我已經創建了一個使用加速度計計算設備速度的速度計應用程序。這裏是代碼: `package com.exacmple.speedo;速度計使用加速度計無輸出
import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;
import android.app.Activity;
import android.content.Context;
import android.hardware.SensorListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.os.Handler;
import android.widget.TextView;
public class Speedometer extends Activity {
SensorManager sensorManager;
TextView myTextView;
float appliedAcceleration = 0;
float currentAcceleration = 0;
float velocity = 0;
Date lastUpdate;
Handler handler = new Handler();
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
myTextView = (TextView) findViewById(R.id.myTextView);
lastUpdate = new Date(System.currentTimeMillis());
sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
sensorManager.registerListener(sensorListener,
SensorManager.SENSOR_ACCELEROMETER,
SensorManager.SENSOR_DELAY_FASTEST);
Timer updateTimer = new Timer("velocityUpdate");
updateTimer.scheduleAtFixedRate(new TimerTask() {
public void run() {
updateGUI();
}
}, 0, 1000);
}
private void updateGUI() {
// Convert from m/s to mph
final double mph = (Math.round(100 * velocity/1.6 * 3.6))/100;
// Update the GUI
handler.post(new Runnable() {
public void run() {
myTextView.setText(String.valueOf(mph) + "mph");
}
});
}
private void updateVelocity() {
// Calculate how long this acceleration has been applied.
Date timeNow = new Date(System.currentTimeMillis());
long timeDelta = timeNow.getTime() - lastUpdate.getTime();
lastUpdate.setTime(timeNow.getTime());
// Calculate the change in velocity at the
// current acceleration since the last update.
float deltaVelocity = appliedAcceleration * (timeDelta/1000);
appliedAcceleration = currentAcceleration;
// Add the velocity change to the current velocity.
velocity += deltaVelocity;
// Convert from meters per second to miles per hour.
double mph = (Math.round(velocity/1.6 * 3.6));
myTextView.setText(String.valueOf(mph) + "mph");
}
private final SensorListener sensorListener = new SensorListener() {
double calibration;
public void onSensorChanged(int sensor, float[] values) {
double x = values[SensorManager.DATA_X];
double y = values[SensorManager.DATA_Y];
double z = values[SensorManager.DATA_Z];
double a = -1
* Math.sqrt(Math.pow(x, 2) + Math.pow(y, 2)
+ Math.pow(z, 2));
if (calibration == Double.NaN)
calibration = a;
else {
updateVelocity();
currentAcceleration = (float) a;
}
}
public void onAccuracyChanged(int sensor, int accuracy) {
}
};
}` 我面臨的問題是,它並沒有顯示在在我的情況0.0英里每小時初始速度的任何變化。我已經在logcat上檢查過它,它顯示了它們的速度,但不會在UI上顯示任何增量。請幫忙。