android 设置 TextEdit 组件滚动条自动滚动且在末尾追加内容

<EditText android:id="@+id/displayText"
android:layout_width="fill_parent"
android:layout_height="match_parent"
android:singleLine="false"
android:scrollbars="vertical"
android:editable="false"
android:textSize="12px"
android:focusable="false"
/>

private EditText displayText = null;
displayText = (EditText)findViewById(R.id.displayText);
displayText.setMovementMethod(ScrollingMovementMethod.getInstance());
displayText.setSelection(displayText.getText().length(), displayText.getText().length());

displayText.getText().append("msg");