尝试使用Here SDK创建简单的MapFragment时出现此错误。我从他们的网站上获取了大部分代码，但我在mapFragment.init()行上得到了一个空引用。起初我认为认证是错误的，但我在manifest检查过几次并且看起来都很好。
我正在使用免费的基本版本，如果这有所作为。
MainActivity.java
package com.parallel.parallel;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import android.Manifest;
import android.app.Activity;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.widget.TextView;
import android.widget.Toast;
import android.util.Log;
import com.here.android.mpa.common.GeoCoordinate;
import com.here.android.mpa.common.OnEngineInitListener;
import com.here.android.mpa.mapping.Map;
import com.here.android.mpa.mapping.MapFragment;
public class MainActivity extends Activity {
private static final String LOG_TAG = MainActivity.class.getSimpleName();
// permissions request code
private final static int REQUEST_CODE_ASK_PERMISSIONS = 1;
/**
* Permissions that need to be explicitly requested from end user.
*/
private static final String[] REQUIRED_SDK_PERMISSIONS = new String[]{
Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.WRITE_EXTERNAL_STORAGE};
// map embedded in the map fragment
private Map map = null;
// map fragment embedded in this activity
private MapFragment mapFragment = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
checkPermissions();
}
private void initialize(){
setContentView(R.layout.activity_main);
// Search for the map fragment to finish setup by calling init().
mapFragment = (MapFragment) getFragmentManager().findFragmentById(R.id.mapfragment);
mapFragment.init(new OnEngineInitListener() {
@Override
public void onEngineInitializationCompleted(OnEngineInitListener.Error error) {
if (error == OnEngineInitListener.Error.NONE) {
// retrieve a reference of the map from the map fragment
map = mapFragment.getMap();
// Set the map center to the Vancouver region (no animation)
map.setCenter(new GeoCoordinate(49.196261, -123.004773, 0.0),
Map.Animation.NONE);
// Set the zoom level to the average between min and max
map.setZoomLevel((map.getMaxZoomLevel() + map.getMinZoomLevel()) / 2);
} else {
Log.e(LOG_TAG, "Cannot initialize MapFragment (" + error + ")");
}
}
});
}
protected void checkPermissions() {
final List<String> missingPermissions = new ArrayList<String>();
// check all required dynamic permissions
for (final String permission : REQUIRED_SDK_PERMISSIONS) {
final int result = ContextCompat.checkSelfPermission(this, permission);
if (result != PackageManager.PERMISSION_GRANTED) {
missingPermissions.add(permission);
}
}
if (!missingPermissions.isEmpty()) {
// request all missing permissions
final String[] permissions = missingPermissions
.toArray(new String[missingPermissions.size()]);
ActivityCompat.requestPermissions(this, permissions, REQUEST_CODE_ASK_PERMISSIONS);
} else {
final int[] grantResults = new int[REQUIRED_SDK_PERMISSIONS.length];
Arrays.fill(grantResults, PackageManager.PERMISSION_GRANTED);
onRequestPermissionsResult(REQUEST_CODE_ASK_PERMISSIONS, REQUIRED_SDK_PERMISSIONS,
grantResults);
}
}
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String permissions[],
@NonNull int[] grantResults) {
switch (requestCode) {
case REQUEST_CODE_ASK_PERMISSIONS:
for (int index = permissions.length - 1; index >= 0; --index) {
if (grantResults[index] != PackageManager.PERMISSION_GRANTED) {
// exit the app if one permission is not granted
Toast.makeText(this, "Required permission '" + permissions[index]
+ "' not granted, exiting", Toast.LENGTH_LONG).show();
finish();
return;
}
}
// all permissions were granted
initialize();
break;
}
}
}
文件的布局：
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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"
tools:context=".MainActivity">
<fragment
android:id="@+id/mapfragment"
class="com.here.android.mpa.mapping.MapFragment"
android:layout_width="fill_parent"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>
堆栈跟踪：
06-08 21:06:22.767 5079-5079/com.parallel.parallel E/InputEventReceiver: Exception dispatching input event.
06-08 21:06:22.767 5079-5079/com.parallel.parallel E/MessageQueue-JNI: Exception in MessageQueue callback: handleReceiveCallback
06-08 21:06:22.768 5079-5079/com.parallel.parallel E/MessageQueue-JNI: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.view.GestureDetector.onTouchEvent(android.view.MotionEvent)' on a null object reference
at com.here.android.mpa.internal.bs.onTouchEvent(MapViewImpl.java:300)
at android.view.View.dispatchTouchEvent(View.java:11725)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2955)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2636)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2961)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2593)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2961)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2593)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2961)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2593)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2961)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2593)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2961)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2593)
at com.android.internal.policy.DecorView.superDispatchTouchEvent(DecorView.java:445)
at com.android.internal.policy.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1828)
at android.app.Activity.dispatchTouchEvent(Activity.java:3292)
at com.android.internal.policy.DecorView.dispatchTouchEvent(DecorView.java:407)
at android.view.View.dispatchPointerEvent(View.java:11964)
at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4776)
at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:4590)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4128)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4181)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4147)
at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:4274)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4155)
at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:4331)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4128)
at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4181)
at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4147)
at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4155)
at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4128)
at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:6642)
at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:6616)
at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:6577)
at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:6745)
at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:185)
at android.os.MessageQueue.nativePollOnce(Native Method)
at android.os.MessageQueue.next(MessageQueue.java:325)
at android.os.Looper.loop(Looper.java:142)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)