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

Question

我按照谷歌doc 关于定位服务开发了一个示例应用程序。 运行它时，我发现 MainActivity 类崩溃，但如果我删除位置回调 GooglePlayServicesClient.ConnectionCallbacks 和 GooglePlayServicesClient.OnConnectionFailedListener 的实现，它就会启动。

我使用的是 Android Studio，我很确定我已经很好地配置了 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)
    [...]

Answer 1

确保此 Extras 文件夹中的软件包已安装或更新到较新版本的 sdk，例如（Google Play 服务、Google 存储库等）