Android™ Application Development - Bahar Ali Khan

Absolute screen coordinates.
int xPosRaw = (int)event.getRawX();
int yPosRaw = (int)event.getRawY();
Chapter 11: Advanced Android Development
The Motion Event parameter also includes the pressure being applied to the screen using getPressure,
a method that returns a value usually between 0 (no pressure) and 1 (normal pressure).
Depending on the calibration of the hardware, it’s possible to return values greater than 1.
Finally, you can also determine the normalized size of the current contact area using the getSize
method. This method returns a value between 0 and 1, where 0 suggests a very precise measurement
and 1 indicates a possible “fat touch” event in which the user may not have intended to press anything.
Tracking Movement
Whenever the current touch contact position, pressure, or size changes, a new onTouchEvent is triggered
with an ACTION_MOVE action.
As well as the fi elds described previously, the Motion Event parameter can include historical values.
This history represents all the movement events that have occurred between the previous onTouchEvent
and this one, allowing Android to buffer rapid movement changes to provide fi ne-grained capture
of movement data.
You can fi nd the size of the history by calling getHistorySize, which returns the number of movement
positions available for the current event. You can then obtain the times, pressures, sizes, and positions
of each of the historical events, using a series of getHistorical* methods and passing in the position
index, as shown in the following code snippet:
int historySize = event.getHistorySize();
for (int i = 0; i < historySize; i++) {
long time = event.getHistoricalEventTime(i);
float pressure = event.getHistoricalPressure(i);
float x = event.getHistoricalX(i);
float y = event.getHistoricalY(i);
float size = event.getHistoricalSize(i);
}
// TODO: Do something with each point
The normal pattern used for handling movement events is to process each of the historical events fi rst,
followed by the current Motion Event values, as shown in the following code snippet:
@Override
public boolean onTouchEvent(MotionEvent event) {
int action = event.getAction();
switch (action) {
case (MotionEvent.ACTION_MOVE)
{
int historySize = event.getHistorySize();
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