关于layoutparam 请铭记。。。。

//rl_pager 是RelativeLayout  
findViewById(R.id.rl_pager).setLayoutParams(new RelativeLayout.LayoutParams(width, width));

当我这么设置layoutparams的时候报错了，原因：

setLayoutParams(params) 这个params 是父布局的 layout，并非自身的layout。。。。

因为我这里 rl_pager的父节点是 linearlayout 所以 我这里正确的应该是：

//rl_pager 是RelativeLayout  
findViewById(R.id.rl_pager).setLayoutParams(new LinearLayout.LayoutParams(width, width));

下面一段对话，参考下吧：

代码设置RelativeLayout宽度时报错？0

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/linearLayout_parent"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:gravity="center_horizontal"
    android:orientation="vertical" >

    <RelativeLayout
        android:id="@+id/relativeLayout1"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
    。。。。。

代码中需要对RelativeLayout的宽度进行设定： 

RelativeLayout relativeLayout = (RelativeLayout)this.findViewById(R.id.relativeLayout1);
RelativeLayout.LayoutParams param = new RelativeLayout.LayoutParams(cell_Width, LayoutParams.MATCH_PARENT);
param.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM, 1);
relativeLayout.setLayoutParams(param);

但是报错： 

04-01 23:49:13.572: E/AndroidRuntime(1246): java.lang.ClassCastException: android.widget.RelativeLayout$LayoutParams cannot be cast to android.widget.LinearLayout$LayoutParams
04-01 23:49:13.572: E/AndroidRuntime(1246):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:587)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:519)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at android.view.View.measure(View.java:10828)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4351)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:267)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at android.view.View.measure(View.java:10828)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:764)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:519)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at android.view.View.measure(View.java:10828)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4351)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:267)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:1889)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at android.view.View.measure(View.java:10828)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at android.view.ViewRoot.performTraversals(ViewRoot.java:938)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at android.view.ViewRoot.handleMessage(ViewRoot.java:2040)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at android.os.Handler.dispatchMessage(Handler.java:99)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at android.os.Looper.loop(Looper.java:132)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at android.app.ActivityThread.main(ActivityThread.java:4123)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at java.lang.reflect.Method.invokeNative(Native Method)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at java.lang.reflect.Method.invoke(Method.java:491)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
04-01 23:49:13.572: E/AndroidRuntime(1246):     at dalvik.system.NativeStart.main(Native Method)

查了些资料，比如：http://blog.csdn.net/id19870510/article/details/6398049 
说是需要设置父layout，但是试了后依然报错，请问到底如何更改？ 
谢谢

Android 

2013年4月02日 00:01

tiwenzhuanyong 
0 
0 0 4

 

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采纳的答案

relativeLayout 是LinearLayout的子控件~它的layoutparam应该是LinearLayout给他的所以应该是LinearLayout.LayoutParam ~~~~不知道你理解了没~~~如果relativeLayout 有子控件的话~那它的子控件用的的就是relativeLayout 给他们的RinearLayout.LayoutParam