每当我尝试运行我的 android 应用程序时，我都会继续收到此错误并崩溃。它应该检索当前的 gps 位置并更新一个名为 log 的数据活动的文本视图。
07-02 09:28:40.978 27682-27682/? W / dalvikvm：threadid = 1：线程退出未捕获的异常（组= 0x416aeba8）07-02 09：28：40.978 27682-27682 /？E/AndroidRuntime：致命异常：主进程：com.novakinc.novak，PID：27682 java.lang.NullPointerException at com.novakinc.novak.MainActivity$1.onLocationChanged(MainActivity.java:52) at android.location.LocationManager$ListenerTransport ._handleMessage(LocationManager.java:279) 在 android.location.LocationManager$ListenerTransport.access$000(LocationManager.java:
AndroidManifest.xml：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.novakinc.novak">
<uses-permission android:name="android.permission.ACCESS_COARSE_INTERNET" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".help" />
<activity android:name=".about" />
<activity android:name=".data"></activity>
</application>
</manifest>
MainActivity.java ：
package com.novakinc.novak;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Build;
import android.os.Bundle;
import android.provider.Settings;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.ActivityCompat;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
private LocationManager locationManager;
private LocationListener listener;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
listener = new LocationListener() {
@Override
public void onLocationChanged(Location location) {
data.log.append("\n " + location.getLongitude() + " " + location.getLatitude());
}
@Override
public void onStatusChanged(String s, int i, Bundle bundle) {
}
@Override
public void onProviderEnabled(String s) {
}
@Override
public void onProviderDisabled(String s) {
Intent i = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivity(i);
}
};
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
requestPermissions(new String[] {Manifest.permission.ACCESS_COARSE_LOCATION,Manifest.permission.ACCESS_FINE_LOCATION,Manifest.permission.INTERNET}
,10);
}
return;
}
// this code won't execute IF permissions are not allowed, because in the line above there is return statement.
locationManager.requestLocationUpdates("gps", 5000, 0, listener);
}
//---------------------------------------Menu---------------------------------------------------
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu, menu);
return true;
}
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.about:
startActivity(new Intent(this, about.class));
return true;
case R.id.help:
startActivity(new Intent(this, help.class));
return true;
case R.id.data:
startActivity(new Intent(this, data.class));
return true;
default:
return super.onOptionsItemSelected(item);
}
}
//---------------------------------------End Menu-----------------------------------------------
}
数据.java：
package com.novakinc.novak;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;
public class data extends AppCompatActivity {
public static TextView log;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_data);
log = (TextView) findViewById(R.id.textView);
}
}