Android 自定义View字母滑动索引

来源：互联网发布：黑莓9900软件下载编辑：程序博客网时间：2024/06/06 22:11
public class AlphaView extends View {    private String[] alphas = {"#", "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 OnTouchingAlphaChangedListener mOnTouchingAlphaChangedListener;    //初始化画笔    private Paint mPaint = new Paint();    //选中索引    private int mChoose = -1;    //是否显示    private boolean mShowBg = false;    public AlphaView(Context context) {        super(context);    }    public AlphaView(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);    }    public AlphaView(Context context, AttributeSet attrs) {        super(context, attrs);    }    @Override    public boolean dispatchTouchEvent(MotionEvent event) {        //事件触摸发生的Y值        float y = event.getY();        //计算选中的字母索引        int index = (int) (y / getHeight() * alphas.length);        switch (event.getAction()) {            case MotionEvent.ACTION_DOWN:            case MotionEvent.ACTION_MOVE:                if (mOnTouchingAlphaChangedListener != null                        && (index >= 0) && (index < alphas.length)) {                    mOnTouchingAlphaChangedListener.onTouchingAlphaChanged(alphas[index]);                }                mChoose = index;                //invalidate()会调用onDraw办法                invalidate();                mShowBg = true;                return true;            case MotionEvent.ACTION_UP:                mShowBg = false;                mChoose = -1;                invalidate();                return true;            default:                break;        }        return super.dispatchTouchEvent(event);    }    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        if (mShowBg) {            canvas.drawColor(Color.parseColor("#40000000"));        }        int viewHeight = getHeight();        int viewWidth = getWidth();        int alphaH = viewHeight / alphas.length;        for (int i = 0; i < alphas.length; i++) {            mPaint.setColor(-1);            mPaint.setTypeface(Typeface.DEFAULT_BOLD);            mPaint.setAntiAlias(true);            mPaint.setTextSize(30);            if (i == mChoose) {                mPaint.setColor(Color.parseColor("#ff1a9c78"));                mPaint.setFakeBoldText(true);            }            float x = viewWidth / 2 - mPaint.measureText(alphas[i]) / 2.0f;            float y = alphaH + alphaH * i;            canvas.drawText(alphas[i], x, y, mPaint);            mPaint.reset();        }    }    public void setOnTouchingAlphaChangedListener(OnTouchingAlphaChangedListener listener) {        mOnTouchingAlphaChangedListener = listener;    }    //定义字母变化监听接口    public interface OnTouchingAlphaChangedListener {        void onTouchingAlphaChanged(String alpha);    }}
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