SideBar类似于手机通讯录或者微信通讯录右侧的A~Z的字母导航。
public class SideBar extends View {
// public static String[] letter = { "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", "#" };
List<String> letters = new ArrayList<>();
private Paint paint = new Paint();
/**
* 计算出来的高度
*/
private int mCalViewHeight;
private int selection = -1;
private TextView mTextDialog;
// 触摸事件
private OnTouchingLetterChangedListener onTouchingLetterChangedListener;
/**
* 为SideBar设置显示字母的TextView
* @param textDialog
*/
public void setTextView(TextView textDialog) {
this.mTextDialog = textDialog;
}
public void setLetterData(List<String> letters){
this.letters = letters;
requestLayout();
invalidate();
}
public SideBar(Context context) {
super(context);
}
public SideBar(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
}
public SideBar(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
public SideBar(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int height = MeasureSpec.getSize(heightMeasureSpec);
if(letters.size() > 0){
mCalViewHeight = (int)((letters.size()) * 30 + (letters.size() - 1) * 6);
}
if(mCalViewHeight > height){
mCalViewHeight = height;
}
super.onMeasure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(mCalViewHeight, MeasureSpec.EXACTLY));
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if(letters.size() == 0){
return;
}
int height = getHeight();
int width = getWidth();
int singleLetterHeight = height / letters.size(); //获取每个字母的高度
for(int i = 0; i < letters.size(); i++){
paint.setColor(Color.parseColor("#4D4D4D")); //字母颜色
paint.setTypeface(Typeface.DEFAULT_BOLD); //字母黑色字体类型
paint.setAntiAlias(true); //抗锯齿,对边界锯齿进行模糊处理
paint.setDither(true); //防抖动,对图像抖动进行模糊平滑处理,使之看起来更柔和
paint.setTextSize(30);
if(i == selection){
paint.setColor(Color.parseColor("#3399ff"));
paint.setFakeBoldText(true); //设置粗体字
}
//X坐标等于中间减去字符串宽度的一半
float xPos = width / 2 - paint.measureText(letters.get(i)) / 2;
float yPos = singleLetterHeight * i + singleLetterHeight;
canvas.drawText(letters.get(i), xPos, yPos, paint);
paint.reset();
}
}
@Override
public boolean dispatchTouchEvent(MotionEvent event) {
float y = event.getY();
int selectedNumber = (int)(y / getHeight() * letters.size()); //点击y坐标所占总高度的比例*letter数组的长度=点击letter中的个数
int oldSelection = selection;
OnTouchingLetterChangedListener listener = onTouchingLetterChangedListener;
switch (event.getAction()){
case MotionEvent.ACTION_UP:
setBackground(new ColorDrawable(0x00000000));
selection = -1;
invalidate();
if(mTextDialog != null){
mTextDialog.setVisibility(GONE);
}
break;
default:
setBackgroundResource(R.drawable.sidebar_background);
if(oldSelection != selectedNumber){
if(selectedNumber >= 0 && selectedNumber < letters.size()){
if(listener != null){
listener.onTouchingLetterChanged(letters.get(selectedNumber));
}
if (mTextDialog != null){
mTextDialog.setText(letters.get(selectedNumber));
mTextDialog.setVisibility(VISIBLE);
}
selection = selectedNumber;
invalidate();
}
}
break;
}
return true;
}
/**
* 触摸事件
* @param onTouchingLetterChangedListener
*/
public void setOnTouchingLetterChangedListener(OnTouchingLetterChangedListener onTouchingLetterChangedListener) {
this.onTouchingLetterChangedListener = onTouchingLetterChangedListener;
}
/**
* @author coder
*
*/
public interface OnTouchingLetterChangedListener {
void onTouchingLetterChanged(String s);
}
}
使用方式:
@BindView(R.id.dialog)
TextView mDialog;
@BindView(R.id.sideBar)
SideBar mSideBar;
mSideBar.setTextView(mDialog);
//设置右侧SideBar触摸监听
mSideBar.setOnTouchingLetterChangedListener(new SideBar.OnTouchingLetterChangedListener() {
@Override
public void onTouchingLetterChanged(String s) {
//该字母首次出现的位置
//int position = mAdapter.getPosition(s);
//if (position != -1) {
//mLayoutManager.scrollToPositionWithOffset(position, 0);
//}
//TODO
}
});
参考:1.SortRecyclerView