修改RelativeLayout的編程基於一個條件

Question

我與XML有點像RelativeLayout：

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/appHolder" 
    android:layout_width="210dp" 
    android:layout_height="100dp" 
    android:background="@drawable/app_container_box" 
    android:paddingBottom="10dp" 
    android:paddingLeft="15dp" 
    android:paddingRight="10dp" 
    android:paddingTop="10dp" > 
    ... 
</RelativeLayout> 

我想以編程方式修改根據一些條件此佈局的寬度。

在GetView()方法，我有：

public View getView(int position, View recycledView, ViewGroup viewGroup) { 
    View row = recycledView; 
    Holder holder; 
    row = inflater.inflate(R.layout.app_icon_tile, viewGroup, false); 
    if (row == null) { 
     /* 
     * I added only the following `if` block 
     * The rest is older code and was working fine 
     */ 
     if (changeWidth) { 
      row.setLayoutParams(new RelativeLayout.LayoutParams(260, 100)); 
     } 
     holder = new Holder(); 
     holder.icon = (ImageView) row.findViewById(R.id.gridAppIcon); 
     holder.appTitle = (TextView) row.findViewById(R.id.gridAppTitle); 
     row.setTag(holder); 
    } else { 
     holder = (Holder) row.getTag(); 
    } 
    return (row); 
} 

但運行此代碼，我的應用程序崩潰，並顯示以下堆棧跟蹤時：

FATAL EXCEPTION: main 
java.lang.ClassCastException: android.widget.RelativeLayout$LayoutParams 
     at android.widget.GridView.onMeasure(GridView.java:937) 
     at android.view.View.measure(View.java:8314) 
     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138) 
     at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1017) 
     at android.widget.LinearLayout.measureVertical(LinearLayout.java:386) 
     at android.widget.LinearLayout.onMeasure(LinearLayout.java:309) 
     at android.view.View.measure(View.java:8314) 
     at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:581) 
     at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:365) 
     at android.view.View.measure(View.java:8314) 
     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138) 
     at android.widget.FrameLayout.onMeasure(FrameLayout.java:250) 
     at android.view.View.measure(View.java:8314) 
     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138) 
     at android.widget.FrameLayout.onMeasure(FrameLayout.java:250) 
     at android.view.View.measure(View.java:8314) 
     at android.view.ViewRoot.performTraversals(ViewRoot.java:843) 
     at android.view.ViewRoot.handleMessage(ViewRoot.java:1866) 
     at android.os.Handler.dispatchMessage(Handler.java:99) 
     at android.os.Looper.loop(Looper.java:130) 
     at android.app.ActivityThread.main(ActivityThread.java:3683) 
     at java.lang.reflect.Method.invokeNative(Native Method) 
     at java.lang.reflect.Method.invoke(Method.java:507) 
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:880) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:638) 
     at dalvik.system.NativeStart.main(Native Method) 

我缺少什麼？

Answer 1

你的問題就在這裏：

if (changeWidth) { 
     row.setLayoutParams(new RelativeLayout.LayoutParams(260, 100)); 
} 

因爲當你設置佈局參數，可以他們應該是父母的類型，不認爲對你正在創建PARAMS本身。

因此，例如，如果您的RelativeLayout在ListView，它應該得到ListView.LayoutParams。