我收到此错误：java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference即使我的活动中没有此类方法。
以下是代码：
public class MyActivity extends AppCompatActivity implements GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener {
AppCompatSpinner iSpinner, nSpinner, dSpinner, vSpinner;
AppCompatButton btnP;
String itemID, currentLatString, currentLngString;
GoogleApiClient mGoogleApiClient;
Location mLastLocation;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
// Create an instance of GoogleAPIClient.
if (mGoogleApiClient == null) {
mGoogleApiClient = new GoogleApiClient.Builder(this)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(LocationServices.API)
.build();
}
iSpinner = (AppCompatSpinner) findViewById(R.id.tag1);
nSpinner = (AppCompatSpinner) findViewById(R.id.tag2);
d = (AppCompatSpinner) findViewById(R.id.tag3);
vSpinner = (AppCompatSpinner) findViewById(R.id.tag4);
btnP = (AppCompatButton) findViewById(R.id.btnP);
DateFormat currentTime = new SimpleDateFormat("h:mm a");
final String time = currentTime.format(Calendar.getInstance().getTime());
final DateFormat utcFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
utcFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
final String utcFormatDateTimeString = utcFormat.format(Calendar.getInstance().getTimeInMillis());
Date utc = null;
try {
utc = utcFormat.parse(utcFormatDateTimeString);
} catch (ParseException e) {
e.printStackTrace();
}
final String utcFormatDateTime = utcFormat.format(utc);
btnP.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (ActivityCompat.checkSelfPermission(PostGameRequest.this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(PostGameRequest.this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
// TODO: Consider calling
// ActivityCompat#requestPermissions
// here to request the missing permissions, and then overriding
// public void onRequestPermissionsResult(int requestCode, String[] permissions,
// int[] grantResults)
// to handle the case where the user grants the permission. See the documentation
// for ActivityCompat#requestPermissions for more details.
return;
}
mLastLocation = LocationServices.FusedLocationApi.getLastLocation(
mGoogleApiClient);
if (mLastLocation != null) {
currentLatString = String.valueOf(mLastLocation.getLatitude());
currentLngString = String.valueOf(mLastLocation.getLongitude());
Toast.makeText(getBaseContext(), currentLatString + ", " + currentLngString, Toast.LENGTH_SHORT).show();
}
if (!currentLatString.isEmpty() || !currentLngString.isEmpty()) {
iSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
iString = adapterView.getItemAtPosition(i).toString();
}
@Override
public void onNothingSelected(AdapterView<?> adapterView) {
}
});
nSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
nString = adapterView.getItemAtPosition(i).toString();
}
@Override
public void onNothingSelected(AdapterView<?> adapterView) {
}
});
dSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
dString = adapterView.getItemAtPosition(i).toString();
}
@Override
public void onNothingSelected(AdapterView<?> adapterView) {
}
});
vSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
vString = adapterView.getItemAtPosition(i).toString();
}
@Override
public void onNothingSelected(AdapterView<?> adapterView) {
}
});
} else {
Snackbar snackbar = Snackbar
.make(coordinatorLayout, "Some error occurred. Please retry.", Snackbar.LENGTH_SHORT);
snackbar.show();
if (ActivityCompat.checkSelfPermission(PostGameRequest.this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(PostGameRequest.this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
// TODO: Consider calling
// ActivityCompat#requestPermissions
// here to request the missing permissions, and then overriding
// public void onRequestPermissionsResult(int requestCode, String[] permissions,
// int[] grantResults)
// to handle the case where the user grants the permission. See the documentation
// for ActivityCompat#requestPermissions for more details.
return;
}
mLastLocation = LocationServices.FusedLocationApi.getLastLocation(
mGoogleApiClient);
if (mLastLocation != null) {
currentLatString = String.valueOf(mLastLocation.getLatitude());
currentLngString = String.valueOf(mLastLocation.getLongitude());
Toast.makeText(getBaseContext(), currentLatString + ", " + currentLngString, Toast.LENGTH_SHORT).show();
}
}
}
});
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
onBackPressed();
return true;
}
return super.onOptionsItemSelected(item);
}
protected void onStart() {
mGoogleApiClient.connect();
super.onStart();
}
protected void onStop() {
mGoogleApiClient.disconnect();
super.onStop();
}
@Override
public void onConnected(@Nullable Bundle bundle) {
}
@Override
public void onConnectionSuspended(int i) {
}
@Override
public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
}
}
这是布局代码：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context="com.playrapp.playr.PostGameRequest"
tools:showIn="@layout/activity_post_game_request">
<android.support.v7.widget.CardView
android:layout_width="match_parent"
android:layout_height="match_parent"
app:contentPadding="10dp">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Tag1:"
android:layout_marginStart="7dp"
android:layout_marginLeft="7dp"
android:textSize="16sp"/>
<android.support.v7.widget.AppCompatSpinner
android:id="@+id/tag1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:layout_marginBottom="16dp"
android:entries="@array/list1"
style="@style/Base.Widget.AppCompat.Spinner">
</android.support.v7.widget.AppCompatSpinner>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Tag2:"
android:layout_marginTop="8dp"
android:layout_marginStart="7dp"
android:layout_marginLeft="7dp"
android:textSize="16sp"/>
<android.support.v7.widget.AppCompatSpinner
android:id="@+id/tag2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:layout_marginBottom="16dp"
android:entries="@array/list2"
style="@style/Base.Widget.AppCompat.Spinner">
</android.support.v7.widget.AppCompatSpinner>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Tag3:"
android:layout_marginTop="8dp"
android:layout_marginStart="7dp"
android:layout_marginLeft="7dp"
android:textSize="16sp"/>
<android.support.v7.widget.AppCompatSpinner
android:id="@+id/tag3"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:layout_marginBottom="16dp"
android:entries="@array/list3"
style="@style/Base.Widget.AppCompat.Spinner">
</android.support.v7.widget.AppCompatSpinner>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Tag4:"
android:layout_marginTop="8dp"
android:layout_marginStart="7dp"
android:layout_marginLeft="7dp"
android:textSize="16sp"/>
<android.support.v7.widget.AppCompatSpinner
android:id="@+id/tag4"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="8dp"
android:layout_marginBottom="25dp"
android:entries="@array/list4"
style="@style/Base.Widget.AppCompat.Spinner">
</android.support.v7.widget.AppCompatSpinner>
<android.support.v7.widget.AppCompatButton
android:id="@+id/btnP"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Text"
android:layout_gravity="end|right"/>
</LinearLayout>
</android.support.v7.widget.CardView>
</RelativeLayout>
这里是strings.xml：
<array name="list1">
<item>11</item>
<item>22</item>
<item>33</item>
</array>
<array name="list2">
<item>a</item>
<item>b</item>
<item>c</item>
</array>
<array name="list3">
<item>A</item>
<item>B</item>
<item>C</item>
</array>
<array name="list4">
<item>2</item>
<item>3</item>
<item>4</item>
<item>5</item>
<item>6</item>
<item>7</item>
<item>8</item>
<item>9</item>
<item>10</item>
<item>11</item>
<item>12</item>
</array>
此外，logcat没有显示错误所在的行！
这是logcat显示的内容：
FATAL EXCEPTION: main
Process: com.app.myapp, PID: 18035
java.lang.NullPointerException: Attempt to invoke virtual method
java.lang.String java.lang.Object.toString()' on a null object reference
at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:394)
at android.widget.ArrayAdapter.getView(ArrayAdapter.java:362)
at android.widget.AbsSpinner.onMeasure(AbsSpinner.java:197)
at android.widget.Spinner.onMeasure(Spinner.java:507)
at android.support.v7.widget.AppCompatSpinner.onMeasure(AppCompatSpinner.java:416)
at android.view.View.measure(View.java:17438)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5464)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:17438)at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5464)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at android.support.v7.widget.CardView.onMeasure(CardView.java:211)at android.view.View.measure(View.java:17438)
at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:728)
at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:464)
at android.view.View.measure(View.java:17438)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5464)
at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:706)
at android.support.design.widget.HeaderScrollingViewBehavior.onMeasureChild(HeaderScrollingViewBehavior.java:90)
at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onMeasureChild(AppBarLayout.java:1364)
at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:771)
at android.view.View.measure(View.java:17438)at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5464)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)
at android.view.View.measure(View.java:17438)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5464)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:17438)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5464)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at android.view.View.measure(View.java:17438)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5464)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:17438)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5464)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2678)
at android.view.View.measure(View.java:17438)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2034)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1191)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1398)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1079)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5839)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:836)
at android.view.Choreographer.doCallbacks(Choreographer.java:635)
at android.view.Choreographer.doFrame(Choreographer.java:601)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:822)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at and
这里出了什么问题？
请告诉我。