我有一个看起来像这样的FrameLayout:
<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>
然而,当我按照程序改变边距时,我得到一个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);
以下是我的尝试方式:
FrameLayout fl = (FrameLayout) findViewById(R.id.main_frag);
FrameLayout.LayoutParams params = (FrameLayout.LayoutParams) fl.getLayoutParams();
params.setMargins(50, 0, 0, 0);
fl.setLayoutParams(params);
以下是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)
我不明白RelativeLayout
是如何参与的?
答案 0 :(得分:3)
LayoutParams
课程由家长决定,而不是孩子。影响LayoutParams
的{{1}}为FrameLayout
。影响RelativeLayout.LayoutParams
的孩子的LayoutParams
将是FrameLayout
。