Android实现输入手机号时自动添加空格

public interface TextWatcher extends NoCopySpan {

    public void beforeTextChanged(CharSequence s, int start, int count, int after);

    public void onTextChanged(CharSequence s, int start, int before, int count);

    public void afterTextChanged(Editable s);
}

This method is called to notify you that, somewhere within s, the text has been changed. It is legitimate to make further changes to s from this callback, but be careful not to get yourself into an infinite loop, because any changes you make will cause this method to be called again recursively. (You are not told where the change took place because other afterTextChanged() methods may already have made other changes and invalidated the offsets. But if you need to know here, you can use setSpan(Object, int, int, int) in onTextChanged(CharSequence, int, int, int) to mark your place and then look up from here where the span ended up.

字符串s内容已经发生了变化.可以在这一步对s进行合理的变更,但是要注意不要进入无限循环,因为字符串的任何变化都会再次递归调用此回调方法.在这个方法中不会告诉你字符串哪些内容发生了变化,因为其他针对字符串的改变已经调用了 afterTextChanged() .如果你想知道哪些发生了变化,可以在 onTextChanged(CharSequence, int, int, int) 使用 setSpan(Object, int, int, int) 做标记.

public class MainActivity extends AppCompatActivity {

    private EditText editText;

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

        editText = (EditText) findViewById(R.id.edit_text);
        editText.addTextChangedListener(textWatcher);
    }

    private final TextWatcher textWatcher = new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
            DLog.d("----------beforeTextChanged----------/n");
            DLog.d("s:" + s + "/n");
            DLog.d("start:" + start + "/n");
            DLog.d("count:" + count + "/n");
            DLog.d("after:" + after + "/n");
        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            DLog.d("----------onTextChanged----------/n");
            DLog.d("s:" + s + "/n");
            DLog.d("start:" + start + "/n");
            DLog.d("before:" + before + "/n");
            DLog.d("count:" + count + "/n");
        }

        @Override
        public void afterTextChanged(Editable s) {
            DLog.d("----------afterTextChanged----------/n");
            DLog.d("s:" + s + "/n");
        }
    };
}

----------beforeTextChanged----------
s:
start:0
count:0
after:1
//注释:在字符串""从索引0处开始的0个字符将被长度为1的新字符串代替
//即""将被1代替
----------onTextChanged----------
s:1
start:0
before:0
count:1
//注释:字符串"1"从索引0处开始的1个字符刚刚替换了长度为0的旧字符串
//即1刚刚代替了""
----------afterTextChanged----------
s:1
//注释:发生变化后的字符串为:"1"

----------beforeTextChanged----------
s:1
start:1
count:0
after:2
//注释:在字符串"1"从索引1开始的0个字符将被长度为2的新字符串代替
//即""将被23代替
----------onTextChanged----------
s:123
start:1
before:0
count:2
//注释:字符串"123"从索引1开始的2个字符刚刚替换了长度为0的旧字符串
//即23刚刚代替了""
----------afterTextChanged----------
s:123
//注释:发生变化后的字符串为:"123"

----------beforeTextChanged----------
s:123
start:3
count:0
after:3
//注释:在字符串"123"从索引3开始的0个字符将被长度为3的新字符串代替
//即""将被456代替
----------onTextChanged----------
s:123456
start:3
before:0
count:3
//注释:字符串"123456"从索引3开始的3个字符刚刚替换了长度为0的旧字符串
//即456刚刚代替了""
----------afterTextChanged----------
s:123456
//注释:发生变化后的字符串为:"123456"

----------beforeTextChanged----------
s:123456
start:5
count:1
after:0
//注释:在字符串"123456"从索引5开始的1个字符将被长度为0的新字符串代替
//即6将被""代替
----------onTextChanged----------
s:12345
start:5
before:1
count:0
//注释:字符串"12345"从索引5开始的0个字符刚刚替换了长度为1的旧字符串
//即""刚刚代替了6
----------afterTextChanged----------
s:12345
//注释:发生变化后的字符串为:"12345"

----------beforeTextChanged----------
s:12345
start:3
count:2
after:0
//注释:在字符串"12345"从索引3开始的2个字符将被长度为0的新字符串代替
//即45将被""代替
----------onTextChanged----------
s:123
start:3
before:2
count:0
//注释:字符串"123"从索引3开始的0个字符刚刚替换了长度为2的旧字符串
//即""刚刚代替了45
----------afterTextChanged----------
s:123
//注释:发生变化后的字符串为:"123"

----------beforeTextChanged----------
s:123
start:2
count:1
after:2
//注释:在字符串"123"从索引2开始的1个字符将被长度为2的新字符串代替
//即3将被ab代替
----------onTextChanged----------
s:12ab
start:2
before:1
count:2
//注释:字符串"12ab"从索引2开始的2个字符刚刚替换了长度为1的旧字符串
//即ab刚刚代替了3
----------afterTextChanged----------
s:12ab
//注释:发生变化后的字符串为:"12ab"

----------beforeTextChanged----------
s:12ab
start:2
count:2
after:1
//注释:在字符串"12ab"从索引2开始的2个字符将被长度为1的新字符串代替
//即ab将被3代替
----------onTextChanged----------
s:123
start:2
before:2
count:1
//注释:字符串"123"从索引2开始的1个字符刚刚替换了长度为2的旧字符串
//即3刚刚代替了ab
----------afterTextChanged----------
s:123
//注释:发生变化后的字符串为:"123"

----------beforeTextChanged----------
s:123
start:2
count:0
after:1
//注释:在字符串"123"从索引2开始的0个字符将被长度为1的新字符串代替
//即""将被5代替
----------onTextChanged----------
s:1253
start:2
before:0
count:1
//注释:字符串"1253"从索引2开始的1个字符刚刚替换了长度为0的旧字符串
//5刚刚代替了""
----------afterTextChanged----------
s:1253
//注释:发生变化后的字符串为:"1253"

public void onTextChanged(CharSequence s, int start, int before, int count) {
    DLog.d("----------onTextChanged----------/n");
    DLog.d("s:" + s + "/n");
    DLog.d("start:" + start + "/n");
    DLog.d("before:" + before + "/n");
    DLog.d("count:" + count + "/n");

    if (count == 1){
        int length = s.toString().length();
        if (length == 3 || length == 8){
            editText.setText(s + " ");
            editText.setSelection(editText.getText().toString().length());
        }
    }
}