右側A-Z導航

package com.bitcare.view;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Typeface;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

/**
 * @date 2013-8-6
 */
public class MySideBar extends View {
	OnTouchingLetterChangedListener onTouchingLetterChangedListener;
	// 26個字母
	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" };
	int choose = -1;
	Paint paint = new Paint();

	public MySideBar(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
	}

	public MySideBar(Context context, AttributeSet attrs) {
		super(context, attrs);
	}

	public MySideBar(Context context) {
		super(context);
	}

	/**
	 * 重寫這個方法
	 */
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);
		int height = getHeight();
		int width = getWidth();
		int singleHeight = height / b.length;
		for (int i = 0; i < b.length; i++) {
			paint.setColor(Color.BLACK);
			paint.setTypeface(Typeface.DEFAULT_BOLD);
			paint.setAntiAlias(true);
			paint.setTextSize(20);
			if (i == choose) {
				paint.setColor(Color.RED);
				paint.setFakeBoldText(true);
			}
			float xPos = width / 2 - paint.measureText(b[i]) / 2;
			float yPos = singleHeight * i + singleHeight;
			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;
		final OnTouchingLetterChangedListener listener = onTouchingLetterChangedListener;
		final int c = (int) (y / getHeight() * b.length);

		switch (action) {
		case MotionEvent.ACTION_DOWN:
			if (oldChoose != c && listener != null) {
				if (c > 0 && c < b.length) {
					listener.onTouchingLetterChanged(b[c]);
					choose = c;
					invalidate();
				}
			}

			break;
		case MotionEvent.ACTION_MOVE:
			if (oldChoose != c && listener != null) {
				if (c > 0 && c < b.length) {
					listener.onTouchingLetterChanged(b[c]);
					choose = c;
					invalidate();
				}
			}
			break;
		case MotionEvent.ACTION_UP:
			listener.onTouchingUp();
			choose = -1;
			invalidate();
			break;
		}
		return true;
	}

	@Override
	public boolean onTouchEvent(MotionEvent event) {
		return super.onTouchEvent(event);
	}

	/**
	 * 向外公開的方法
	 * 
	 * @param onTouchingLetterChangedListener
	 */
	public void setOnTouchingLetterChangedListener(OnTouchingLetterChangedListener onTouchingLetterChangedListener) {
		this.onTouchingLetterChangedListener = onTouchingLetterChangedListener;
	}

	/**
	 * 接口
	 */
	public interface OnTouchingLetterChangedListener {
		public void onTouchingLetterChanged(String s);//改變事件
		public void onTouchingUp();//擡手事件
	}
}

Activity中的代碼

TextView overlay;// 顯示選中哪一個字母
	private void initOverlay() {
		overlay = new TextView(context);
		overlay.setGravity(Gravity.CENTER);
		overlay.setBackgroundResource(R.color.white);
		overlay.setTextColor(getResources().getColor(R.color.blue_side_txt));
		overlay.setTextSize(70);
		overlay.setWidth(140);
		overlay.setHeight(140);
		overlay.setVisibility(View.INVISIBLE);
		WindowManager.LayoutParams lp = new WindowManager.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT, WindowManager.LayoutParams.TYPE_APPLICATION,
				WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE, PixelFormat.TRANSLUCENT);
		WindowManager windowManager = (WindowManager) this.getSystemService(Context.WINDOW_SERVICE);
		windowManager.addView(overlay, lp);
	}

在onCreate中使用該方法，初始化彈出的

private OnTouchingLetterChangedListener changedListener = new OnTouchingLetterChangedListener() {

		@Override
		public void onTouchingLetterChanged(String s) {
			overlay.setText(s);
			overlay.setVisibility(View.VISIBLE);
			if (firstAlphabet.get(s) != null) {
				lvCity.setSelection(firstAlphabet.get(s));
			}
		}

		@Override
		public void onTouchingUp() {
			overlay.setVisibility(View.INVISIBLE);
		}
	};

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