android.os.Looper对空对象引用的android.content.Context.getMainLooper（） _空对象

【android.os.Looper对空对象引用的android.content.Context.getMainLooper（）】少年乘勇气，百战过乌孙。这篇文章主要讲述android.os.Looper对空对象引用的android.content.Context.getMainLooper（）相关的知识，希望能为你提供帮助。
我正在关注tutorial学习使用谷歌地图，但我一直在收到错误。这是教程的链接：
注意：在真实设备上进行测试。 HUAWEI TIT-U02 android 5.1 API 22
这是我得到的错误。

E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.android.tw_location, PID: 24183 java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.android.tw_location/com.example.android.tw_location.MapsActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.os.Looper android.content.Context.getMainLooper()' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2444) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2619) at android.app.ActivityThread.access$700(ActivityThread.java:183) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1485) at android.os.Handler.dispatchMessage(Handler.java:111) at android.os.Looper.loop(Looper.java:194) at android.app.ActivityThread.main(ActivityThread.java:5668) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:963) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:758) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.os.Looper android.content.Context.getMainLooper()' on a null object reference at android.content.ContextWrapper.getMainLooper(ContextWrapper.java:101) at com.google.android.gms.common.api.GoogleApiClient$Builder.< init> (Unknown Source) at com.example.android.tw_location.MapsActivity.< init> (MapsActivity.java:46) at java.lang.reflect.Constructor.newInstance(Native Method) at java.lang.Class.newInstance(Class.java:1606) at android.app.Instrumentation.newActivity(Instrumentation.java:1071) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2434) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2619) at android.app.ActivityThread.access$700(ActivityThread.java:183) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1485) at android.os.Handler.dispatchMessage(Handler.java:111) at android.os.Looper.loop(Looper.java:194) at android.app.ActivityThread.main(ActivityThread.java:5668) 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:963) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:758)

这是MapsActivity.Java

package com.example.android.tw_location; import android.content.pm.PackageManager; import android.location.Location; import android.os.Build; import android.support.v4.app.ActivityCompat; import android.support.v4.app.FragmentActivity; import android.os.Bundle; import android.support.v4.content.ContextCompat; import android.widget.Toast; import com.google.android.gms.common.ConnectionResult; import com.google.android.gms.common.api.GoogleApiClient; import com.google.android.gms.drive.Drive; import com.google.android.gms.location.LocationListener; import com.google.android.gms.location.LocationRequest; import com.google.android.gms.location.LocationServices; import com.google.android.gms.maps.CameraUpdateFactory; import com.google.android.gms.maps.GoogleMap; import com.google.android.gms.maps.OnMapReadyCallback; import com.google.android.gms.maps.SupportMapFragment; import com.google.android.gms.maps.model.BitmapDescriptorFactory; import com.google.android.gms.maps.model.LatLng; import com.google.android.gms.maps.model.Marker; import com.google.android.gms.maps.model.MarkerOptions; public class MapsActivity extends FragmentActivity implements OnMapReadyCallback, GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener, LocationListener{private GoogleMap mMap; Location mLastLocation; Marker mCurrLocationMarker; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_maps); // Obtain the SupportMapFragment and get notified when the map is ready to be used. SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager() .findFragmentById(R.id.map); mapFragment.getMapAsync(this); }GoogleApiClient mGoogleApiClient = new GoogleApiClient.Builder(this) .enableAutoManage(this /* FragmentActivity */, this /* OnConnectionFailedListener */) .addApi(Drive.API) .addScope(Drive.SCOPE_FILE) .setAccountName("aymanshaltut@gmail.com") .build(); /** * Manipulates the map once available. * This callback is triggered when the map is ready to be used. * This is where we can add markers or lines, add listeners or move the camera. In this case, * we just add a marker near Sydney, Australia. * If Google Play services is not installed on the device, the user will be prompted to install * it inside the SupportMapFragment. This method will only be triggered once the user has * installed Google Play services and returned to the app. */ @Override public void onMapReady(GoogleMap googleMap) { mMap = googleMap; // Add a marker in Sydney and move the camera LatLng sydney = new LatLng(-34, 151); mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney")); mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney)); mMap = googleMap; mMap.setMapType(GoogleMap.MAP_TYPE_HYBRID); //Initialize Google Play Services if (android.os.Build.VERSION.SDK_INT > = Build.VERSION_CODES.M) { if (ContextCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) { buildGoogleApiClient(); mMap.setMyLocationEnabled(true); } } else { buildGoogleApiClient(); mMap.setMyLocationEnabled(true); } }protected synchronized void buildGoogleApiClient() { mGoogleApiClient = new GoogleApiClient.Builder(this) .addConnectionCallbacks(this) .addOnConnectionFailedListener(this) .addApi(LocationServices.API) .build(); mGoogleApiClient.connect(); }@Override public void onConnected( Bundle bundle) { LocationRequest mLocationRequest = new LocationRequest(); mLocationRequest.setInterval(1000); mLocationRequest.setFastestInterval(1000); mLocationRequest.setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY); if (ContextCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) { LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this); }}@Override public void onConnectionSuspended(int i) {}@Override public void onConnectionFailed( ConnectionResult connectionResult) {}@Override public void onLocationChanged(Location location) { {mLastLocation = location; if (mCurrLocationMarker != null) { mCurrLocationMarker.remove(); } //Place current location marker LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude()); MarkerOptions markerOptions = new MarkerOptions(); markerOptions.position(latLng); markerOptions.title("Current Position"); markerOptions.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_MAGENTA)); mCurrLocationMarker = mMap.addMarker(markerOptions); //move map camera mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng)); mMap.animateCamera(CameraUpdateFactory.zoomTo(11)); //stop location updates if (mGoogleApiClient != null) { LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this); } }} public static final int MY_PERMISSIONS_REQUEST_LOCATION = 99; public boolean checkLocationPermission(){ if (ContextCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {// Asking user if explanation is needed if (ActivityCompat.shouldShowRequestPermissionRationale(this, android.Manifest.permission.ACCESS_FINE_LOCATION)) {// Show an expanation to the user *asynchronously* -- don't block // this thread waiting for the user's response! After the user // sees the explanation, try again to request the permission.//Prompt the user once explanation has been shown ActivityCompat.requestPermissions(this, new String[]{android.Manifest.permission.ACCESS_FINE_LOCATION}, MY_PERMISSIONS_REQUEST_LOCATION); } else { // No explanation needed, we can request the permission. ActivityCompat.requestPermissions(this, new String[]{android.Manifest.permission.ACCESS_FINE_LOCATION}, MY_PERMISSIONS_REQUEST_LOCATION); } return false; } else { return true; } } @Override public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) { switch (requestCode) { case MY_PERMISSIONS_REQUEST_LOCATION: { // If request is cancelled, the result arrays are empty. if (grantResults.length > 0 & & grantResults[0] == PackageManager.PERMISSION_GRANTED) {// Permission was granted. if (ContextCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {if (mGoogleApiClient == null) { buildGoogleApiClient(); } mMap.setMyLocationEnabled(true); }} else {// Permission denied, Disable the functionality that depends on this permission. Toast.makeText(this, "permission denied", Toast.LENGTH_LONG).show(); } return; }// other 'case' lines to check for other permissions this app might request. //You can add here other case statements according to your requirement. } } }

这是清单

< ?xml version="1.0" encoding="utf-8"?> < manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.android.tw_location"> < !--The ACCESS_COARSE/FINE_LOCATION permissions are not required to use Google Maps Android API v2, but you must specify either coarse or fine location permissions for the 'MyLocation' functionality. --> < uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" /> < uses-permission android:name="android.permission.INTERNET" /> < uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" /> < uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/> < application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:supportsRtl="true" android:theme="@style/AppTheme"> < !-- The API key for Google Maps-based APIs is defined as a string resource. (See the file "res/values/google_maps_api.xml"). Note that the API key is linked to the encryption key used to sign the APK. You need a different API key for each encryption key, including the release key that is used to sign the APK for publishing. You can define the keys for the debug and release targets in src/debug/ and src/release/. --> < meta-data android:name="com.google.android.geo.API_KEY" android:value="https://www.songbingjia.com/android/@string/google_maps_key" /> < activity android:name=".MapsActivity" android:label="@string/title_activity_maps"> < intent-filter> < action android:name="android.intent.action.MAIN" /> < category android:name="android.intent.category.LAUNCHER" /> < /intent-filter> < /activity> < /application> < /manifest>

答案GoogleApiClient初始化应该在onCreate方法内：

GoogleApiClient mGoogleApiClient; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_maps); // Obtain the SupportMapFragment and get notified when the map is ready to be used. SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager() .findFragmentById(R.id.map); mapFragment.getMapAsync(this); mGoogleApiClient = new GoogleApiClient.Builder(this) .enableAutoManage(this /* FragmentActivity */, this /* OnConnectionFailedListener */) .addApi(Drive.API) .addScope(Drive.SCOPE_FILE) .setAccountName("aymanshaltut@gmail.com") .build(); }

另一答案尝试在空对象引用上调用虚方法android.os.Looper android.content.Context.getMainLooper()是由于传递的上下文引起的mGoogleApiClient = new GoogleApiClient.Builder(getcontext())为null，它试图通过上下文调用getMainLooper()。
检查GoogleApiClient构造函数。
方案：

@Override public void onActivityResult(int requestCode, int resultCode, Intent data) { super.onActivityResult(requestCode, resultCode, data); if (getContext() == null) { return; } }