Question

Working with SharedPreferences, this activity crashes upon launching. First I’ll post the activity code, and then I’ll post my LogCat. Thank you so much guys, you guys are always such big help! 🙂

Activity Code;

package com.creativecoders.gymbuddy;

import com.creativecoders.gymbuddy.R;

import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.EditText;
import android.widget.TextView;

public class Benchmark extends Activity {

public static final String GB_PREFERENCES_BENCH = "Bench";
public static final String GB_PREFERENCES_FLIES = "Flies";

SharedPreferences settings = getSharedPreferences("gBValues", 
     Context.MODE_PRIVATE);

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_benchmark);
    }

public void onStart() {
    super.onStart();

    findViewById(R.id.button5).setOnClickListener(new handleButton5());

}

class handleButton5 implements OnClickListener {
    public void onClick(View v) {

        EditText editText1 = (EditText)findViewById(R.id.editText1);
        String sWeight = editText1.getText().toString();
        final double dWeight = Double.parseDouble(sWeight);

        EditText editText2 = (EditText)findViewById(R.id.editText2);
        String sPush = editText2.getText().toString();
        final double dPush = Double.parseDouble(sPush);

        EditText editText3 = (EditText)findViewById(R.id.editText3);
        String sSit = editText3.getText().toString();
        final double dSit = Double.parseDouble(sSit);

        EditText editText4 = (EditText)findViewById(R.id.editText4);
        String sPull = editText4.getText().toString();
        final double dPull = Double.parseDouble(sPull);

        double dBench = (((Math.floor(dWeight*.0664))*10)-10)+dPush;
        double dFlies = (Math.floor(((Math.floor(dBench*.6)/10)*10)));

        int iBench = (int)dBench;
        int iFlies = (int)dFlies;

        String sBench = "" + iBench;
        String sFlies = "" + iFlies;

        SharedPreferences.Editor editor1 = settings.edit();
        editor1.putString(GB_PREFERENCES_BENCH, sBench);
        editor1.commit();

        SharedPreferences.Editor editor2 = settings.edit();
        editor2.putString(GB_PREFERENCES_FLIES, sFlies);
        editor2.commit();

        TextView TextView1 = (TextView)findViewById(R.id.textView1);
        TextView1.setText(String.valueOf("Bench Press "+ iBench +" lbs"));

        TextView TextView2 = (TextView)findViewById(R.id.textView2);
        TextView2.setText(String.valueOf("Bar Curls "+ iCurls +" lbs"));
        }
    }

}

Here’s my LogCat;

09-28 21:18:52.636: E/AndroidRuntime(686): FATAL EXCEPTION: main
09-28 21:18:52.636: E/AndroidRuntime(686): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.creativecoders.gymbuddy/com.creativecoders.gymbuddy.Benchmark}: java.lang.NullPointerException
09-28 21:18:52.636: E/AndroidRuntime(686):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1879)
09-28 21:18:52.636: E/AndroidRuntime(686):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
09-28 21:18:52.636: E/AndroidRuntime(686):  at android.app.ActivityThread.access$600(ActivityThread.java:122)
09-28 21:18:52.636: E/AndroidRuntime(686):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
09-28 21:18:52.636: E/AndroidRuntime(686):  at android.os.Handler.dispatchMessage(Handler.java:99)
09-28 21:18:52.636: E/AndroidRuntime(686):  at android.os.Looper.loop(Looper.java:137)
09-28 21:18:52.636: E/AndroidRuntime(686):  at android.app.ActivityThread.main(ActivityThread.java:4340)
09-28 21:18:52.636: E/AndroidRuntime(686):  at java.lang.reflect.Method.invokeNative(Native Method)
09-28 21:18:52.636: E/AndroidRuntime(686):  at java.lang.reflect.Method.invoke(Method.java:511)
09-28 21:18:52.636: E/AndroidRuntime(686):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
09-28 21:18:52.636: E/AndroidRuntime(686):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
09-28 21:18:52.636: E/AndroidRuntime(686):  at dalvik.system.NativeStart.main(Native Method)
09-28 21:18:52.636: E/AndroidRuntime(686): Caused by: java.lang.NullPointerException
09-28 21:18:52.636: E/AndroidRuntime(686):  at android.content.ContextWrapper.getSharedPreferences(ContextWrapper.java:153)
09-28 21:18:52.636: E/AndroidRuntime(686):  at com.creativecoders.gymbuddy.Benchmark.<init>(Benchmark.java:35)
09-28 21:18:52.636: E/AndroidRuntime(686):  at java.lang.Class.newInstanceImpl(Native Method)
09-28 21:18:52.636: E/AndroidRuntime(686):  at java.lang.Class.newInstance(Class.java:1319)
09-28 21:18:52.636: E/AndroidRuntime(686):  at android.app.Instrumentation.newActivity(Instrumentation.java:1023)
09-28 21:18:52.636: E/AndroidRuntime(686):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1870)
09-28 21:18:52.636: E/AndroidRuntime(686):  ... 11 more

Answer 1

You have to access the shared preferences AFTER onCreate is called. Or else the context would be null 🙂 that’s why you’re getting a null pointer exception

move this line :

SharedPreferences settings = getSharedPreferences("gBValues", 
     Context.MODE_PRIVATE);

in the onCreate()