自定义文本视图错误

Question

我创建了一个类myTextView，当我尝试为同一个类创建对象时，它扩展了TextView：动态工作：myTextView mytv=new myTextView（this.MainActivity）；它起作用了。但myTextView mtv=（myTextView）findViewById（R.id.mytV）；

它会出错。请参阅Log Cat输出。即使我将xml中的标签从TextView更改为它也不起作用。我是android的新手。请。帮助。代码：

package com.example.exttest;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.widget.RelativeLayout;
public class MainActivity extends Activity {
    myTextView mtv  =   null;
    RelativeLayout rtv  =   null;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        rtv =   (RelativeLayout)findViewById(R.id.parent);
        mtv =   new myTextView(getApplicationContext());
        mtv.setText("Hey Bub");
        mtv =   (myTextView)findViewById(R.id.text1);
        //rtv.addView(mtv);
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
}

XML：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity"
   android:id="@+id/parent" >

  <com.example.exttest.myTextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Custom Text View"
        android:id="@+id/text1" />
</RelativeLayout>

日志猫：

Answer 1

your code should look like this 
        mtv =   (myTextView)findViewById(R.id.text1);
        mtv.setText("Hey Bub");
remove this line  mtv =   new myTextView(getApplicationContext());