illegal state exception on clicking a button

Question

here the next button is a method called upon clicking a button.When i click on the button it gives me an illegal state exception.

code:

 public class Shapes extends Activity {

    int i=3;
    ShapeView shape;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_shapes);

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.shapes, menu);
        return true;
    }
    public void next(View view)
    {
        i++;
        shape=(ShapeView)findViewById(R.id.shape_view);
        shape.nextshape(i);
    }

     } 

here nextshape(i) is a method defined in a custom view class.And the following is the message in logcat

Logcat :

     08-19 12:09:15.348: E/AndroidRuntime(812): FATAL EXCEPTION: main
     08-19 12:09:15.348: E/AndroidRuntime(812): java.lang.IllegalStateException: Could not       execute method of the activity
     08-19 12:09:15.348: E/AndroidRuntime(812):     at     android.view.View$1.onClick(View.java:2072)
     08-19 12:09:15.348: E/AndroidRuntime(812):     at android.view.View.performClick(View.java:2408)
     08-19 12:09:15.348: E/AndroidRuntime(812):     at android.view.View$PerformClick.run(View.java:8816)  
     08-19 12:09:15.348: E/AndroidRuntime(812):     at android.os.Handler.handleCallback(Handler.java:587)
     08-19 12:09:15.348: E/AndroidRuntime(812):     at android.os.Handler.dispatchMessage(Handler.java:92)
     08-19 12:09:15.348: E/AndroidRuntime(812):     at android.os.Looper.loop(Looper.java:123)
     08-19 12:09:15.348: E/AndroidRuntime(812):     at android.app.ActivityThread.main(ActivityThread.java:4627)
     08-19 12:09:15.348: E/AndroidRuntime(812):     at java.lang.reflect.Method.invokeNative(Native Method)
     08-19 12:09:15.348: E/AndroidRuntime(812):     at java.lang.reflect.Method.invoke(Method.java:521)
     08-19 12:09:15.348: E/AndroidRuntime(812):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
     08-19 12:09:15.348: E/AndroidRuntime(812):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)  
     08-19 12:09:15.348: E/AndroidRuntime(812):     at dalvik.system.NativeStart.main(Native Method)
     08-19 12:09:15.348: E/AndroidRuntime(812): Caused by: java.lang.reflect.InvocationTargetException
     08-19 12:09:15.348: E/AndroidRuntime(812):     at org.example.m_pustika.Shapes.next(Shapes.java:29)
     08-19 12:09:15.348: E/AndroidRuntime(812):     at java.lang.reflect.Method.invokeNative(Native Method)
     08-19 12:09:15.348: E/AndroidRuntime(812):     at java.lang.reflect.Method.invoke(Method.java:521)
     08-19 12:09:15.348: E/AndroidRuntime(812):     at android.view.View$1.onClick(View.java:2067)
     08-19 12:09:15.348: E/AndroidRuntime(812):     ... 11 more
     08-19 12:09:15.348: E/AndroidRuntime(812): Caused by: java.lang.NullPointerException

xmlfile:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".Shapes" >

    <org.example.m_pustika.ShapeView
        android:id="@+id/shape_view"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_below="@+id/next_button" />

    <Button
        android:id="@+id/next_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:text="@string/next_button"
        android:onClick="next" />

     </RelativeLayout>

CustomView:

   public class ShapeView extends View {

Paint cPaint;
Random r=new Random();
int n=3;
public ShapeView(Context context,AttributeSet attrs) {
    super(context);
    // TODO Auto-generated constructor stub
    cPaint = new Paint();
    cPaint.setColor(Color.BLACK);


}
public void nextshape(int n)
{
    this.n=n;
}

public void onDraw(Canvas canvas)
{
    Log.d("n","n= " +n);
    for(int i=1;i<=n;i++)
    {
        int x=r.nextInt(canvas.getWidth()-50);
        int y=r.nextInt(canvas.getHeight()-200);
        canvas.drawCircle(x, y, 10, cPaint);
    }
}

}

Answer 1

I guess you are shape object is null

You probably want to do

          ShapeView shape = new ShapeView(Shapes.this);

to initalize and then call shapenext

Add appropriate constructors also

Edit:

As a side note to refresh or update view call invalidate() on your view or call postInvalidate() from a thread (non ui thread).

Answer 2

Try this once. remove shape=(ShapeView)findViewById(R.id.shape_view); from next()

  @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_shapes);
            shape=(ShapeView)findViewById(R.id.shape_view);


        }

or please make a call of next() in onCreate()

Answer 3

I think you called the method next() before running the onCreate() method.

Try this instead of you current next() method:

public void next(View view)
{
    setContentView(R.layout.activity_shapes);
    shape=(ShapeView)findViewById(R.id.shape_view);
    shape.nextshape(i);
}