在这段代码中发现我的错误确实很困难。被困在上面很长一段时间，很尴尬。任何发现问题的帮助都会有很大帮助。
这是抛出错误的类
package ggow.teamt.mdrs;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesClient;
import com.google.android.gms.common.GooglePlayServicesClient.ConnectionCallbacks;
import com.google.android.gms.common.GooglePlayServicesUtil;
import com.google.android.gms.location.LocationClient;
import com.google.android.gms.location.LocationListener;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.GoogleMap.OnMyLocationButtonClickListener;
import com.google.android.gms.maps.MapFragment;
import android.location.Location;
import android.os.Bundle;
import android.app.Activity;
import android.app.Dialog;
import android.content.Intent;
import android.content.IntentSender;
import android.support.v4.app.DialogFragment;
import android.support.v4.app.FragmentActivity;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.Toast;
public class MapViewActivity extends FragmentActivity
implements
GooglePlayServicesClient.ConnectionCallbacks,
GooglePlayServicesClient.OnConnectionFailedListener,
LocationListener,
OnMyLocationButtonClickListener{
private final static int
CONNECTION_FAILURE_RESOLUTION_REQUEST = 9000;
private static final String LOG_TAG = "MapView - MDRS";
private GoogleMap mMap;
private LocationClient mLocationClient;
public Location mCurrentLocation;
public final static String START_LOCATION = "ggow.teamt.mdrs.location";
@Override
protected void onCreate(Bundle savedInstanceState) {
Log.v(LOG_TAG, "into onCreate");
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_map_view);
setUpMapIfNeeded();
mLocationClient = new LocationClient(this, this, this);
mCurrentLocation = mLocationClient.getLastLocation();
Toast.makeText(this, "Current location found.",
Toast.LENGTH_SHORT).show();
Log.v(LOG_TAG, "made it to the end of onCreate");
}
@Override
protected void onStart() {
super.onStart();
Log.v(LOG_TAG, "into onStart");
// Connect the client.
mLocationClient.connect();
}
@Override
protected void onStop() {
// Disconnecting the client invalidates it.
mLocationClient.disconnect();
super.onStop();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.map_view, menu);
return true;
}
public void startRecording(View view){
Intent intent = new Intent(this, RecordingActivity.class);
intent.putExtra(START_LOCATION, mCurrentLocation);
}
private void setUpMapIfNeeded() { //would be used onResume I would assume
Log.v(LOG_TAG, "into SuMiN");
// Do a null check to confirm that we have not already instantiated the map.
if (mMap == null) {
mMap = ((MapFragment) getFragmentManager().findFragmentById(R.id.map))
.getMap();
mMap.setMyLocationEnabled(true);
mMap.getUiSettings().setCompassEnabled(true);
mMap.getUiSettings().setMyLocationButtonEnabled(true);
mMap.setMapType(GoogleMap.MAP_TYPE_HYBRID);
// Check if we were successful in obtaining the map.
if (mMap != null) {
Log.e(LOG_TAG, "Map's all good brah");
}
}
}
@Override
public boolean onMyLocationButtonClick() {
System.err.println("in onMyLocationButtonClick()");
return false;
}
@Override
public void onLocationChanged(Location arg0) {
System.err.println("in onLocChanged");
}
@SuppressWarnings("deprecation")
@Override
public void onConnectionFailed(ConnectionResult connectionResult) {
System.err.println("Connection failed");
/*
* Google Play services can resolve some errors it detects.
* If the error has a resolution, try sending an Intent to
* start a Google Play services activity that can resolve
* error.
*/
if (connectionResult.hasResolution()) {
try {
// Start an Activity that tries to resolve the error
connectionResult.startResolutionForResult(
this,
CONNECTION_FAILURE_RESOLUTION_REQUEST);
/*
* Thrown if Google Play services cancelled the original
* PendingIntent
*/
} catch (IntentSender.SendIntentException e) {
// Log the error
e.printStackTrace();
}
} else {
/*
* If no resolution is available, display a dialog to the
* user with the error.
*/
showDialog(connectionResult.getErrorCode());
}
}
/**
* Callback called when connected to GCore. Implementation of {@link ConnectionCallbacks}.
*/
@Override
public void onConnected(Bundle connectionHint) {
Toast.makeText(this, "Connected", Toast.LENGTH_SHORT).show();
}
/**
* Callback called when disconnected from GCore. Implementation of {@link ConnectionCallbacks}.
*/
@Override
public void onDisconnected() {
Toast.makeText(this, "Disconnected. Please re-connect.",
Toast.LENGTH_SHORT).show();
}
public static class ErrorDialogFragment extends DialogFragment {
// Global field to contain the error dialog
private Dialog mDialog;
// Default constructor. Sets the dialog field to null
public ErrorDialogFragment() {
super();
mDialog = null;
}
// Set the dialog to display
public void setDialog(Dialog dialog) {
mDialog = dialog;
}
// Return a Dialog to the DialogFragment.
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
return mDialog;
}
}
/*
* Handle results returned to the FragmentActivity
* by Google Play services
*/
@Override
protected void onActivityResult(
int requestCode, int resultCode, Intent data) {
// Decide what to do based on the original request code
switch (requestCode) {
case CONNECTION_FAILURE_RESOLUTION_REQUEST :
/*
* If the result code is Activity.RESULT_OK, try
* to connect again
*/
switch (resultCode) {
case Activity.RESULT_OK :
/*
* Try the request again
*/
break;
}
}
}
@SuppressWarnings("unused")
private boolean servicesConnected() {
// Check that Google Play services is available
int resultCode =
GooglePlayServicesUtil.
isGooglePlayServicesAvailable(this);
// If Google Play services is available
if (ConnectionResult.SUCCESS == resultCode) {
// In debug mode, log the status
Log.d("Location Updates",
"Google Play services is available.");
// Continue
return true;
// Google Play services was not available for some reason
} else {
// Get the error code
Dialog errorDialog = GooglePlayServicesUtil.getErrorDialog(
resultCode,
this,
CONNECTION_FAILURE_RESOLUTION_REQUEST);
// If Google Play services can provide an error dialog
if (errorDialog != null) {
// Create a new DialogFragment for the error dialog
ErrorDialogFragment errorFragment =
new ErrorDialogFragment();
// Set the dialog in the DialogFragment
errorFragment.setDialog(errorDialog);
// Show the error dialog in the DialogFragment
errorFragment.show(getSupportFragmentManager(),
"Location Updates");
}
return false;
}
}
}
这是它的 .xml 布局文件:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:map="http://schemas.android.com/apk/res-auto"
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"
tools:context=".MapViewActivity" >
<ImageButton
android:id="@+id/recButton"
android:layout_width="100dp"
android:layout_height="100dp"
android:contentDescription="@string/recButtonContentDescription"
android:onClick="startRecording" />
<fragment
android:id="@+id/map"
android:name="com.google.android.gms.maps.MapFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
class="com.google.android.gms.maps.SupportMapFragment"
/>
</RelativeLayout>
以及应用程序的 list (以防需要):
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="ggow.teamt.mdrs"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="14"
android:targetSdkVersion="19" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.STORAGE" />
<uses-permission android:name="android.permission.RECORD_AUDIO" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<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_NETWORK_STATE" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="ggow.teamt.mdrs.MapViewActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="ggow.teamt.mdrs.SettingsActivity"
android:label="@string/title_activity_settings"
android:parentActivityName="MapViewActivity" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="MapViewActivity" />
</activity>
<activity
android:name="ggow.teamt.mdrs.RecordingActivity"
android:label="@string/title_activity_recording" >
</activity>
<activity
android:name="ggow.teamt.mdrs.UploadActivity"
android:label="@string/title_activity_upload"
android:parentActivityName="MapViewActivity" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="MapViewActivity" />
</activity>
<meta-data
android:name="com.google.android.gms.version"
android:value="@integer/google_play_services_version" />
<meta-data
android:name="com.google.android.maps.v2.API_KEY"
android:value="AIzaSyAK8ETmyOtd9DZ0RvG9DjEgRnc7Ps3uHkU" />
</application>
</manifest>
这给我带来了真正的问题，我已经仔细研究过它，但似乎无法弄清楚。如有任何帮助，我们将不胜感激。
编辑: 这是堆栈跟踪。抱歉。
01-24 10:42:19.491: V/MapView - MDRS(24003): into onCreate
01-24 10:42:19.591: D/dalvikvm(24003): GC_FOR_ALLOC freed 232K, 2% free 17008K/17272K, paused 11ms, total 12ms
01-24 10:42:19.671: D/dalvikvm(24003): GC_FOR_ALLOC freed 333K, 3% free 17172K/17544K, paused 14ms, total 14ms
01-24 10:42:19.721: D/dalvikvm(24003): GC_FOR_ALLOC freed 252K, 2% free 17432K/17716K, paused 13ms, total 13ms
01-24 10:42:19.761: D/dalvikvm(24003): GC_FOR_ALLOC freed 156K, 2% free 17726K/17932K, paused 12ms, total 16ms
01-24 10:42:19.801: D/dalvikvm(24003): GC_FOR_ALLOC freed 62K, 1% free 18062K/18232K, paused 11ms, total 11ms
01-24 10:42:19.801: V/MapView - MDRS(24003): into SuMiN
01-24 10:42:19.811: E/MapView - MDRS(24003): Map's all good brah
01-24 10:42:19.811: D/AndroidRuntime(24003): Shutting down VM
01-24 10:42:19.811: W/dalvikvm(24003): threadid=1: thread exiting with uncaught exception (group=0x4158bba8)
01-24 10:42:19.811: E/AndroidRuntime(24003): FATAL EXCEPTION: main
01-24 10:42:19.811: E/AndroidRuntime(24003): Process: ggow.teamt.mdrs, PID: 24003
01-24 10:42:19.811: E/AndroidRuntime(24003): java.lang.RuntimeException: Unable to start activity ComponentInfo{ggow.teamt.mdrs/ggow.teamt.mdrs.MapViewActivity}: java.lang.IllegalStateException: Not connected. Call connect() and wait for onConnected() to be called.
01-24 10:42:19.811: E/AndroidRuntime(24003): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
01-24 10:42:19.811: E/AndroidRuntime(24003): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
01-24 10:42:19.811: E/AndroidRuntime(24003): at android.app.ActivityThread.access$800(ActivityThread.java:135)
01-24 10:42:19.811: E/AndroidRuntime(24003): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
01-24 10:42:19.811: E/AndroidRuntime(24003): at android.os.Handler.dispatchMessage(Handler.java:102)
01-24 10:42:19.811: E/AndroidRuntime(24003): at android.os.Looper.loop(Looper.java:136)
01-24 10:42:19.811: E/AndroidRuntime(24003): at android.app.ActivityThread.main(ActivityThread.java:5017)
01-24 10:42:19.811: E/AndroidRuntime(24003): at java.lang.reflect.Method.invokeNative(Native Method)
01-24 10:42:19.811: E/AndroidRuntime(24003): at java.lang.reflect.Method.invoke(Method.java:515)
01-24 10:42:19.811: E/AndroidRuntime(24003): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
01-24 10:42:19.811: E/AndroidRuntime(24003): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
01-24 10:42:19.811: E/AndroidRuntime(24003): at dalvik.system.NativeStart.main(Native Method)
01-24 10:42:19.811: E/AndroidRuntime(24003): Caused by: java.lang.IllegalStateException: Not connected. Call connect() and wait for onConnected() to be called.
01-24 10:42:19.811: E/AndroidRuntime(24003): at com.google.android.gms.internal.dk.bB(Unknown Source)
01-24 10:42:19.811: E/AndroidRuntime(24003): at com.google.android.gms.internal.fm.a(Unknown Source)
01-24 10:42:19.811: E/AndroidRuntime(24003): at com.google.android.gms.internal.fm$c.bB(Unknown Source)
01-24 10:42:19.811: E/AndroidRuntime(24003): at com.google.android.gms.internal.fl.getLastLocation(Unknown Source)
01-24 10:42:19.811: E/AndroidRuntime(24003): at com.google.android.gms.internal.fm.getLastLocation(Unknown Source)
01-24 10:42:19.811: E/AndroidRuntime(24003): at com.google.android.gms.location.LocationClient.getLastLocation(Unknown Source)
01-24 10:42:19.811: E/AndroidRuntime(24003): at ggow.teamt.mdrs.MapViewActivity.onCreate(MapViewActivity.java:47)
01-24 10:42:19.811: E/AndroidRuntime(24003): at android.app.Activity.performCreate(Activity.java:5231)
01-24 10:42:19.811: E/AndroidRuntime(24003): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
01-24 10:42:19.811: E/AndroidRuntime(24003): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
01-24 10:42:19.811: E/AndroidRuntime(24003): ... 11 more
01-24 10:42:19.971: D/dalvikvm(24003): GC_FOR_ALLOC freed 336K, 2% free 18233K/18604K, paused 10ms, total 10ms
01-24 10:42:20.031: W/ActivityThread(24003): ClassLoader.loadClass: The class loader returned by Thread.getContextClassLoader() may fail for processes that host multiple applications. You should explicitly specify a context class loader. For example: Thread.setContextClassLoader(getClass().getClassLoader());
最佳答案
您说您收到 NullPointerException，但您发布的堆栈跟踪列出了 IllegalStateException。这行可能是一条线索:
01-24 10:42:19.811: E/AndroidRuntime(24003): Caused by: java.lang.IllegalStateException: Not connected. Call connect() and wait for onConnected() to be called.
查看您的代码，似乎在您的 onCreate() 方法中您将直接请求位置:
mLocationClient = new LocationClient(this, this, this);
mCurrentLocation = mLocationClient.getLastLocation();
在调用 onConnected() 回调之前，不应调用 getLastLocation()。 The documentation is a little unclear ，但我的建议是将 getLastLocation() 调用放在 onConnected() 方法中，然后运行需要当前位置的任何逻辑。
关于java - 无法启动 Activity ... java.lang.NullPointerException，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/21330100/