Android aplikace přestane pracovat

Zduř,

mám androidí aplikaci a v té si dělám dynamicky ovladací prvek - tlačítko.

K vytvoření tlačítka používám tento kód:

                Button myButton = new Button(getApplicationContext ());
                myButton.setText("Muj text");
                /*
                ViewGroup.LayoutParams params = myButton.getLayoutParams();
                params.width = 40;
                params.height = 80;

                myButton.setLayoutParams(params);
              */
	             setContentView(myButton);

Tento kód projde OK. Ale když odkomentuju část, která by měla zmenšit button (jinak je na celou obrazovku), tak to spadne:

08-19 05:31:34.339: W/dalvikvm(1549): threadid=1: thread exiting with uncaught exception (group=0x414c4700)
08-19 05:31:34.383: E/AndroidRuntime(1549): FATAL EXCEPTION: main
08-19 05:31:34.383: E/AndroidRuntime(1549): java.lang.NullPointerException
08-19 05:31:34.383: E/AndroidRuntime(1549): at com.example.test.MainActivity$1.onClick(MainActivi ty.java:53)
08-19 05:31:34.383: E/AndroidRuntime(1549): at android.view.View.performClick(View.java:4240)
08-19 05:31:34.383: E/AndroidRuntime(1549): at android.view.View$PerformClick.run(View.java:17721 )
08-19 05:31:34.383: E/AndroidRuntime(1549): at android.os.Handler.handleCallback(Handler.java:730 )
08-19 05:31:34.383: E/AndroidRuntime(1549): at android.os.Handler.dispatchMessage(Handler.java:92 )
08-19 05:31:34.383: E/AndroidRuntime(1549): at android.os.Looper.loop(Looper.java:137)
08-19 05:31:34.383: E/AndroidRuntime(1549): at android.app.ActivityThread.main(ActivityThread.jav a:5103)
08-19 05:31:34.383: E/AndroidRuntime(1549): at java.lang.reflect.Method.invokeNative(Native Method)
08-19 05:31:34.383: E/AndroidRuntime(1549): at java.lang.reflect.Method.invoke(Method.java:525)
08-19 05:31:34.383: E/AndroidRuntime(1549): at com.android.internal.os.ZygoteInit$MethodAndArgsCa ller.run(ZygoteInit.java:737)
08-19 05:31:34.383: E/AndroidRuntime(1549): at com.android.internal.os.ZygoteInit.main(ZygoteInit .java:553)
08-19 05:31:34.383: E/AndroidRuntime(1549): at dalvik.system.NativeStart.main(Native Method)