Two, MotionEvent Profile
Before talking about Android event distribution mechanism you a quick view of some MotionEvent, because it is this "event." The following description of the section taken in the source code:
1 ...... 2 * <p> 3 * Motion events describe movements in terms of an action code and a set of axis values. 4 * The action code specifies the state change that occurred such as a pointer going 5 * down or up. The axis values describe the position and other movement properties. 6 * </p> 7 ...... 8 public final class MotionEvent extends InputEvent implements Parcelable { 9 public static final int ACTION_DOWN = 0; 10 public static final int ACTION_UP = 1; 11 public static final int ACTION_MOVE = 2; 12 ...... 13 }
MotionEvent, as the name suggests, action events mean. To describe an operation by an action code and a set of coordinate values. action code specifies the state when the pointer is pressed or lifted as change events such as the coordinate values of the position and the other acts described event attribute values in the screen. The following is MotionEvent toString method of printing out the results:
MotionEvent { action=ACTION_DOWN, actionButton=0, id[0]=0, x[0]=173.0, y[0]=138.0, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x2, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=34268429, downTime=34268429, deviceId=8, source=0x1002 }
From here you can see, a lot of information action events, time, coordinates, etc. This article in being only concerned aciton this field, "action = ACTION_DOWN" expressed presses.
Usually when you touch the screen, one of the most simple events include a "ACTION_DOWN" and "ACTION_UP", "ACTION_DOWN" in which a finger is pressed, and "" ACTION_UP "represents a finger up, and two action will constitute a complete event. If you have to move your finger on the screen, will also include "ACTION_MOVE", this time a complete event including "ACTION_DOWN", more "ACTION_MOVE", "ACTION_UP". of course, the actual work will be a lot of complex situations, There may be some other aciton, in order to facilitate the presentation of this paper, considering only "ACTION_DOWN" and "ACTION_UP" scene.