android 仿微信通讯录旁边的bar

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import android.content.Context;import android.graphics.Bitmap;import android.graphics.Canvas;import android.graphics.Paint;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.View;/** * 仿微信通讯录旁边的bar */public class SideBar extends View {    private String[] letters;    private OnLetterTouchListener letterTouchListener;    public SideBar(Context context) {        super(context);    }    public SideBar(Context context, AttributeSet attrs) {        super(context, attrs);    }    public SideBar(Context context, AttributeSet attrs, int defStyle) {        super(context, attrs, defStyle);    }    /**     * 每一项的高度     */    private float itemHeight = -1;    private Paint paint;    private Bitmap letterBitmap;    @Override    protected void onDraw(Canvas canvas) {        if (letters == null) {            return;        }        if (itemHeight == -1) {            itemHeight = getHeight() / letters.length;        }        if (paint == null) {            //初始化画笔            paint = new Paint();            paint.setTextSize(itemHeight - 4);            //字体颜色            paint.setColor(getResources().getColor(R.color.white));            paint.setFlags(Paint.ANTI_ALIAS_FLAG);            //创建一张包含所有列表的图            Canvas mCanvas = new Canvas();            letterBitmap = Bitmap.createBitmap(getMeasuredWidth(), getMeasuredHeight(),                    Bitmap.Config.ARGB_8888);            mCanvas.setBitmap(letterBitmap);            float widthCenter = getMeasuredWidth() / 2.0F;            //画字符上图片中            for (int i = 0; i < letters.length; i++) {                mCanvas.drawText(letters[i], widthCenter - paint.measureText(letters[i]) / 2,                        itemHeight * i + itemHeight, paint);            }        }        if (letterBitmap != null) {//图片不为空就画图            canvas.drawBitmap(letterBitmap, 0, 0, paint);        }        super.onDraw(canvas);    }    @Override    public boolean onTouchEvent(MotionEvent event) {        super.onTouchEvent(event);        if (letterTouchListener == null || letters == null) {            return false;        }        switch (event.getAction()) {            case MotionEvent.ACTION_DOWN:            case MotionEvent.ACTION_MOVE:                LogUtil.v(TAG, "action down or move");                int position = (int) (event.getY() / itemHeight + 1);                if (position >= 0 && position < letters.length) {                    letterTouchListener.onLetterTouch(letters[position], position);                }                return true;            case MotionEvent.ACTION_OUTSIDE:            case MotionEvent.ACTION_UP:                LogUtil.v(TAG, "action up");                letterTouchListener.onActionUp();                return true;        }        return false;    }    /**     * 设置显示在边栏上的字母     * @param letters     */    public void setShowString(String[] letters) {        this.letters = letters;    }    /**     * 设置点击某个字母的时候     * @param listener     */    public void setOnLetterTouchListener(OnLetterTouchListener listener) {        this.letterTouchListener = listener;    }    public interface OnLetterTouchListener {        /**         * 某个字母被按下的时候         * @param letter         * @param position         */        public void onLetterTouch(String letter, int position);        /**         * 触控手指离开的时候         */        public void onActionUp();    }}
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