Android Wear Step Counter崩溃应用程序

Question

我正在编写一个应用程序，使用android wear设备读取心率和步数。心率传感器工作正常，但步数引起了问题。但是，在注释步进计数器的侦听器并在onResume（）中注册一个空值时，应用程序可以使用心率传感器。我没有得到任何关于这个的日志，否则我会把它贴在这里。这是我使用的代码

import android.app.Activity;
import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.support.wearable.view.WatchViewStub;
import android.util.Log;
import android.widget.TextView;

import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.common.api.PendingResult;
import com.google.android.gms.common.api.ResultCallback;
import com.google.android.gms.wearable.Node;
import com.google.android.gms.wearable.NodeApi;
import com.google.android.gms.wearable.Wearable;

import java.nio.ByteBuffer;
import java.util.List;

public class MainActivity extends Activity {

    private SensorManager mSensorManager;
    private TextView mTextViewHeart, mTextViewStep;
    private Sensor mHeartRateSensor, mStepCounterSensor;
    private GoogleApiClient mGoogleApiClient;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        WatchViewStub stub = (WatchViewStub) findViewById(R.id.watch_view_stub);
        stub.setOnLayoutInflatedListener(new WatchViewStub.OnLayoutInflatedListener() {
            @Override
            public void onLayoutInflated(WatchViewStub stub) {
                mTextViewHeart = (TextView) stub.findViewById(R.id.value_heart);
                mTextViewStep = (TextView) stub.findViewById(R.id.value_step);
            }
        });

        mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
        mHeartRateSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_HEART_RATE);
        mStepCounterSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_STEP_COUNTER);

        mGoogleApiClient = new GoogleApiClient.Builder(this).addApi(Wearable.API).build();
        mGoogleApiClient.connect();
    }

    @Override
    protected void onResume() {
        super.onResume();
        mSensorManager.registerListener(heartListener, mHeartRateSensor, SensorManager.SENSOR_DELAY_NORMAL);
        mSensorManager.registerListener(stepListener, mStepCounterSensor, SensorManager.SENSOR_DELAY_FASTEST);
    }

    @Override
    protected void onPause() {
        super.onPause();
        mSensorManager.unregisterListener(heartListener, mHeartRateSensor);
    }

    SensorEventListener heartListener = new SensorEventListener() {
        @Override
        public void onSensorChanged(SensorEvent event) {
            if (event.sensor.getType() == Sensor.TYPE_HEART_RATE) {
                if (event.values.length > 0) {
                    if (event.values[0] > 0.0f) {
                        mTextViewHeart.setBackgroundResource(android.R.color.holo_green_light);
                        mTextViewHeart.setText(Float.toString(event.values[0]));
                        sendToHandheld(Math.round(event.values[0]), Sensor.TYPE_HEART_RATE);
                    }
                }
            }
        }

        @Override
        public void onAccuracyChanged(Sensor sensor, int accuracy) {

        }
    };

    SensorEventListener stepListener = new SensorEventListener() {
        @Override
        public void onSensorChanged(SensorEvent event) {

            if (event.sensor.getType() == Sensor.TYPE_STEP_COUNTER) {
                if (event.values.length > 0) {
                    mTextViewStep.setBackgroundResource(android.R.color.holo_green_light);
                    mTextViewStep.setText(Float.toString(event.values[0]));
                    sendToHandheld(Math.round(event.values[0]), Sensor.TYPE_STEP_COUNTER);
                }
            }
        }

        @Override
        public void onAccuracyChanged(Sensor sensor, int accuracy) {

        }
    };

    private void sendToHandheld(final int val, final int type) {
        final PendingResult<NodeApi.GetConnectedNodesResult> nodes = Wearable.NodeApi.getConnectedNodes(mGoogleApiClient);
        nodes.setResultCallback(new ResultCallback<NodeApi.GetConnectedNodesResult>() {
            @Override
            public void onResult(NodeApi.GetConnectedNodesResult result) {
                final List<Node> nodes = result.getNodes();
                if (nodes != null) {
                    for (int i = 0; i < nodes.size(); i++) {
                        final Node node = nodes.get(i);
                        Wearable.MessageApi.sendMessage(mGoogleApiClient, node.getId(), "/" + type, ByteBuffer.allocate(4).putInt(val).array());
                        Log.d("Sending", type + ":" + val);
                    }
                }
            }
        });
    }
}

更新

06-15 11:46:02.342    3355-3355/com.hsc.fit E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.hsc.fit, PID: 3355
    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setBackgroundResource(int)' on a null object reference
            at com.hsc.fit.MainActivity$3.onSensorChanged(MainActivity.java:92)
            at android.hardware.SystemSensorManager$SensorEventQueue.dispatchSensorEvent(SystemSensorManager.java:405)
            at android.os.MessageQueue.nativePollOnce(Native Method)
            at android.os.MessageQueue.next(MessageQueue.java:143)
            at android.os.Looper.loop(Looper.java:122)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

Answer 1

修好了。WatchViewStub的SetOnLayoutInflatedListener()在OnResume()之后调用，并且我的传感器在OnResume()中注册。由于我的文本视图是在传感器的侦听器中使用的，而它还没有被分配一个refrence，所以我得到了一个NullPointerException。我在WatchViewStub的侦听器中移动了传感器注册表，现在它可以工作了。