自定义View实现索引效果

来源：互联网发布：树莓派zerow ubuntu 编辑：程序博客网时间：2024/05/19 18:42
效果图展示
图片名称
实现代码
public class SideLetterBar extends View {    private static final 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;    private Paint paint = new Paint();    private boolean showBg = false;    private OnLetterChangedListener onLetterChangedListener;    private TextView overlay;    public SideLetterBar(Context context, AttributeSet attrs, int defStyle) {        super(context, attrs, defStyle);    }    public SideLetterBar(Context context, AttributeSet attrs) {        super(context, attrs);    }    public SideLetterBar(Context context) {        super(context);    }    /**     * 设置悬浮的textview     * @param overlay     */    public void setOverlay(TextView overlay){        this.overlay = overlay;    }    @SuppressWarnings("deprecation")    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        if (showBg) {            //选中时画布的背景            canvas.drawColor(getResources().getColor(R.color.shadow));        }        //画出索引字母        int height = getHeight();  //获得控件高度        int width = getWidth();    //获得控件宽度        int singleHeight = height / b.length;    //得到每一个字母的高度        //循环画出所有的文字和字母        for (int i = 0; i < b.length; i++) {            paint.setTextSize(getResources().getDimension(R.dimen.side_letter_bar_letter_size));            paint.setColor(getResources().getColor(R.color.gray));            paint.setAntiAlias(true);//设置画笔抗锯齿            //手指摁下时当前字母颜色变为红色            if (i == choose) {                paint.setColor(Color.RED);                paint.setFakeBoldText(true);  //加粗            }            //计算相应字母的距离居中            float xPos = width / 2 - paint.measureText(b[i]) / 2;  //控件宽度的一半，减去当前字符宽度的一半，得到X轴坐标            float yPos = singleHeight * i + singleHeight;   //前面所有字符的高度，加上当前字符的高度，得到y轴坐标（文字绘制是从文字基线开始绘制）            canvas.drawText(b[i], xPos, yPos, paint);            paint.reset();  //重置画笔        }    }    // 设置中间显示的结果    @Override    public boolean dispatchTouchEvent(MotionEvent event) {        final int action = event.getAction();        final float y = event.getY();        final int oldChoose = choose;        final OnLetterChangedListener listener = onLetterChangedListener;        //相应高度的比例乘以字符数组长度就是我们要的字母        final int c = (int) (y / getHeight() * b.length);        switch (action) {            case MotionEvent.ACTION_DOWN:  //按下                showBg = true;                if (oldChoose != c && listener != null) {                    if (c >= 0 && c < b.length) {                        listener.onLetterChanged(b[c]);                        choose = c;                        invalidate();  //刷新View                        if (overlay != null){                            overlay.setVisibility(VISIBLE);                            overlay.setText(b[c]);                        }                    }                }                break;            case MotionEvent.ACTION_MOVE:  //触摸                if (oldChoose != c && listener != null) {                    if (c >= 0 && c < b.length) {                        listener.onLetterChanged(b[c]);                        choose = c;                        invalidate();                        if (overlay != null){                            overlay.setVisibility(VISIBLE);                            overlay.setText(b[c]);                        }                    }                }                break;            case MotionEvent.ACTION_UP:  //抬起                showBg = false;                choose = -1;                invalidate();                if (overlay != null){                    overlay.setVisibility(GONE);                }                break;        }        return true;    }    @Override    public boolean onTouchEvent(MotionEvent event) {        return super.onTouchEvent(event);    }    public void setOnLetterChangedListener(OnLetterChangedListener onLetterChangedListener) {        this.onLetterChangedListener = onLetterChangedListener;    }    /**     * 定义回调接口用来传值     */    public interface OnLetterChangedListener {        void onLetterChanged(String letter);    }}
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