自定义ViewGroup - 第五大布局容器(流式布局)

效果图.png

自定义布局

public class TagLayout extends ViewGroup {
    private List<List<View>> mChildViews = new ArrayList<>();

    private BaseAdapter mAdapter;

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

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

    public TagLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    // 2.1 onMeasure() 指定宽高
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        // 清空集合
        mChildViews.clear();

        int childCount = getChildCount();

        // 获取到宽度
        int width = MeasureSpec.getSize(widthMeasureSpec);

        // 高度需要计算
        int height = getPaddingTop() + getPaddingBottom();

        // 一行的宽度
        int lineWidth = getPaddingLeft();

        ArrayList<View> childViews = new ArrayList<>();
        mChildViews.add(childViews);

        // 子View高度不一致的情况下
        int maxHeight = 0;

        for (int i = 0; i < childCount; i++) {

            // 2.1.1 for循环测量子View
            View childView = getChildAt(i);

            if(childView.getVisibility() == GONE){
                continue;
            }

            // 这段话执行之后就可以获取子View的宽高，因为会调用子View的onMeasure
            measureChild(childView, widthMeasureSpec, heightMeasureSpec);

            // margin值 ViewGroup.LayoutParams 没有 就用系统的MarginLayoutParams
            // LinearLayout有自己的 LayoutParams  会复写一个非常重要的方法
            MarginLayoutParams params = (MarginLayoutParams) childView.getLayoutParams();

            // 什么时候需要换行，一行不够的情况下 考虑 margin
            if (lineWidth + (childView.getMeasuredWidth() + params.rightMargin + params.leftMargin) > width) {
                // 换行,累加高度  加上一行条目中最大的高度
                height += maxHeight;
                lineWidth = childView.getMeasuredWidth() + params.rightMargin + params.leftMargin;
                childViews = new ArrayList<>();
                mChildViews.add(childViews);
            } else {
                lineWidth += childView.getMeasuredWidth() + params.rightMargin + params.leftMargin;
                maxHeight = Math.max(childView.getMeasuredHeight() + params.bottomMargin + params.topMargin, maxHeight);
            }

            childViews.add(childView);
        }

        height += maxHeight;

        Log.e("TAG", "width -> " + width + " height-> " + height);
        // 2.1.2 根据子View计算和指定自己的宽高
        setMeasuredDimension(width, height);
    }

    @Override
    protected LayoutParams generateLayoutParams(LayoutParams p) {
        return super.generateLayoutParams(p);
    }

    @Override
    public LayoutParams generateLayoutParams(AttributeSet attrs) {
        return new MarginLayoutParams(getContext(), attrs);
    }

    /**
     * 摆放子View
     */
    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        int childCount = getChildCount();
        int left, top = getPaddingTop(), right, bottom;

        for (List<View> childViews : mChildViews) {
            left = getPaddingLeft();
            int maxHeight = 0;
            for (View childView : childViews) {

                if(childView.getVisibility() == GONE){
                    continue;
                }

                MarginLayoutParams params = (MarginLayoutParams) childView.getLayoutParams();
                left += params.leftMargin;
                int childTop = top + params.topMargin;
                right = left + childView.getMeasuredWidth();
                bottom = childTop + childView.getMeasuredHeight();
                Log.e("TAG", childView.toString());

                Log.e("TAG", "left -> " + left + " top-> " + childTop + " right -> " + right + " bottom-> " + bottom);

                // 摆放
                childView.layout(left, childTop, right, bottom);
                // left 叠加
                left += childView.getMeasuredWidth() + params.rightMargin;

                // 不断的叠加top值
                int childHeight = childView.getMeasuredHeight()+ params.topMargin+params.bottomMargin;
                maxHeight = Math.max(maxHeight,childHeight);
            }

            top += maxHeight;
        }
    }

    /**
     * 设置Adapter
     * @param adapter
     */
    public void setAdapter(BaseAdapter adapter){
        if(adapter == null){
            // 抛空指针异常
        }

        // 清空所有子View
        removeAllViews();

        mAdapter = adapter;

        // 获取数量
        int childCount = mAdapter.getCount();
        for (int i=0;i<childCount;i++){
            // 通过位置获取View
            View childView = mAdapter.getView(i,this);
            addView(childView);
        }
    }
}

BaseAdapter适配器模式

public abstract class BaseAdapter {
    // 1.有多少个条目
    public abstract int getCount();

    // 2.getView通过position
    public abstract View getView(int position, ViewGroup parent);


    // 3.观察者模式及时通知更新
    public void unregisterDataSetObserver(DataSetObserver observer){

    }

    public void registerDataSetObserver(DataSetObserver observer){

    }

使用

public class MainActivity extends AppCompatActivity {


    private TagLayout mTagLayout;
    private List<String> mItems;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mTagLayout = (TagLayout) findViewById(R.id.tag_layout);
        // 标签 后台获取 很多的实现方式  加List<String> 的集合
        mItems = new ArrayList<>();
        mItems.add("春去春又回");
        mItems.add("春天又一次拖着长长的裙裾回归季节的怀抱");
        mItems.add("一缕暖香飞上岁月的枝头");
        mItems.add("染绿了杨柳");
        mItems.add("染绿了大地");
        mItems.add("莫愁湖畔水盈盈");
        mItems.add("一颦一笑总关情");
        mItems.add("万水千山走遍");
        mItems.add("依然走不出念你的那一泉深潭");
        mItems.add("世界最美的爱情");
        mItems.add("是从青丝到白头");
        mItems.add("你做我的情有独钟");
        mItems.add("总拥有一份执手相看两不厌的缱绻");
        mItems.add("我定让如水的心绪在素笺上缓缓流淌");
        mTagLayout.setAdapter(new BaseAdapter() {
            @Override
            public int getCount() {
                return mItems.size();
            }

            @Override
            public View getView(int position, ViewGroup parent) {
                final TextView tagTv = (TextView) LayoutInflater.from(MainActivity.this)
                        .inflate(R.layout.item_tag, parent, false);
                tagTv.setText(mItems.get(position));
                tagTv.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Toast.makeText(MainActivity.this,tagTv.getText().toString(),Toast.LENGTH_LONG).show();
                    }
                });
                return tagTv;
            }
        });
    }


}