如何向android小部件添加传感器？

Question

我做了一个简单的加速度计应用程序，我想做一个配套的小部件。但是每次向widgetprovider添加传感器时，都会出现以下错误：

07-25 10:31:01.337:E/AndroidRuntime（8908）：致命异常：main 07-25 10:31:01.337:E/AndroidRuntime（8908）：java.lang.RuntimeException：无法启动接收器com.example.axelo.axeloAppWidgetProvider：java.lang.NullPointerException 07-25 10:31:01.337:E/AndroidRuntime（8908）：at Android.app.ActivityThread.HandlereCeiver（ActivityThread.java：2153）Read.Access$1500(ActivityThread.java:127)07-25 10:31:01.337:E/AndroidRuntime(8908):at Android.app.ActivityThread$H.HandleMessage(ActivityThread.java:1208)07-25 10:31:01.337:E/AndroidRuntime(8908):at Android.os.handler.DispatchMessage(handler.java:99)07-25 10:31:01.337:E/AndroidRuntime(8908):at 8908）：at android.app.activitythread.main（activitythread.java:4448）07-25 10:31:01.337:e/androidruntime（8908）：at java.lang.reflect.Method.invokenative（本机方法）07-25 10:31:01.337:e/androidruntime(8908):at java.lang.reflect.Method.invoke(Method.java:511)07-25 10:31:01.337:e/androidruntime(8908):at com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:823)07-25 10:31:01.337:e/androidruntime(8908):at com.android.internal.os.zygoteinite.java:590)07-25 10:31:01.337:at.main（本机方法）07-25 10:31:01.337:e/AndroidRuntime(8908):原因:java.lang.nullPointerException 07-25 10:31:01.337:e/AndroidRuntime(8908):at com.example.axelo.axeloAppWidgetProvider.onUpdate(AxeloAppWidgetProvider.java:29)07-25 10:31:01.337:e/AndroidRuntime(8908):at App.ActivityThread.HandleReceiver（ActivityThread.java:2146)07-25 10:31:01.337:e/AndroidRuntime(8908):...10多个

这就是我的小部件类的样子

package com.example.axelo;

import android.app.PendingIntent;
import android.appwidget.AppWidgetManager;
import android.appwidget.AppWidgetProvider;
import android.content.Context;
import android.content.Intent;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.util.Log;
import android.widget.RemoteViews;
import android.widget.TextView;

public class AxeloAppWidgetProvider extends AppWidgetProvider implements SensorEventListener {

    private SensorManager mSensorManager;
    private Sensor mSensor;

    public void onUpdate(Context context, AppWidgetManager appWidgetManager,
              int[] appWidgetIds) {
        final int N = appWidgetIds.length;

        // Perform this loop procedure for each App Widget that belongs to this provider
        for (int i=0; i<N; i++) {
            int appWidgetId = appWidgetIds[i];

            mSensorManager = (SensorManager) context.getSystemService(Context.SENSOR_SERVICE);
            mSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
            if (mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER) != null){
                  Log.v("SENSOR_SERVICE","accelerometer found!");
                  }
                else {
                    Log.v("SENSOR_SERVICE","Not found!");
                }

            // Create an Intent to launch MainActivity
            Intent intent = new Intent(context, MainActivity.class);
            PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, intent, 0);

            // Get the layout for the App Widget and attach an on-click listener
            // to the button
            RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.axelo_widget);
            views.setOnClickPendingIntent(R.id.button, pendingIntent);

//         // Show changes on screen.
            views.setTextViewText(R.id.coord_X, Float.toString(linear_acceleration[0]));

            views.setTextViewText(R.id.coord_Y, Float.toString(linear_acceleration[1]));

            views.setTextViewText(R.id.coord_Z, Float.toString(linear_acceleration[2]));

            // Tell the AppWidgetManager to perform an update on the current app widget
            appWidgetManager.updateAppWidget(appWidgetId, views);
        }
    }

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

    }

    float[] gravity={(float) 9.81,(float) 9.81,(float) 9.81};
    float[] linear_acceleration=new float[3];

    @Override
    public void onSensorChanged(SensorEvent event) {
        // TODO Auto-generated method stub
        final float alpha = (float) 0.8;

      Log.v("SENSOR_SERVICE", "on sensor change");

   // Isolate the force of gravity with the low-pass filter.
      gravity[0] = alpha * gravity[0] + (1 - alpha) * event.values[0];
      gravity[1] = alpha * gravity[1] + (1 - alpha) * event.values[1];
      gravity[2] = alpha * gravity[2] + (1 - alpha) * event.values[2];

      // Remove the gravity contribution with the high-pass filter.
      linear_acceleration[0] = event.values[0] - gravity[0];
      linear_acceleration[1] = event.values[1] - gravity[1];
      linear_acceleration[2] = event.values[2] - gravity[2];        
    }       

}

请告诉我哪里出错了，还是没有办法向小部件添加传感器？

Answer 1

我认为传感器小部件不适用这种方式，您应该扩展Activity而不是AppWidgetProvider，不要忘记RegisterListener/UnRegisterListener，您还可以做更多的事情您可以将Activity类添加到小部件清单中，并将代码正常地放在该类中，您可以从widget中为该活动设置一个按钮ClickPendingIntent。