Android用Java编程，如何使用R.id

studio创建一个android应用程序，该应用程序从输入id为的editText中添加字符串，并将其显示到输出id为的textView中。但是

EditText input = EditText(findViewById(R.id.input)); 

及

无法按预期的方法调用工作。任何形式的帮助都会很好，谢谢

package com.example.toshb.myapplication;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity
{
    private Model model;
    public MainActivity() {model = new Model();}
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    public void processInput(View view)
    {
        EditText input = EditText(findViewById(R.id.input));
        TextView output = TextView(findViewById(R.id.output));
        model.addString(editText.getText().toString());
        output.setText(model.getList());
        input.setText("");
    }
}

---

您需要添加EditText和TextView的正确声明。在编写代码之前，请查看以下内容：

package com.example.toshb.myapplication;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity
{
    private Model model;
    public MainActivity() {model = new Model();}
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    public void processInput(View view)
    {
        EditText input = EditText(findViewById(R.id.input));
        TextView output = TextView(findViewById(R.id.output));
        model.addString(editText.getText().toString());
        output.setText(model.getList());
        input.setText("");
    }
}

EditText input = (EditText)findViewById(R.id.input);
TextView output =(TextView)findViewById(R.id.output);
model.addString(input.getText().toString());