Search code examples
androidandroid-relativelayoutclasscastexceptionandroid-framelayout

Programatcally remove margin from FrameLayout with LayoutParams

I have a FrameLayout that looks like this:

 <RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <FrameLayout
        android:layout_marginTop="56dp"
        android:layout_marginBottom="50dp"
        android:id="@+id/main_frag"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

          // other stuff


     </RelativeLayout>

However when I change the margins programitcally I get a ClassCastException.

        FrameLayout fl = (FrameLayout) findViewById(R.id.main_frag);
        FrameLayout.LayoutParams params = (FrameLayout.LayoutParams) fl.getLayoutParams();
        params.setMargins(50, 0, 0, 0);
        fl.setLayoutParams(params);

Here is how I am trying:

        FrameLayout fl = (FrameLayout) findViewById(R.id.main_frag);
        FrameLayout.LayoutParams params = (FrameLayout.LayoutParams) fl.getLayoutParams();
        params.setMargins(50, 0, 0, 0);
        fl.setLayoutParams(params);

Here is LogCat:

04-25 16:18:08.385: E/AndroidRuntime(27682): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.---.---/com.------.---.MainFragmentActivity}: java.lang.ClassCastException: android.widget.RelativeLayout$LayoutParams cannot be cast to android.widget.FrameLayout$LayoutParams
04-25 16:18:08.385: E/AndroidRuntime(27682):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2314)
04-25 16:18:08.385: E/AndroidRuntime(27682):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2388)
04-25 16:18:08.385: E/AndroidRuntime(27682):    at android.app.ActivityThread.access$800(ActivityThread.java:148)
04-25 16:18:08.385: E/AndroidRuntime(27682):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1292)
04-25 16:18:08.385: E/AndroidRuntime(27682):    at android.os.Handler.dispatchMessage(Handler.java:102)
04-25 16:18:08.385: E/AndroidRuntime(27682):    at android.os.Looper.loop(Looper.java:135)
04-25 16:18:08.385: E/AndroidRuntime(27682):    at android.app.ActivityThread.main(ActivityThread.java:5312)
04-25 16:18:08.385: E/AndroidRuntime(27682):    at java.lang.reflect.Method.invoke(Native Method)
04-25 16:18:08.385: E/AndroidRuntime(27682):    at java.lang.reflect.Method.invoke(Method.java:372)
04-25 16:18:08.385: E/AndroidRuntime(27682):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
04-25 16:18:08.385: E/AndroidRuntime(27682):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
04-25 16:18:08.385: E/AndroidRuntime(27682): Caused by: java.lang.ClassCastException: android.widget.RelativeLayout$LayoutParams cannot be cast to android.widget.FrameLayout$LayoutParams
04-25 16:18:08.385: E/AndroidRuntime(27682):    at com.---.---.MainFragmentActivity.onCreate(MainFragmentActivity.java:81)
04-25 16:18:08.385: E/AndroidRuntime(27682):    at android.app.Activity.performCreate(Activity.java:5953)
04-25 16:18:08.385: E/AndroidRuntime(27682):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1128)
04-25 16:18:08.385: E/AndroidRuntime(27682):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2267)

I don't understand how the RelativeLayout is involved here?

Solution

  • The LayoutParams class is dictated by the parent, not the child. The LayoutParams that affect the FrameLayout is a RelativeLayout.LayoutParams. The LayoutParams that affects the child of the FrameLayout would be a FrameLayout.LayoutParams.