android触控 MotionEvent (转)

/**
     * Bit mask of the parts of the action code that are the action itself.
     */
    public static final int ACTION_MASK             = 0xff;

/**
     * Return the kind of action being performed.
     * Consider using {<A class=referer href="http://my.oschina.net/link1212" target=_blank>@link</A>  #getActionMasked} and {<A class=referer href="http://my.oschina.net/link1212" target=_blank>@link</A>  #getActionIndex} to retrieve
     * the separate masked action and pointer index.
     * @return The action, such as {<A class=referer href="http://my.oschina.net/link1212" target=_blank>@link</A>  #ACTION_DOWN} or
     * the combination of {<A class=referer href="http://my.oschina.net/link1212" target=_blank>@link</A>  #ACTION_POINTER_DOWN} with a shifted pointer index.
     */
    public final int getAction() {
        return mAction;
    }

  /**
     * Return the masked action being performed, without pointer index information.
     * Use {<A class=referer href="http://my.oschina.net/link1212" target=_blank>@link</A>  #getActionIndex} to return the index associated with pointer actions.
     * @return The action, such as {<A class=referer href="http://my.oschina.net/link1212" target=_blank>@link</A>  #ACTION_DOWN} or {<A class=referer href="http://my.oschina.net/link1212" target=_blank>@link</A>  #ACTION_POINTER_DOWN}.
     */
    public final int getActionMasked() {
        return mAction & ACTION_MASK;
    }

 /**
     * action码的位掩码部分就是action本身
     */
    public static final int ACTION_MASK             = 0xff;

/**
  返回action的类型,考虑使用getActionMasked()和getActionIndex()来获得单独的经过掩码的action和触控点的索引.
 @return action例如ACTION_DOWN或者ACTION_POINTER_DOWN与转换的触控点索引的合成值
     */
    public final int getAction() {
        return mAction;
    }

  /**
   返回经过掩码的action,没有触控点索引信息.
   通过getActionIndex()来得到触控操作点的索引.
@return action,例如ACTION_DOWN,ACTION_POINTER_DOWN

 
     */
    public final int getActionMasked() {
        return mAction & ACTION_MASK;
    }

 public static final int ACTION_MASK             = 0xff;
public static final int ACTION_POINTER_INDEX_MASK  = 0xff00;

/**
   * Bit shift for the action bits holding the pointer index as
   * defined by {<A class=referer href="http://my.oschina.net/link1212" target=_blank>@link</A>  #ACTION_POINTER_INDEX_MASK}.
   */
  public static final int ACTION_POINTER_INDEX_SHIFT = 8;

public final int getActionIndex() {
    return (mAction & ACTION_POINTER_INDEX_MASK) >> ACTION_POINTER_INDEX_SHIFT;
}

public final float getX(int pointerIndex) {
    return mDataSamples[(pointerIndex*NUM_SAMPLE_DATA) + SAMPLE_X];
}

public final float getX(int pointerIndex) {
     return nativeGetAxisValue(mNativePtr, AXIS_X, pointerIndex, HISTORY_CURRENT);
 }