Question

好的，这就是我正在做的......我有两个自定义布局：

HandedLayout extends ViewGroup

和

HandedPathLayout extends HandedLayout

所以在根布局中，我有一个自定义LayoutParameters来接受一个名为handed的布局属性。这是

中的布局参数类

    public static class LayoutParams extends ViewGroup.LayoutParams {
    public int handed;
    public LayoutParams(Context c, AttributeSet attrs) {
        super(c, attrs);
        TypedArray a =
                c.obtainStyledAttributes(attrs, R.styleable.HandedLayout_LayoutParams);
        handed = a.getInt(R.styleable.HandedLayout_LayoutParams_layout_handed,
                HandedLayout.RIGHT_HANDED);
        a.recycle();
    }
    public LayoutParams(int width, int height) {
        super(width, height);
    }
}

正如我所理解的那样（看起来很糟糕），我还需要覆盖HandedLayout中的3个类。他们在这里：

@Override
    public HandedLayout.LayoutParams generateLayoutParams(AttributeSet attrs) {
        return new HandedLayout.LayoutParams(getContext(), attrs);

    }

    @Override
    protected boolean checkLayoutParams(ViewGroup.LayoutParams p) {
        return p instanceof LayoutParams;
    }

    @Override
    protected HandedLayout.LayoutParams generateDefaultLayoutParams() {
        return new HandedLayout.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
    }

所以在内部自定义布局（HandedPathLayout）中，我需要大量的布局参数，所以我做的完全一样！这是HandedPathLayout中的LayoutParameters类：

public static class LayoutParams extends HandedLayout.LayoutParams {

    public int[] endSides;
    public int[] endPositions;
    public int[] anchorSides;
    public int[] anchorPositions;
    public int controlPointDistance;

    public LayoutParams(int width, int height) {
        super(width, height);
    }

    public LayoutParams(Context context, AttributeSet attrs) {
        super(context, attrs);

        endSides = new int[2];
        endPositions = new int[2];
        anchorSides = new int[2];
        anchorPositions = new int[2];

        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.HandedPathLayout_LayoutParams);;
        try {
            //this is the second place that the default handedness is set, watch out!
            //handed = a.getInteger(R.styleable.HandedLayout_LayoutParams_layout_handed, HandedLayout.RIGHT_HANDED);
            endSides[0] = a.getInteger(R.styleable.HandedPathLayout_LayoutParams_layout_from_side, HandedLayout.BOTTOM_SIDE);
            endSides[1] = a.getInteger(R.styleable.HandedPathLayout_LayoutParams_layout_to_side, HandedLayout.PINKIE_SIDE);
            endPositions[0] = a.getDimensionPixelSize(R.styleable.HandedPathLayout_LayoutParams_layout_from_position, 0);
            endPositions[1] = a.getDimensionPixelSize(R.styleable.HandedPathLayout_LayoutParams_layout_to_position, 0);
            anchorSides[0] = a.getInteger(R.styleable.HandedPathLayout_LayoutParams_layout_anchor_up_side, HandedLayout.TOP_SIDE);
            anchorSides[1] = a.getInteger(R.styleable.HandedPathLayout_LayoutParams_layout_anchor_down_side, HandedLayout.BOTTOM_SIDE);
            //todo: should these positions be set relative to handedness?  which direction is zero?
            anchorPositions[0] = a.getDimensionPixelSize(R.styleable.HandedPathLayout_LayoutParams_layout_anchor_up_position, 0);
            anchorPositions[1] = a.getDimensionPixelSize(R.styleable.HandedPathLayout_LayoutParams_layout_anchor_down_position, 0);
            controlPointDistance = a.getInteger(R.styleable.HandedPathLayout_LayoutParams_layout_control_point_position, HandedLayout.BOTTOM_SIDE);

        } finally {
            a.recycle();
        }

    }

}

然后再次在HandedPathLayout类中，确保我们获得正确类型的LayoutParams的三个函数：

    @Override
protected boolean checkLayoutParams(ViewGroup.LayoutParams p) {
    return p instanceof HandedPathLayout.LayoutParams;
}

@Override
public HandedPathLayout.LayoutParams generateLayoutParams(AttributeSet attrs) {
    return new HandedPathLayout.LayoutParams(getContext(), attrs);
}

@Override
protected HandedPathLayout.LayoutParams generateDefaultLayoutParams() {
    return new HandedPathLayout.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
}

我在使用和没有完全限定的LayoutParams类名称的情况下尝试了这个。

所以，现在已经全部在那里编译好了，然后在onMeasure的根ViewGroup，HandedLayout，我循环遍历孩子并尝试获取他们的getLayoutParams（）所以我可以找出去哪里把它们以及如何测量它们，我得到这个ClassCastException！

05-29 18：16：35.061 9391-9391 / com.codesolutions.onehandkeyboard E / AndroidRuntime：FATAL EXCEPTION：main 处理：com.codesolutions.onehandkeyboard，PID：9391 java.lang.ClassCastException：com.codesolutions.pathlayout.HandedLayout $ LayoutParams无法强制转换为com.codesolutions.pathlayout.HandedPathLayout $ LayoutParams 在com.codesolutions.pathlayout.HandedLayout.onMeasure（HandedLayout.java:90）

这个异常是从这个演员抛出的，看起来它应该是正确的类型，在调试器中我已经确认孩子确实是HandedPathLayout，并且所有迹象都表明LayoutParams是正确的型！

                HandedPathLayout.LayoutParams lp =
                    (HandedPathLayout.LayoutParams)child.getLayoutParams();

我只是不明白为什么LayoutParams的类型不正确！

关于这个我还没有得到的另一件事是关于我想要放入HandedPathLayout的自定义View（扩展TextView）。它需要一个自定义的layout_rows XML属性，所以我需要将它设置为自己的LayoutParams吗？那些只适用于ViewGroups，对吧？但是，它是需要应用该属性的视图，而不是ViewGroup。

更新：

因此，当我运行调试器并在我的演员失败之前停止时，在HandedLayout的onMeasure中...我发现，确实，LayoutParams对象不是我期望的类型！父级的getLayoutParams（HandedLayout）返回一个FrameLayout.LayoutParams（这对我来说毫无意义），而子级（HandedPathLayout）有一个HandedLayout.LayoutParams！为什么？！我在这里不理解什么？

谢谢！

android自定义布局参数ClassCastException以及View怎么样？

0 个答案: