Android example source code file (Compass.java)

This example Android source code file (Compass.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, compass, graphicsactivity, hardware, override, paint, path, sampleview, sensoreventlistener, sensormanager, string, tag, ui, util, utilities, utils

The Compass.java Android example source code

/*
 * Copyright (C) 2007 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 com.example.android.apis.graphics;

import android.content.Context;
import android.graphics.*;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.util.Config;
import android.util.Log;
import android.view.View;

public class Compass extends GraphicsActivity {

    private static final String TAG = "Compass";

    private SensorManager mSensorManager;
    private Sensor mSensor;
    private SampleView mView;
    private float[] mValues;
    
    private final SensorEventListener mListener = new SensorEventListener() {
        public void onSensorChanged(SensorEvent event) {
            if (Config.LOGD) Log.d(TAG,
                    "sensorChanged (" + event.values[0] + ", " + event.values[1] + ", " + event.values[2] + ")");
            mValues = event.values;
            if (mView != null) {
                mView.invalidate();
            }
        }

        public void onAccuracyChanged(Sensor sensor, int accuracy) {
        }
    };

    @Override
    protected void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        mSensorManager = (SensorManager)getSystemService(Context.SENSOR_SERVICE);
        mSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_ORIENTATION);
        mView = new SampleView(this);
        setContentView(mView);
    }

    @Override
    protected void onResume()
    {
        if (Config.LOGD) Log.d(TAG, "onResume");
        super.onResume();

        mSensorManager.registerListener(mListener, mSensor,
                SensorManager.SENSOR_DELAY_GAME);
    }
    
    @Override
    protected void onStop()
    {
        if (Config.LOGD) Log.d(TAG, "onStop");
        mSensorManager.unregisterListener(mListener);
        super.onStop();
    }

    private class SampleView extends View {
        private Paint   mPaint = new Paint();
        private Path    mPath = new Path();
        private boolean mAnimate;
        private long    mNextTime;

        public SampleView(Context context) {
            super(context);

            // Construct a wedge-shaped path
            mPath.moveTo(0, -50);
            mPath.lineTo(-20, 60);
            mPath.lineTo(0, 50);
            mPath.lineTo(20, 60);
            mPath.close();
        }
    
        @Override protected void onDraw(Canvas canvas) {
            Paint paint = mPaint;

            canvas.drawColor(Color.WHITE);
            
            paint.setAntiAlias(true);
            paint.setColor(Color.BLACK);
            paint.setStyle(Paint.Style.FILL);

            int w = canvas.getWidth();
            int h = canvas.getHeight();
            int cx = w / 2;
            int cy = h / 2;

            canvas.translate(cx, cy);
            if (mValues != null) {            
                canvas.rotate(-mValues[0]);
            }
            canvas.drawPath(mPath, mPaint);
        }
    
        @Override
        protected void onAttachedToWindow() {
            mAnimate = true;
            super.onAttachedToWindow();
        }
        
        @Override
        protected void onDetachedFromWindow() {
            mAnimate = false;
            super.onDetachedFromWindow();
        }
    }
}