Android 自动完成文本视图在1个字符后不显示下拉列表

我正在使用autocomplete textview显示google places api中的位置。我还将阈值设置为1，如果用户键入字符，则会出现下拉列表。当用户键入2个字符时，会出现这种情况。我不知道为什么会发生这种情况。请帮我解决

代码

XML

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在onPostExecute中尝试此操作

  if (address != null) {
        adapter = new ArrayAdapter<String>(context,android.R.layout.simple_dropdown_item_1line, address);
        autoCompleteTextView.setThreshold(1);
        autoCompleteTextView.setAdapter(adapter);
        progressBar.setVisibility(View.GONE);
        autoCompleteTextView.showDropDown();
    } 

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#ff0dffb7">


    <AutoCompleteTextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/act_get_source"
        android:layout_margin="10dp"
        android:hint="SOURCE"
        android:gravity="center"
        android:completionThreshold="1" />


    <AutoCompleteTextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/act_get_destination"
        android:layout_margin="10dp"
        android:hint="DESTINSTION"
        android:layout_below="@+id/act_get_source"
        android:gravity="center"
        android:completionThreshold="1" />

    <Button
        style="?android:attr/buttonStyleSmall"
        android:layout_width="wrap_content"
        android:layout_height="45dp"
        android:text="Clear"
        android:visibility="gone"
        android:id="@+id/bt_source_clear"
        android:layout_alignParentTop="true"
        android:layout_alignRight="@+id/act_get_source"
        android:layout_alignEnd="@+id/act_get_source" />

    <Button
        style="?android:attr/buttonStyleSmall"
        android:layout_width="wrap_content"
        android:layout_height="45dp"
        android:text="Clear"
        android:id="@+id/bt_destination_clear"
        android:visibility="gone"
        android:layout_below="@+id/act_get_source"
        android:layout_alignRight="@+id/act_get_destination"
        android:layout_alignEnd="@+id/act_get_destination" />

    <ProgressBar
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/pb_source"
        android:visibility="gone"
        android:layout_alignParentTop="true"
        android:layout_alignLeft="@+id/act_get_source"
        android:layout_alignStart="@+id/act_get_source"
        android:layout_alignBottom="@+id/act_get_source" />

    <ProgressBar
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/pb_destination"
        android:visibility="gone"
        android:layout_below="@+id/act_get_source"
        android:layout_alignLeft="@+id/act_get_destination"
        android:layout_alignStart="@+id/act_get_destination" />


</RelativeLayout>

  if (address != null) {
        adapter = new ArrayAdapter<String>(context,android.R.layout.simple_dropdown_item_1line, address);
        autoCompleteTextView.setThreshold(1);
        autoCompleteTextView.setAdapter(adapter);
        progressBar.setVisibility(View.GONE);
        autoCompleteTextView.showDropDown();
    }