Android Wear应用程式已停止在Android Studio模拟器中运作

Question

我试图在我的android studio模拟器中运行代码，但是运行它后，模拟器不断显示“（（应用程序名称）已停止。再次打开应用程序”。

这是一个从Android Wear获取加速度计和陀螺仪传感器数据的应用程序。

我检查了logcat并在此过程中发现此错误。

03-06 04:18:57.364 3189-3189/com.drejkim.androidwearmotionsensors E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                Process: com.drejkim.androidwearmotionsensors, PID: 3189
                                                                                java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.hardware.Sensor.getStringType()' on a null object reference
                                                                                    at com.drejkim.androidwearmotionsensors.SensorFragment.onCreateView(SensorFragment.java:63)
                                                                                    at android.app.Fragment.performCreateView(Fragment.java:2353)
                                                                                    at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:995)
                                                                                    at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1171)
                                                                                    at android.app.BackStackRecord.run(BackStackRecord.java:816)
                                                                                    at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1578)
                                                                                    at android.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:563)
                                                                                    at android.support.wearable.view.FragmentGridPagerAdapter.finishUpdate(FragmentGridPagerAdapter.java:196)
                                                                                    at android.support.wearable.view.GridViewPager.populate(GridViewPager.java:1161)
                                                                                    at android.support.wearable.view.GridViewPager.populate(GridViewPager.java:1008)
                                                                                    at android.support.wearable.view.GridViewPager.onMeasure(GridViewPager.java:1322)
                                                                                    at android.view.View.measure(View.java:19857)
                                                                                    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083)
                                                                                    at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
                                                                                    at android.view.View.measure(View.java:19857)
                                                                                    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083)
                                                                                    at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
                                                                                    at android.support.wearable.view.WatchViewStub.onMeasure(WatchViewStub.java:136)
                                                                                    at android.view.View.measure(View.java:19857)
                                                                                    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083)
                                                                                    at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
                                                                                    at android.view.View.measure(View.java:19857)
                                                                                    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6083)
                                                                                    at android.widget.FrameLayout.onMeasure(FrameLayout.java:185)
                                                                                    at com.android.internal.policy.DecorView.onMeasure(DecorView.java:690)
                                                                                    at android.view.View.measure(View.java:19857)
                                                                                    at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2275)
                                                                                    at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1366)
                                                                                    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1675)
                                                                                    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1254)
                                                                                    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6338)
                                                                                    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:874)
                                                                                    at android.view.Choreographer.doCallbacks(Choreographer.java:686)
                                                                                    at android.view.Choreographer.doFrame(Choreographer.java:621)
                                                                                    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:860)
                                                                                    at android.os.Handler.handleCallback(Handler.java:751)
                                                                                    at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                                    at android.os.Looper.loop(Looper.java:154)
                                                                                    at android.app.ActivityThread.main(ActivityThread.java:6119)
                                                                                    at java.lang.reflect.Method.invoke(Native Method)
                                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

这是我的三个Java代码：

SensorFragments.java：

package com.drejkim.androidwearmotionsensors;

import android.app.Fragment;
import android.content.Context;
import android.graphics.Color;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.util.FloatMath;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class SensorFragment extends Fragment implements SensorEventListener {

    private static final float SHAKE_THRESHOLD = 1.1f;
    private static final int SHAKE_WAIT_TIME_MS = 250;
    private static final float ROTATION_THRESHOLD = 2.0f;
    private static final int ROTATION_WAIT_TIME_MS = 100;

    private View mView;
    private TextView mTextTitle;
    private TextView mTextValues;
    private SensorManager mSensorManager;
    private Sensor mSensor;
    private int mSensorType;
    private long mShakeTime = 0;
    private long mRotationTime = 0;

    public static SensorFragment newInstance(int sensorType) {
        SensorFragment f = new SensorFragment();

        // Supply sensorType as an argument
        Bundle args = new Bundle();
        args.putInt("sensorType", sensorType);
        f.setArguments(args);

        return f;
    }

    @Override public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        Bundle args = getArguments();
        if(args != null) {
            mSensorType = args.getInt("sensorType");
        }

        mSensorManager = (SensorManager) getActivity().getSystemService(Context.SENSOR_SERVICE);
        mSensor = mSensorManager.getDefaultSensor(mSensorType);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        mView = inflater.inflate(R.layout.sensor, container, false);

        mTextTitle = (TextView) mView.findViewById(R.id.text_title);
        mTextTitle.setText(mSensor.getStringType());
        mTextValues = (TextView) mView.findViewById(R.id.text_values);

        return mView;
    }

    @Override
    public void onResume() {
        super.onResume();
        mSensorManager.registerListener(this, mSensor, SensorManager.SENSOR_DELAY_NORMAL);
    }

    @Override
    public void onPause() {
        super.onPause();
        mSensorManager.unregisterListener(this);
    }

    @Override
    public void onSensorChanged(SensorEvent event) {
        // If sensor is unreliable, then just return
        if (event.accuracy == SensorManager.SENSOR_STATUS_UNRELIABLE)
        {
            return;
        }

        mTextValues.setText(
                "x = " + Float.toString(event.values[0]) + "\n" +
                "y = " + Float.toString(event.values[1]) + "\n" +
                "z = " + Float.toString(event.values[2]) + "\n"
        );

        if(event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {
            detectShake(event);
        }
        else if(event.sensor.getType() == Sensor.TYPE_GYROSCOPE) {
            detectRotation(event);
        }
    }

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

    }


    // References:
    //  - http://jasonmcreynolds.com/?p=388
    //  - http://code.tutsplus.com/tutorials/using-the-accelerometer-on-android--mobile-22125
    private void detectShake(SensorEvent event) {
        long now = System.currentTimeMillis();

        if((now - mShakeTime) > SHAKE_WAIT_TIME_MS) {
            mShakeTime = now;

            float gX = event.values[0] / SensorManager.GRAVITY_EARTH;
            float gY = event.values[1] / SensorManager.GRAVITY_EARTH;
            float gZ = event.values[2] / SensorManager.GRAVITY_EARTH;

            // gForce will be close to 1 when there is no movement
            float gForce = FloatMath.sqrt(gX*gX + gY*gY + gZ*gZ);

            // Change background color if gForce exceeds threshold;
            // otherwise, reset the color
            if(gForce > SHAKE_THRESHOLD) {
                mView.setBackgroundColor(Color.rgb(0, 100, 0));
            }
            else {
                mView.setBackgroundColor(Color.BLACK);
            }
        }
    }

    private void detectRotation(SensorEvent event) {
        long now = System.currentTimeMillis();

        if((now - mRotationTime) > ROTATION_WAIT_TIME_MS) {
            mRotationTime = now;

            // Change background color if rate of rotation around any
            // axis and in any direction exceeds threshold;
            // otherwise, reset the color
            if(Math.abs(event.values[0]) > ROTATION_THRESHOLD ||
               Math.abs(event.values[1]) > ROTATION_THRESHOLD ||
               Math.abs(event.values[2]) > ROTATION_THRESHOLD) {
                mView.setBackgroundColor(Color.rgb(0, 100, 0));
            }
            else {
                mView.setBackgroundColor(Color.BLACK);
            }
        }
    }
}

MainActivity.Java：

package com.drejkim.androidwearmotionsensors;

import android.app.Activity;
import android.os.Bundle;
import android.support.wearable.view.DotsPageIndicator;
import android.support.wearable.view.GridViewPager;
import android.support.wearable.view.WatchViewStub;

public class MainActivity extends Activity {

    @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) {
                final GridViewPager pager = (GridViewPager) findViewById(R.id.pager);
                pager.setAdapter(new SensorFragmentPagerAdapter(getFragmentManager()));

                DotsPageIndicator indicator = (DotsPageIndicator) findViewById(R.id.page_indicator);
                indicator.setPager(pager);
            }
        });
    }
}

SensorFragmentPagerAdapter.java：

package com.drejkim.androidwearmotionsensors;

import android.app.Fragment;
import android.app.FragmentManager;
import android.hardware.Sensor;
import android.support.wearable.view.FragmentGridPagerAdapter;

public class SensorFragmentPagerAdapter extends FragmentGridPagerAdapter {

    private int[] sensorTypes = {
            Sensor.TYPE_ACCELEROMETER,
            Sensor.TYPE_GYROSCOPE
    };

    public SensorFragmentPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getFragment(int row, int column) {
        return SensorFragment.newInstance(sensorTypes[column]);
    }

    @Override
    public int getRowCount() {
        return 1; // fix to 1 row
    }

    @Override
    public int getColumnCount(int row) {
        return sensorTypes.length;
    }
}

AndroidManifest.xml：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.drejkim.androidwearmotionsensors" >

    <uses-feature android:name="android.hardware.type.watch" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@android:style/Theme.DeviceDefault" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

有人可以帮我吗？ 我从某些来源获得了此代码，但我不知道如何解决它，因为logcat显示了一个致命的长异常脚本，以红色突出显示。 谢谢，如果有人可以帮助，我将不胜感激。

Answer 1

从LogCat中的错误消息中，您可以看到在尝试执行时mSensor为null

mTextTitle.setText(mSensor.getStringType());

这意味着您的传感器管理器无法找到与请求的类型匹配的默认传感器

mSensor = mSensorManager.getDefaultSensor(mSensorType);

如文档所述 。