setLayoutParams（）方法不起作用

Question

我正在製作一個代碼，根據其應用程序提供的屏幕大小更改其大小。它通過View的onSizeChanged（）和onDraw（）方法獲得整個寬度和高度（或其適當的視圖的w和h）。

它在另一個代碼中運行良好，但是現在每當我嘗試將命令'setLayoutParams（）'顯示時都會顯示一條錯誤消息請你幫我弄清楚這個問題嗎？ setLayoutParams（）實際上不能在代碼中的任何地方工作。以下是主要的班級代碼。

 
public class ManipulateDesign extends Activity { 
    private LinearLayout ll; 
    private ScrollView sv; 
    private TextView tv; 
    /** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 

     ll = (LinearLayout) findViewById(R.id.ll); 
     sv = (ScrollView) findViewById(R.id.sv); 
     tv = new TextView(this); 

     tv.setText("You're in the first ScrollView\n" + 
       "- Living Universe \n" + 
       "Wish (upon a star) Hope to (be again)\n" + 
       "The one you find, when all is done and through!\n" + 
       "If all, made a wish to save, the star would it be in vain?\n" + 
       "So much it holds, too dear to part, many ways to see the light of answers!\n" + 
       "For all was once, just taken away, that one hope all disappeared so none can break nor brittle my heart\n" + 
       "no, never again, until the end"); 

     sv.addView(tv); 
     ChangeSizeView csv = new ChangeSizeView(getApplicationContext()); 
     ll.addView(csv); 
    } 

    class ChangeSizeView extends View{ 
     int newWidth; 
     int newHeight; 

     public ChangeSizeView(Context context) { 
      super(context); 
     } 

     @Override 
     protected void onSizeChanged(int w, int h, int oldw, int oldh) { 
      newWidth = w; 
      newHeight = h; 
      super.onSizeChanged(w, h, oldw, oldh); 
     } 

     @Override 
     protected void onDraw(Canvas canvas) { 
      // THIS COMMAND MAKES AN ERROR(not just in this method but anywhere in the entire code) BUT WORKED WELL IN ANOTHER CODE  
      sv.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, (newHeight - 100)));   

      super.onDraw(canvas); 
     } 
    } 
}

，這是我的main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:orientation="vertical" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:id="@+id/ll" 
    > 
    <ScrollView android:id="@+id/sv" 
       android:layout_height="wrap_content" 
       android:layout_width="wrap_content"> 
    </ScrollView> 
</LinearLayout> 

這是logcat的標誌，顯示錯誤信息

04-11 06:39:52.148: ERROR/AndroidRuntime(2952): FATAL EXCEPTION: main 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952): java.lang.ClassCastException: android.view.ViewGroup$LayoutParams 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at android.widget.LinearLayout.measureVertical(LinearLayout.java:355) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:304) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at android.view.View.measure(View.java:8171) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:245) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at android.view.View.measure(View.java:8171) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at android.widget.LinearLayout.measureVertical(LinearLayout.java:526) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:304) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at android.view.View.measure(View.java:8171) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:245) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at android.view.View.measure(View.java:8171) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at android.view.ViewRoot.performTraversals(ViewRoot.java:801) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at android.view.ViewRoot.handleMessage(ViewRoot.java:1727) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at android.os.Handler.dispatchMessage(Handler.java:99) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at android.os.Looper.loop(Looper.java:123) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at android.app.ActivityThread.main(ActivityThread.java:4627) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at java.lang.reflect.Method.invokeNative(Native Method) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at java.lang.reflect.Method.invoke(Method.java:521) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 
04-11 06:39:52.148: ERROR/AndroidRuntime(2952):  at dalvik.system.NativeStart.main(Native Method) 

Answer 1

你應該完全限定你需要哪些LayoutParams，因爲它包含在LinearLayout中，您需要使用new LinearLayout.LayoutParams