Java Android Studio代码可以编译但不会运行
使用加速度计制作步进计数器。 代码编译没有错误，但当我在手机上运行它（S5）时失败 主活动中的代码Java Android Studio代码可以编译但不会运行,java,android,Java,Android,使用加速度计制作步进计数器。 代码编译没有错误，但当我在手机上运行它（S5）时失败 主活动中的代码 public class MainActivity extends Activity implements SensorEventListener{ TextView display; float g; @Override public void onCreate(Bundle savedInstanceState){ super
public class MainActivity extends Activity implements SensorEventListener{
TextView display;
float g;
@Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
display = (TextView) findViewById(R.id.testView); // Correction
SensorManager mgr = (SensorManager) getSystemService(SENSOR_SERVICE);
Sensor GSensor = mgr.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
mgr.registerListener(this, GSensor, SensorManager.SENSOR_DELAY_NORMAL);
String mytext = Float.toString(g);
display.setText(mytext);
}
@Override
public void onSensorChanged(SensorEvent event){
float x = event.values[0];
float y = event.values[1];
float z = event.values[2];
g = (x * x + y * y + z *z)/(SensorManager.GRAVITY_EARTH *SensorManager.GRAVITY_EARTH);
}
@Override
public void onAccuracyChanged(Sensor sensor, int accuracy){
}
}
05-20 09:35:44.773 11142-11142/com.liamoc.stepcounteraccel1 E/Zygote: MountEmulatedStorage()
05-20 09:35:44.773 11142-11142/com.liamoc.stepcounteraccel1 E/Zygote: v2
05-20 09:35:44.773 11142-11142/com.liamoc.stepcounteraccel1 I/libpersona: KNOX_SDCARD checking this for 10199
05-20 09:35:44.773 11142-11142/com.liamoc.stepcounteraccel1 I/libpersona: KNOX_SDCARD not a persona
05-20 09:35:44.793 11142-11142/com.liamoc.stepcounteraccel1 I/SELinux: Function: selinux_compare_spd_ram , priority [2] , priority version is VE=SEPF_SM-G900F_5.0-1_0032
05-20 09:35:44.793 11142-11142/com.liamoc.stepcounteraccel1 E/SELinux: [DEBUG] get_category: variable seinfo: default sensitivity: NULL, cateogry: NULL
05-20 09:35:44.793 11142-11142/com.liamoc.stepcounteraccel1 I/art: Late-enabling -Xcheck:jni
05-20 09:35:44.823 11142-11142/com.liamoc.stepcounteraccel1 D/TimaKeyStoreProvider: TimaSignature is unavailable
05-20 09:35:44.823 11142-11142/com.liamoc.stepcounteraccel1 D/ActivityThread: Added TimaKeyStore provider
05-20 09:35:44.863 11142-11142/com.liamoc.stepcounteraccel1 D/ResourcesManager: creating new AssetManager and set to /data/app/com.liamoc.stepcounteraccel1-2/base.apk
05-20 09:35:44.883 11142-11142/com.liamoc.stepcounteraccel1 W/art: Failed to find OatDexFile for DexFile /data/data/com.liamoc.stepcounteraccel1/files/instant-run/dex/slice-slice_6-classes.dex ( canonical path /data/data/com.liamoc.stepcounteraccel1/files/instant-run/dex/slice-slice_6-classes.dex) with checksum 0x1ff97ab0 in OatFile /data/data/com.liamoc.stepcounteraccel1/cache/slice-slice_6-classes.dex
05-20 09:35:45.053 11142-11142/com.liamoc.stepcounteraccel1 D/AndroidRuntime: Shutting down VM
05-20 09:35:45.053 11142-11142/com.liamoc.stepcounteraccel1 E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.liamoc.stepcounteraccel1, PID: 11142
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.liamoc.stepcounteraccel1/com.liamoc.stepcounteraccel1.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2515)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2723)
at android.app.ActivityThread.access$900(ActivityThread.java:172)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1422)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5832)
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:1399)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference
at android.app.Activity.findViewById(Activity.java:2168)
at com.liamoc.stepcounteraccel1.MainActivity.<init>(MainActivity.java:29)
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.Class.newInstance(Class.java:1650)
at android.app.Instrumentation.newActivity(Instrumentation.java:1079)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2505)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2723)
at android.app.ActivityThread.access$900(ActivityThread.java:172)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1422)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5832)
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:1399)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
05-20 09:35:44.773 11142-11142/com.liamoc.stepcounteraccel1 E/合子：mountSimulatedStorage（）
05-20 09:35:44.773 11142-11142/com.liamoc.step1 E/合子：v2
05-20 09:35:44.773 11142-11142/com.liamoc.stepcounteraccel1 I/libpersona:KNOX_SDCARD检查10199
05-20 09:35:44.773 11142-11142/com.liamoc.stepcounteraccel1 I/libpersona:KNOX_SDCARD不是人物角色
05-20 09:35:44.793 11142-11142/com.liamoc.stepcounteraccel1 I/SELinux：功能：SELinux比较spd内存，优先级[2]，优先级版本为VE=SEPF_SM-G900F_5.0-1_0032
05-20 09:35:44.793 11142-11142/com.liamoc.stepcounteraccel1 E/SELinux:[调试]获取类别：变量seinfo:默认灵敏度：NULL，类别：NULL
05-20 09:35:44.793 11142-11142/com.liamoc.stepcounteraccel1 I/art:Late enabling-Xcheck:jni
05-20 09:35:44.823 11142-11142/com.liamoc.stepcounteraccel1 D/TimaKeyStoreProvider:TimaSignature不可用
05-20 09:35:44.823 11142-11142/com.liamoc.stepcounteraccel1 D/ActivityThread:添加了TimaKeyStore提供程序
05-20 09:35:44.863 11142-11142/com.liamoc.stepcounteraccel1 D/ResourcesManager:创建新资产管理器并设置为/data/app/com.liamoc.stepcounteraccel1-2/base.apk
05-20 09:35:44.883 11142-11142/com.liamoc.stepcounteraccel1 W/art:找不到DexFile/data/data/com.liamoc.stepcounteraccel1/files/instant-run/dex/slice-slice_6-classes.dex的OatDexFile（规范路径/data/data/com.liamoc.stepcounteraccel1/files/instant run/dex/slice-slice_6-classes.dex）在OatFile/data/data/com.liamoc.stepcounteraccel1/cache/slice-slice_6-classes.dex中使用校验和0x1ff97ab0
05-20 09:35:45.053 11142-11142/com.liamoc.stepcounteraccel1 D/AndroidRuntime:关闭虚拟机
05-20 09:35:45.053 11142-11142/com.liamoc.stepcounteraccel1 E/AndroidRuntime:致命异常：主
进程：com.liamoc.stepcounteraccel1，PID:11142
java.lang.RuntimeException:无法实例化活动组件信息{com.liamoc.stepcounteraccel1/com.liamoc.stepcounteraccel1.MainActivity}:java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法“android.view.view android.view.Window.findViewById（int）”
在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2515）上
位于android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2723）
在android.app.ActivityThread.access$900（ActivityThread.java:172）
在android.app.ActivityThread$H.handleMessage（ActivityThread.java:1422）
位于android.os.Handler.dispatchMessage（Handler.java:102）
位于android.os.Looper.loop（Looper.java:145）
位于android.app.ActivityThread.main（ActivityThread.java:5832）
位于java.lang.reflect.Method.invoke（本机方法）
位于java.lang.reflect.Method.invoke（Method.java:372）
在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run（ZygoteInit.java:1399）上
位于com.android.internal.os.ZygoteInit.main（ZygoteInit.java:1194）
原因：java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法“android.view.view android.view.Window.findViewById（int）”
在android.app.Activity.findviewbyd（Activity.java:2168）
位于com.liamoc.stepcounteraccel1.MainActivity。（MainActivity.java:29）
位于java.lang.reflect.Constructor.newInstance（本机方法）
位于java.lang.Class.newInstance（Class.java:1650）
位于android.app.Instrumentation.newActivity（Instrumentation.java:1079）
在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2505）上
位于android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2723）
在android.app.ActivityThread.access$900（ActivityThread.java:172）
在android.app.ActivityThread$H.handleMessage（ActivityThread.java:1422）
位于android.os.Handler.dispatchMessage（Handler.java:102）
位于android.os.Looper.loop（Looper.java:145）
TextView display;
@Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
display = (TextView) findViewById(R.id.testView);
SensorManager mgr = (SensorManager) getSystemService(SENSOR_SERVICE);
Sensor GSensor = mgr.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
mgr.registerListener(this, GSensor, SensorManager.SENSOR_DELAY_NORMAL);
}
@Override
public void onSensorChanged(SensorEvent event){
float x = event.values[0];
float y = event.values[1];
float z = event.values[2];
g = (x * x + y * y + z *z)/(SensorManager.GRAVITY_EARTH *SensorManager.GRAVITY_EARTH);
String mytext = Float.toString(g);
display.setText(mytext);
}