altosdroid: Show direction to target in recover tab

This takes the bearing to target and current direction of motion (from
the Android API) and computes a turn amount and displays that so you
don't have to know which way is north when walking towards the rocket.

Signed-off-by: Keith Packard <keithp@keithp.com>

2 files changed, 32 insertions, 0 deletions

diff --git a/altosdroid/src/org/altusmetrum/AltosDroid/AltosDroid.java b/altosdroid/src/org/altusmetrum/AltosDroid/AltosDroid.java
index 6cd9463a..f1da27d8 100644
--- a/altosdroid/src/org/altusmetrum/AltosDroid/AltosDroid.java
+++ b/altosdroid/src/org/altusmetrum/AltosDroid/AltosDroid.java
@@ -990,4 +990,29 @@ public class AltosDroid extends FragmentActivity implements AltosUnitsListener {
 		}
 		return false;
 	}
+
+	static String direction(AltosGreatCircle from_receiver,
+			     Location receiver) {
+		if (!receiver.hasBearing())
+			return null;
+
+		float	bearing = receiver.getBearing();
+		float	heading = (float) from_receiver.bearing - bearing;
+
+		while (heading <= -180.0f)
+			heading += 360.0f;
+		while (heading > 180.0f)
+			heading -= 360.0f;
+
+		int iheading = (int) (heading + 0.5f);
+
+		if (-1 < iheading && iheading < 1)
+			return "ahead";
+		else if (iheading < -179 || 179 < iheading)
+			return "backwards";
+		else if (iheading < 0)
+			return String.format("left %d", -iheading);
+		else
+			return String.format("right %d", iheading);
+	}
 }
diff --git a/altosdroid/src/org/altusmetrum/AltosDroid/TabRecover.java b/altosdroid/src/org/altusmetrum/AltosDroid/TabRecover.java
index 0ab20f5f..cb394dbe 100644
--- a/altosdroid/src/org/altusmetrum/AltosDroid/TabRecover.java
+++ b/altosdroid/src/org/altusmetrum/AltosDroid/TabRecover.java
@@ -30,6 +30,7 @@ import android.location.Location;
 
 public class TabRecover extends AltosDroidTab {
 	private TextView mBearingView;
+	private TextView mDirectionView;
 	private TextView mDistanceView;
 	private TextView mTargetLatitudeView;
 	private TextView mTargetLongitudeView;
@@ -44,6 +45,7 @@ public class TabRecover extends AltosDroidTab {
 		View v = inflater.inflate(R.layout.tab_recover, container, false);
 
 		mBearingView   = (TextView) v.findViewById(R.id.bearing_value);
+		mDirectionView = (TextView) v.findViewById(R.id.direction_value);
 		mDistanceView  = (TextView) v.findViewById(R.id.distance_value);
 		mTargetLatitudeView  = (TextView) v.findViewById(R.id.target_lat_value);
 		mTargetLongitudeView = (TextView) v.findViewById(R.id.target_lon_value);
@@ -62,6 +64,11 @@ public class TabRecover extends AltosDroidTab {
 		if (from_receiver != null) {
 			mBearingView.setText(String.format("%3.0f°", from_receiver.bearing));
 			set_value(mDistanceView, AltosConvert.distance, 6, from_receiver.distance);
+			String direction = AltosDroid.direction(from_receiver, receiver);
+			if (direction == null)
+				mDirectionView.setText("");
+			else
+				mDirectionView.setText(direction);
 		}
 		if (state != null && state.gps != null) {
 			mTargetLatitudeView.setText(AltosDroid.pos(state.gps.lat, "N", "S"));