New onClickListener with NullPointerException (Android)

Question

I create a few textViews with onClickListeners at run time.

But I get a NullPointer... I think the reason is the View, he dosnt know where the textView should be.

How could I solve this?

The interesting lines of the class ShowSomething:

textView.setOnClickListener(new OnClickListener() {

    @Override
    public void onClick(View v) {

        Toast.makeText(ShowSomething.this, textView.getText().toString(), Toast.LENGTH_LONG).show();
        }
    });
    layout.addView(t);

Full class ShowSomething:

public class ShowSomething extends Activity {

    public void showData(final String[][] array, final int i, int j, LinearLayout layout, final TextView t, TextView t2, int color) {
        String Text = null;
        int size = 12;
        int top = 0;
        int bot = 0;

        if (j == 0) {
            size = 14;
            Text = array[j][i];
            top = 5;
            bot = 0;

        }
        if (j == 1) {
            size = 10;
            Text = "  " + array[j][i];
            top = 5;
            bot = 5;
        }
        t.setTextSize(TypedValue.COMPLEX_UNIT_DIP, size);
        t.setTextColor(color);
        t.setPadding(0, top, 0, bot);
        t.setClickable(false);
        t.setText(Text);
        t.setId(j + i);
        t.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {

                Toast.makeText(ShowSomething.this, t.getText().toString(), Toast.LENGTH_LONG).show();
            }
        });
        layout.addView(t);
    }
}

The interesting lines of the class ProjectsActivity:

    setContentView(R.layout.activity_projects);
    int j = 0;
    //result    
    for (i = 0; i < array[0].length; i++) {
        while (j <2) {
            LinearLayout layout = (LinearLayout) findViewById(R.id.mainLayout);
            final TextView t = new TextView(getApplicationContext());
            final TextView t2 = new TextView(getApplicationContext());
            ShowSomething.showData(array, i, j, layout, t, t2, color);

Full class ProjectsActivity:

public class ProjectsActivity extends Activity {
public String[][] array = null;
public int i = 0;
int color;
ShowSomething show = new ShowSomething();
@SuppressLint("NewApi")
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_projects);

    int j = 0;

    array = Connect.printJobList();

    for (i = 0; i < array[0].length; i++) {
        while (j < 2) {
            LinearLayout layout = (LinearLayout) findViewById(R.id.mainLayout);
            final TextView t = new TextView(getApplicationContext());
            final TextView t2 = new TextView(getApplicationContext());

            if (j == 0){    
                color = getResources().getColor(R.color.Project1);
            }
            if (j == 1){
                color = getResources().getColor(R.color.Project2);
            }

            show.showData(array, i, j, layout, t, t2, color);
            if (j == 1){
                t2.setLayoutParams(new LinearLayout.LayoutParams(LayoutParams.MATCH_PARENT, 1));
                t2.setBackgroundColor(getResources().getColor(R.color.Line));
                layout.addView(t2);
            }
            j++;
        }
        j = 0;
    }       
}

}

LogCat:

03-26 08:19:38.294: D/AndroidRuntime(1991): Shutting down VM
03-26 08:19:38.294: W/dalvikvm(1991):       threadid=1: thread exiting with uncaught exception (group=0x414c4700)
03-26 08:19:38.332: E/AndroidRuntime(1991): FATAL EXCEPTION: main
03-26 08:19:38.332: E/AndroidRuntime(1991): java.lang.NullPointerException
03-26 08:19:38.332: E/AndroidRuntime(1991):     at android.app.Activity.setContentView(Activity.java:1895)
03-26 08:19:38.332: E/AndroidRuntime(1991):     at de.xcom.mobilenav.ShowSomething$1.onClick(ShowSomething.java:47)
03-26 08:19:38.332: E/AndroidRuntime(1991):     at android.view.View.performClick(View.java:4240)
03-26 08:19:38.332: E/AndroidRuntime(1991):     at android.view.View$PerformClick.run(View.java:17721)
03-26 08:19:38.332: E/AndroidRuntime(1991):     at android.os.Handler.handleCallback(Handler.java:730)
03-26 08:19:38.332: E/AndroidRuntime(1991):     at android.os.Handler.dispatchMessage(Handler.java:92)
03-26 08:19:38.332: E/AndroidRuntime(1991):     at android.os.Looper.loop(Looper.java:137)
03-26 08:19:38.332: E/AndroidRuntime(1991):     at android.app.ActivityThread.main(ActivityThread.java:5103)
03-26 08:19:38.332: E/AndroidRuntime(1991):     at java.lang.reflect.Method.invokeNative(Native Method)
03-26 08:19:38.332: E/AndroidRuntime(1991):     at java.lang.reflect.Method.invoke(Method.java:525)
03-26 08:19:38.332: E/AndroidRuntime(1991):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
03-26 08:19:38.332: E/AndroidRuntime(1991):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
03-26 08:19:38.332: E/AndroidRuntime(1991):     at dalvik.system.NativeStart.main(Native Method)

Line 47 of ShowSomething: (ignore the comments)

43 public void onClick(View v) { 
44 //Intent intent = new Intent(ShowSomething.this, ProjectDetailActivity.class); 
45 //intent.putExtra("Project", array[0][i]); 
46   
47 //startActivity(intent); 
48 
49 Toast.makeText(ShowSomething.this, t.getText().toString(), Toast.LENGTH_LONG).show();

Changed the class ShowSomething:

public class ShowSomething {
.
.
.   t.setOnClickListener(new OnClickListener() {

    @Override
    public void onClick(View v) {
        Intent intent = new Intent(ShowSomething.this, ProjectDetailActivity.class);
        intent.putExtra("Project", array[0][i]);

        startActivity(intent);

        //Toast.makeText(getApplicationContext() , t.getText().toString(), Toast.LENGTH_LONG).show();
        }
    });

But now I get an error: The contructor Intent(ShowSomething, Class) is undefined...

Please post logcat. Without it it will be difficult to pinpoint the problem. — Xaver Kapeller, Mar 26 '14 at 12:49
Where is Activity Life cycle methods and SetContentView And method callings..You need to first look at this http://developer.android.com/reference/android/app/Activity.html — kalyan pvs, Mar 26 '14 at 12:49
First step in fixing null pointer exceptions is to figure out which variable is null. Check the log to see what line is generating the exception and then see what variables are on that line, and check which of them is null at the time. — Bob, Mar 26 '14 at 12:56
change `getApplicationContext()` to `ActivityName.this` may be thats the problem — Rat-a-tat-a-tat Ratatouille, Mar 26 '14 at 13:07
Stacktrace says you're calling `setContentView()` in an `onClick()` under `ShowSomething` but the code you posted doesn't agree with that. The exception could occur e.g. if the activity is not properly initialized (in essence, it has no `Window`). — laalto, Mar 26 '14 at 13:07
@Rat-a-tat-a-tat Ratatouille added these lines to my first post — user3464157, Mar 26 '14 at 13:38

score 2 · Answer 1 · edited May 23 '17 at 12:11

2

ShowSomething show = new ShowSomething();

You cannot instantiate activities with new.

Looks like ShowSomething should not be an activity at all. You can pass a Context to it as a method argument, for example.

To pass data from an activity to another, use intents. See How do I pass data between Activities in Android application?

edited May 23 '17 at 12:11

Community

1
1

answered Mar 26 '14 at 13:35

laalto

150,114
66
286
303

Nexowski · Accepted Answer · 2014-03-26T14:14:45.477

Maybe you have a problem with the context, first argument of the .makeText. You need to check in which line you have the NPE. Look at the LogCat window, you will see something like:

Caused by: java.lang.NullPointerException at yourpackagename.ShowSomething.showData(ShowSomething.java:123)

Then you will know where you have the NPE, or just ask further.

After Edit:

So you're trying to start an Intent now withou any context (ShowSomething isn't extendig activity right now)

You need to pass the Context to your ShowSomething class, maybe in constructor, and then use it:

public class ShowSomething {
...
Context mContext;

public ShowSomething(Context context){
   this.mContext=context;
}

calling: mContext.startActivity(intent); in the onClickListener

Creating your ShowSomething object then in your main activity:

ShowSomething myClass = new ShowSomething(getApplicationContext());

I also had to insert this: intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); ....but yeah... it works now, many many thanks! — user3464157, Mar 26 '14 at 14:37

score 0 · Answer 3 · answered Mar 26 '14 at 13:35

0

Toast.makeText(ShowSomething.this, t.getText().toString(), Toast.LENGTH_LONG).show();

Are you sure that t != null ?

answered Mar 26 '14 at 13:35

Alessandro Verona

1,157
9
23

it isnt null... test before Toast=> if (t == null){ Log.d("Test", "hello world"); } – user3464157 Mar 26 '14 at 13:40
There is something weird with your approach, why are you extending Activity for ShowSomething? Maybe you should use it with a utility class but extend Activity and call new Activity()... is wrong. – Alessandro Verona Mar 26 '14 at 13:44

score -1 · Answer 4 · edited Mar 26 '14 at 13:33

-1

First you have to create the object for the textview like this:

TextView t=(TextView) findViewById(R.id.text);

edited Mar 26 '14 at 13:33

slavoo

5,798
64
37
39

answered Mar 26 '14 at 13:02

Venkatesh venki

82
2

How? At this time i dont know the ID, because it does not exists. – user3464157 Mar 26 '14 at 13:06
Create the object for the textview in oncreate() method,,,,, and try again,,,,,,,,,,, – Venkatesh venki Mar 26 '14 at 13:08

New onClickListener with NullPointerException (Android)

4 Answers4