NullPointerException when using properties file in android application

Question

I want to use a properties file to read out some config data in my android app. When I place the properties file within the class folder of the handler everything works fine, but I want to place the properties file in the project root. I already tried it with relative paths (../../../ etc.), but it didn't work.

Is there an "easy" way to do this (/config.properties also didn't work)?

Here is my code:

    private Properties prop;

    public PropertiesHandler() {
        this.prop = new Properties();
        InputStream input = null;

        try {
            input = getClass().getResourceAsStream("config.properties");
            //input = new FileInputStream("config.properties");
            prop.load(input);
        } catch (IOException ex) {
            ex.printStackTrace();
        } finally {
            if (input != null) {
                try {
                    input.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

Any help would be greatly appreciated.

EDIT:

Unfortunately I got this Exception when applying the suggested solution:

10-08 15:10:05.903: E/AndroidRuntime(967): FATAL EXCEPTION: main
10-08 15:10:05.903: E/AndroidRuntime(967): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.dev.app1234/com.dev.app1234.Register}: java.lang.NullPointerException
10-08 15:10:05.903: E/AndroidRuntime(967):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1983)
10-08 15:10:05.903: E/AndroidRuntime(967):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
10-08 15:10:05.903: E/AndroidRuntime(967):  at android.app.ActivityThread.access$600(ActivityThread.java:130)
10-08 15:10:05.903: E/AndroidRuntime(967):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
10-08 15:10:05.903: E/AndroidRuntime(967):  at android.os.Handler.dispatchMessage(Handler.java:99)
10-08 15:10:05.903: E/AndroidRuntime(967):  at android.os.Looper.loop(Looper.java:137)
10-08 15:10:05.903: E/AndroidRuntime(967):  at android.app.ActivityThread.main(ActivityThread.java:4745)
10-08 15:10:05.903: E/AndroidRuntime(967):  at java.lang.reflect.Method.invokeNative(Native Method)
10-08 15:10:05.903: E/AndroidRuntime(967):  at java.lang.reflect.Method.invoke(Method.java:511)
10-08 15:10:05.903: E/AndroidRuntime(967):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
10-08 15:10:05.903: E/AndroidRuntime(967):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-08 15:10:05.903: E/AndroidRuntime(967):  at dalvik.system.NativeStart.main(Native Method)
10-08 15:10:05.903: E/AndroidRuntime(967): Caused by: java.lang.NullPointerException
10-08 15:10:05.903: E/AndroidRuntime(967):  at android.content.ContextWrapper.getApplicationContext(ContextWrapper.java:101)
10-08 15:10:05.903: E/AndroidRuntime(967):  at com.dev.app1234.Register.<init>(Register.java:68)
10-08 15:10:05.903: E/AndroidRuntime(967):  at java.lang.Class.newInstanceImpl(Native Method)
10-08 15:10:05.903: E/AndroidRuntime(967):  at java.lang.Class.newInstance(Class.java:1319)
10-08 15:10:05.903: E/AndroidRuntime(967):  at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
10-08 15:10:05.903: E/AndroidRuntime(967):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1974)
10-08 15:10:05.903: E/AndroidRuntime(967):  ... 11 more

Here is my code:

public PropertiesHandler(Context context) {
        this.prop = new Properties();
        InputStream input = null;

        try {
            input = context.getAssets().open("config.properties");

And I call it like this:

private final String URL = new PropertiesHandler(this.getApplicationContext()).getUrl()
                + "url.php";

EDIT 2:

Code:

private final String URL = new PropertiesHandler(Register.this).getUrl()
            + "url.php";

Stack Trace:

10-08 20:45:14.421: E/AndroidRuntime(1024): FATAL EXCEPTION: main
10-08 20:45:14.421: E/AndroidRuntime(1024): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.dev.app1234/com.dev.app1234.Register}: java.lang.NullPointerException
10-08 20:45:14.421: E/AndroidRuntime(1024):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1983)
10-08 20:45:14.421: E/AndroidRuntime(1024):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
10-08 20:45:14.421: E/AndroidRuntime(1024):     at android.app.ActivityThread.access$600(ActivityThread.java:130)
10-08 20:45:14.421: E/AndroidRuntime(1024):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
10-08 20:45:14.421: E/AndroidRuntime(1024):     at android.os.Handler.dispatchMessage(Handler.java:99)
10-08 20:45:14.421: E/AndroidRuntime(1024):     at android.os.Looper.loop(Looper.java:137)
10-08 20:45:14.421: E/AndroidRuntime(1024):     at android.app.ActivityThread.main(ActivityThread.java:4745)
10-08 20:45:14.421: E/AndroidRuntime(1024):     at java.lang.reflect.Method.invokeNative(Native Method)
10-08 20:45:14.421: E/AndroidRuntime(1024):     at java.lang.reflect.Method.invoke(Method.java:511)
10-08 20:45:14.421: E/AndroidRuntime(1024):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
10-08 20:45:14.421: E/AndroidRuntime(1024):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-08 20:45:14.421: E/AndroidRuntime(1024):     at dalvik.system.NativeStart.main(Native Method)
10-08 20:45:14.421: E/AndroidRuntime(1024): Caused by: java.lang.NullPointerException
10-08 20:45:14.421: E/AndroidRuntime(1024):     at android.content.ContextWrapper.getAssets(ContextWrapper.java:75)
10-08 20:45:14.421: E/AndroidRuntime(1024):     at com.dev.app1234.model.PropertiesHandler.<init>(PropertiesHandler.java:25)
10-08 20:45:14.421: E/AndroidRuntime(1024):     at com.dev.app1234.Register.<init>(Register.java:68)
10-08 20:45:14.421: E/AndroidRuntime(1024):     at java.lang.Class.newInstanceImpl(Native Method)
10-08 20:45:14.421: E/AndroidRuntime(1024):     at java.lang.Class.newInstance(Class.java:1319)
10-08 20:45:14.421: E/AndroidRuntime(1024):     at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
10-08 20:45:14.421: E/AndroidRuntime(1024):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1974)
10-08 20:45:14.421: E/AndroidRuntime(1024):     ... 11 more

About your edit : try without using the application context. private final String URL = new PropertiesHandler(AnActivity.this).getUrl() + "url.php"; For instance, if an activity is reachable. — ToYonos
– ToYonos, Commented Oct 8, 2014 at 19:06
Thanks for the tip, but I got the same exception. Activity should be reachable -> public class Register extends Activity — user3475602
– user3475602, Commented Oct 8, 2014 at 19:45
Could you try initializing URL in the OnCreate method (remove the final for test purpose), maybe the inline init of the private variable causes the issue — ToYonos
– ToYonos, Commented Oct 8, 2014 at 20:51

x-code · Accepted Answer · 2014-10-09 13:20:25Z

This call:

private final String URL = new PropertiesHandler(Register.this).getUrl() + "url.php";

needs to be placed inside the activity's onCreate() method. Like so:

class Register extends Activity {

    private String URL;

    // ...

    protected void onCreate(Bundle savedInstanceState) {
        // ...
        URL = new PropertiesHandler(Register.this).getUrl() + "url.php";
        // ...
    }
}

By creating your custom class before the activity has been created, you are effectively passing null in this code: new PropertiesHandler(Register.this), hence the null pointer error that appears in the stack trace.

Errors like this one occur often because so many useful system calls in Android require a Context. A good clue that this is happening is seeing in the stack trace a reference to the <init> virtual method, which refers to all the variable initializers in a class that are not enclosed in some other method. Like this line in the stack trace given:

10-08 20:45:14.421: E/AndroidRuntime(1024): at com.dev.app1234.Register.<init>(Register.java:68)

ToYonos · Accepted Answer · 2014-10-07 17:53:28Z

1

If i were you, i would put my config file in the asset folder and get an InputStream on it like this :

InputStream is = context.getAssets().open("config.properties");

Where context is your activity for instance.

answered Oct 7, 2014 at 17:53

ToYonos

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6 Comments

user3475602 Over a year ago

Thanks for your help. How do I call it from my activity?

ToYonos Over a year ago

If you call within the activity you can directly write : InputStream is = getAssets().open("config.properties");

user3475602 Over a year ago

No, I don't call it directly within the activity. I tried it likes this: new PropertiesHandler(this).getPropertyURL() but I got a NullPointerException in this line: InputStream is = context.getAssets().open("config.properties");.

ToYonos Over a year ago

In the class where you made the call, you must have a reference to a Context, Activity or Application for instance.

user3475602 Over a year ago

Thanks for the tip. But new PropertiesHandler(this.getApplicationContext()).getPropertyURL() also gave me a NullPointerException. Any ideas?

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