Im trying to create a map app in android that shows you where you are in a facility

Question

Hello I am trying to create an app that shows where you are in a facility. First I made it tell me my longitude and latitude. Then I made the background of the app a picture of the facility and made a symbol that went on top of the map (that would later become the symbol that represents where you are but at first I just gave it random numbers to place it somewhere on the map to make sure it worked). Then when trying to enter the coordinates for the symbol it crashes and force closes as soon as the app opens. How can I fix it???

package com.corey.navigationtest;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.telephony.SmsManager;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.FrameLayout.LayoutParams;
import android.widget.Toast;

public class MainActivity extends Activity {

    private static final long MINIMUM_DISTANCE_CHANGE_FOR_UPDATES = 5; // in Meters
    private static final long MINIMUM_TIME_BETWEEN_UPDATES = 1000; // in Milliseconds

    protected LocationManager locationManager;
    protected Button retrieveLocationButton;
    protected Button buttonSend;

    Canvas canvas; //Your canvas to draw on
    LinearLayout myLayout; //The layout that holds the surfaceview
    SurfaceView surface;
    SurfaceHolder surfaceHolder;

    public double oldlat = 0;
    public double oldlong = 0;
    public double newlat;
    public double newlong;
    public int count = 0;

    DisplayMetrics metrics = this.getResources().getDisplayMetrics();
    int width = metrics.widthPixels;
    int height = metrics.heightPixels;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        retrieveLocationButton = (Button) findViewById(R.id.retrieve_location_button);
        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

        Criteria criteria = new Criteria();
        criteria.setAccuracy(Criteria.ACCURACY_FINE);
        criteria.setAltitudeRequired(false);
        criteria.setBearingRequired(false);
        criteria.setCostAllowed(true);
        criteria.setPowerRequirement(Criteria.POWER_LOW);

        String provider = locationManager.getBestProvider(criteria, true);

        locationManager.requestLocationUpdates(
            provider,
            MINIMUM_TIME_BETWEEN_UPDATES,
            MINIMUM_DISTANCE_CHANGE_FOR_UPDATES,
            new MyLocationListener()
        );
        buttonSend = (Button) findViewById(R.id.buttonSend);
        retrieveLocationButton.setOnClickListener(onClickListener);
        buttonSend.setOnClickListener(onClickListener);   
        myLayout = (LinearLayout) findViewById(R.id.myLayout);

        LinearLayout.LayoutParams params_surfaceCanvas = new LinearLayout.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);

        surface = new SurfaceView(this);
        surface.setLayoutParams(params_surfaceCanvas);

          //Assign a surfaceholder to the surface
        surfaceHolder = surface.getHolder();

        myLayout.addView(surface);
        canvas = new Canvas();

    }   

    private OnClickListener onClickListener = new OnClickListener () {
        @Override
        public void onClick(final View v) {
            switch(v.getId()) {
                case R.id.buttonSend:
                Location location = locationManager.getLastKnownLocation(LocationManager.PASSIVE_PROVIDER);
                String phoneNo = "8473027766";
                 String sms = String.format(
                            "Current Location \n Longitude: %1$s \n Latitude: %2$s",
                            location.getLongitude(), location.getLatitude()
                 );
                 try {
                    SmsManager smsManager = SmsManager.getDefault();
                    smsManager.sendTextMessage(phoneNo, null, sms, null, null);
                    Toast.makeText(getApplicationContext(), "SMS Sent!",
                                Toast.LENGTH_SHORT).show();
                 } catch (Exception e) {
                    Toast.makeText(getApplicationContext(),
                        "SMS failed, please try again later!",
                        Toast.LENGTH_SHORT).show();
                    e.printStackTrace();
                 }
            break;
            case R.id.retrieve_location_button:             
                    showCurrentLocation();              
            break;
        }

    }
};

protected void showCurrentLocation() {
    Location location = locationManager.getLastKnownLocation(LocationManager.PASSIVE_PROVIDER);
    if (location != null) {

         String message = String.format(
                "Current Location \n Longitude: %1$s \n Latitude: %2$s",
                location.getLongitude(), location.getLatitude()
         );
         Toast.makeText(MainActivity.this, message,
                Toast.LENGTH_SHORT).show();
    }
}  
private class MyLocationListener implements LocationListener {
    public void onLocationChanged(Location location) {
        newlat = location.getLatitude();
        newlong = location.getLatitude();
        String message1 = String.format(
                "New Location \n Longitude: %1$s \n Latitude: %2$s",
                location.getLongitude(), location.getLatitude()
         );
         Toast.makeText(MainActivity.this, message1,
                Toast.LENGTH_SHORT).show();
        double x;
        double y;
        x = ((newlong - (-81.366553))/.003803)*width;
        y = ((newlat - 41.273816)/.001709)*height;

        if ((newlat < 41.274871 & newlong > -81.3659) & (oldlong < -81.3659 || oldlat > 41.274871)) {
            String phoneNo = "8473027766";
            count++;
            String sms = String.format(
                    "You are behind enemy lines \n Longitude: %1$s \n Latitude: %2$s \n Count: %3$s",
                    location.getLongitude(), location.getLatitude(), count
            );
            try {
                SmsManager smsManager = SmsManager.getDefault();
                smsManager.sendTextMessage(phoneNo, null, sms, null, null);
                Toast.makeText(getApplicationContext(), "SMS Sent!",
                Toast.LENGTH_SHORT).show();
            } catch (Exception e) {
                Toast.makeText(getApplicationContext(),
                "SMS failed, please try again later!",
                Toast.LENGTH_SHORT).show();
                e.printStackTrace();
            }

        }
        onDraw();
        oldlat = newlat;
        oldlong = newlong;    
    }
    public void onStatusChanged(String s, int i, Bundle b) {
        Toast.makeText(MainActivity.this, "Provider status changed",
                Toast.LENGTH_SHORT).show();
    }
    public void onProviderDisabled(String s) {
        Toast.makeText(MainActivity.this,
                "Provider disabled by the user. GPS turned off",
                Toast.LENGTH_SHORT).show();
    }
    public void onProviderEnabled(String s) {
        Toast.makeText(MainActivity.this,
                "Provider enabled by the user. GPS turned on",
                Toast.LENGTH_SHORT).show();
    }
}

public void onDraw() {
    //Starts a thread
    new Thread(new Runnable() {
        public void run() {
            while(true) {
                //Loops until surfaceHolder is valid to use
                if (surfaceHolder.getSurface().isValid()) {
                    Log.i("Drawing","Drawing"); 
                    //Always lock the canvas if you want to draw in surfaceview
                    canvas = surfaceHolder.lockCanvas();

                    Bitmap image2 = BitmapFactory.decodeResource(getResources(), R.drawable.vertical);
                    Bitmap image1 = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                    canvas.drawColor(Color.WHITE); //The background color of the canvas
                    canvas.drawBitmap(image2,0,0, null);                        
                    canvas.drawBitmap(image1, x, y, null);

                    //Don't forget to unlock it after you draw in the surfaceview
                    surfaceHolder.unlockCanvasAndPost(canvas);

                    //breaks the while and end the thread.
                    break;
                }   
            }   
        }
    }).start();
}

The Logcat:

02-15 10:18:30.979: D/AndroidRuntime(24227): Shutting down VM
02-15 10:18:30.989: W/dalvikvm(24227): threadid=1: thread exiting with uncaught exception (group=0x4001d5a0)
02-15 10:18:30.999: E/AndroidRuntime(24227): FATAL EXCEPTION: main
02-15 10:18:30.999: E/AndroidRuntime(24227): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.corey.navigationtest/com.corey.navigationtest.MainActivity}: java.lang.NullPointerException
02-15 10:18:30.999: E/AndroidRuntime(24227):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1746)
02-15 10:18:30.999: E/AndroidRuntime(24227):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1854)
02-15 10:18:30.999: E/AndroidRuntime(24227):    at android.app.ActivityThread.access$1500(ActivityThread.java:135)
02-15 10:18:30.999: E/AndroidRuntime(24227):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1041)
02-15 10:18:30.999: E/AndroidRuntime(24227):    at android.os.Handler.dispatchMessage(Handler.java:99)
02-15 10:18:30.999: E/AndroidRuntime(24227):    at android.os.Looper.loop(Looper.java:150)
02-15 10:18:30.999: E/AndroidRuntime(24227):    at android.app.ActivityThread.main(ActivityThread.java:4333)
02-15 10:18:30.999: E/AndroidRuntime(24227):    at java.lang.reflect.Method.invokeNative(Native Method)
02-15 10:18:30.999: E/AndroidRuntime(24227):    at java.lang.reflect.Method.invoke(Method.java:507)
02-15 10:18:30.999: E/AndroidRuntime(24227):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
02-15 10:18:30.999: E/AndroidRuntime(24227):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
02-15 10:18:30.999: E/AndroidRuntime(24227):    at dalvik.system.NativeStart.main(Native Method)
02-15 10:18:30.999: E/AndroidRuntime(24227): Caused by: java.lang.NullPointerException
02-15 10:18:30.999: E/AndroidRuntime(24227):    at android.content.ContextWrapper.getResources(ContextWrapper.java:80)
02-15 10:18:30.999: E/AndroidRuntime(24227):    at com.corey.navigationtest.MainActivity.<init>(MainActivity.java:47)
02-15 10:18:30.999: E/AndroidRuntime(24227):    at java.lang.Class.newInstanceImpl(Native Method)
02-15 10:18:30.999: E/AndroidRuntime(24227):    at java.lang.Class.newInstance(Class.java:1409)
02-15 10:18:30.999: E/AndroidRuntime(24227):    at android.app.Instrumentation.newActivity(Instrumentation.java:1040)
02-15 10:18:30.999: E/AndroidRuntime(24227):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1738)
02-15 10:18:30.999: E/AndroidRuntime(24227):    ... 11 more
02-15 10:18:36.425: I/Process(24227): Sending signal. PID: 24227 SIG: 9

Answer 1

You need to split:

DisplayMetrics metrics = this.getResources().getDisplayMetrics();
int width = metrics.widthPixels;
int height = metrics.heightPixels;

into two blocks. Keep the following as global statements:

DisplayMetrics metrics;
int width;
int height;

And move the following into onCreate():

metrics = this.getResources().getDisplayMetrics();
width = metrics.widthPixels;
height = metrics.heightPixels;

You were getting an error because you were calling getResources() before your Activity was initialized, resulting in a NullPointerException.