Android源码分享-自动换行LinearLayout

Android开发中，很多人会遇到满行就自动换到下一行的界面需求，而Android自带的LinearLayout布局自能横排或者竖排，不够显示就加ScrollView，横竖混排就不行了。这里给大家分享一个可以实现自动换行的LinearLayout。

import java.util.Hashtable;

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

/**
* 自动换行的LinearLayout
* @author idengpan
*
*/
@SuppressWarnings({ “unchecked”,”rawtypes” })
public class AutoNextLineLinearlayout extends LinearLayout {
int mLeft, mRight, mTop, mBottom;
Hashtable map = new Hashtable();

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

public AutoNextLineLinearlayout(Context context, int horizontalSpacing, int verticalSpacing) {
super(context);
}

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

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

int mWidth = MeasureSpec.getSize(widthMeasureSpec);
int mCount = getChildCount();
int mX = 0;
int mY = 0;
mLeft = 0;
mRight = 0;
mTop = 5;
mBottom = 0;

int j = 0;

View lastview = null;
for (int i = 0; i < mCount; i++) {
final View child = getChildAt(i);

child.measure(MeasureSpec.UNSPECIFIED, MeasureSpec.UNSPECIFIED);
// 此处增加onlayout中的换行判断，用于计算所需的高度
int childw = child.getMeasuredWidth();
int childh = child.getMeasuredHeight();
mX += childw; // 将每次子控件宽度进行统计叠加，如果大于设定的高度则需要换行，高度即Top坐标也需重新设置

Position position = new Position();
mLeft = getPosition(i – j, i);
mRight = mLeft + child.getMeasuredWidth();
if (mX >= mWidth) {
mX = childw;
mY += childh;
j = i;
mLeft = 0;
mRight = mLeft + child.getMeasuredWidth();
mTop = mY + 5;
// PS：如果发现高度还是有问题就得自己再细调了
}
mBottom = mTop + child.getMeasuredHeight();
mY = mTop; // 每次的高度必须记录 否则控件会叠加到一起
position.left = mLeft;
position.top = mTop + 3;
position.right = mRight;
position.bottom = mBottom;
map.put(child, position);
}
setMeasuredDimension(mWidth, mBottom);
}

@Override
protected LayoutParams generateDefaultLayoutParams() {
return new LayoutParams(0, 0); // default of 1px spacing
}

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

int count = getChildCount();
for (int i = 0; i < count; i++) {
View child = getChildAt(i);
Position pos = (Position) map.get(child);
if (pos != null) {
child.layout(pos.left, pos.top, pos.right, pos.bottom);
} else {
Log.i(“MyLayout”, “error”);
}
}
}

private class Position {
int left, top, right, bottom;
}

public int getPosition(int IndexInRow, int childIndex) {
if (IndexInRow > 0) {
return getPosition(IndexInRow – 1, childIndex – 1) + getChildAt(childIndex – 1).getMeasuredWidth() + 8;
}
return getPaddingLeft();
}
}

用法和普通的LinearLayout类似，在XML布局文件中写入这个自定义类的完整路径，将android:orientation属性指定为horizontal（默认）即可。