本来是项目要用到，发现网上有很多类似的代码了。思路也都差不多

利用监视器TextWatcher 

如果往edittext输入的的字符串大于10

那么就设置edittext的gettext为0到10

public class EditViewFontMax {

	protected int num;
	public EditText et_content;

	public void num(EditText et, int n) {
		this.et_content = et;
		this.num = n;
		et_content.addTextChangedListener(new TextWatcher() {
			private CharSequence temp;
			private int selectionStart;
			private int selectionEnd;

			@Override
			public void onTextChanged(CharSequence s, int start, int before,
					int count) {
				temp = s;
				System.out.println("s=" + s);
			}

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

			@Override
			public void afterTextChanged(Editable s) {
				int number = num - s.length();
				// tv_num.setText("" + number);
				selectionStart = et_content.getSelectionStart();
				selectionEnd = et_content.getSelectionEnd();
				// System.out.println("start="+selectionStart+",end="+selectionEnd);
				if (temp.length() > num) {
					s.delete(selectionStart - 1, selectionEnd);
					int tempSelection = selectionStart;
					et_content.setText(s);
					et_content.setSelection(tempSelection);// 设置光标在最后
				}
			}

		});
	}
}