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Android example source code file (

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

Java - Android tags/keywords

ambiguousdirection, directionpoint, horizonal, unknown, vertical

The Android example source code

 * Copyright (C) 2008 Google Inc.
 * 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
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.

 * To specify a dividing line, a user hits the screen and drags in a
 * certain direction.  Once the line has been drawn long enough and mostly
 * in a particular direction (vertical, or horizontal), we can decide we
 * know what they mean.  Otherwise, it is unknown.
 * This is also nice because if the user decides they don't want to send
 * a dividing line, they can just drag their finger back to where they first
 * touched and let go, cancelling.
public class DirectionPoint {
    enum AmbiguousDirection {

    private float mX;
    private float mY;

    private float endLineX;
    private float endLineY;

    public DirectionPoint(float x, float y) {
        mX = x;
        mY = y;
        endLineX = x;
        endLineY = y;

    public void updateEndPoint(float x, float y) {
        endLineX = x;
        endLineY = y;

    public float getX() {
        return mX;

    public float getY() {
        return mY;

     * We know the direction when the line is at leat 20 pixels long,
     * and the angle is no more than PI / 6 away from a definitive direction.
    public AmbiguousDirection getDirection() {
        float dx = endLineX - mX;
        double distance = Math.hypot(dx, endLineY - mY);
        if (distance < 10) {
            return AmbiguousDirection.Unknown;
        double angle = Math.acos(dx / distance);
        double thresh = Math.PI / 6;
        if ((angle < thresh || (angle > (Math.PI - thresh)))) {
            return AmbiguousDirection.Horizonal;
        if ((angle > 2 * thresh) && angle < 4*thresh) {
            return AmbiguousDirection.Vertical;
        return AmbiguousDirection.Unknown;

Other Android examples (source code examples)

Here is a short list of links related to this Android source code file:

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