Java JNI函数给出一个错误；由信号（2）终止；

我有一个本机库，由从UI调用的JNI函数调用。它只运行一次，执行一个命令，在第二次运行时退出。我得到了下面的打印

D/Zygote  ( 111): Process 921 terminated by signal (2)   

信号（2）是什么意思？我能从这条消息中推断出进程终止的原因吗？本机库可以在第一次执行时完全正常工作

我的第二个问题是关于加速度计：

package com.example.android.accelerometerplay;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.BitmapFactory.Options;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.os.PowerManager;
import android.os.PowerManager.WakeLock;
import android.util.DisplayMetrics;
import android.view.Display;
import android.view.Surface;
import android.view.View;
import android.view.WindowManager;

/**
 * This is an example of using the accelerometer to integrate the device's
 * acceleration to a position using the Verlet method. This is illustrated with
 * a very simple particle system comprised of a few iron balls freely moving on
 * an inclined wooden table. The inclination of the virtual table is controlled
 * by the device's accelerometer.
 * 
 * @see SensorManager
 * @see SensorEvent
 * @see Sensor
 */

public class AccelerometerPlayActivity extends Activity {

    private SimulationView mSimulationView;
    private SensorManager mSensorManager;
    private PowerManager mPowerManager;
    private WindowManager mWindowManager;
    private Display mDisplay;
    private WakeLock mWakeLock;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Get an instance of the SensorManager
        mSensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);

        // Get an instance of the PowerManager
        mPowerManager = (PowerManager) getSystemService(POWER_SERVICE);

        // Get an instance of the WindowManager
        mWindowManager = (WindowManager) getSystemService(WINDOW_SERVICE);
        mDisplay = mWindowManager.getDefaultDisplay();

        // Create a bright wake lock
        mWakeLock = mPowerManager.newWakeLock(PowerManager.SCREEN_BRIGHT_WAKE_LOCK, getClass()
                .getName());

        // instantiate our simulation view and set it as the activity's content
        mSimulationView = new SimulationView(this);
        setContentView(mSimulationView);
    }

    @Override
    protected void onResume() {
        super.onResume();
        /*
         * when the activity is resumed, we acquire a wake-lock so that the
         * screen stays on, since the user will likely not be fiddling with the
         * screen or buttons.
         */
        mWakeLock.acquire();

        // Start the simulation
        mSimulationView.startSimulation();
    }

    @Override
    protected void onPause() {
        super.onPause();
        /*
         * When the activity is paused, we make sure to stop the simulation,
         * release our sensor resources and wake locks
         */

        // Stop the simulation
        mSimulationView.stopSimulation();

        // and release our wake-lock
        mWakeLock.release();
    }

    class SimulationView extends View implements SensorEventListener {
        // diameter of the balls in meters
        private static final float sBallDiameter = 0.004f;
        private static final float sBallDiameter2 = sBallDiameter * sBallDiameter;

        // friction of the virtual table and air
        private static final float sFriction = 0.1f;

        private Sensor mAccelerometer;
        private long mLastT;
        private float mLastDeltaT;

        private float mXDpi;
        private float mYDpi;
        private float mMetersToPixelsX;
        private float mMetersToPixelsY;
        private Bitmap mBitmap;
        private Bitmap mWood;
        private float mXOrigin;
        private float mYOrigin;
        private float mSensorX;
        private float mSensorY;
        private long mSensorTimeStamp;
        private long mCpuTimeStamp;
        private float mHorizontalBound;
        private float mVerticalBound;
        private final ParticleSystem mParticleSystem = new ParticleSystem();

        /*
         * Each of our particle holds its previous and current position, its
         * acceleration. for added realism each particle has its own friction
         * coefficient.
         */
        class Particle {
            private float mPosX;
            private float mPosY;
            private float mAccelX;
            private float mAccelY;
            private float mLastPosX;
            private float mLastPosY;
            private float mOneMinusFriction;

            Particle() {
                // make each particle a bit different by randomizing its
                // coefficient of friction
                final float r = ((float) Math.random() - 0.5f) * 0.2f;
                mOneMinusFriction = 1.0f - sFriction + r;
            }

            public void computePhysics(float sx, float sy, float dT, float dTC) {
                // Force of gravity applied to our virtual object
                final float m = 1000.0f; // mass of our virtual object
                final float gx = -sx * m;
                final float gy = -sy * m;

                /*
                 * ·F = mA <=> A = ·F / m We could simplify the code by
                 * completely eliminating "m" (the mass) from all the equations,
                 * but it would hide the concepts from this sample code.
                 */
                final float invm = 1.0f / m;
                final float ax = gx * invm;
                final float ay = gy * invm;

                /*
                 * Time-corrected Verlet integration The position Verlet
                 * integrator is defined as x(t+Æt) = x(t) + x(t) - x(t-Æt) +
                 * a(t)Ætö2 However, the above equation doesn't handle variable
                 * Æt very well, a time-corrected version is needed: x(t+Æt) =
                 * x(t) + (x(t) - x(t-Æt)) * (Æt/Æt_prev) + a(t)Ætö2 We also add
                 * a simple friction term (f) to the equation: x(t+Æt) = x(t) +
                 * (1-f) * (x(t) - x(t-Æt)) * (Æt/Æt_prev) + a(t)Ætö2
                 */
                final float dTdT = dT * dT;
                final float x = mPosX + mOneMinusFriction * dTC * (mPosX - mLastPosX) + mAccelX
                        * dTdT;
                final float y = mPosY + mOneMinusFriction * dTC * (mPosY - mLastPosY) + mAccelY
                        * dTdT;
                mLastPosX = mPosX;
                mLastPosY = mPosY;
                mPosX = x;
                mPosY = y;
                mAccelX = ax;
                mAccelY = ay;
            }

            /*
             * Resolving constraints and collisions with the Verlet integrator
             * can be very simple, we simply need to move a colliding or
             * constrained particle in such way that the constraint is
             * satisfied.
             */
            public void resolveCollisionWithBounds() {
                final float xmax = mHorizontalBound;
                final float ymax = mVerticalBound;
                final float x = mPosX;
                final float y = mPosY;
                if (x > xmax) {
                    mPosX = xmax;
                } else if (x < -xmax) {
                    mPosX = -xmax;
                }
                if (y > ymax) {
                    mPosY = ymax;
                } else if (y < -ymax) {
                    mPosY = -ymax;
                }
            }
        }

        /*
         * A particle system is just a collection of particles
         */
        class ParticleSystem {
            static final int NUM_PARTICLES = 15;
            private Particle mBalls[] = new Particle[NUM_PARTICLES];

            ParticleSystem() {
                /*
                 * Initially our particles have no speed or acceleration
                 */
                for (int i = 0; i < mBalls.length; i++) {
                    mBalls[i] = new Particle();
                }
            }

            /*
             * Update the position of each particle in the system using the
             * Verlet integrator.
             */
            private void updatePositions(float sx, float sy, long timestamp) {
                final long t = timestamp;
                if (mLastT != 0) {
                    final float dT = (float) (t - mLastT) * (1.0f / 1000000000.0f);
                    if (mLastDeltaT != 0) {
                        final float dTC = dT / mLastDeltaT;
                        final int count = mBalls.length;
                        for (int i = 0; i < count; i++) {
                            Particle ball = mBalls[i];
                            ball.computePhysics(sx, sy, dT, dTC);
                        }
                    }
                    mLastDeltaT = dT;
                }
                mLastT = t;
            }

            /*
             * Performs one iteration of the simulation. First updating the
             * position of all the particles and resolving the constraints and
             * collisions.
             */
            public void update(float sx, float sy, long now) {
                // update the system's positions
                updatePositions(sx, sy, now);

                // We do no more than a limited number of iterations
                final int NUM_MAX_ITERATIONS = 10;

                /*
                 * Resolve collisions, each particle is tested against every
                 * other particle for collision. If a collision is detected the
                 * particle is moved away using a virtual spring of infinite
                 * stiffness.
                 */
                boolean more = true;
                final int count = mBalls.length;
                for (int k = 0; k < NUM_MAX_ITERATIONS && more; k++) {
                    more = false;
                    for (int i = 0; i < count; i++) {
                        Particle curr = mBalls[i];
                        for (int j = i + 1; j < count; j++) {
                            Particle ball = mBalls[j];
                            float dx = ball.mPosX - curr.mPosX;
                            float dy = ball.mPosY - curr.mPosY;
                            float dd = dx * dx + dy * dy;
                            // Check for collisions
                            if (dd <= sBallDiameter2) {
                                /*
                                 * add a little bit of entropy, after nothing is
                                 * perfect in the universe.
                                 */
                                dx += ((float) Math.random() - 0.5f) * 0.0001f;
                                dy += ((float) Math.random() - 0.5f) * 0.0001f;
                                dd = dx * dx + dy * dy;
                                // simulate the spring
                                final float d = (float) Math.sqrt(dd);
                                final float c = (0.5f * (sBallDiameter - d)) / d;
                                curr.mPosX -= dx * c;
                                curr.mPosY -= dy * c;
                                ball.mPosX += dx * c;
                                ball.mPosY += dy * c;
                                more = true;
                            }
                        }
                        /*
                         * Finally make sure the particle doesn't intersects
                         * with the walls.
                         */
                        curr.resolveCollisionWithBounds();
                    }
                }
            }

            public int getParticleCount() {
                return mBalls.length;
            }

            public float getPosX(int i) {
                return mBalls[i].mPosX;
            }

            public float getPosY(int i) {
                return mBalls[i].mPosY;
            }
        }

        public void startSimulation() {
            /*
             * It is not necessary to get accelerometer events at a very high
             * rate, by using a slower rate (SENSOR_DELAY_UI), we get an
             * automatic low-pass filter, which "extracts" the gravity component
             * of the acceleration. As an added benefit, we use less power and
             * CPU resources.
             */
            mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_UI);
        }

        public void stopSimulation() {
            mSensorManager.unregisterListener(this);
        }

        public SimulationView(Context context) {
            super(context);
            mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);

            DisplayMetrics metrics = new DisplayMetrics();
            getWindowManager().getDefaultDisplay().getMetrics(metrics);
            mXDpi = metrics.xdpi;
            mYDpi = metrics.ydpi;
            mMetersToPixelsX = mXDpi / 0.0254f;
            mMetersToPixelsY = mYDpi / 0.0254f;

            // rescale the ball so it's about 0.5 cm on screen
            Bitmap ball = BitmapFactory.decodeResource(getResources(), R.drawable.ball);
            final int dstWidth = (int) (sBallDiameter * mMetersToPixelsX + 0.5f);
            final int dstHeight = (int) (sBallDiameter * mMetersToPixelsY + 0.5f);
            mBitmap = Bitmap.createScaledBitmap(ball, dstWidth, dstHeight, true);

            Options opts = new Options();
            opts.inDither = true;
            opts.inPreferredConfig = Bitmap.Config.RGB_565;
            mWood = BitmapFactory.decodeResource(getResources(), R.drawable.wood, opts);
        }

        @Override
        protected void onSizeChanged(int w, int h, int oldw, int oldh) {
            // compute the origin of the screen relative to the origin of
            // the bitmap
            mXOrigin = (w - mBitmap.getWidth()) * 0.5f;
            mYOrigin = (h - mBitmap.getHeight()) * 0.5f;
            mHorizontalBound = ((w / mMetersToPixelsX - sBallDiameter) * 0.5f);
            mVerticalBound = ((h / mMetersToPixelsY - sBallDiameter) * 0.5f);
        }

        @Override
        public void onSensorChanged(SensorEvent event) {
            if (event.sensor.getType() != Sensor.TYPE_ACCELEROMETER)
                return;
            /*
             * record the accelerometer data, the event's timestamp as well as
             * the current time. The latter is needed so we can calculate the
             * "present" time during rendering. In this application, we need to
             * take into account how the screen is rotated with respect to the
             * sensors (which always return data in a coordinate space aligned
             * to with the screen in its native orientation).
             */

            switch (mDisplay.getRotation()) {
                case Surface.ROTATION_0:
                    mSensorX = event.values[0];
                    mSensorY = event.values[1];
                    break;
                case Surface.ROTATION_90:
                    mSensorX = -event.values[1];
                    mSensorY = event.values[0];
                    break;
                case Surface.ROTATION_180:
                    mSensorX = -event.values[0];
                    mSensorY = -event.values[1];
                    break;
                case Surface.ROTATION_270:
                    mSensorX = event.values[1];
                    mSensorY = -event.values[0];
                    break;
            }

            mSensorTimeStamp = event.timestamp;
            mCpuTimeStamp = System.nanoTime();
        }

        @Override
        protected void onDraw(Canvas canvas) {

            /*
             * draw the background
             */

            canvas.drawBitmap(mWood, 0, 0, null);

            /*
             * compute the new position of our object, based on accelerometer
             * data and present time.
             */

            final ParticleSystem particleSystem = mParticleSystem;
            final long now = mSensorTimeStamp + (System.nanoTime() - mCpuTimeStamp);
            final float sx = mSensorX;
            final float sy = mSensorY;

            particleSystem.update(sx, sy, now);

            final float xc = mXOrigin;
            final float yc = mYOrigin;
            final float xs = mMetersToPixelsX;
            final float ys = mMetersToPixelsY;
            final Bitmap bitmap = mBitmap;
            final int count = particleSystem.getParticleCount();
            for (int i = 0; i < count; i++) {
                /*
                 * We transform the canvas so that the coordinate system matches
                 * the sensors coordinate system with the origin in the center
                 * of the screen and the unit is the meter.
                 */

                final float x = xc + particleSystem.getPosX(i) * xs;
                final float y = yc - particleSystem.getPosY(i) * ys;
                canvas.drawBitmap(bitmap, x, y, null);
            }

            // and make sure to redraw asap
            invalidate();
        }

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

package com.example.android.accelerometerplay；
导入android.app.Activity；
导入android.content.Context；
导入android.graphics.Bitmap；
导入android.graphics.BitmapFactory；
导入android.graphics.Canvas；
导入android.graphics.BitmapFactory.Options；
导入android.hardware.Sensor；
导入android.hardware.SensorEvent；
导入android.hardware.SensorEventListener；
导入android.hardware.SensorManager；
导入android.os.Bundle；
导入android.os.PowerManager；
导入android.os.PowerManager.WakeLock；
导入android.util.DisplayMetrics；
导入android.view.Display；
导入android.view.Surface；
导入android.view.view；
导入android.view.WindowManager；
/**
*这是一个使用加速计集成设备的示例
*使用Verlet方法加速到某个位置。这是用一个例子来说明的
*一个非常简单的粒子系统，由几个自由移动的铁球组成
*倾斜的木桌。控制虚拟工作台的倾斜
*通过设备的加速计。
* 
*@见传感器管理器
*@见SensorEvent
*@见传感器
*/
公共类AccelerometerPlayActivity扩展了活动{
私有模拟视图mSimulationView；
私人传感器管理器；
私人电源管理器mPowerManager；
专用窗口管理器mWindowManager；
专用显示器；
私人WakeLock mWakeLock；
/**在首次创建活动时调用*/
@凌驾
创建时的公共void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
//获取SensorManager的实例
msSensorManager=（SensorManager）getSystemService（传感器服务）；
//获取PowerManager的一个实例
mPowerManager=（PowerManager）getSystemService（POWER\u服务）；
//获取WindowManager的实例
mWindowManager=（窗口管理器）getSystemService（窗口服务）；
mDisplay=mWindowManager.getDefaultDisplay（）；
//创建一个明亮的尾迹锁
mWakeLock=mPowerManager.newWakeLock（PowerManager.SCREEN\u BRIGHT\u WAKE\u LOCK，getClass（））
.getName（））；
//实例化我们的模拟视图并将其设置为活动的内容
mSimulationView=新的模拟视图（此）；
setContentView（mSimulationView）；
}
@凌驾
受保护的void onResume（）{
super.onResume（）；
/*
*当活动恢复时，我们获得一个唤醒锁，以便
*屏幕保持打开状态，因为用户可能不会摆弄屏幕
*屏幕或按钮。
*/
mWakeLock.acquire（）；
//开始模拟
mSimulationView.startSimulation（）；
}
@凌驾
受保护的void onPause（）{
super.onPause（）；
/*
*当活动暂停时，我们确保停止模拟，
*释放传感器资源和唤醒锁
*/
//停止模拟
mSimulationView.stopSimulation（）；
//释放我们的唤醒锁
mWakeLock.release（）；
}
类SimulationView扩展视图实现SensorEventListener{
//球的直径（米）
专用静态最终浮球直径=0.004f；
专用静态最终浮子sBallDiameter2=sBallDiameter*sBallDiameter；
//虚拟工作台与空气的摩擦力
专用静态最终浮点数F=0.1f；
专用传感器mAccelerometer；
私人长途旅行；
私人浮动mLastDeltaT；
私有浮动mXDpi；
私人浮动mYDpi；
私有浮动mMetersToPixelsX；
私人浮点数；
私有位图mBitmap；
私人木屋；
私人来源；
私人漂浮肌原蛋白；
私有浮动传感器；
私有浮动传感器；
私有长时间戳；
私人长途电话；
私人游船沿水平方向行驶；
私人浮动mVerticalBound；
私有最终ParticleSystem mParticleSystem=新ParticleSystem（）；
/*
*我们的每个粒子都保持其先前和当前的位置，即
*为了增加真实感，每个粒子都有自己的摩擦力
*系数。
*/
类粒子{
私人浮动mPosX；
私家车；
私人浮动mAccelX；
私人浮动麦凯利；
私有浮动mLastPosX；
私人浮动保险；
私人浮动汇率制度；
粒子（）{
//通过随机化每个粒子的
//摩擦系数
最终浮点r=（（浮点）数学随机（）-0.5f）*0.2f；
摩阻=1.0f-摩擦+r；
}
公共无效计算物理（浮点sx、浮点sy、浮点dT、浮点dTC）{
//施加在虚拟物体上的重力
最终浮点m=1000.0f；//虚拟对象的质量
最终浮子gx=-sx*m；
最终浮子gy=-sy*m；
/*
*·F=mA A=·F/m我们可以通过
*从所有方程中完全消除“m”（质量），
*但是它会从这个示例代码中隐藏这些概念。
*/
最终浮点数m=1.0f/m；
最终浮动ax=gx*invm