ScrollView清除TextView文本后停止滚动

Question

I have a TextView inside a ScrollView:

<ScrollView
    android:id="@+id/scrollView1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_weight="1"
    android:scrollbars="vertical" 
    android:fillViewport="true">

    <TextView
        android:id="@+id/textview"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
     />

</ScrollView>

I append text to the TextView and after doing so, the scrolling works ok. However, if I clear the text via

textView.setText("");

and then append more text, the scrolling no longer works.

The java code I'm using is like this:

public class MainActivity extends Activity {
  protected TextView textView;

  protected void onCreate(Bundle savedInstanceState){    
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    textView = (TextView) findViewById(R.id.textview);
    setClickListeners();
  }
  private void setClickListeners() {
    ((Button) findViewById(R.id.clear)).setOnClickListener(new OnClickListener() {
      public void onClick(View arg0) {
        textView.setText("");
      }
    });
  }
}

I would expect the scrolling to still work. Could anyone say why it doesn't?

Answer 1

You need to change the TextView's height to be "wrap_content" instead of "fill_parent" so that it expands to be as large as its content, not just as large as the parent. That way, the ScrollView will have something to scroll to.

I can only guess that rotating the screen causes the elements to resize themselves to fit their content causing the discrepancy you saw...