上一篇文章虽然实现了ListView 快速索引的效果，但是有一个小小的Bug。这个Bug我在前面也说了，这篇文章就来解决这个Bug。
我研究的时候发现只要showBg值为true，中间的字母就显示，而当showBg 的值为false的时候中间的字母就可以消失。只要SlideBar的状态为ACTION_DOWN和ACTION_MOVE 的时候showBg的值为true，而ACTION_UP的时候showBg的值就为false；
所以根据上面这个特征，我们只要把OnToucheLetterChange()这个回调函数的参数改一下就可以了。改成onTouchLetterChange(boolean isTouched, String s)
boolean类型的参数直接把showBg传过去就可以了。
改进后的代码如下：
package com.folyd.tuan.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; /**
* 自定义的View，实现ListView A~Z快速索引效果
*
* @author Folyd
*
*/
public class SlideBar extends View {
private Paint paint = new Paint();
private OnTouchLetterChangeListenner listenner;
// 是否画出背景
private boolean showBg = false;
// 选中的项
private int choose = -1;
// 准备好的A~Z的字母数组
public static String[] letters = { "#", "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" }; // 构造方法
public SlideBar(Context context) {
super(context);
} public SlideBar(Context context, AttributeSet attrs) {
super(context, attrs);
} @Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
// 获取宽和高
int width = getWidth();
int height = getHeight();
// 每个字母的高度
int singleHeight = height / letters.length;
if (showBg) {
// 画出背景
canvas.drawColor(Color.parseColor("#55000000"));
}
// 画字母
for (int i = 0; i < letters.length; i++) {
paint.setColor(Color.BLACK);
// 设置字体格式
paint.setTypeface(Typeface.DEFAULT_BOLD);
paint.setAntiAlias(true);
paint.setTextSize(20f);
// 如果这一项被选中，则换一种颜色画
if (i == choose) {
paint.setColor(Color.parseColor("#F88701"));
paint.setFakeBoldText(true);
}
// 要画的字母的x,y坐标
float posX = width / 2 - paint.measureText(letters[i]) / 2;
float posY = i * singleHeight + singleHeight;
// 画出字母
canvas.drawText(letters[i], posX, posY, paint);
// 重新设置画笔
paint.reset();
}
} /**
* 处理SlideBar的状态
*/
@Override
public boolean dispatchTouchEvent(MotionEvent event) {
final float y = event.getY();
// 算出点击的字母的索引
final int index = (int) (y / getHeight() * letters.length);
// 保存上次点击的字母的索引到oldChoose
final int oldChoose = choose;
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
showBg = true;
if (oldChoose != index && listenner != null && index > 0
&& index < letters.length) {
choose = index;
listenner.onTouchLetterChange(showBg, letters[index]);
invalidate();
}
break; case MotionEvent.ACTION_MOVE:
if (oldChoose != index && listenner != null && index > 0
&& index < letters.length) {
choose = index;
listenner.onTouchLetterChange(showBg, letters[index]);
invalidate();
}
break;
case MotionEvent.ACTION_UP:
showBg = false;
choose = -1;
if (listenner != null) {
if (index <= 0) {
listenner.onTouchLetterChange(showBg, "A");
} else if (index > 0 && index < letters.length) {
listenner.onTouchLetterChange(showBg, letters[index]);
} else if (index >= letters.length) {
listenner.onTouchLetterChange(showBg, "Z");
}
}
invalidate();
break;
}
return true;
} /**
* 回调方法，注册监听器
*
* @param listenner
*/
public void setOnTouchLetterChangeListenner(
OnTouchLetterChangeListenner listenner) {
this.listenner = listenner;
} /**
* SlideBar 的监听器接口
*
* @author Folyd
*
*/
public interface OnTouchLetterChangeListenner { void onTouchLetterChange(boolean isTouched, String s);
} }
Activity中就很容易处理了：
mSlideBar
.setOnTouchLetterChangeListenner(new OnTouchLetterChangeListenner() { @Override
public void onTouchLetterChange(boolean isTouched, String s) { float_letter.setText(s);
if (isTouched) {
float_letter.setVisibility(View.VISIBLE);
} else {
float_letter.postDelayed(new Runnable() { @Override
public void run() {
float_letter.setVisibility(View.GONE);
}
}, 100);
}
int position = array.indexOf(s);
mListView.setSelection(position);
}
});
这样就解决Bug了。哈哈。