侧边栏导航布局的实现

来源：互联网发布：联盟挂机软件下载编辑：程序博客网时间：2024/05/06 06:14

代码：

/** * Created on 2017/8/4. * 继承自View的自定义View，SideBar * 主要实现3个方面： * 1.重写Draw方法，定制如何去画出字母表 * 2.重写dispatchTouchEvent方法，定制在接收到不同的事件时，如何去做UI响应 * 3.设置接口，用于实现外部RecyclerView的响应 */public class SideBar extends View {    private OnTouchingLetterChangedListener onTouchingLetterChangedListener;    public static String[] b = { "A", "B", "C", "D", "E", "F", "G", "H", "I",            "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V",            "W", "X", "Y", "Z", "#" };    private int choose = -1;  //以对应的位置的值表示被选中    private Paint paint = new Paint();    private TextView mTextDialog;    /**     * 为SideBar设置显示字母的TextView     * @param textDialog     */    public void setTextView(TextView textDialog) {        this.mTextDialog = textDialog;    }    public SideBar(Context context, AttributeSet attrs, int defStyle) {        super(context, attrs, defStyle);    }    public SideBar(Context context, AttributeSet attrs) {        super(context, attrs);    }    public SideBar(Context context) {        super(context);    }    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        int height = getHeight(); //默认时match_parent        int width = getWidth();        int singleHeight = height / b.length;// 获取每一个字母的高度        for (int i = 0; i < b.length; i++) {            paint.setColor(Color.rgb(33, 65, 98));            paint.setTypeface(Typeface.DEFAULT_BOLD);  //字体加粗            paint.setAntiAlias(true);  //设置抗锯齿            paint.setTextSize(30);            if (i == choose) {// 选中的状态,在点击时改变choose的值                paint.setColor(Color.parseColor("#3399ff"));                paint.setFakeBoldText(true);            }            // x坐标等于中间-字符串宽度的一半,最后对应画的起点            float xPos = width / 2 - paint.measureText(b[i]) / 2;            float yPos = singleHeight * i + singleHeight; //跟写字母的顺序一样，从底部画起            //指定画的内容、起点、画笔            canvas.drawText(b[i], xPos, yPos, paint);            paint.reset();        }    }    @Override    public boolean dispatchTouchEvent(MotionEvent event) {        final int action = event.getAction();        final float y = event.getY();        final int oldChoose = choose;  //一个事件序列创建一次，用于对比改变的        final OnTouchingLetterChangedListener listener = onTouchingLetterChangedListener;        final int c = (int) (y / getHeight() * b.length);// 点击y坐标所占总高度的比例*b数组的长度就等于点击b中的个数        switch (action) {            //UP事件产生：1.清除背景颜色 2.隐藏textView            case MotionEvent.ACTION_UP:                setBackground(new ColorDrawable(0x00000000));                choose = -1;//清除被选中的值                invalidate();                if (mTextDialog != null) {                    mTextDialog.setVisibility(View.INVISIBLE);                }                break;            //DOWN、MOVE事件产生：1.设置背景颜色 2.列表滚动 3.显示字母            default:                setBackgroundResource(R.drawable.sidebar_background);                if (oldChoose != c) {                    if (c >= 0 && c < b.length) {                        if (listener != null) {                            //让RecyclerView一起滚动                            listener.onTouchingLetterChanged(b[c]);                        }                        if (mTextDialog != null) {                            //设置显示字母                            mTextDialog.setText(b[c]);                            mTextDialog.setVisibility(View.VISIBLE);                        }                        choose = c;                        invalidate(); //重新绘画，保证点击字母颜色改变                    }                }                break;        }        return true;    }    /**     * 触摸事件     * @param onTouchingLetterChangedListener     */    public void setOnTouchingLetterChangedListener(            OnTouchingLetterChangedListener onTouchingLetterChangedListener) {        this.onTouchingLetterChangedListener = onTouchingLetterChangedListener;    }    public interface OnTouchingLetterChangedListener {        void onTouchingLetterChanged(String s);    }}

对于列表的监听代码：

//设置右侧SideBar触摸监听        sideBar.setOnTouchingLetterChangedListener(new SideBar.OnTouchingLetterChangedListener() {            @Override            public void onTouchingLetterChanged(String s) {                //该字母首次出现的位置                int position = adapter.getPositionForSection(s.charAt(0));                if (position != -1) {                    layoutManager.scrollToPositionWithOffset(position, 0);                }            }        });

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