Java can'；t在文本视图中设置文本

我遇到无法在UITextView中设置文本的问题。请参阅下面的代码，在setText（）之后，TwxtView值不会更改。当我按下“hello word”按钮时不会改变。 当我按下按钮时，我想把“你好，世界”改为“你好”

MAinActivity.java

public class MainActivity extends ActionBarActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
     }
    public void showPopup(View view){

            final TextView hello = (TextView)findViewById(R.id.textView1);
            System.out.println(hello.getText().toString());
            String how = "how are you";
            hello.setText(how);
            System.out.println(hello.getText().toString());
            setContentView(R.layout.activity_main);
    }

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_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="com.example.popup.MainActivity" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="hello world"
         />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/textView1"
        android:layout_centerHorizontal="true"
        android:onClick="showPopup"
        android:text="Button" />

</RelativeLayout>

从

showPopup

中删除

setContentView

。这是将布局和文本视图重置为原始文本。

无需设置两次视图。使用以下代码

public class MainActivity extends ActionBarActivity {

TextView hello;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    hello = (TextView)findViewById(R.id.textView1);
 }

public void showPopup(View view){
        String how = "How are you";
        hello.setText(how);
}
}