Android：具有现有布局的自定义视图的多个视图子视图

Question

我必须在 Android 中构建一个更复杂的自定义视图。最终布局应如下所示：

<RelativeLayout>
  <SomeView />
  <SomeOtherView />
  <!-- maybe more layout stuff here later -->
  <LinearLayout>
    <!-- the children -->
  </LinearLayout>
</RelativeLayout>

但是，我只想在 XML 文件中定义这个（不定义 SomeView、SomeOtherView 等）：

<MyCustomView>
  <!-- the children -->
</MyCustomView>

这在 Android 中是否可行，如果可以：最干净的方法是什么？ 我想到的可能解决方案是“覆盖 addView() 方法”和“删除所有视图并稍后再添加”，但我不确定该走哪条路……

非常感谢您的帮助！ :)

Answer 1

创建自定义容器视图是绝对可行的，并且受到鼓励。这就是 Android 所说的复合控件。所以：

public class MyCustomView extends RelativeLayout {
    private LinearLayout mContentView;

    public MyCustomView(Context context) {
        this(context, null);
    }

    public MyCustomView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public MyCustomView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        //Inflate and attach your child XML
        LayoutInflater.from(context).inflate(R.layout.custom_layout, this);
        //Get a reference to the layout where you want children to be placed
        mContentView = (LinearLayout) findViewById(R.id.content);

        //Do any more custom init you would like to access children and do setup
    }

    @Override
    public void addView(View child, int index, ViewGroup.LayoutParams params) {
        if(mContentView == null){
            super.addView(child, index, params);
        } else {
            //Forward these calls to the content view
            mContentView.addView(child, index, params);
        }
    }
}

您可以根据需要覆盖任意多个版本的addView()，但最终它们都会回调到我放置在示例中的版本。仅覆盖此方法将使框架将在其 XML 标记中找到的所有子容器传递给特定的子容器。

然后像这样修改XML：

res/layout/custom_layout.xml

<merge>
  <SomeView />
  <SomeOtherView />
  <!-- maybe more layout stuff here later -->
  <LinearLayout
      android:id="@+id/content" />
</merge>

使用<merge> 的原因是为了简化层次结构。所有子视图都将附加到您的自定义类，即RelativeLayout。如果您不使用<merge>，您最终会将RelativeLayout 附加到另一个RelativeLayout 附加到所有子级，这可能会导致问题。

---

Kotlin 版本：

    private fun expand(view: View) {
        val parentWidth = (view.parent as View).width
        val matchParentMeasureSpec = MeasureSpec.makeMeasureSpec(parentWidth, MeasureSpec.EXACTLY)
        val wrapContentMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED)

        view.measure(matchParentMeasureSpec, wrapContentMeasureSpec)
        val targetHeight = view.measuredHeight
        view.isVisible = true
        val animation: Animation = getExpandAnimation(view, targetHeight)

        view.startAnimation(animation)
    }

    private fun getExpandAnimation(
        view: View,
        targetHeight: Int
    ): Animation = object : Animation() {
        override fun applyTransformation(
            interpolatedTime: Float,
            transformation: Transformation
        ) {
            view.layoutParams.height =
                if (interpolatedTime == 1f) {
                    LayoutParams.WRAP_CONTENT
                } else {
                    (targetHeight * interpolatedTime).toInt()
                }

            view.requestLayout()
        }

        override fun willChangeBounds(): Boolean {
            return true
        }
    }.apply {
        duration = getDuration(targetHeight, view)
    }

    private fun collapse(view: View) {
        val initialHeight = view.measuredHeight
        val animation: Animation = getCollapseAnimation(view, initialHeight)

        view.startAnimation(animation)
    }

    private fun getCollapseAnimation(
        view: View,
        initialHeight: Int
    ): Animation = object : Animation() {
        override fun applyTransformation(
            interpolatedTime: Float,
            transformation: Transformation
        ) {
            if (interpolatedTime == 1f) {
                view.isVisible = false
            } else {
                view.layoutParams.height =
                    initialHeight - (initialHeight * interpolatedTime).toInt()
                view.requestLayout()
            }
        }

        override fun willChangeBounds(): Boolean = true

    }.apply {
        duration = getDuration(initialHeight, view)
    }

    /**
     * Speed = 1dp/ms
     */
    private fun getDuration(initialHeight: Int, view: View) =
        (initialHeight / view.context.resources.displayMetrics.density).toLong()