Android FlowLayout-优快云博客

本文链接：https://blog.youkuaiyun.com/iteye_10104/article/details/82342401

本文介绍了一个自定义的FlowLayout布局实现方式，该布局允许子视图在父容器中水平排列，并在达到容器宽度限制时换行。文章详细展示了FlowLayout类的源码，包括其构造方法、onMeasure方法及onLayout方法。

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[url]https://github.com/ApmeM/android-flowlayout[/url] 使用这个类库。


import android.content.Context;

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

/**
 *
 * @author RAW
 */
public class FlowLayout extends ViewGroup {
    private final static int PAD_H = 2, PAD_V = 2; // Space between child views.
    private int mHeight;

    public FlowLayout(Context context) {
        super(context);
    }

    public FlowLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        assert (MeasureSpec.getMode(widthMeasureSpec) != MeasureSpec.UNSPECIFIED);
        final int width = MeasureSpec.getSize(widthMeasureSpec) - getPaddingLeft() - getPaddingRight();
        int height = MeasureSpec.getSize(heightMeasureSpec) - getPaddingTop() - getPaddingBottom();
        final int count = getChildCount();
        int xpos = getPaddingLeft();
        int ypos = getPaddingTop();
        int childHeightMeasureSpec;
        if(MeasureSpec.getMode(heightMeasureSpec) == MeasureSpec.AT_MOST)
            childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.AT_MOST);
        else
            childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
        mHeight = 0;
        for(int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if(child.getVisibility() != GONE) {
                child.measure(MeasureSpec.makeMeasureSpec(width, MeasureSpec.AT_MOST), childHeightMeasureSpec);
                final int childw = child.getMeasuredWidth();
                mHeight = Math.max(mHeight, child.getMeasuredHeight() + PAD_V);
                if(xpos + childw > width) {
                    xpos = getPaddingLeft();
                    ypos += mHeight;
                }
                xpos += childw + PAD_H;
            }
        }
        if(MeasureSpec.getMode(heightMeasureSpec) == MeasureSpec.UNSPECIFIED) {
            height = ypos + mHeight;
        } else if(MeasureSpec.getMode(heightMeasureSpec) == MeasureSpec.AT_MOST) {
            if(ypos + mHeight < height) {
                height = ypos + mHeight;
            }
        }
        height += 5; // Fudge to avoid clipping bottom of last row.
        setMeasuredDimension(width, height);
    } // end onMeasure()

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        final int width = r - l;
        int xpos = getPaddingLeft();
        int ypos = getPaddingTop();
        for(int i = 0; i < getChildCount(); i++) {
            final View child = getChildAt(i);
            if(child.getVisibility() != GONE) {
                final int childw = child.getMeasuredWidth();
                final int childh = child.getMeasuredHeight();
                if(xpos + childw > width) {
                    xpos = getPaddingLeft();
                    ypos += mHeight;
                }
                child.layout(xpos, ypos, xpos + childw, ypos + childh);
                xpos += childw + PAD_H;
            }
        }
    } // end onLayout()
}