我开发了一个简单的 mapActivity，它要求用户通过使用对话框警报和定位服务的意图来检查他是否启用了 gps 系统。如果启用了 gps，它会直接进入 mapView，但这不会发生在我身上。当我按下去地图视图时，它让我强制关闭。
这是对话框代码：
public void onClick(View arg0) {
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(
context);
// set title
alertDialogBuilder.setTitle("Your Title");
// set dialog message
alertDialogBuilder
.setMessage("Click yes TO ENABLE GPS")
.setCancelable(false)
.setPositiveButton("Yes",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,
int id) {
// if this button is clicked, close
// current activity
Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivityForResult(intent, 1);
}
})
.setNegativeButton("No",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,
int id) {
// if this button is clicked, just close
// the dialog box and do nothing
//dialog.cancel();
Intent intent = new Intent(MainActivity.this, AndroidGoogleMapsActivity.class);
context.startActivity(intent);
}
});
// create alert dialog
AlertDialog alertDialog = alertDialogBuilder.create();
// show it
alertDialog.show();
}
});
}
这是清单文件：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.mkyong.android"
android:versionCode="1"
android:versionName="1.0" ><uses-sdk android:minSdkVersion="8" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name" >
<uses-library
android:name="com.google.android.maps"
android:required="true" />
<activity
android:name=".MainActivity"
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=".AndroidGoogleMapsActivity" >
</activity>
</application>
</manifest>
这是 AndroidGoogleMapsActivity 类的代码
公共类 AndroidGoogleMapsActivity 扩展 MapActivity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// Displaying Zooming controls
MapView mapView = (MapView) findViewById(R.id.mapView);
Log.d("error", "the negative button befor the line 27 ");
mapView.setBuiltInZoomControls(true);
Log.d("error", "the negative button after the line 27 befor the map view settings ");
mapView.setSatellite(true); // Satellite View
Log.d("error", "the negative button after the line 27 after satellite view ");
mapView.setStreetView(false); // Street View
Log.d("error", "the negative button after the line 27 after street view ");
mapView.setTraffic(true); // Traffic view
Log.d("error", "the negative button after the line 27 after the map view settings ");
MapController mc = mapView.getController();
Log.d("error", "the negative button after the line 27 after the mapController ");
double lat = Double.parseDouble("33.823862");// kehale
double lon = Double.parseDouble("35.590248");// kehale
GeoPoint geoPoint = new GeoPoint((int)(lat * 1E6), (int)(lon * 1E6));
mc.animateTo(geoPoint);
mc.setZoom(15);
mapView.invalidate();
Log.d("error", "the negative button befor the GeoPoint");
@Override
protected boolean isRouteDisplayed() {
return false;
}
}
这是我得到的错误：
09-20 05:16:22.512: D/AndroidRuntime(309): Shutting down VM
09-20 05:16:22.512: W/dalvikvm(309): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
09-20 05:16:22.543: E/AndroidRuntime(309): FATAL EXCEPTION: main
09-20 05:16:22.543: E/AndroidRuntime(309): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mkyong.android/com.mkyong.android.AndroidGoogleMapsActivity}: java.lang.NullPointerException
09-20 05:16:22.543: E/AndroidRuntime(309): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
09-20 05:16:22.543: E/AndroidRuntime(309): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
09-20 05:16:22.543: E/AndroidRuntime(309): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
09-20 05:16:22.543: E/AndroidRuntime(309): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
09-20 05:16:22.543: E/AndroidRuntime(309): at android.os.Handler.dispatchMessage(Handler.java:99)
09-20 05:16:22.543: E/AndroidRuntime(309): at android.os.Looper.loop(Looper.java:123)
09-20 05:16:22.543: E/AndroidRuntime(309): at android.app.ActivityThread.main(ActivityThread.java:4627)
09-20 05:16:22.543: E/AndroidRuntime(309): at java.lang.reflect.Method.invokeNative(Native Method)
09-20 05:16:22.543: E/AndroidRuntime(309): at java.lang.reflect.Method.invoke(Method.java:521)
09-20 05:16:22.543: E/AndroidRuntime(309): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
09-20 05:16:22.543: E/AndroidRuntime(309): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
09-20 05:16:22.543: E/AndroidRuntime(309): at dalvik.system.NativeStart.main(Native Method)
09-20 05:16:22.543: E/AndroidRuntime(309): Caused by: java.lang.NullPointerException
09-20 05:16:22.543: E/AndroidRuntime(309): at com.mkyong.android.AndroidGoogleMapsActivity.onCreate(AndroidGoogleMapsActivity.java:27)
09-20 05:16:22.543: E/AndroidRuntime(309): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
09-20 05:16:22.543: E/AndroidRuntime(309): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
09-20 05:16:22.543: E/AndroidRuntime(309): ... 11 more
09-20 05:16:25.141: I/Process(309): Sending signal. PID: 309 SIG: 9