如果实现GooglePlayServicesClient.ConnectionCallbacks / OnConnectionFailedListener,则找不到主活动类

我在Google 文档中介绍了一个关于位置服务的示例应用程序。 运行它我find了MainActivity类的崩溃,但是如果我删除位置callback的实现,它将启动GooglePlayServicesClient.ConnectionCallbacks和GooglePlayServicesClient.OnConnectionFailedListener。

我正在使用Android Studio,而且我确定我已经很好地configuration了Google Play服务和AVD(Nexus 7 Google API 19)。

这是主要活动:

package com.demo.app; import android.support.v7.app.ActionBarActivity; import android.support.v4.app.Fragment; import android.os.Bundle; import android.view.LayoutInflater; import android.view.Menu; import android.view.MenuItem; import android.view.View; import android.view.ViewGroup; import android.widget.ProgressBar; import android.widget.TextView; import com.google.android.gms.common.ConnectionResult; import com.google.android.gms.common.GooglePlayServicesClient; import com.google.android.gms.location.LocationClient; import com.google.android.gms.location.LocationRequest; public class MainActivity extends ActionBarActivity implements GooglePlayServicesClient.ConnectionCallbacks, GooglePlayServicesClient.OnConnectionFailedListener { // Handles to UI widgets private TextView mLatLng; private TextView mAddress; private ProgressBar mActivityIndicator; private TextView mConnectionState; private TextView mConnectionStatus; // A request to connect to Location Services private LocationRequest mLocationRequest; // Stores the current instantiation of the location client in this object private LocationClient mLocationClient; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); if (savedInstanceState == null) { getSupportFragmentManager().beginTransaction() .add(R.id.container, new PlaceholderFragment()) .commit(); } // Get handles to the UI view objects mLatLng = (TextView) findViewById(R.id.lat_lng); mAddress = (TextView) findViewById(R.id.address); mActivityIndicator = (ProgressBar) findViewById(R.id.address_progress); mConnectionState = (TextView) findViewById(R.id.text_connection_state); mConnectionStatus = (TextView) findViewById(R.id.text_connection_status); /* * Create a new location client, using the enclosing class to * handle callbacks. */ //mLocationClient = new LocationClient(this, this, this); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { // Handle action bar item clicks here. The action bar will // automatically handle clicks on the Home/Up button, so long // as you specify a parent activity in AndroidManifest.xml. int id = item.getItemId(); if (id == R.id.action_settings) { return true; } return super.onOptionsItemSelected(item); } @Override public void onConnected(Bundle bundle) { } @Override public void onDisconnected() { } @Override public void onConnectionFailed(ConnectionResult connectionResult) { } /** * A placeholder fragment containing a simple view. */ public static class PlaceholderFragment extends Fragment { public PlaceholderFragment() { } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View rootView = inflater.inflate(R.layout.fragment_main, container, false); return rootView; } } } 

例外是:

 java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.demo.app/com.demo.app.MainActivity}: java.lang.ClassNotFoundException: com.demo.app.MainActivity in loader dalvik.system.PathClassLoader[/data/app/com.demo.app- 2.apk] at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2591) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2685) at android.app.ActivityThread.access$2300(ActivityThread.java:126) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2038) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:123) at android.app.ActivityThread.main(ActivityThread.java:4633) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:521) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) at dalvik.system.NativeStart.main(Native Method) Caused by: java.lang.ClassNotFoundException: com.demo.app.MainActivity in loader dalvik.system.PathClassLoader[/data/app/com.demo.app-2.apk] at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:243) at java.lang.ClassLoader.loadClass(ClassLoader.java:573) at java.lang.ClassLoader.loadClass(ClassLoader.java:532) [...] 

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