方位传感器(重力小球)

准备一张名为ball的小球图片。

在main.xml中：

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout

xmlns:android="http://schemas.android.com/apk/res/android"

android:orientation="vertical"

android:layout_width="fill_parent"

android:layout_height="fill_parent">

<com.li.sensor.BallView

android:layout_width="fill_parent"

android:layout_height="wrap_content" />

</LinearLayout>

在BallView.java中：

package com.li.sensor;

import android.content.Context;

import android.graphics.Bitmap;

import android.graphics.BitmapFactory;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.graphics.Point;

import android.hardware.Sensor;

import android.hardware.SensorEvent;

import android.hardware.SensorEventListener;

import android.hardware.SensorManager;

import android.util.AttributeSet;

import android.view.View;

public class BallView extends View implements SensorEventListener {

private Bitmap ball = null;

private float[] allValue;

private Point point = new Point();

private int xSpeed = 0;

private int ySpeed = 0;

public BallView(Context context, AttributeSet attrs) {

super(context, attrs);

super.setBackgroundColor(Color.GREEN); // 底色为绿色

this.ball = BitmapFactory.decodeResource(super.getResources(),

R.drawable.ball);

SensorManager manager = (SensorManager) context

.getSystemService(Context.SENSOR_SERVICE); // 现在只是找到了一个传感器，但是没有定义类型

manager.registerListener(this,

manager.getDefaultSensor(Sensor.TYPE_ORIENTATION),

SensorManager.SENSOR_DELAY_GAME); // 创建了一个适合于游戏操作的方位传感器

}

public void onAccuracyChanged(Sensor sensor, int accuracy) {

}

public void onSensorChanged(SensorEvent event) { // 传感器方位改变

if (event.sensor.getType() == Sensor.TYPE_ORIENTATION) { // 现在是方位传感器

float value[] = event.values; // 取得所有的偏离数据

BallView.this.allValue = value; // 取得三个轴的值

super.postInvalidate(); // 主线程的现实需要重绘

}

}

@Override

protected void onDraw(Canvas canvas) {

super.onDraw(canvas);

Paint p = new Paint(); // 根据传感器的数值来改变球的速度

if (this.allValue != null) { // 已经取得了数据

this.xSpeed = (int) -this.allValue[2]; // 计算X轴速度

this.ySpeed = (int) -this.allValue[1];

}

this.point.x += this.xSpeed;

this.point.y += this.ySpeed;

if (this.point.x < 0) {

this.point.x = 0;

}

if (this.point.y < 0) {

this.point.y = 0;

}

if (point.x > super.getWidth() - this.ball.getWidth()) { // X轴已经显示过了

this.point.x = super.getWidth() - this.ball.getWidth();

}

if (point.y > super.getHeight() - this.ball.getHeight()) {

this.point.y = super.getHeight() - this.ball.getWidth(); // 设置Y 轴的边界

}

canvas.drawBitmap(this.ball, this.point.x, this.point.y, p);

}

}

在MySensorDemo.java中：

package com.li.sensor;

import android.app.Activity;

import android.os.Bundle;

public class MySensorDemo extends Activity {

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

}

}

修改AndroidManifest.xml，设置为竖屏。

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

package="com.li.sensor"

android:versionCode="1"

android:versionName="1.0" >

<uses-sdk

android:minSdkVersion="8"

android:targetSdkVersion="15" />

<application

android:icon="@drawable/ic_launcher"

android:label="@string/app_name"

android:theme="@style/AppTheme" >

<activity

android:name=".MySensorDemo"

android:label="@string/title_activity_my_sensor_demo"

android:screenOrientation="portrait">

<intent-filter>

<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />

</intent-filter>

</activity>

</application>

</manifest>