android EditText 字数监听并显示

在开发应用的时候，经常会限制用户输入的字数，比如发表评论或者其它什么的，下面来个简单的demo

EditText et_content;//定义一个文本输入框
TextView tv_num;// 用来显示剩余字数
int num = 10;//限制的最大字数 

et_content = (EditText) findViewById(R.id.et_content);
tv_num = (TextView) findViewById(R.id.tv_num); 
tv_num.setText("10");

下面为EditText文本框添加监听

 

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
                }
            }
        });

这样就可以实现了