1. A multi-character continuous handwriting input method, comprising the following steps: Step 110 : touching a touch screen with a handwriting pen or a finger to start inputting a stroke; Step 120 : moving the handwriting pen or the finger on the touch screen; recording a stroke track and displaying the stroke track on a handwriting area on the touch screen; Step 130 : moving the handwriting pen or the finger away from the touch screen, current stroke input being finished; Step 140 : determining whether the currently written stroke and a previously input stroke belong to the same character; if yes, going to Step 150 ; otherwise, going to Step 170 ; wherein the determining whether the currently written stroke and a previously input stroke belong to the same character is performed according to a relationship between geometric position information of the currently written stroke and geometric position information of a character formed of all the previously input strokes, comprising the following steps: Step 141 : determining whether the current stroke is the first stroke inputted by the user; if yes, going to Step 146 ; otherwise, going to Step 142 ; Step 142 : determining whether the current stroke is a new character stroke on the right side of a previous stroke; if yes, going to Step 145 ; otherwise, going to Step 143 ; Step 143 : determining whether the current stroke overlaps another previously written stroke; if yes, going to Step 144 ; otherwise, going to Step 145 ; Step 144 : determining whether an overlapping degree between the current stroke and the previously written stroke is greater than a given threshold; if yes, going to Step 146 ; otherwise, going to Step 145 ; Step 145 : returning a determination result that the currently input stroke and the previously input stroke probably belong to the same character; and Step 146 : returning a determination result that the currently input stroke and the previously input stroke do not belong to the same character; Step 150 : determining whether a new stroke is inputted; if yes, going to Step 120 ; otherwise, going to Step 160 ; Step 160 : submitting a currently written character track to a recognition engine for recognition, and outputting a recognition result; going to Step 220 ; Step 170 : determining whether some character on the touch screen is dimmed; if yes, going to Step 180 ; otherwise, going to Step 190 , wherein the dimmed character refers to a previous handwritten character that has been written and recognized, and a stroke color thereof has been processed in Step 200 ; Step 180 : clearing a previous dimmed character; Step 190 : combining all strokes except the current stroke into a handwritten character, submitting the handwritten character to the recognition engine for recognition, and outputting a recognition result; Step 200 : dimming the stroke color of the handwritten character formed of all the strokes except the current stroke, or making colors of an (i+1) th character and an i th character different, wherein the character is defined as a dimmed character; and Step 210 : determining whether a new stroke is inputted; if yes, going to Step 120 ; otherwise, going to Step 160 ; and Step 220 : ending.