My all time favorite tutorial maker Derek Banas has an extensive catalogue of programming tutorials on his Youtube channel. I’ve used those a lot, especially in my studies. His series on design patterns are golden!
I really like the tempo in them. Very hands-on and very organised.
He has a bunch of videos that covers entire techniques in a single video. Perfect if you’re a somewhat experienced developer that need to get up to speed in something.
Here’s and example:
Sometimes when you share a link to you site on Facebook it uses old thumbnails or the link image. There’s a ton of useful info about your site here:
https://developers.facebook.com/tools/debug
This method will find out if screen is a tablet size.
You could of course make this even more corner case-compliant by getting the units dpi (dot per inch) and use the Pythagorean theorem to find the actual inch size of the diagonal. But this will probably suffice for most case.
[java]
private boolean isLargeScreen() {
DisplayMetrics metrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(metrics);
// Get the density of the screen (dp)
float density = metrics.density;
// Find out if the smallest of x/y is largeer than 600 (7" tablet. For 10" use 720)
return Math.min(metrics.widthPixels / density, metrics.heightPixels / density) > 600;
}
[/java]
Here’s one pretty simple way to get your custom view to restore its current state after an orientation change:
You can of course put any values in there, for example if you need to restore fields.
(quickly plotted code. Haven’t run it, but it should work)
[java]
@Override
protected Parcelable onSaveInstanceState() {
Bundle bundle = new Bundle();
bundle.putParcelable("instanceState", super.onSaveInstanceState());
bundle.putString("myString", myEditText.getText().toString());
return bundle;
}
@Override
protected void onRestoreInstanceState(Parcelable state) {
if (state instanceof Bundle) {
Bundle bundle = (Bundle) state;
myEditText.setText(bundle.getString("myString"));
state = bundle.getParcelable("instanceState");
}
super.onRestoreInstanceState(state);
}
[/java]
[java]
// Create new bitmap based on the size and config of the old
Bitmap newBitmap = Bitmap.createBitmap(oldBitmap.getWidth(), oldBitmap.getHeight(), oldBitmap.getConfig());
// Instantiate a canvas and prepare it to paint to the new bitmap
Canvas canvas = new Canvas(newBitmap);
// Paint it white (or whatever color you want)
canvas.drawColor(Color.WHITE);
// Draw the old bitmap ontop of the new white one
canvas.drawBitmap(oldBitmap, 0, 0, null);
[/java]
A simple function to convert dp into pixels. Use when you have to pass pixels to a method and want to keep everything to scale.
[java]
private int dp2px(int dp) {
float scale = getResources().getDisplayMetrics().density;
int pixels = (int) (dp * scale + 0.5f);
return pixels;
}
[/java]
From Android Developer Center :
px
Pixels – Corresponds to actual pixels on the screen. This unit of measure is not recommended because the actual representation can vary across devices; each devices may have a different number of pixels per inch and may have more or fewer total pixels available on the screen.
dp
Density-independent Pixels – An abstract unit that is based on the physical density of the screen. These units are relative to a 160 dpi (dots per inch) screen, on which 1dp is roughly equal to 1px. When running on a higher density screen, the number of pixels used to draw 1dp is scaled up by a factor appropriate for the screen’s dpi. Likewise, when on a lower density screen, the number of pixels used for 1dp is scaled down. The ratio of dp-to-pixel will change with the screen density, but not necessarily in direct proportion. Using dp units (instead of px units) is a simple solution to making the view dimensions in your layout resize properly for different screen densities. In other words, it provides consistency for the real-world sizes of your UI elements across different devices.
Set your number picker to show leading zeros by applying a formatter to it.
Example is using an anonymous instance, but of course it doesn’t have to.
[java]
myNumberPicker.setFormatter(new NumberPicker.Formatter() {
@Override
public String format(int value) {
return String.format("%02d", value);
}
});
[/java]
For %02d this goes:
To get the keyboard to pop up after creating a dialog:
[java]dialog.getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_VISIBLE);
dialog.show();[/java]
For a nice string representation, using the TimeUnit lib:
[java]
String.format("%02d:%02d",
TimeUnit.MILLISECONDS.toMinutes(milliSeconds),
TimeUnit.MILLISECONDS.toSeconds(milliSeconds) –
TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes(milliSeconds)));
[/java]
or simply do the math:
[java]
int minutes = (int) (milliSeconds/ 1000) / 60;
int seconds = (int) (milliSeconds/ 1000) % 60;
[/java]
and back to miliseconds again:
[java]
long milliSeconds= ((minutes * 60) + seconds) * 1000;
[/java]
Add to activity in manifest:
[xml]android:configChanges="keyboardHidden|orientation|screenSize"[/xml]