android設定布局最小高度,動态更改Android上的線性布局寬度或高度

我試圖改變線性布局或任何其他視窗小部件寬度或高度動态但抛出異常。

我的布局是：

android:id="@+id/abc"

android:orientation="vertical"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

>

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:text="ghghjkgj ghjg hjgj ghj g hjgjgh jhg "

/>

我的活動是：

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

LinearLayout ll = (LinearLayout)findViewById(R.id.abc);

ll.setLayoutParams(new LinearLayout.LayoutParams(30,60));

}

投擲以下例外：

E/AndroidRuntime(16052): java.lang.ClassCastException: android.widget.LinearLayout$LayoutParams

E/AndroidRuntime(16052): at android.widget.FrameLayout.onLayout(FrameLayout.java:288)

E/AndroidRuntime(16052): at android.view.View.layout(View.java:7035)

E/AndroidRuntime(16052): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1249)

E/AndroidRuntime(16052): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1125)

E/AndroidRuntime(16052): at android.widget.LinearLayout.onLayout(LinearLayout.java:1042)

E/AndroidRuntime(16052): at android.view.View.layout(View.java:7035)

E/AndroidRuntime(16052): at android.widget.FrameLayout.onLayout(FrameLayout.java:333)

E/AndroidRuntime(16052): at android.view.View.layout(View.java:7035)

E/AndroidRuntime(16052): at android.view.ViewRoot.performTraversals(ViewRoot.java:1045)

E/AndroidRuntime(16052): at android.view.ViewRoot.handleMessage(ViewRoot.java:1727)

E/AndroidRuntime(16052): at android.os.Handler.dispatchMessage(Handler.java:99)

E/AndroidRuntime(16052): at android.os.Looper.loop(Looper.java:123)

E/AndroidRuntime(16052): at android.app.ActivityThread.main(ActivityThread.java:4627)

E/AndroidRuntime(16052): at java.lang.reflect.Method.invokeNative(Native Method)

E/AndroidRuntime(16052): at java.lang.reflect.Method.invoke(Method.java:521)

E/AndroidRuntime(16052): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)

E/AndroidRuntime(16052): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)

E/AndroidRuntime(16052): at dalvik.system.NativeStart.main(Native Method)

那麼如何動态地改變尺寸？