今天跟大家分享一下FlowLayout，最近專案中有遇到熱門標籤這個樣的佈局（文章末尾可下載原始碼），如下圖：

一，建立FlowLayout並繼承ViewGroup

FlowLayout 類主要實現onMeasure，onLayout和generateLayoutParams方法，具體如下看程式碼註釋；

public class FlowLayout extends ViewGroup 
{


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

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

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

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

        int sizeWidth = MeasureSpec.getSize(widthMeasureSpec);
        int
 
 modeWidth = MeasureSpec.getMode(widthMeasureSpec);
        int sizeHeight = MeasureSpec.getSize(heightMeasureSpec);
        int modeHeight = MeasureSpec.getMode(heightMeasureSpec);

        // 如果是warp_content情況下，記錄寬和高  
        int width = 0;
        int height = 0;

        // 記錄每一行的寬度與高度
        int lineWidth = 0
 
;
        int lineHeight = 0;

        // 得到內部元素的個數
        int cCount = getChildCount();

        for (int i = 0; i < cCount; i++)
        {
            // 通過索引拿到每一個子view
            View child = getChildAt(i);
            // 測量子View的寬和高,系統提供的measureChild
            measureChild(child, widthMeasureSpec, heightMeasureSpec);
            // 得到LayoutParams
            MarginLayoutParams lp = (MarginLayoutParams) child
                                                                .getLayoutParams();

            // 子View佔據的寬度
            int childWidth = child.getMeasuredWidth() + lp.leftMargin
                                + lp.rightMargin;
            // 子View佔據的高度
            int childHeight = child.getMeasuredHeight() + lp.topMargin
                                + lp.bottomMargin;

            // 換行 判斷 當前的寬度大於 開闢新行
            if (lineWidth + childWidth > sizeWidth - getPaddingLeft() - getPaddingRight())
            {
                // 對比得到最大的寬度
                width = Math.max(width, lineWidth);
                // 重置lineWidth
                lineWidth = childWidth;
                // 記錄行高
                height += lineHeight;
                lineHeight = childHeight;
            }
            else
            // 未換行
            {
                // 疊加行寬
                lineWidth += childWidth;
                // 得到當前行最大的高度
                lineHeight = Math.max(lineHeight, childHeight);
            }
            // 特殊情況,最後一個控制元件
            if (i == cCount - 1)
            {
                width = Math.max(lineWidth, width);
                height += lineHeight;
            }
        }
        setMeasuredDimension(
                                modeWidth == MeasureSpec.EXACTLY ? sizeWidth : width + getPaddingLeft() + getPaddingRight(),
                                modeHeight == MeasureSpec.EXACTLY ? sizeHeight : height + getPaddingTop() + getPaddingBottom()//
        );

    }

    /**
     * 儲存所有的View
     */
    private List<List<View>>    mAllViews   = new ArrayList<List<View>>();
    /**
     * 每一行的高度
     */
    private List<Integer>       mLineHeight = new ArrayList<Integer>();

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b)
    {
        mAllViews.clear();
        mLineHeight.clear();

        // 當前ViewGroup的寬度
        int width = getWidth();

        int lineWidth = 0;
        int lineHeight = 0;

        // 存放每一行的子view
        List<View> lineViews = new ArrayList<View>();

        int cCount = getChildCount();

        for (int i = 0; i < cCount; i++)
        {
            View child = getChildAt(i);
            MarginLayoutParams lp = (MarginLayoutParams) child
                                                                .getLayoutParams();

            int childWidth = child.getMeasuredWidth();
            int childHeight = child.getMeasuredHeight();

            // 如果需要換行
            if (childWidth + lineWidth + lp.leftMargin + lp.rightMargin > width - getPaddingLeft() - getPaddingRight())
            {
                // 記錄LineHeight
                mLineHeight.add(lineHeight);
                // 記錄當前行的Views
                mAllViews.add(lineViews);

                // 重置我們的行寬和行高
                lineWidth = 0;
                lineHeight = childHeight + lp.topMargin + lp.bottomMargin;
                // 重置我們的View集合
                lineViews = new ArrayList<View>();
            }
            lineWidth += childWidth + lp.leftMargin + lp.rightMargin;
            lineHeight = Math.max(lineHeight, childHeight + lp.topMargin
                                                + lp.bottomMargin);
            lineViews.add(child);

        }// for end
            // 處理最後一行
        mLineHeight.add(lineHeight);
        mAllViews.add(lineViews);

        // 設定子View的位置

        int left = getPaddingLeft();
        int top = getPaddingTop();

        // 行數
        int lineNum = mAllViews.size();

        for (int i = 0; i < lineNum; i++)
        {
            // 當前行的所有的View
            lineViews = mAllViews.get(i);
            lineHeight = mLineHeight.get(i);

            for (int j = 0; j < lineViews.size(); j++)
            {
                View    child = lineViews.get(j);
                // 判斷child的狀態
                if (child.getVisibility() == View.GONE)
                {
                    continue;
                }

                MarginLayoutParams lp = (MarginLayoutParams) child
                                                                    .getLayoutParams();

                int lc = left + lp.leftMargin;
                int tc = top + lp.topMargin;
                int rc = lc + child.getMeasuredWidth();
                int bc = tc + child.getMeasuredHeight();

                // 為子View進行佈局
                child.layout(lc, tc, rc, bc);

                left += child.getMeasuredWidth() + lp.leftMargin
                        + lp.rightMargin;
            }
            left = getPaddingLeft();
            top += lineHeight;
        }

    }

    /**
     * 與當前ViewGroup對應的LayoutParams
     */
    @Override
    public LayoutParams generateLayoutParams(AttributeSet attrs)
    {
        return new MarginLayoutParams(getContext(), attrs);
    }


}

二，在MainActivity呼叫實現

public class MainActivity extends ActionBarActivity {
    private String[] mVals = new String[] { "蘋果手機", "膝上型電腦", "電飯煲 ", "臘肉",
            "特產", "剃鬚刀", "寶寶", "康佳" };
    private LayoutInflater mInflater;
    private FlowLayout mFlowLayout;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mInflater = LayoutInflater.from(this);
        mFlowLayout = (FlowLayout) findViewById(R.id.id_flowlayout);
        initData();
    }
    public void initData() {
        /**
         * 找到搜尋標籤的控制元件
         */
        for (int i = 0; i < mVals.length; i++) {
            TextView tv = (TextView) mInflater.inflate(
                    R.layout.search_label_tv, mFlowLayout, false);
            tv.setText(mVals[i]);
            final String str = tv.getText().toString();
            //點選事件
            tv.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {

                }
            });
            mFlowLayout.addView(tv);//新增到父View
        }
    }

}

1，MainActivity的xml佈局
注意 佈局當中的com.example.com.lff.test.FlowLayout

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.com.lff.test.MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />
    <com.example.com.lff.test.FlowLayout
          android:id="@+id/id_flowlayout"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:background="#FFFFFF"
                android:padding="10dp" >
    </com.example.com.lff.test.FlowLayout>
</RelativeLayout>

2，單個標籤空間的佈局，也就是上述Activity中的search_label_tv.xml

search_label_tv

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_margin="5dp"
    android:textColor="#3f3e3e"
    android:background="@drawable/search_label_bg"
    android:textSize="14sp"
    android:text="Helloworld" >

</TextView>

結束語：簡單，清晰，明瞭。歡迎大家指正吐槽。