android EditText 银行卡4位加空格

package cn.example.uppaydemo;

import android.os.Bundle;
import android.text.Editable;
import android.text.Selection;
import android.text.TextWatcher;
import android.widget.EditText;
import android.app.Activity;

public class MainActivity extends Activity {

	private EditText et_pay;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);

		et_pay = (EditText) this.findViewById(R.id.et_pay);
		bankCardNumAddSpace(et_pay);
	}

	/**
	 * 银行卡四位加空格
	 * 
	 * @param mEditText
	 */
	protected void bankCardNumAddSpace(final EditText mEditText) {
		mEditText.addTextChangedListener(new TextWatcher() {
			int beforeTextLength = 0;
			int onTextLength = 0;
			boolean isChanged = false;

			int location = 0;// 记录光标的位置
			private char[] tempChar;
			private StringBuffer buffer = new StringBuffer();
			int konggeNumberB = 0;

			@Override
			public void beforeTextChanged(CharSequence s, int start, int count,
					int after) {
				beforeTextLength = s.length();
				if (buffer.length() > 0) {
					buffer.delete(0, buffer.length());
				}
				konggeNumberB = 0;
				for (int i = 0; i < s.length(); i++) {
					if (s.charAt(i) == ' ') {
						konggeNumberB++;
					}
				}
			}

			@Override
			public void onTextChanged(CharSequence s, int start, int before,
					int count) {
				onTextLength = s.length();
				buffer.append(s.toString());
				if (onTextLength == beforeTextLength || onTextLength <= 3
						|| isChanged) {
					isChanged = false;
					return;
				}
				isChanged = true;
			}

			@Override
			public void afterTextChanged(Editable s) {
				if (isChanged) {
					location = mEditText.getSelectionEnd();
					int index = 0;
					while (index < buffer.length()) {
						if (buffer.charAt(index) == ' ') {
							buffer.deleteCharAt(index);
						} else {
							index++;
						}
					}

					index = 0;
					int konggeNumberC = 0;
					while (index < buffer.length()) {
						if ((index == 4 || index == 9 || index == 14 || index == 19)) {
							buffer.insert(index, ' ');
							konggeNumberC++;
						}
						index++;
					}

					if (konggeNumberC > konggeNumberB) {
						location += (konggeNumberC - konggeNumberB);
					}

					tempChar = new char[buffer.length()];
					buffer.getChars(0, buffer.length(), tempChar, 0);
					String str = buffer.toString();
					if (location > str.length()) {
						location = str.length();
					} else if (location < 0) {
						location = 0;
					}

					mEditText.setText(str);
					Editable etable = mEditText.getText();
					Selection.setSelection(etable, location);
					isChanged = false;
				}
			}
		});
	}

}