Android方向传感器实践——自己动手做水平尺

这是基于上一篇博文Android方向传感器实践（指南针）的后续探索，这里将会为大家介绍如何利用方向传感器Y轴上的读数制作一个水平尺，具体的代码和源文件将会全部和大家分享。

下面附上LevelActivity类和LevelView类的代码，同时提供源程序的下载，如果有什么问题的话随时可以与我联系，我的qq：264965161，电子邮箱[e-mail]，本人非常乐意与大家一起交流，希望大家能共同进步。

源代码下载地址：http://download.csdn.net/source/2933499

package com.app;

import android.app.Activity;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.view.Window;
import android.view.WindowManager;

import java.util.List;

import android.content.pm.ActivityInfo;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;

public class LevelActivity extends Activity implements SensorEventListener
{
	private float          _srcDegree = 0;
	private LevelView      _levelView;
	private boolean		   mRegisteredSensor;
	//定义SensorManager
	private SensorManager  mSensorManager;
	
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        
        // 设置为横向
        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);

	    //设置为无标题栏        
        requestWindowFeature( Window.FEATURE_NO_TITLE );
        
        //设置为全屏模式
        getWindow().setFlags( WindowManager.LayoutParams.FLAG_FULLSCREEN, 
        					  WindowManager.LayoutParams.FLAG_FULLSCREEN );
        
        _levelView = new LevelView(this);
        setContentView(_levelView);

		mRegisteredSensor = false;
		//取得SensorManager实例
		mSensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);

    }
    
    @Override
	protected void onResume()
	{
		super.onResume();

		//接受SensorManager的一个列表(Listener)
		//这里我们指定类型为TYPE_ORIENTATION(方向感应器)
		List<Sensor> sensors = mSensorManager.getSensorList(Sensor.TYPE_ORIENTATION);

		if (sensors.size() > 0)
		{
			Sensor sensor = sensors.get(0);
			//注册SensorManager
			//this->接收sensor的实例
			//接收传感器类型的列表
			//接受的频率
			mRegisteredSensor = mSensorManager.registerListener(this, sensor, SensorManager.SENSOR_DELAY_FASTEST);
		}
	}
	
	@Override
	protected void onPause()
	{
		if (mRegisteredSensor)
		{
			//如果调用了registerListener
			//这里我们需要unregisterListener来卸载/取消注册
			mSensorManager.unregisterListener(this);
			mRegisteredSensor = false;
		}
		super.onPause();
	}
	//当进准度发生改变时
	//sensor->传感器
	//accuracy->精准度
	@Override
	public void onAccuracyChanged(Sensor sensor, int accuracy)
	{
		
	}
	// 当传感器在被改变时触发
	@Override
	public void onSensorChanged(SensorEvent event)
	{
		// 接受方向感应器的类型
		if (event.sensor.getType() == Sensor.TYPE_ORIENTATION)
		{
			// 这里我们可以得到数据，然后根据需要来处理
			float y = event.values[SensorManager.DATA_Y];
			
			if(Math.abs(y - _srcDegree) < 50)
			{
				_levelView.setDegree(y);
				
				_srcDegree = y;
			}
			

		}
	}
}

package com.app;

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

public class LevelView extends View implements Runnable
{
	private Paint    _mPaint    = new Paint();
	private Bitmap   _level;
	private Bitmap   _graduation;
	private String   _message   = "0.0°";
	private float    _decDegree = 0;
	private int      _screenWidth = 480;

	public LevelView(Context context)
	{
		super(context);
		// 载入图片
		_level       = BitmapFactory.decodeResource(getResources(), R.drawable.rl001);
		_graduation  = BitmapFactory.decodeResource(getResources(), R.drawable.rl002);
		
		// 开启线程否则无法更新画面
		new Thread(this).start();
	}

	@Override
	public void run()
	{
		while(!Thread.currentThread().isInterrupted())
		{
			try
			{
				Thread.sleep(100);
			}
			catch(InterruptedException e)
			{
				Thread.currentThread().interrupt();
			}
			
			postInvalidate();
		}
		
	}
	
	protected void onDraw(Canvas canvas)
	{
		canvas.drawColor(Color.BLACK);
		
		_mPaint.setColor(Color.WHITE);
		_mPaint.setTextSize(30);
		_mPaint.setFlags(Paint.FAKE_BOLD_TEXT_FLAG);
		
		// 横向距离161 
		//float dx = 322 / 180;
		float dx = 1.78f;
		
		System.out.println(dx);
		
		// 设置几何变换矩阵
		Matrix mat = new Matrix();
		
		if(_decDegree < -90)
		{
			_decDegree = -90;
		}
		
		if(_decDegree > 90)
		{
			_decDegree = 90;
		}
			
		_decDegree = _decDegree + 90;
		
		mat.setTranslate(362 - (dx * _decDegree), 106);

		// 绘制图像
		canvas.drawBitmap(_graduation, 0, 0, null);
		canvas.drawBitmap(_level, mat, _mPaint);
		
		canvas.drawText(_message, 80, 85, _mPaint);
	}
	
	// 更新水平尺刻度
	public void setDegree(float degree)
	{
		_decDegree = degree;
		
		String degreeStr = String.valueOf(_decDegree);
		
		_message = degreeStr + "°";
		
		
	}

}

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