从ArrayList检索数据时发生NullPointerException

Question

Android 2.3.3

I have an ArrayList, with 3 values. While i am trying to retrieve values from the arraylist, i get a NullPointerException. I am trying to get the value from arraylist and set it to a textview.

Here is the code :::

System.out.println(alAngleResult.toString());

        txtViewResult.setText("");

        int i = 0;
        while(i < alAngleResult.size())
        {
            txtViewResult.append(alAngleResult.get(i).toString());
                    // Exception at above line
            txtViewResult.append("\n");

            i++;
        }

LogCat output :::

01-25 01:32:26.599: I/System.out(18437): [10.0 Degrees, 0.17453292519943295 Radians, 10.0 Gradians] => Output
01-25 01:32:26.599: W/dalvikvm(18437): threadid=1: thread exiting with uncaught exception (group=0x40184560)
01-25 01:32:26.599: E/AndroidRuntime(18437): FATAL EXCEPTION: main
01-25 01:32:26.599: E/AndroidRuntime(18437): java.lang.NullPointerException
01-25 01:32:26.599: E/AndroidRuntime(18437):    at com.xx.xx.xx.performConvertionForAngle(UnitConverter.java:416)
01-25 01:32:26.599: E/AndroidRuntime(18437):    at com.xx.xx.xx.performConvertion(UnitConverter.java:368)
01-25 01:32:26.599: E/AndroidRuntime(18437):    at com.xx.xx.xx.onClick(UnitConverter.java:356)
01-25 01:32:26.599: E/AndroidRuntime(18437):    at android.view.View.performClick(View.java:2485)
01-25 01:32:26.599: E/AndroidRuntime(18437):    at android.view.View$PerformClick.run(View.java:9080)
01-25 01:32:26.599: E/AndroidRuntime(18437):    at android.os.Handler.handleCallback(Handler.java:587)
01-25 01:32:26.599: E/AndroidRuntime(18437):    at android.os.Handler.dispatchMessage(Handler.java:92)
01-25 01:32:26.599: E/AndroidRuntime(18437):    at android.os.Looper.loop(Looper.java:130)
01-25 01:32:26.599: E/AndroidRuntime(18437):    at android.app.ActivityThread.main(ActivityThread.java:3687)
01-25 01:32:26.599: E/AndroidRuntime(18437):    at java.lang.reflect.Method.invokeNative(Native Method)
01-25 01:32:26.599: E/AndroidRuntime(18437):    at java.lang.reflect.Method.invoke(Method.java:507)
01-25 01:32:26.599: E/AndroidRuntime(18437):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:878)
01-25 01:32:26.599: E/AndroidRuntime(18437):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:636)
01-25 01:32:26.599: E/AndroidRuntime(18437):    at dalvik.system.NativeStart.main(Native Method)

EDIT ::: Just had to clean the project. It works fine now.

Answer 1

您的数组很可能包含null值，因此最终调用null.toString（）

Answer 2

Just a typical Eclipse Problem. Just had to clean the project, and everything worked fine.

Answer 3

Glad it's working for you now.

Re the code snip, wouldn't it be easier to read and less effort as a for-each loop?