setLayoutParams() method doesn't work

Question

I am making a code that changes its size according to the screen size its application provides. It gets the entire width and height(or its appropriate view's w and h) by onSizeChanged() and onDraw() methods of View.

It worked well in another code however now it shows an error message whenever I tried to put command 'setLayoutParams()' Would you please help me to figure out this problem? The setLayoutParams() actually does not work anywhere in the code. Below is the main class code.

public class ManipulateDesign extends Activity {
    private LinearLayout ll;
    private ScrollView sv;
    private TextView tv;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        ll = (LinearLayout) findViewById(R.id.ll);
        sv = (ScrollView) findViewById(R.id.sv);
        tv = new TextView(this);

        tv.setText("You're in the first ScrollView\n" +
                "- Living Universe \n" +
                "Wish (upon a star) Hope to (be again)\n" +
                "The one you find, when all is done and through!\n" +
                "If all, made a wish to save, the star would it be in vain?\n" +
                "So much it holds, too dear to part, many ways to see the light of answers!\n" +
                "For all was once, just taken away, that one hope all disappeared so none can break nor brittle my heart\n" +
                "no, never again, until the end");

        sv.addView(tv);
        ChangeSizeView csv = new ChangeSizeView(getApplicationContext());
        ll.addView(csv);
    }

    class ChangeSizeView extends View{
        int newWidth;
        int newHeight;

        public ChangeSizeView(Context context) {
            super(context);
        }

        @Override
        protected void onSizeChanged(int w, int h, int oldw, int oldh) {
            newWidth = w;
            newHeight = h;
            super.onSizeChanged(w, h, oldw, oldh);
        }

        @Override
        protected void onDraw(Canvas canvas) {
            // THIS COMMAND MAKES AN ERROR(not just in this method but anywhere in the entire code) BUT WORKED WELL IN ANOTHER CODE     
            sv.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, (newHeight - 100)));         

            super.onDraw(canvas);
        }
    }
}

And this is my main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:id="@+id/ll"
    >
    <ScrollView android:id="@+id/sv"
                android:layout_height="wrap_content"
                android:layout_width="wrap_content">
    </ScrollView>
</LinearLayout>

This is the logcat logo that shows error messages

04-11 06:39:52.148: ERROR/AndroidRuntime(2952): FATAL EXCEPTION: main
04-11 06:39:52.148: ERROR/AndroidRuntime(2952): java.lang.ClassCastException: android.view.ViewGroup$LayoutParams
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:355)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:304)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at android.view.View.measure(View.java:8171)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at android.view.View.measure(View.java:8171)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:526)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:304)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at android.view.View.measure(View.java:8171)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at android.view.View.measure(View.java:8171)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at android.view.ViewRoot.performTraversals(ViewRoot.java:801)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1727)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at android.os.Handler.dispatchMessage(Handler.java:99)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at android.os.Looper.loop(Looper.java:123)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at android.app.ActivityThread.main(ActivityThread.java:4627)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at java.lang.reflect.Method.invokeNative(Native Method)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at java.lang.reflect.Method.invoke(Method.java:521)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

You should fully qualify which LayoutParams you need, since it is contained in a LinearLayout, you need to use new LinearLayout.LayoutParams