WidthAutoAdjustLinearLayout

WidthAutoAdjustLinearLayout.java

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.widget.LinearLayout;

/**
 * 根据可以完整显示的所有子view的总宽度自动调整自身的宽度.
 * <p/>
 * 当第n个childView可以完整显示，第n+1个childView无法完整显示时，不显示n+1及其以后的childView，
 * 并将宽度调整为n个childView的总宽度.
 * <p/>
 * Created by soloslxu on 2015/12/21.
 */
public class WidthAutoAdjustLinearLayout extends LinearLayout {

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

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

    public WidthAutoAdjustLinearLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        setOrientation(HORIZONTAL);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        // 减左右padding后得到children可用的宽度
        int availableWidth = getMeasuredWidth() - getPaddingLeft() - getPaddingRight();
        int totalWidth = 0;
        int maxTotalWidth = -1;
        boolean maxChildIndexFound = false;
        for (int i = 0; i < getChildCount(); i++) {
            View child = getChildAt(i);
            if (child == null || child.getVisibility() == GONE) {
                continue;
            }
            if (maxChildIndexFound) {
                // 已找到最多可容纳的child，后面的child都设为GONE，直接跳过layout
                child.setVisibility(GONE);
            } else {
                LayoutParams lp = (LayoutParams) child.getLayoutParams();
                // 获取childView不被截断时的完整宽度，不要重新measure height，
                // 否则会使child的height的match_parent属性无效
                child.measure(0, heightMeasureSpec);
                int childWidth = child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;
                totalWidth += childWidth;
                if (totalWidth > availableWidth) {
                    // 记录可完整显示的children的总长度
                    maxChildIndexFound = true;
                    if (i == 0) {
                        // 如果第一个长度就超了,对第一个进行截断处理，不要GONE掉
                        maxTotalWidth = availableWidth;
                        child.measure(MeasureSpec.makeMeasureSpec(availableWidth, MeasureSpec.EXACTLY),
                                MeasureSpec.makeMeasureSpec(child.getMeasuredHeight(), MeasureSpec.EXACTLY));
                    } else {
                        // 后面的如果超了，GONE掉
                        maxTotalWidth = totalWidth - childWidth;
                        child.setVisibility(GONE);
                    }
                } else if (totalWidth == availableWidth) {
                    // 如果前0~i正好达到最大宽度，第i个child的宽度不需要减掉，也不需要隐藏，
                    // 仅需记录标志位，让后面的child隐藏。
                    maxChildIndexFound = true;
                    maxTotalWidth = totalWidth;
                }
            }
        }
        // 重设宽度
        if (maxChildIndexFound) {
            // 不能完整显示所有child，设为计算出的最大宽度maxTotalWidth
            setMeasuredDimension(maxTotalWidth, getMeasuredHeight());
        } else {
            // 可以完整显示所有child，设为所有child的总宽度之和
            setMeasuredDimension(totalWidth, getMeasuredHeight());
        }
    }
}