io, ioexception, paint, parcelable, path, rectf, ui

The Gesture.java Android example source code

/*
 * Copyright (C) 2008-2009 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.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.RectF;
import android.os.Parcel;
import android.os.Parcelable;
import android.util.Log;

import java.io.IOException;
import java.io.DataOutputStream;
import java.io.DataInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ByteArrayInputStream;
import java.util.ArrayList;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * A gesture is a hand-drawn shape on a touch screen. It can have one or multiple strokes.
 * Each stroke is a sequence of timed points. A user-defined gesture can be recognized by 
 * a GestureLibrary and a built-in alphabet gesture can be recognized by a LetterRecognizer. 
 */

public class Gesture implements Parcelable {
    private static final long GESTURE_ID_BASE = System.currentTimeMillis();

    private static final int BITMAP_RENDERING_WIDTH = 2;

    private static final boolean BITMAP_RENDERING_ANTIALIAS = true;
    private static final boolean BITMAP_RENDERING_DITHER = true;

    private static final AtomicInteger sGestureCount = new AtomicInteger(0);

    private final RectF mBoundingBox = new RectF();

    // the same as its instance ID
    private long mGestureID;

    private final ArrayList<GestureStroke> mStrokes = new ArrayList();

    public Gesture() {
        mGestureID = GESTURE_ID_BASE + sGestureCount.incrementAndGet();
    }

    @Override
    public Object clone() {
        Gesture gesture = new Gesture();
        gesture.mBoundingBox.set(mBoundingBox.left, mBoundingBox.top, 
                                        mBoundingBox.right, mBoundingBox.bottom);
        final int count = mStrokes.size();
        for (int i = 0; i < count; i++) {
            GestureStroke stroke = mStrokes.get(i);
            gesture.mStrokes.add((GestureStroke)stroke.clone());
        }
        return gesture;
    }
    
    /**
     * @return all the strokes of the gesture
     */
    public ArrayList<GestureStroke> getStrokes() {
        return mStrokes;
    }

    /**
     * @return the number of strokes included by this gesture
     */
    public int getStrokesCount() {
        return mStrokes.size();
    }

    /**
     * Adds a stroke to the gesture.
     * 
     * @param stroke
     */
    public void addStroke(GestureStroke stroke) {
        mStrokes.add(stroke);
        mBoundingBox.union(stroke.boundingBox);
    }

    /**
     * Calculates the total length of the gesture. When there are multiple strokes in
     * the gesture, this returns the sum of the lengths of all the strokes.
     * 
     * @return the length of the gesture
     */
    public float getLength() {
        int len = 0;
        final ArrayList<GestureStroke> strokes = mStrokes;
        final int count = strokes.size();

        for (int i = 0; i < count; i++) {
            len += strokes.get(i).length;
        }

        return len;
    }

    /**
     * @return the bounding box of the gesture
     */
    public RectF getBoundingBox() {
        return mBoundingBox;
    }

    public Path toPath() {
        return toPath(null);
    }

    public Path toPath(Path path) {
        if (path == null) path = new Path();

        final ArrayList<GestureStroke> strokes = mStrokes;
        final int count = strokes.size();

        for (int i = 0; i < count; i++) {
            path.addPath(strokes.get(i).getPath());
        }

        return path;
    }

    public Path toPath(int width, int height, int edge, int numSample) {
        return toPath(null, width, height, edge, numSample);
    }

    public Path toPath(Path path, int width, int height, int edge, int numSample) {
        if (path == null) path = new Path();

        final ArrayList<GestureStroke> strokes = mStrokes;
        final int count = strokes.size();

        for (int i = 0; i < count; i++) {
            path.addPath(strokes.get(i).toPath(width - 2 * edge, height - 2 * edge, numSample));
        }

        return path;
    }

    /**
     * Sets the id of the gesture.
     * 
     * @param id
     */
    void setID(long id) {
        mGestureID = id;
    }

    /**
     * @return the id of the gesture
     */
    public long getID() {
        return mGestureID;
    }

    /**
     * Creates a bitmap of the gesture with a transparent background.
     * 
     * @param width width of the target bitmap
     * @param height height of the target bitmap
     * @param edge the edge
     * @param numSample
     * @param color
     * @return the bitmap
     */
    public Bitmap toBitmap(int width, int height, int edge, int numSample, int color) {
        final Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        final Canvas canvas = new Canvas(bitmap);

        canvas.translate(edge, edge);

        final Paint paint = new Paint();
        paint.setAntiAlias(BITMAP_RENDERING_ANTIALIAS);
        paint.setDither(BITMAP_RENDERING_DITHER);
        paint.setColor(color);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeJoin(Paint.Join.ROUND);
        paint.setStrokeCap(Paint.Cap.ROUND);
        paint.setStrokeWidth(BITMAP_RENDERING_WIDTH);

        final ArrayList<GestureStroke> strokes = mStrokes;
        final int count = strokes.size();

        for (int i = 0; i < count; i++) {
            Path path = strokes.get(i).toPath(width - 2 * edge, height - 2 * edge, numSample);
            canvas.drawPath(path, paint);
        }

        return bitmap;
    }

    /**
     * Creates a bitmap of the gesture with a transparent background.
     * 
     * @param width
     * @param height
     * @param inset
     * @param color
     * @return the bitmap
     */
    public Bitmap toBitmap(int width, int height, int inset, int color) {
        final Bitmap bitmap = Bitmap.createBitmap(width, height,
                Bitmap.Config.ARGB_8888);
        final Canvas canvas = new Canvas(bitmap);

        final Paint paint = new Paint();
        paint.setAntiAlias(BITMAP_RENDERING_ANTIALIAS);
        paint.setDither(BITMAP_RENDERING_DITHER);
        paint.setColor(color);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeJoin(Paint.Join.ROUND);
        paint.setStrokeCap(Paint.Cap.ROUND);
        paint.setStrokeWidth(BITMAP_RENDERING_WIDTH);

        final Path path = toPath();
        final RectF bounds = new RectF();
        path.computeBounds(bounds, true);

        final float sx = (width - 2 * inset) / bounds.width();
        final float sy = (height - 2 * inset) / bounds.height();
        final float scale = sx > sy ? sy : sx;
        paint.setStrokeWidth(2.0f / scale);

        path.offset(-bounds.left + (width - bounds.width() * scale) / 2.0f,
                -bounds.top + (height - bounds.height() * scale) / 2.0f);

        canvas.translate(inset, inset);
        canvas.scale(scale, scale);

        canvas.drawPath(path, paint);

        return bitmap;
    }

    void serialize(DataOutputStream out) throws IOException {
        final ArrayList<GestureStroke> strokes = mStrokes;
        final int count = strokes.size();

        // Write gesture ID
        out.writeLong(mGestureID);
        // Write number of strokes
        out.writeInt(count);

        for (int i = 0; i < count; i++) {
            strokes.get(i).serialize(out);
        }
    }

    static Gesture deserialize(DataInputStream in) throws IOException {
        final Gesture gesture = new Gesture();

        // Gesture ID
        gesture.mGestureID = in.readLong();
        // Number of strokes
        final int count = in.readInt();

        for (int i = 0; i < count; i++) {
            gesture.addStroke(GestureStroke.deserialize(in));
        }

        return gesture;
    }

    public static final Parcelable.Creator<Gesture> CREATOR = new Parcelable.Creator() {
        public Gesture createFromParcel(Parcel in) {
            Gesture gesture = null;
            final long gestureID = in.readLong();

            final DataInputStream inStream = new DataInputStream(
                    new ByteArrayInputStream(in.createByteArray()));

            try {
                gesture = deserialize(inStream);
            } catch (IOException e) {
                Log.e(GestureConstants.LOG_TAG, "Error reading Gesture from parcel:", e);
            } finally {
                GestureUtils.closeStream(inStream);
            }

            if (gesture != null) {
                gesture.mGestureID = gestureID;
            }

            return gesture;
        }

        public Gesture[] newArray(int size) {
            return new Gesture[size];
        }
    };

    public void writeToParcel(Parcel out, int flags) {
        out.writeLong(mGestureID);

        boolean result = false;
        final ByteArrayOutputStream byteStream =
                new ByteArrayOutputStream(GestureConstants.IO_BUFFER_SIZE);
        final DataOutputStream outStream = new DataOutputStream(byteStream);

        try {
            serialize(outStream);
            result = true;
        } catch (IOException e) {
            Log.e(GestureConstants.LOG_TAG, "Error writing Gesture to parcel:", e);
        } finally {
            GestureUtils.closeStream(outStream);
            GestureUtils.closeStream(byteStream);
        }

        if (result) {
            out.writeByteArray(byteStream.toByteArray());
        }
    }

    public int describeContents() {
        return 0;
    }
}