Android最简洁的自动换行布局组件

自动换行是一种布局特性，理所当然应该在布局组件中实现。

我们基于ViewGroup实现了最简洁和稳定的自动换行布局组件AutoLinefeedLayout。该组件无需特别设置，只要将孩子塞给它，就会自动换行显示，无任何限制。

源码如下：

package melandru.android.sdk.widget;

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;

public class AutoLinefeedLayout extends ViewGroup {

	public AutoLinefeedLayout(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
	}

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

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

	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
		layoutHorizontal();
	}

	private void layoutHorizontal() {
		final int count = getChildCount();
		final int lineWidth = getMeasuredWidth() - getPaddingLeft()
				- getPaddingRight();
		int paddingTop = getPaddingTop();
		int childTop = 0;
		int childLeft = getPaddingLeft();

		int availableLineWidth = lineWidth;
		int maxLineHight = 0;

		for (int i = 0; i < count; i++) {
			final View child = getChildAt(i);
			if (child == null) {
				continue;
			} else if (child.getVisibility() != GONE) {
				final int childWidth = child.getMeasuredWidth();
				final int childHeight = child.getMeasuredHeight();

				if (availableLineWidth < childWidth) {
					availableLineWidth = lineWidth;
					paddingTop = paddingTop + maxLineHight;
					childLeft = getPaddingLeft();
					maxLineHight = 0;
				}
				childTop = paddingTop;
				setChildFrame(child, childLeft, childTop, childWidth,
						childHeight);
				childLeft += childWidth;
				availableLineWidth = availableLineWidth - childWidth;
				maxLineHight = Math.max(maxLineHight, childHeight);
			}
		}
	}

	private void setChildFrame(View child, int left, int top, int width,
			int height) {
		child.layout(left, top, left + width, top + height);
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
		int count = getChildCount();
		for (int i = 0; i < count; i++) {
			measureChild(getChildAt(i), widthMeasureSpec, heightMeasureSpec);
		}
		if (heightMode == MeasureSpec.AT_MOST||heightMode == MeasureSpec.UNSPECIFIED) {
			final int width = MeasureSpec.getSize(widthMeasureSpec);
			super.onMeasure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(
					getDesiredHeight(width), MeasureSpec.EXACTLY));
		} else {
			super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		}
	}

	private int getDesiredHeight(int width) {
		final int lineWidth = width - getPaddingLeft() - getPaddingRight();
		int availableLineWidth = lineWidth;
		int totalHeight = getPaddingTop() + getPaddingBottom();
		int lineHeight = 0;
		for (int i = 0; i < getChildCount(); i++) {
			View child = getChildAt(i);
			final int childWidth = child.getMeasuredWidth();
			final int childHeight = child.getMeasuredHeight();
			if (availableLineWidth < childWidth) {
				availableLineWidth = lineWidth;
				totalHeight = totalHeight + lineHeight;
				lineHeight = 0;
			}
			availableLineWidth = availableLineWidth - childWidth;
			lineHeight = Math.max(childHeight, lineHeight);
		}
		totalHeight = totalHeight + lineHeight;
		return totalHeight;
	}

}

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作者：

薄荷记账     优秀源码探索者     简洁   稳定   优雅   无限可能！

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