xml文件

MainActivity源码

package com.example.administrator.helloword; import android.os.Bundle; import android.support.v7.app.AppCompatActivity; import android.text.Editable; import android.text.TextWatcher; import android.widget.EditText; import android.widget.TextView; public class MainActivity extends AppCompatActivity {
      private EditText ed;     private TextView showResult_tv;     private String getResult;     @Override     protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);         ed = (EditText)findViewById(R.id.editText);         showResult_tv = (TextView)findViewById(R.id.textView);         showResult_tv.setHint("没有内容");         //设置文本改变监听         ed.addTextChangedListener(tw);     }     //文本改变监听器     TextWatcher tw = new TextWatcher() {
          //文字改变前的监听         @Override         public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {
          }         //文本改变时的监听         @Override         public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
              if (ed.getText().toString() == null || ed.getText().toString() == "") {
                  showResult_tv.setText("");             } else {
                  showResult_tv.setText(ed.getText().toString());             }         }         //文字改变后的监听         @Override         public void afterTextChanged(Editable editable) {
          }     }; }