Android Open Source - arcgis-runtime-samples-android Compass

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License

The source code is released under:

Apache License

Java Source Code

/* Copyright 2014 ESRI
 *//from  w w w .  j  a  v a 2  s . c  om
 * All rights reserved under the copyright laws of the United States
 * and applicable international laws, treaties, and conventions.
 *
 * You may freely redistribute and use this sample code, with or
 * without modification, provided you include the original copyright
 * notice and use restrictions.
 *
 * See the sample code usage restrictions document for further information.
 *
 */

package com.arcgis.android.samples.maps.maprotation;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;

import com.esri.android.map.MapView;
import com.esri.android.map.event.OnPinchListener;

/**
 * This class defines a custom view that draws an image of a compass. The angle of the compass changes when the
 * setRotationAngle method is called. If a MapView is passed to the constructor, an OnPinchListener is set in order to
 * update the compass rotation angle when the pinch gesture is used on the MapView.
 */
public class Compass extends View {

    float mAngle = 0;
    Paint mPaint;
    Bitmap mBitmap;
    Matrix mMatrix;

    MapView mMapView;

    // Called when the Compass view is inflated from XML. In this case, no attributes are initialized from XML.
    public Compass(Context context, AttributeSet attrs) {
        super(context, attrs);

        // Create a Paint, Matrix and Bitmap that will be re-used together to draw the
        // compass image each time the onDraw method is called.
        mPaint = new Paint();
        mMatrix = new Matrix();

        // Create the bitmap of the compass from a resource.
        mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.compass);
    }

    /** Overloaded constructor that takes a MapView, from which the compass rotation angle will be set. */
    public Compass(Context context, AttributeSet attrs, MapView mapView) {
        this(context, attrs);

        // Save reference to the MapView passed in to this compass.
        mMapView = mapView;
        if (mMapView != null) {

            // Set an OnPinchListener on the map to listen for the pinch gesture which may change the map rotation.
            mMapView.setOnPinchListener(new OnPinchListener() {

                private static final long serialVersionUID = 1L;

                @Override
                public void prePointersUp(float arg0, float arg1, float arg2, float arg3, double arg4) {
                }

                @Override
                public void prePointersMove(float arg0, float arg1, float arg2, float arg3, double arg4) {
                }

                @Override
                public void prePointersDown(float arg0, float arg1, float arg2, float arg3, double arg4) {
                }

                @Override
                public void postPointersUp(float arg0, float arg1, float arg2, float arg3, double arg4) {
                }

                @Override
                public void postPointersMove(float arg0, float arg1, float arg2, float arg3, double arg4) {
                    // Update the compass angle from the map rotation angle (the arguments passed in to the method are not
                    // relevant in this case).
                    setRotationAngle(mMapView.getRotationAngle());
                }

                @Override
                public void postPointersDown(float arg0, float arg1, float arg2, float arg3, double arg4) {
                }
            });
        }
    }

    /** Updates the angle, in degrees, at which the compass is draw within this view. */
    public void setRotationAngle(double angle) {
        // Save the new rotation angle.
        mAngle = (float) angle;

        // Force the compass to re-paint itself.
        postInvalidate();
    }

    /** Draws the compass image at the current angle of rotation on the canvas. */
    @Override
    protected void onDraw(Canvas canvas) {

        // Reset the matrix to default values.
        mMatrix.reset();

        // Pass the current rotation angle to the matrix. The center of rotation is set to be the center of the bitmap.
        mMatrix.postRotate(-this.mAngle, mBitmap.getHeight() / 2, mBitmap.getWidth() / 2);

        // Use the matrix to draw the bitmap image of the compass.
        canvas.drawBitmap(mBitmap, mMatrix, mPaint);
        super.onDraw(canvas);

    }

}

Java Source Code List

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