Android中限制EditText（輸入框）文字輸入長度

開發過程經常遇到要輸入用戶名等類似要限制輸入字數的要求，我們可以用InputFilter來實現，

下面是繼承的InputFilter:

public class MyInputFilter implements InputFilter {

   private Paint mPaint;

   private int mMaxWidth;

   private static final String TAG = "MyInputFilter";

   private int EDIT_WIDTH = 280;

   private int mPadding = 10;

   public MyInputFilter(Paint paint, int maxWidth) {
      if (paint != null) {
         mPaint = paint;
      } else {
         mPaint = new Paint();
         mPaint.setTextSize(30F);
      }

      if (maxWidth > 0) {
         mMaxWidth = maxWidth - mPadding;
      } else {
         mMaxWidth = EDIT_WIDTH;
      }

   }


   @Override
   public CharSequence filter(CharSequence source, int start, int end,
         Spanned dest, int dstart, int dend) {

      float w = mPaint.measureText(dest.toString() + source.toString());
      if (w > mMaxWidth) {
         //TODO: remind the user not to input anymore
         return "";
      }

      return source;
   }

}

 /*
    * Set edit text input max length constraint to border.
    */
   public static void setEditTextFilter(EditText edit) {

      int width = edit.getWidth();

      Utils.log("Uitls", "edit width = " + width);

      Paint paint = new Paint();
      paint.setTextSize(edit.getTextSize());

      InputFilter[] filters = { new MyInputFilter(paint, width) };

      edit.setFilters(filters);
   }