Android过滤表情，没有之一

工具类：

package com.example.test;

public class EmojiFilter {

    /**
     * 检测是否有emoji字符
     * @param source
     * @return FALSE，包含图片
     */
    public static boolean containsEmoji(String source) {
        if (source.equals("")) {
            return false;
        }
        
        int len = source.length();
        
        for (int i = 0; i < len; i++) {
            char codePoint = source.charAt(i);
            
            if (isEmojiCharacter(codePoint)) {
                //do nothing，判断到了这里表明，确认有表情字符
                return true;
            }
        }
        
        return false;
    }

    private static boolean isEmojiCharacter(char codePoint) {
        return (codePoint == 0x0) ||
                (codePoint == 0x9) ||                            
                (codePoint == 0xA) ||
                (codePoint == 0xD) ||
                ((codePoint >= 0x20) && (codePoint <= 0xD7FF)) ||
                ((codePoint >= 0xE000) && (codePoint <= 0xFFFD)) ||
                ((codePoint >= 0x10000) && (codePoint <= 0x10FFFF));
    }
    
    /**
     * 过滤emoji 或者 其他非文字类型的字符
     * @param source
     * @return
     */
    public static String filterEmoji(String source) {
        
        if (!containsEmoji(source)) {
            return source;//如果不包含，直接返回
        }
        //到这里铁定包含
        StringBuilder buf = null;
        
        int len = source.length();
        
        for (int i = 0; i < len; i++) {
            char codePoint = source.charAt(i);
            
            if (isEmojiCharacter(codePoint)) {
                if (buf == null) {
                    buf = new StringBuilder(source.length());
                }
                
                buf.append(codePoint);
            } else {
            }
        }
        
        if (buf == null) {
            return source;//如果没有找到 emoji表情，则返回源字符串
        } else {
            if (buf.length() == len) {//这里的意义在于尽可能少的toString，因为会重新生成字符串
                buf = null;
                return source;
            } else {
                return buf.toString();
            }
        }
        
    }
}

实现类：

package com.example.test;

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

public class MainActivity extends Activity {
    private String tmp = "";
    // 是否重置了EditText的内容
    private boolean resetText;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        final EditText sign_text = (EditText) findViewById(R.id.editText1);

        sign_text.addTextChangedListener(new TextWatcher() {

            @Override
            public void onTextChanged(CharSequence s, int start, int arg2, int arg3) {
                if (!resetText) {
                    if ((arg3 == 2) && (!EmojiFilter.containsEmoji(s.toString().substring(start, start + 2)))) {
                        resetText = true;
                        sign_text.setText(tmp);
                        sign_text.invalidate();
                        if (sign_text.getText().length() > 1)
                            Selection.setSelection(sign_text.getText(), sign_text.getText().length());
                        Toast.makeText(MainActivity.this, "不支持表情输入", 0).show();
                    }
                } else {
                    resetText = false;
                }
            }

            @Override
            public void beforeTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) {
                if (!resetText)
                    tmp = arg0.toString();

            }

            @Override
            public void afterTextChanged(Editable arg0) {
                // TODO Auto-generated method stub

            }
        });

    }

}