Question

我想要更改视图的高度和宽度，（可能是按钮视图，图像视图，linearlayout，framelayout或任何类型的视图）。我使用方法traverseRootViewAndSetLayoutParam（View，双，双），改变这样做。如果我对这些行进行评论，它的工作原理。

    if (view.getClass().equals(LinearLayout.class)) {
         LinearLayout.LayoutParams layoutParams = new
         LinearLayout.LayoutParams(
         (int) (((double) widthRatio) * (view.getWidth())),
         (int) (((double) heightRatio) * (view.getHeight())));
         view.setLayoutParams(layoutParams);
    } else if (view.getClass().equals(FrameLayout.class)) {
        FrameLayout.LayoutParams layoutParams = new FrameLayout.LayoutParams(
                (int) (((double) widthRatio) * (view.getWidth())),
                (int) (((double) heightRatio) * (view.getHeight())));
        view.setLayoutParams(layoutParams);
    }

，但如果我运行的所有代码都比我在onCreate（）方法中获得ClassCastException，

我调试代码，方法traverseRootViewAndSetLayoutParam（View，double，double）没有给出异常，但是在控制传递了onCreate（）之后，它给出了ClassCastException。我检查控件是否在线，System.outprintln（＆gt;＆gt; oncreate end＆gt;＆gt;）。此时我没有收到任何错误，但是会发生穿越oncreate方法异常。

我在onCreate方法中调用的代码行，

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
            ...
            ...
            ...
    try {
        traverseRootViewAndSetLayoutParam(rootLinearLayout, widthRatio,
                heightRatio);
    } catch (Exception e) {
        e.printStackTrace();
    }
System.out.println(">>> oncreate end >>> ");
   }

traverseRootViewAndSetLayoutParam（）方法，

public void traverseRootViewAndSetLayoutParam(View view,
        double heightRatio, double widthRatio) {

    System.out.println(">>> iCount >>> " + iCount++);

    if (view.getClass().equals(LinearLayout.class)) {
         LinearLayout.LayoutParams layoutParams = new
         LinearLayout.LayoutParams(
         (int) (((double) widthRatio) * (view.getWidth())),
         (int) (((double) heightRatio) * (view.getHeight())));
         view.setLayoutParams(layoutParams);
    } else if (view.getClass().equals(FrameLayout.class)) {
        FrameLayout.LayoutParams layoutParams = new FrameLayout.LayoutParams(
                (int) (((double) widthRatio) * (view.getWidth())),
                (int) (((double) heightRatio) * (view.getHeight())));
        view.setLayoutParams(layoutParams);
    }
    // else {
    // ViewGroup.LayoutParams layoutParams = new ViewGroup.LayoutParams(
    // (int) (((double) widthRatio) * (view.getWidth())),
    // (int) (((double) heightRatio) * (view.getHeight())));
    // view.setLayoutParams(layoutParams);
    // }

    if (view instanceof LinearLayout || view instanceof FrameLayout) {
        if (view instanceof LinearLayout) {
            System.out.println(">>> LinearLayout Class >>> "
                    + view.getClass());
            int childcount = ((LinearLayout) view).getChildCount();
            for (int i = 0; i < childcount; i++) {
                View childView = ((LinearLayout) view).getChildAt(i);
                traverseRootViewAndSetLayoutParam(childView, heightRatio,
                        widthRatio);
            }
        } else if (view instanceof FrameLayout) {
            System.out.println(">>> FrameLayout Class >>> "
                    + view.getClass());
            int childcount = ((FrameLayout) view).getChildCount();
            for (int i = 0; i < childcount; i++) {
                View childView = ((FrameLayout) view).getChildAt(i);
                traverseRootViewAndSetLayoutParam(childView, heightRatio,
                        widthRatio);
            }
        }
    }
}

错误日志，

12-16 00:30:12.791: W/dalvikvm(277): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
12-16 00:30:12.952: E/AndroidRuntime(277): FATAL EXCEPTION: main
12-16 00:30:12.952: E/AndroidRuntime(277): java.lang.ClassCastException: android.widget.FrameLayout$LayoutParams
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.widget.LinearLayout.measureVertical(LinearLayout.java:355)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:304)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.view.View.measure(View.java:8171)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1012)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:696)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:306)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.view.View.measure(View.java:8171)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1012)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.widget.LinearLayout.measureVertical(LinearLayout.java:381)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:304)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.view.View.measure(View.java:8171)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1012)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.widget.LinearLayout.measureVertical(LinearLayout.java:381)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:304)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.view.View.measure(View.java:8171)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.view.View.measure(View.java:8171)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.view.View.measure(View.java:8171)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.view.ViewRoot.performTraversals(ViewRoot.java:801)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.view.ViewRoot.handleMessage(ViewRoot.java:1727)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.os.Handler.dispatchMessage(Handler.java:99)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.os.Looper.loop(Looper.java:123)
12-16 00:30:12.952: E/AndroidRuntime(277):  at android.app.ActivityThread.main(ActivityThread.java:4627)
12-16 00:30:12.952: E/AndroidRuntime(277):  at java.lang.reflect.Method.invokeNative(Native Method)
12-16 00:30:12.952: E/AndroidRuntime(277):  at java.lang.reflect.Method.invoke(Method.java:521)
12-16 00:30:12.952: E/AndroidRuntime(277):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
12-16 00:30:12.952: E/AndroidRuntime(277):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
12-16 00:30:12.952: E/AndroidRuntime(277):  at dalvik.system.NativeStart.main(Native Method)
12-16 00:30:42.751: I/Process(277): Sending signal. PID: 277 SIG: 9

Answer 1

您将收到此异常，因为LayoutParams始终相对于父视图组。

e.g。你有一个RelativeLayout，在这个RelativeLayout里面你有一个LinearLayout，这个LinearLayout的LayoutParams将是一个RelativeLayout.LayoutParams。

那是因为这些参数与父在其区域内布局视图的方式有关。

Answer 2

if (view.getClass().equals(LinearLayout.class)) {
     LinearLayout.LayoutParams layoutParams = new
     LinearLayout.LayoutParams(
     (int) (((double) widthRatio) * (view.getWidth())),
     (int) (((double) heightRatio) * (view.getHeight())));
     view.setLayoutParams(layoutParams);
} else if (view.getClass().equals(FrameLayout.class)) {
    FrameLayout.LayoutParams layoutParams = new FrameLayout.LayoutParams(
            (int) (((double) widthRatio) * (view.getWidth())),
            (int) (((double) heightRatio) * (view.getHeight())));
    view.setLayoutParams(layoutParams);
}

在这里，您正在检查视图的类型，而不是视图的父级。如果视图的父级是LinearLayout且视图本身是FrameLayout，那么您将给它FrameLayout.LayoutParams，这是不正确的。

由于您没有使用权重或任何特定于布局类型的内容，我建议您使用ViewGroup.LayoutParams：

ViewGroup.LayoutParams layoutParams = new
ViewGroup.LayoutParams(
    (int) (((double) widthRatio) * (view.getWidth())),
    (int) (((double) heightRatio) * (view.getHeight())));
view.setLayoutParams(layoutParams);

我在onCreate（）方法中得到ClassCastException？

2 个答案: