GC_FOR_ALLOC不断出现，应用程序冻结

Question

我是android编程的新手，我已经完成了我的第一个程序。但是，程序在运行后冻结，log cat出现如下：

05-21 14:41:24.853: D/dalvikvm(5024): GC_FOR_ALLOC freed 496K, 70% free 8328K/27200K, paused 19ms, total 19ms

我在网上搜索过，他们说这是内存管理问题。但是我能做些什么来减少记忆？我在我的程序中使用加速度计和磁场传感器，每当我运行该活动时，它就会冻结。堆大小达到365M最高，但是我不运行该活动，它将正常工作，堆大小将只有1xxM。为什么这个活动占用了这么多内存？请给我一些建议。 下面是我在DDMS中的分配跟踪器和堆。

以下是导致冻结的活动：

    package com.example.suntracking;

import android.app.Activity;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.widget.TextView;

public class Accelerometer extends Activity implements SensorEventListener{
    Sensor accelerometer,magnetometer;
    SensorManager sm;
    private int samintval;
    private float uxtemp,ux,uytemp,uy,ax,ay,axtemp ,aytemp ,sx,sy,axdiff,aydiff,latnew,latold,longnew,longold;
    private TextView showax,showay,showaxtemp,showaytemp;

    private float[] mLastAccelerometer = new float[3];
    private float[] mLastMagnetometer = new float[3];
    private boolean mLastAccelerometerSet = false;
    private boolean mLastMagnetometerSet = false;

    private float[] mR = new float[9];
    private float[] mhold = new float[3];

    private float yaw,roll,pitch,rollold,pitchold;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        initialize();
        sm.registerListener(this, accelerometer,SensorManager.SENSOR_DELAY_GAME);
        sm.registerListener(this, magnetometer,SensorManager.SENSOR_DELAY_GAME);
        loadsavedPref();
        finish();
    }


    @Override
    protected void onResume()
    {
    super.onResume();
    }
    @Override
    protected void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
        sm.unregisterListener(this);
    }

    @Override
    protected void onPause() {
        // TODO Auto-generated method stub
        super.onPause();
    //  sm.unregisterListener(this);
    }


    private void initialize() {
        // TODO Auto-generated method stub
        sm=(SensorManager)getSystemService(SENSOR_SERVICE);
        accelerometer=sm.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
        magnetometer=sm.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);
    }

    private void loadsavedPref() {
        // TODO Auto-generated method stub
        SharedPreferences savedata= getSharedPreferences("savealldata",0);
        samintval = savedata.getInt("samintval", 1000);
        latold = savedata.getFloat("latval", 0);
        longold = savedata.getFloat("longval", 0);
    }

    private void cal_displace() {
        // TODO Auto-generated method stub
        //setting axis
        ax *=  (-1);
        ay *=  (-1);
        ax = (float) (ax * (Math.cos(Math.toRadians(roll))));
        ay = (float) (ay * (Math.cos(Math.toRadians(pitch))));
        //
        ux = uxtemp + ax *(samintval / 1000);
        uy = uytemp + ay * (samintval / 1000);
        axdiff= (ax - axtemp)/(samintval / 1000);
        aydiff = (ay - aytemp)/(samintval / 1000);
        sx = (ux *(samintval / 1000)) + ((axdiff) * (samintval / 1000)* (samintval / 1000)) / 2;
        sy = (uy *(samintval / 1000)) + ((aydiff) * (samintval / 1000)* (samintval / 1000)) / 2;
        latnew = (float) (latold + (sy / 111229.0));
        longnew = (float) (longold + (sx / 71695.8));
        axtemp = ax;
        aytemp = ay;
        uxtemp = ux;
        uytemp = uy;
    }



    @Override
    public void onAccuracyChanged(Sensor arg0, int arg1) {
        // TODO Auto-generated method stub

    }
    @Override
    public void onSensorChanged(SensorEvent event) {
        // TODO Auto-generated method stub

        if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER)
        {
          System.arraycopy(event.values, 0, mLastAccelerometer, 0, event.values.length);
         mLastAccelerometerSet = true;
          ax = event.values[0];
          ay = event.values[1];

        }else if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) {
            System.arraycopy(event.values, 0, mLastMagnetometer, 0, event.values.length);
            mLastMagnetometerSet = true;
        }
          if ((mLastAccelerometerSet) && (mLastMagnetometerSet))
          {
            SensorManager.getRotationMatrix(mR, null, mLastAccelerometer, mLastMagnetometer);
            SensorManager.getOrientation(mR, mhold);
            yaw = ((float)Math.toDegrees(mhold[0]));
            pitch = ((float)Math.toDegrees(mhold[1]));
            roll = ((float)Math.toDegrees(mhold[2]));
            savePreferences();
          }
          cal_displace();
          savePreferences();
        }


    private void savePreferences() {
        // TODO Auto-generated method stub
        SharedPreferences savedata = getSharedPreferences("savealldata",0);
        Editor editor=savedata.edit();
        editor.putFloat("ax", ax);
        editor.putFloat("ay", ay);
        editor.putFloat("axtemp", axtemp);
        editor.putFloat("aytemp", aytemp);
        editor.putFloat("axdiff", axdiff);
        editor.putFloat("aydiff", aydiff);
        editor.putFloat("sx", sx);
        editor.putFloat("sy", sy);
        editor.putFloat("alatval", latnew);
        editor.putFloat("alongval", longnew);
        editor.putFloat("yaw", yaw);
        editor.putFloat("pval", pitch);
        editor.putFloat("rval", roll);      
        editor.commit();
    }

}