EditText addTextChangedListener不能正常工作

Question

我有两个EditText输入，当文本在计算后发生变化时，我必须在同一活动中的textView上显示结果。addTextChangedListener对我不起作用

Activity.java code:
width.addTextChangedListener(new TextWatcher() {
        public void beforeTextChanged(CharSequence s, int start, int count,
                                      int after) {
        }

        public void afterTextChanged(Editable s) {

        }

        public void onTextChanged(CharSequence s, int start, int before,
                                  int count) {
            if(!s.equals("") ) {
                TextView perimeterdetails = (TextView) findViewById(R.id.perimeterdetails);
                perimeterdetails.setText(s);
            }
        }
    });

XML代码：

<EditText
    android:id="@+id/width"
    android:layout_width="0dp"
    android:background="@drawable/edittextbackground"
    android:layout_weight="1"
    android:inputType="numberDecimal"
    android:layout_height="wrap_content"/>
<TextView
    android:id="@+id/perimeterdetails"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_weight="1"
    android:text="TextView" />

Answer 1

按如下所示更改代码在onCreate中定义此代码

TextView perimeterdetails = (TextView) findViewById(R.id.perimeterdetails);

在onTextChanged中比较你的字符串，如下所示

if(!TextUtils.isEmpty(s.toString())) {
                perimeterdetails.setText(s);
            }

Answer 2

因为您是在onTextChanged中定义文本视图

剪切此行TextView perimeterdetails = (TextView) findViewById(R.id.perimeterdetails);

在addTextChangedListener之前

Answer 3

尝尝这个

  TextView perimeterdetails = (TextView) findViewById(R.id.perimeterdetails);

    width.addTextChangedListener(new TextWatcher() {
        public void beforeTextChanged(CharSequence s, int start, int count,
                                      int after) {
        }

        public void afterTextChanged(Editable s) {

        }

        public void onTextChanged(CharSequence s, int start, int before,
                                  int count) {
            if(!s.equals("") ) {

                perimeterdetails.setText(s);
            }
        }
    });