java - 如何向 Android 小部件添加传感器？

Question

我制作了一个简单的加速度计应用程序，我想制作一个配套小部件。但每次我向 widgetprovider 添加传感器时，都会收到以下错误:

07-25 10:31:01.337: E/AndroidRuntime(8908): FATAL EXCEPTION: main 07-25 10:31:01.337: E/AndroidRuntime(8908): java.lang.RuntimeException: Unable to start receiver com.example.axelo.AxeloAppWidgetProvider: java.lang.NullPointerException 07-25 10:31:01.337: E/AndroidRuntime(8908): at android.app.ActivityThread.handleReceiver(ActivityThread.java:2153) 07-25 10:31:01.337: E/AndroidRuntime(8908): at android.app.ActivityThread.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 android.os.Looper.loop(Looper.java:137) 07-25 10:31:01.337: E/AndroidRuntime(8908): at android.app.ActivityThread.main(ActivityThread.java:4448) 07-25 10:31:01.337: E/AndroidRuntime(8908): at java.lang.reflect.Method.invokeNative(Native Method) 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.ZygoteInit.main(ZygoteInit.java:590) 07-25 10:31:01.337: E/AndroidRuntime(8908): at dalvik.system.NativeStart.main(Native Method) 07-25 10:31:01.337: E/AndroidRuntime(8908): Caused by: 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 android.appwidget.AppWidgetProvider.onReceive(AppWidgetProvider.java:66) 07-25 10:31:01.337: E/AndroidRuntime(8908): at android.app.ActivityThread.handleReceiver(ActivityThread.java:2146) 07-25 10:31:01.337: E/AndroidRuntime(8908): ... 10 more

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];        
    }       

}

请告诉我哪里出了问题，或者是否无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 并且不要忘记 registerListener/unregisterListener，您可以做更多的事情，您可以将 Activity 类添加到小部件 list 并将您的代码放入其中像平常一样，您可以从小部件中为该 Activity 设置 OnClickPendingIntent 按钮。