Android從0到1實(shí)現(xiàn)流布局控件

/** * description 流布局viewGroup */public class FlowLayoutView extends ViewGroup {    private List<Row> rows = new ArrayList<>();    private int usedWidth;    /**     * 當(dāng)前需要操作的行     */    private Row curRow;    private int verticalPadding = 30;    private int horizontalPadding = 40;
    public FlowLayoutView(Context context) {        super(context);    }
    public FlowLayoutView(Context context, AttributeSet attrs) {        super(context, attrs);    }
    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        restoreLine();  //每次重新布局，屬性要初始化，避免onMeasure重復(fù)調(diào)用混亂問題
        //子view設(shè)置寬高為父view大小減去padding值        int width = MeasureSpec.getSize(widthMeasureSpec);        int height = MeasureSpec.getSize(heightMeasureSpec);        int widthMode = MeasureSpec.getMode(widthMeasureSpec);        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        //設(shè)置每個(gè)子view寬高，并且將每個(gè)子View歸到自己的行        for (int i = 0; i < getChildCount(); i++) {            View childView = getChildAt(i);
            //設(shè)置子view設(shè)置AT_MOST模式，即布局屬性為wrap_content            int childWidthSpec = MeasureSpec.makeMeasureSpec(width, widthMode == MeasureSpec.EXACTLY ? MeasureSpec.AT_MOST : widthMode);            int childHeightSpec = MeasureSpec.makeMeasureSpec(height, heightMode == MeasureSpec.EXACTLY ? MeasureSpec.AT_MOST : heightMode);            childView.measure(childWidthSpec, childHeightSpec);
            if (curRow == null) {                curRow = new Row();            }
            //根據(jù)當(dāng)前childview寬度和剩余寬度判斷是否能放進(jìn)當(dāng)前行，放不了就要換行            if (childView.getMeasuredWidth() + horizontalPadding > width - usedWidth) {                //先換行，再放入                nextLine();            }
            usedWidth += childView.getMeasuredWidth() + horizontalPadding;            curRow.addView(childView);        }
        //將最后一個(gè)row加入到rows中        rows.add(curRow);
        //根據(jù)子view組成的高度重設(shè)自己高度        int finalHeight = 0;        for (Row row : rows) {            finalHeight += row.height + verticalPadding;        }
        setMeasuredDimension(width, finalHeight);    }
    @Override    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        int top = 0;        //遍歷每一行，將每一行子view布局        for (Row row : rows) {            row.layout(top);            top = top + row.height + verticalPadding;        }    }
    /**     * 換行，需要將當(dāng)前row存儲(chǔ)，并且創(chuàng)建新的row，新的行使用空間置0     */    private void nextLine() {        rows.add(curRow);        curRow = new Row();        usedWidth = 0;    }
    /**     * 每次onmeasure需要重置信息     */    private void restoreLine() {        rows.clear();        curRow = new Row();        usedWidth = 0;    }
    /**     * 用于記錄每一行放置子View的信息     */    class Row {        /**         * 該行放置的子view         */        private List<View> childViews = new ArrayList<>();        private int height;
        public void addView(View view) {            childViews.add(view);            height = view.getMeasuredHeight() > height ? view.getMeasuredHeight() : height;  //高度取最高子view的高度        }
        public int getSize() {            return childViews.size();        }
        /**         * 將當(dāng)前childViews進(jìn)行布局         * top 當(dāng)前hang處于的頂部高度         */        public void layout(int top) {            int leftMargin = 0;            for (int i = 0; i < childViews.size(); i++) {                View view = childViews.get(i);                view.layout(leftMargin, top, leftMargin + view.getMeasuredWidth(), top + view.getMeasuredHeight());                leftMargin = leftMargin + view.getMeasuredWidth() + horizontalPadding;            }        }    }}

public class MainActivity extends AppCompatActivity {    private FlowLayoutView flowLayoutView;
    private String[] tagTextArray = new String[]{"天貓精靈", "充電臺(tái)燈", "睡衣", "手表", "創(chuàng)意水杯", "夏天T恤男", "燈光機(jī)械鍵盤",            "計(jì)算機(jī)原理", "學(xué)霸筆記本", "可口可樂", "跑步機(jī)", "旅行箱", "竹漿衛(wèi)生紙", "吹風(fēng)機(jī)", "洗面奶", "窗簾"};
    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);
        init();    }
    private void init() {        flowLayoutView = findViewById(R.id.flowlayout);
        TextView tvAddTag = findViewById(R.id.tv_addtag);        tvAddTag.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                View view = LayoutInflater.from(getApplicationContext()).inflate(R.layout.item_tagview, null);                TextView tvContent = view.findViewById(R.id.tv_content);                tvContent.setText(tagTextArray[(int) (Math.random()*tagTextArray.length)]);                flowLayoutView.addView(view);            }        });    }}