App Crashing on Start Up - Null pointer

Question

I am getting this LogCat from an app that resumes (after the Activity has long been gone (not everytime). It is actually a specific Fragment , so it's when the FragmentActivity resumes.

12-18 18:45:33.315: E/AndroidRuntime(7593): FATAL EXCEPTION: AsyncTask #1
12-18 18:45:33.315: E/AndroidRuntime(7593): java.lang.RuntimeException: An error occured while executing doInBackground()
12-18 18:45:33.315: E/AndroidRuntime(7593):     at android.os.AsyncTask$3.done(AsyncTask.java:299)
12-18 18:45:33.315: E/AndroidRuntime(7593):     at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
12-18 18:45:33.315: E/AndroidRuntime(7593):     at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
12-18 18:45:33.315: E/AndroidRuntime(7593):     at java.util.concurrent.FutureTask.run(FutureTask.java:239)
12-18 18:45:33.315: E/AndroidRuntime(7593):     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
12-18 18:45:33.315: E/AndroidRuntime(7593):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
12-18 18:45:33.315: E/AndroidRuntime(7593):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
12-18 18:45:33.315: E/AndroidRuntime(7593):     at java.lang.Thread.run(Thread.java:856)
12-18 18:45:33.315: E/AndroidRuntime(7593): Caused by: java.lang.NullPointerException
12-18 18:45:33.315: E/AndroidRuntime(7593):     at com.---.---.DebtDataSource.payoffDebt(DebtDataSource.java:229)
12-18 18:45:33.315: E/AndroidRuntime(7593):     at com.---.---.PlannerFragment$PlannerTask.doInBackground(PlannerFragment.java:131)
12-18 18:45:33.315: E/AndroidRuntime(7593):     at com.---.---.PlannerFragment$PlannerTask.doInBackground(PlannerFragment.java:1)
12-18 18:45:33.315: E/AndroidRuntime(7593):     at android.os.AsyncTask$2.call(AsyncTask.java:287)
12-18 18:45:33.315: E/AndroidRuntime(7593):     at java.util.concurrent.FutureTask.run(FutureTask.java:234)
12-18 18:45:33.315: E/AndroidRuntime(7593):     ... 4 more

The Main Activity has this:

@Override
protected void onDestroy() {
    super.onDestroy();
    datasource.close();
    finish();

}

Nothing in the onResume() .

The Fragment calls an AsyncTask when the Activity has been in the background after along time.

The problem is DoInBackground base on the Log. ( PlannerFragment )

@Override
    protected Void doInBackground(String... params) {


    if (paymentTotal > allFee) {

        totalMonths = datasource.payoffDebt(Double.valueOf(columnDebtTotal)); // this is line 131
        finalDate = datasource.getDate(totalMonths);
        allFeeLife = datasource.getLiftimeFees();

    }

    return null;

}

Then the Nullpointer is after Nullpointer tries to grab data from my SQLite DB.

( DebtDataSource Class)

public int payoffDebt(Double totalDebt) {
Cursor c = null;

if (DebtPlanner.PlanType.equals("highint")) { // line 229 -- NULL CRASH!
    c = database.rawQuery("SELECT *  FROM debt ORDER BY CAST("
            + MySQLiteHelper.COLUMN_APR + " as integer) DESC;", null);
}

Again, this only crashes when the Activity resumes after a long time in the background (long enough to require the task above in the onActivityCreated to be called again).

Answer 1

NullPointerException is thrown when executing: DebtPlanner.PlanType.equals("highint") . There are two possible reasons:

(1) DebtPlanner is null , or (2) PlanType is null

Solution Verify that both these fields have been initialized and are not null when this line is executed. That should fix the problem.

Answer 2

对于更长的操作， LoaderManager和AsyncTaskLoader优于AsyncTask。