Droidin' out tips and tricks from an android developer

How to ensure views are set below the fold on a device.

Did you ever have a view that you needed to make sure started off below the screen so the user could scroll to it later?
Sounds weird but I had to do that for a designer's crazy ass UI.
Wasn't as simple as I first thought so I wanted to share the code.
Turns out that onLayout() doesn't always work. you sometimes don't get all of the dimensions for the views you're interested in and it's just a mess. I guess all the measures() for each view haven't happened yet. Who knows, or rather who cares. It didn't work so I had to find a way that did.

Turns out you can listen for layout change events by adding a listener to the ViewTreeObserver of a view, which notifies of many layout changes on your view. If you add a OnGlobalLayoutListener to the ViewTreeObserver of the view you're interested in you are guaranteed to have gotten the measure() values at that point.
You can then use any way you want to set the position of your view. In my case I chose to use padding. Anyone have a better suggestion?

	ViewTreeObserver vto = bottomContainer.getViewTreeObserver();
	vto.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
	    @Override
	    public void onGlobalLayout() {
		Display display = getWindowManager().getDefaultDisplay();

		LinearLayout bottomContainer = (LinearLayout) findViewById(R.id.footer_container);
		ViewGroup profileBar = (ViewGroup) findViewById(R.id.profileBar);
		RelativeLayout sv = (RelativeLayout) findViewById(R.id.main);
		bottomContainer.setPadding(0, display.getHeight(), 0, 0);

		bottomContainer.getViewTreeObserver().removeGlobalOnLayoutListener(this);
		bottomContainer.forceLayout();

	    }
	});

Sandip Chitale’s Blog: LinearLayout gravity and layout_gravity explained

Sandip Chitale's Blog: LinearLayout gravity and layout_gravity explained.

Very helpful visualization of how gravity and layout_gravity play with each other.

Android bluetooth example

I'm starting more detailed work on Bluetooth sharing.
I found this snippet of code on the dev guide that looked very similar to a TCP socket which I did a while ago.
The code below is taken from :
http://developer.android.com/guide/topics/wireless/bluetooth.html

private class ConnectedThread extends Thread {
    private final BluetoothSocket mmSocket;
    private final InputStream mmInStream;
    private final OutputStream mmOutStream;

    public ConnectedThread(BluetoothSocket socket) {
        mmSocket = socket;
        InputStream tmpIn = null;
        OutputStream tmpOut = null;

        // Get the input and output streams, using temp objects because
        // member streams are final
        try {
            tmpIn = socket.getInputStream();
            tmpOut = socket.getOutputStream();
        } catch (IOException e) { }

        mmInStream = tmpIn;
        mmOutStream = tmpOut;
    }

    public void run() {
        byte[] buffer = new byte[1024];  // buffer store for the stream
        int bytes; // bytes returned from read()

        // Keep listening to the InputStream until an exception occurs
        while (true) {
            try {
                // Read from the InputStream
                bytes = mmInStream.read(buffer);
                // Send the obtained bytes to the UI Activity
                mHandler.obtainMessage(MESSAGE_READ, bytes, -1, buffer)
                        .sendToTarget();
            } catch (IOException e) {
                break;
            }
        }
    }

    /* Call this from the main Activity to send data to the remote device */
    public void write(byte[] bytes) {
        try {
            mmOutStream.write(bytes);
        } catch (IOException e) { }
    }

    /* Call this from the main Activity to shutdown the connection */
    public void cancel() {
        try {
            mmSocket.close();
        } catch (IOException e) { }
    }
}

android and JDK compliance – how to fix @override errors

From time to time when working with other people's projects I run into build errors that are caused by the @override annotation. It took me a while to understand why that was happening as I was usually able to solve it by simply deleting the @override annotation or adding it where needed.

an example of an error caused by @override

Turns out the problem is because of of a mismatch in the JDK different developers are using.

Starting in Java 6 the @override annotation no longer applies to interface methods. So most methods derived from an interface no longer need them. They are however needed with Java 5.  The problem arises if a dev with Java 5 creates an android project, By default the project will get set with whatever JDK compliance is valid in their environment, in this  Java 1.5. If a developer with java 6 opens the same project all  @override annotations will be flagged as errors when appearing above interface methods.

Thankfully, this is easy to fix.

You simply need to go to your android project properties, choose the java compiler and select the appropriate JDK compliance level for your environment.

Project Properties > Java Compiler

Click enable project specific settings to be able to select the appropriate JDK version to use.

Don't know which hava version you have? No problem. Simply type java -version in your command line to get that info. It will look like below

how to check your jdk version

Don't want to have to do this every time you and another developer have mismatching JDKs? You can configure it as a default on your workspace.

From the same Java Compiler properties window, click "Configure Workspace Settings"

That will bring you to the window below where you can choose your default Compiler compliance level for your JDK Compliance.

configure your default workspace settings

As per usual i'd like to thank the fine folks @ stackoverflow for their help.

Android units – pixels, density, dpi, dip, dp, dps, sp, sip | Edwin Evans

A bit more on dealing with android units.

Android units – pixels, density, dpi, dip, dp, dps, sp, sip | Edwin Evans.