String replace method error

Question

Hello. I don't if it's okay that I'm posting this post in this forum. It's is not related to the Treehouse videos. But I'm am working on a little Android App. When the users logs into the app, the user will see the name and the balance registered to the account.

My code (the comments on the right is the value of the variable:

    // get user data from session
    HashMap<String, String> user = session.getUserDetails();

    // name
    String name = user.get(SessionManager.KEY_NAME); // "Stefan Bols"
    String balance = user.get(SessionManager.KEY_BALANCE); // "466"

    String newLblName = getString(R.string.welcomeReplaceName_sentence); // "Din saldo er: {{BALANCE}} kr."
    String newLblBalance = getString(R.string.yourBalanceIs_sentence); // "Velkommen {{NAME}}!"

    newLblName = newLblName.replace("{{NAME}}", name);
    newLblBalance = newLblBalance.replace("{{BALANCE}}", balance);

    lblName.setText(newLblName);
    lblBalance.setText(newLblBalance);

The thing I wanna do is in my string resources I've declared these:

    <string name="yourBalanceIs_sentence">Din saldo er: {{BALANCE}} kr.</string>
    <string name="welcomeReplaceName_sentence">Velkommen {{NAME}}!</string>

And the code, pasted in the top should replace {{BALANCE}} and {{NAME}} with the given variables:

            newLblName = newLblName.replace("{{NAME}}", name);
            newLblBalance = newLblBalance.replace("{{BALANCE}}", balance);

But the problem is that it works for some time, and then with no change in the code or the external data the app simply just crashes all the time. In the LogCat I can see that it's the .replace method there causes the crash... but I can't find out what I've done wrong?

If anyone can help, I would really appreciate it!

Best, Stefan

LogCat: 08-30 12:30:01.105: D/dalvikvm(8625): GC_FOR_ALLOC freed 43K, 8% free 12272K/13251K, paused 21ms, total 21ms

08-30 12:30:01.145: D/dalvikvm(8625): GC_CONCURRENT freed 90K, 8% free 12644K/13639K, paused 3ms+2ms, total 27ms

08-30 12:30:01.145: D/dalvikvm(8625): WAIT_FOR_CONCURRENT_GC blocked 14ms

08-30 12:30:01.185: D/AndroidRuntime(8625): Shutting down VM

08-30 12:30:01.185: W/dalvikvm(8625): threadid=1: thread exiting with uncaught exception (group=0x41f142a0)

08-30 12:30:01.190: E/AndroidRuntime(8625): FATAL EXCEPTION: main

08-30 12:30:01.190: E/AndroidRuntime(8625): java.lang.RuntimeException: Unable to start activity ComponentInfo{net.imbols.omnihuset.saldotjek/net.imbols.omnihuset.saldotjek.MainActivity}: java.lang.NullPointerException: replacement == null

08-30 12:30:01.190: E/AndroidRuntime(8625): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2100)

08-30 12:30:01.190: E/AndroidRuntime(8625): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2125)

08-30 12:30:01.190: E/AndroidRuntime(8625): at android.app.ActivityThread.access$600(ActivityThread.java:140)

08-30 12:30:01.190: E/AndroidRuntime(8625): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1227)

08-30 12:30:01.190: E/AndroidRuntime(8625): at android.os.Handler.dispatchMessage(Handler.java:99)

08-30 12:30:01.190: E/AndroidRuntime(8625): at android.os.Looper.loop(Looper.java:137)

08-30 12:30:01.190: E/AndroidRuntime(8625): at android.app.ActivityThread.main(ActivityThread.java:4898)

08-30 12:30:01.190: E/AndroidRuntime(8625): at java.lang.reflect.Method.invokeNative(Native Method)

08-30 12:30:01.190: E/AndroidRuntime(8625): at java.lang.reflect.Method.invoke(Method.java:511)

08-30 12:30:01.190: E/AndroidRuntime(8625): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1006)

08-30 12:30:01.190: E/AndroidRuntime(8625): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773)

08-30 12:30:01.190: E/AndroidRuntime(8625): at dalvik.system.NativeStart.main(Native Method)

08-30 12:30:01.190: E/AndroidRuntime(8625): Caused by: java.lang.NullPointerException: replacement == null

08-30 12:30:01.190: E/AndroidRuntime(8625): at java.lang.String.replace(String.java:1358)

08-30 12:30:01.190: E/AndroidRuntime(8625): at net.imbols.omnihuset.saldotjek.MainActivity.onCreate(MainActivity.java:56)

08-30 12:30:01.190: E/AndroidRuntime(8625): at android.app.Activity.performCreate(Activity.java:5206)

08-30 12:30:01.190: E/AndroidRuntime(8625): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1083)

08-30 12:30:01.190: E/AndroidRuntime(8625): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2064)

08-30 12:30:01.190: E/AndroidRuntime(8625): ... 11 more

Answer 1 · 2013-09-03T02:07:15Z

September 3, 2013 2:07am

We're happy to have you post in here! We want this to be a supportive community for Treehouse students whether working on Treehouse or personal projects.

I'm not much of a troubleshooter without full code that I can debug. Just one thought...Where is your session variable being declared? The fact that the error says "replacement == null" makes me think that name or balance are not getting set properly. Since they both come from that session variable, maybe something is causing that to be destroyed or reset? This could be a lifecycle problem, like if the Activity is destroyed because the system is low on memory. Depending on how you handle that, maybe the session variable isn't being recreated properly?

Can you post the full Activity code in here? I can't promise a solution, but I (and hopefully others) can take a look!

Answer 2 · 2013-09-03T21:06:16Z

September 3, 2013 9:06pm

Hi Ben. I can't see how I did miss the "replacement == null". But I tried a new way to fix my problem, the first idea was to try to recreate the problem without the app crashing. With this code:

    String name = user.get(SessionManager.KEY_NAME); // "Stefan Bols"
    String balance = user.get(SessionManager.KEY_BALANCE); // "466"
    Boolean err = false;

    if (name==""||name==null||balance==""||balance==null) {
        Log.e("Tis","Pis lort!");
        err = true;
    }


    String newLblName = getString(R.string.welcomeReplaceName_sentence);
    String newLblBalance = getString(R.string.yourBalanceIs_sentence);

    if (!err) {
        newLblName = newLblName.replace("{{NAME}}", name);
        newLblBalance = newLblBalance.replace("{{BALANCE}}", balance);
    }

    lblName.setText(newLblName);
    lblBalance.setText(newLblBalance);

This brick of code, almost does the same as it did before. But if the name or balance is equal to nothing or is "null", then the replacement methods will not be called and the lblName and lblBalance will be set to the standard String from Strings.xml.

Now I thought I could recreate this ugly app-crash... but no, I simply can't get the app to crash - neither to write the standard string.

The whole app seems to work just fine. I've simulated texts, incoming calls, killing the process and so on... nothing crashes the app or forces it not to call replace methods.

I should be happy, but I'm a bit scared to publish the app - what if the users experiences the crash? I can't force the crash/error, but I don't trust my work to be perfect enough to publish? What can I do? I'll be happy to post the whole code if you want that?

(I hope that you can understand my english)

Best, Stefan

Answer 3 · 2013-09-05T16:55:24Z

September 5, 2013 4:55pm

I'll try that, thanks... and now another thing, I can se an edit label at your reply - and I can edit it... but getting an error message when doing it. Maybe you have to change that :) ?

Again, thanks for all you help :)

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Stefan Bols

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String replace method error

3 Answers

Ben Jakuben

Ben Jakuben

Stefan Bols

Stefan Bols

Stefan Bols

Stefan Bols

Ben Jakuben

Ben Jakuben

Stefan Bols

Stefan Bols

Ben Jakuben

Ben Jakuben

Stefan Bols

Stefan Bols