如何将传感器添加到 android 小部件？

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。但是每次我将传感器添加到我的小部件提供程序时，我都会收到以下错误：

07-25 10:31:01.337：E/AndroidRuntime(8908)：致命异常：主要 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)：在 android.app.ActivityThread.handleReceiver(ActivityThread.java:2153) 07-25 10:31:01.337: E/AndroidRuntime(8908): 在 android.app.ActivityThread.access$1500(ActivityThread.java:127) 07-25 10:31:01.337：E/AndroidRuntime（8908）：在 android.app.ActivityThread$H.handleMessage(ActivityThread.java:1208) 07-25 10:31:01.337: E/AndroidRuntime(8908): 在 android.os.Handler.dispatchMessage(Handler.java:99) 07-25 10:31:01.337：E/AndroidRuntime（8908）：在 android.os.Looper.loop(Looper.java:137) 07-25 10:31:01.337: E/AndroidRuntime(8908)：在 android.app.ActivityThread.main(ActivityThread.java:4448) 07-25 10:31:01.337：E/AndroidRuntime（8908）：在 java.lang.reflect.Method.invokeNative(Native Method) 07-25 10:31:01.337：E/AndroidRuntime（8908）：在 java.lang.reflect.Method.invoke(Method.java:511) 07-25 10:31:01.337: E/AndroidRuntime(8908)：在 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:823) 07-25 10:31:01.337: E/AndroidRuntime(8908): 在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:590) 07-25 10:31:01.337：E/AndroidRuntime（8908）：在 dalvik.system.NativeStart.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): 在 com.example.axelo.AxeloAppWidgetProvider.onUpdate(AxeloAppWidgetProvider.java:29) 07-25 10:31:01.337: E/AndroidRuntime(8908): 在 android.appwidget.AppWidgetProvider.onReceive(AppWidgetProvider.java:66) 07-25 10:31:01.337: E/AndroidRuntime(8908): 在 android.app.ActivityThread.handleReceiver(ActivityThread.java:2146) 07-25 10:31:01.337: E/AndroidRuntime(8908): ... 10 更多

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，或者有没有办法在小部件中添加传感器？

Answer 1

我认为传感器小部件不会以这种方式适用，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，您可以将活动类添加到小部件清单并将您的代码放入其中像往常一样类，从小部件中，您可以 setOnClickPendingIntent 为该 Activity 设置按钮。