Android：使用现有布局为自定义视图创建多个视图子项

Question

Android：使用现有布局为自定义视图创建多个视图子项

javaandroidxmlandroid-layoutandroid-custom-view

41

我需要在Android中构建一个更复杂的自定义视图。最终布局应该像这样：

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

但是，在XML文件中，我只想定义它（而不定义SomeView、SomeOtherView等内容）：

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

在Android中是否可能实现此功能，如果可以的话，最干净的方法是什么？我想到了两种可能的解决方案：'覆盖addView()方法'和'删除所有视图然后稍后再添加它们'，但我不确定应该选择哪种方法...

非常感谢您的帮助！ :)

- mreichelt

1个回答

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- devunwired · Accepted Answer

完全可以创建自定义容器视图，并且这是可行的和被鼓励的。在Android中，这被称为复合控件。

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);
        }
    }
}

您可以覆盖尽可能多的addView()版本，但最终它们都会回调我放置在示例中的版本。仅覆盖此方法将使框架将其XML标记内找到的所有子项传递给特定的子容器。然后按如下修改XML： res/layout/custom_layout.xml

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

使用 <merge> 的原因是为了简化布局层次结构。所有子视图都将附加到您的自定义类，即 RelativeLayout。如果不使用 <merge>，则最终会得到一个与所有子项关联的 RelativeLayout 附加到另一个 RelativeLayout 的情况，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()