Compass.java

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The file containing the source code shown below is located in the corresponding directory in <sdk>/samples/android-<version>/...

/*
 * 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.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 (false) 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 (false) Log.d(TAG, "onResume");
        super.onResume();

        mSensorManager.registerListener(mListener, mSensor,
                SensorManager.SENSOR_DELAY_GAME);
    }

    @Override
    protected void onStop()
    {
        if (false) 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;

        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;
            if (false) Log.d(TAG, "onAttachedToWindow. mAnimate=" + mAnimate);
            super.onAttachedToWindow();
        }

        @Override
        protected void onDetachedFromWindow() {
            mAnimate = false;
            if (false) Log.d(TAG, "onDetachedFromWindow. mAnimate=" + mAnimate);
            super.onDetachedFromWindow();
        }
    }
}