android 关于EditText中关于输入字数的控制

 

计算输入的字数:

declareView.addTextChangedListener(new DeclareTextWatcher());

设置一个当输入框改变时触发的事件

class DeclareTextWatcher implements TextWatcher {
  @Override
  public void onTextChanged(CharSequence s, int start, int before,
    int count) {

  }

  @Override
  public void beforeTextChanged(CharSequence s, int start, int count,
    int after) {
  }

  @Override
  public void afterTextChanged(Editable s) {
   TextView t = (TextView) findViewById(R.id.cr);
   t.setText(String.valueOf(s.length()));
   // 输入字数的控制
   if (s.length() >= 500) {
    Toast.makeText(ShowShopping.this.getApplicationContext(),
      "输入字数已满！", Toast.LENGTH_SHORT).show();
    declareView.setFilters(new InputFilter[] { new InputFilter() {
     public CharSequence filter(CharSequence source, int start,
       int end, Spanned dest, int dstart, int dend) {
      return source.length() < 1 ? dest.subSequence(dstart,
        dend) : "";
     }
    } });
   }
  }
 }

  熟悉android中的EditText组件都知道当设置 android:editable为false时还是一样可以输入，那么必须filter来设置文本框的输入，利用setFilter()方法来控制

 declareView.setFilters(new InputFilter[] { new InputFilter() {
     public CharSequence filter(CharSequence source, int start,
       int end, Spanned dest, int dstart, int dend) {

     //return 下面时则不可以继续输入
      return source.length() < 1 ? dest.subSequence(dstart,
        dend) : "";

    //retrurn null;则不可以继续输入
     }
    } });

 

 当输入到了规定的字数时就设置上面的filter ，但是此时应该可以输入退格键，所以declare还必须设置一个键盘事件监听，当输入是退格键时则上面的filter返回null

 

declareView.setOnKeyListener(new OnKeyListener() {
   @Override
   public boolean onKey(View v, int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_DEL) {
     declareView
       .setFilters(new InputFilter[] { new InputFilter() {
        public CharSequence filter(CharSequence source,
          int start, int end, Spanned dest,
          int dstart, int dend) {
         return null;
        }
       } });
    }
    return false;
   }
  });