地理codeR初始化失败

问题描述

我想申报地理codeR在我的应用程序时，得到一个NullPointerException异常。我有以下声明：

I am getting a NullPointerException when trying to declare the Geocoder in my application. I have the following declaration :

public class MainActivity extends Activity {

private Geocoder geocoder = new Geocoder(this, Locale.getDefault());

    ...
 }

我得到以下LogCat中：

I get the following LogCat :

03-20 10:48:55.729: D/AndroidRuntime(604): Shutting down VM
03-20 10:48:55.729: W/dalvikvm(604): threadid=1: thread exiting with uncaught exception

(group=0x40a71930)
03-20 10:48:56.209: E/AndroidRuntime(604): FATAL EXCEPTION: main
03-20 10:48:56.209: E/AndroidRuntime(604): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.coord/com.example.coord.MainActivity}: java.lang.NullPointerException
03-20 10:48:56.209: E/AndroidRuntime(604):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
03-20 10:48:56.209: E/AndroidRuntime(604):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
03-20 10:48:56.209: E/AndroidRuntime(604):  at android.app.ActivityThread.access$600(ActivityThread.java:141)
03-20 10:48:56.209: E/AndroidRuntime(604):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
03-20 10:48:56.209: E/AndroidRuntime(604):  at android.os.Handler.dispatchMessage(Handler.java:99)
03-20 10:48:56.209: E/AndroidRuntime(604):  at android.os.Looper.loop(Looper.java:137)
03-20 10:48:56.209: E/AndroidRuntime(604):  at android.app.ActivityThread.main(ActivityThread.java:5041)
03-20 10:48:56.209: E/AndroidRuntime(604):  at java.lang.reflect.Method.invokeNative(Native Method)
03-20 10:48:56.209: E/AndroidRuntime(604):  at java.lang.reflect.Method.invoke(Method.java:511)
03-20 10:48:56.209: E/AndroidRuntime(604):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
03-20 10:48:56.209: E/AndroidRuntime(604):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
03-20 10:48:56.209: E/AndroidRuntime(604):  at dalvik.system.NativeStart.main(Native Method)
03-20 10:48:56.209: E/AndroidRuntime(604): Caused by: java.lang.NullPointerException
03-20 10:48:56.209: E/AndroidRuntime(604):  at android.content.ContextWrapper.getApplicationContext(ContextWrapper.java:109)
03-20 10:48:56.209: E/AndroidRuntime(604):  at com.example.coord.MainActivity.<init>(MainActivity.java:21)
03-20 10:48:56.209: E/AndroidRuntime(604):  at java.lang.Class.newInstanceImpl(Native Method)
03-20 10:48:56.209: E/AndroidRuntime(604):  at java.lang.Class.newInstance(Class.java:1319)
03-20 10:48:56.209: E/AndroidRuntime(604):  at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
03-20 10:48:56.209: E/AndroidRuntime(604):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)

21号线是我的缘codeR声明。有什么不对我的code？

Line 21 is my Geocoder declaration. What is wrong with my code?

推荐答案

在活动启动，所以你不能初始化类体地缘codeR的上下文才可用。尝试在OnCreate或onResume方法来初始化它，而不是...

The context is only available when the activity is started so you cannot initialize the geocoder in the class body. Try to initialize it in the onCreate or onResume method instead...

public class MainActivity extends Activity {
  private Geocoder mGeocoder;

  @Override
  protected void onCreate(Bundle _icicle) {
    super.onCreate(_icicle);
    mGeocoder = new Geocoder(getApplicationContext(), Locale.getDefault());
  }
}

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