Question

I am trying to show a pair of hidden buttons (using setVisibility(View.VISIBLE), within a RelativeLayout), but it doesn’t always work. The button shows OK on a Galaxy Tab 10.1″ but not in a smaller tablet (not sure which model), nor on an Android 4.0 emulator.

I randomly discovered that, for a certain TextView t, the following code causes the buttons to become visible:

t.setText(t.getText());
...
button.setVisibility(View.VISIBLE);

t is located in the same RelativeLayout but is not related to the buttons (their locations are independent and non-overlapping).

Edit: In case some Android dev wants to track this down…

I was able to reduce the code to the following layout that exhibits the problem on an Android 4.0.3 emulator but not a Galaxy Tab. I found that I need a SurfaceView or the problem does not occur (for example, change it to TextView and the problem disappears).

<?xml version="1.0" encoding="utf-8"?>
<!-- layout/test.xml -->
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"        
    android:id="@+id/relativeLayout"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <SurfaceView
        android:id="@+id/mapCtrl"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_above="@+id/bottomPanel"
        android:text="Placeholder"
        android:layout_marginTop="18dip" />
    <TextView
        android:id="@+id/title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:text="@string/map_mode_title" />

    <!--=================================================-->
    <!-- Bottom bar: current road name and current speed -->
    <LinearLayout
        android:id="@+id/bottomPanel"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:background="#f228"
        android:orientation="horizontal"
        android:textColor="#ffff" >
        <Button
            android:id="@+id/btnNavMode"
            android:layout_width="wrap_content"
            android:layout_height="fill_parent"
            android:layout_marginRight="3dip"
            android:textColor="#fff"
            android:text="Switch to\nNav Mode" />
        <RelativeLayout
            android:id="@+id/currentStreetPanel"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:onClick="onClick"
            android:clickable="true"
            android:orientation="vertical" >
            <TextView
                android:id="@+id/currentStreetHdg"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignParentLeft="true"
                android:layout_alignParentTop="true"
                android:text="Current street"
                android:textColor="#fff"
                android:textSize="10dip" />
            <TextView
                android:id="@+id/currentStreet"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignParentLeft="true"
                android:layout_below="@+id/currentStreetHdg"
                android:layout_marginTop="-8dip"
                android:singleLine="true"
                android:text="Current street"
                android:textColor="#fff"
                android:textSize="30dip" />
        </RelativeLayout>
        <RelativeLayout
            android:id="@+id/RelativeLayout2"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:background="#ff606060"
            android:orientation="vertical" >
            <TextView
                android:id="@+id/yourSpeedHdg"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignParentLeft="true"
                android:layout_alignParentTop="true"
                android:layout_marginLeft="3dip"
                android:text="Your speed"
                android:textColor="#fff"
                android:textSize="10dip" />
            <TextView
                android:id="@+id/speed"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignParentLeft="true"
                android:layout_below="@+id/yourSpeedHdg"
                android:layout_marginLeft="3dip"
                android:layout_marginTop="-8dip"
                android:text="0"
                android:textColor="#fff"
                android:textSize="30dip" />
            <TextView
                android:id="@+id/speedUnit"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignBaseline="@+id/speed"
                android:layout_marginLeft="5dip"
                android:layout_toRightOf="@+id/speed"
                android:text="kph"
                android:textColor="#fff"
                android:textSize="18dip" />
        </RelativeLayout>
    </LinearLayout>

    <!--================-->
    <!-- On-map buttons -->
    <Button
        android:id="@+id/btnClearRoute"
        android:background="#F00"
        android:textColor="#fff"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Clear\nroute"/>
    <ZoomControls
        android:id="@+id/zoomControls"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/mapCtrl"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="-25dip"
        android:orientation="horizontal" />
    <Button
        android:id="@+id/btnFindRoute"
        android:layout_width="100dip"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/mapCtrl"
        android:layout_alignParentRight="true"
        android:layout_marginRight="2dip"
        android:layout_marginBottom="65dip"
        android:text="Route to selected location"
        android:textSize="17dip"/>
    <Button
        android:id="@+id/btnUnselect"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/btnFindRoute"
        android:layout_alignTop="@+id/btnFindRoute"
        android:layout_alignParentLeft="true"
        android:layout_marginLeft="2dip"
        android:text="Unselect" />
    <LinearLayout
        android:id="@+id/showMePanel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/btnFindRoute"
        android:layout_alignRight="@+id/btnFindRoute"
        android:layout_alignLeft="@+id/btnFindRoute"
        android:padding="4dip"
        android:background="#bbbb"
        android:gravity="center"
        android:orientation="vertical">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Show me..."
            android:textColor="#fff"/>
        <Button
            android:id="@+id/btnShowVehicle"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:text="My car"/>
        <Button
            android:id="@+id/btnShowRoute"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:text="The route"/>
        <Button
            android:id="@+id/btnShowDestination"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:text="Destination"/>
        <Button
            android:id="@+id/btnShowMap"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:text="The map"/>
    </LinearLayout>
</RelativeLayout>

The Activity class simply toggles the visibility of the two buttons when any of the buttons are clicked. Again, on some devices it works, on others it does not.

package mentor.simplegps;

import android.app.*;
import android.os.Bundle;
import android.view.*;
import android.widget.*;

public class TestActivity extends Activity implements View.OnClickListener
{
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.test);
        boilerplate();
        setVisibilities();
    }

    Button _btnShowMap, _btnShowVehicle, _btnShowRoute, _btnShowDestination;
    Button _btnUnselect, _btnFindRoute, _btnNavMode;
    TextView _title;

    void boilerplate()
    {
        _btnUnselect = attachBtn(R.id.btnUnselect);
        _btnShowMap = attachBtn(R.id.btnShowMap);
        _btnShowVehicle = attachBtn(R.id.btnShowVehicle);
        _btnShowRoute = attachBtn(R.id.btnShowRoute);
        _btnShowDestination = attachBtn(R.id.btnShowDestination);
        _btnFindRoute = attachBtn(R.id.btnFindRoute);
        _btnNavMode = attachBtn(R.id.btnNavMode);
        _title = (TextView)findViewById(R.id.title);
    }
    private Button attachBtn(int btnId) {
        Button b = (Button)findViewById(btnId);
        b.setOnClickListener(this);
        return b;
    }

    boolean haveSel;
    public void onClick(View v)
    {
        haveSel = !haveSel;
        setVisibilities();
    }
    void setVisibilities()
    {
        _btnFindRoute.setVisibility(haveSel ? View.VISIBLE : View.INVISIBLE);
        _btnUnselect.setVisibility (haveSel ? View.VISIBLE : View.INVISIBLE);

        // Fixes the problem
        //_title.setText(_title.getText());
    }
}

Answer 1

SurfaceView is the sole culprit (of course, this also applies to GLSurfaceView, RSSurfaceView and VideoView, all of which inherits from SurfaceView). It exposes lots of weird behaviours when dealing with other views on top of it. Playing with View.setVisibility() is one of those issues. Clearly, SurfaceView has not been designed to be used with other views (even though the official doc says it ought to be) but as a standalone view for videos, games or OpenGL stuffs.

For the visibility issue, I’ve found that using View.GONE instead of View.INVISIBLE resolve it. If you don’t want to use GONE, try changing the focus for example (and back to the one that had focus before), or changing other states. The goal is to wake up the underlying UI system somehow.

In short: when something weird happens with your views and you have a SurfaceView (or subclass) somewhere, try replacing it with something else so you don’t lose hours searching what you’re doing wrong when you’re doing it right (and no false beliefs). This way, you know SurfaceView is to blame and you can hack around it with beautiful comments to piss on it without qualms.