怎么在Android应用中实现一个九宫格手势锁

package com.ninegrid;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
/**
 * Created by Administrator on 2017/6/24.
 */
public class SuduView extends View {
  //定义默认常量
  private static final int DEFAULT_CELL_WIDTH = 200 ;
  private static final int DEFAULT_CELL_STROKE_WIDTH = 10 ;
  private static final int DEFAULT_SPACE = 100 ;
  //九宫格数组
  private Cell mCells[] = new Cell[9] ;
  //直径
  private int mCellWidth;
  //半径
  private int mCellRadius;
  //边框宽度
  private int mCellStrokeWidth;
  //空白部分
  private int mSpace ;
  //定义画笔
  private Paint mPaintNormal ;
  private Paint mPaintSelected ;
  private float mCurrentX ;
  private float mCurrentY ;
  //判断是否结束的标识
  private boolean mFinish = false ;
  private StringBuffer mSbSelected = new StringBuffer(20);
  public SuduView(Context context) {
    super(context);
    init();
  }
  public SuduView(Context context, AttributeSet attrs) {
    super(context, attrs);
    init();
  }
  public SuduView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    init();
  }
  private void init(){
    //初始化画笔
    mCellWidth = DEFAULT_CELL_WIDTH ;
    mCellRadius = DEFAULT_CELL_WIDTH >> 1 ;
    mCellStrokeWidth = DEFAULT_CELL_STROKE_WIDTH ;
    mSpace = DEFAULT_SPACE ;
    mPaintNormal = new Paint();
    mPaintNormal.setColor(Color.WHITE);
    mPaintNormal.setStrokeWidth(mCellStrokeWidth);
    mPaintNormal.setStyle(Paint.Style.STROKE);
    mPaintNormal.setAntiAlias(true);
    mPaintSelected = new Paint();
    mPaintSelected.setColor(Color.CYAN);
    mPaintSelected.setStrokeWidth(mCellStrokeWidth);
    mPaintSelected.setStyle(Paint.Style.STROKE);
    mPaintSelected.setAntiAlias(true);
    Cell cell ;
    float x;
    float y;
    //计算每个格子的坐标
    for( int i = 0 ; i < 9 ; i ++ ){
      x = mSpace * ( i%3 + 1 ) + mCellRadius + mCellWidth * ( i%3 ) ;
      y = mSpace * ( i/3 + 1 ) + mCellRadius + mCellWidth * ( i/3 ) ;
      cell = new Cell(x , y);
      mCells[i] = cell ;
    }
  }
  @Override
  protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    drawCell(canvas);
    drawLine(canvas);
  }
  //绘制连接线
  private void drawLine( Canvas canvas ){
    if("".equals(mSbSelected.toString())){
      return;
    }
    String[] selectedIndexs = mSbSelected.toString().split(",");
    Cell cell = mCells[Integer.valueOf(selectedIndexs[0])];
    Cell nextCell ;
    //绘制每两个格子中心点之间的连接线
    if( selectedIndexs.length > 1) {
      for (int i = 1; i < selectedIndexs.length; i++) {
        nextCell = mCells[Integer.valueOf(selectedIndexs[i])];
        canvas.drawLine(cell.getCenterX(), cell.getCenterY(), nextCell.getCenterX(), nextCell.getCenterY(), mPaintSelected);
        cell = nextCell;
      }
    }
    //绘制格子到其他空白位置的连接线
    if( !mFinish ) {
      canvas.drawLine(cell.getCenterX(), cell.getCenterY(), mCurrentX, mCurrentY, mPaintSelected);
    }
  }
  private void drawCell( Canvas canvas ){
    for ( int i = 0 ; i < 9 ; i ++ ){
      canvas.drawCircle(mCells[i].getCenterX(), mCells[i].getCenterY() , mCellRadius ,
          mCells[i].isSelected() ? mPaintSelected : mPaintNormal );
    }
  }
  //处理点击事件
  @Override
  public boolean onTouchEvent(MotionEvent event) {
    switch ( event.getAction()){
      case MotionEvent.ACTION_DOWN:
        //如果手指已经松开，则所有格子变为初始状态
        if( mFinish ){
          for ( int i = 0 ; i < 9 ; i ++ ){
            mCells[i].setSelected(false);
          }
          mFinish = false ;
          mSbSelected.delete(0,mSbSelected.length());
          invalidate();
          return false;
        }
        handleDownEvent(event);
        break;
      //松开则结束
      case MotionEvent.ACTION_UP:
        mFinish = true ;
        break;
      case MotionEvent.ACTION_MOVE:
        handleMoveEvent(event);
        break;
    }
    //表示已处理，不向上传递
    return true ;
  }
  //处理手指移动的事件
  private void handleMoveEvent( MotionEvent event ){
    int index = findCellIndex(event.getX(),event.getY());
    if( index != -1 ){
      mCells[index].setSelected(true);
      mSbSelected.append(index).append(",");
    }
    invalidate();
    mCurrentX = event.getX();
    mCurrentY = event.getY();
  }
  //处理手指按下的事件
  private void handleDownEvent( MotionEvent event){
    int index = findCellIndex(event.getX(),event.getY());
    if( index != -1 ){
      mCells[index].setSelected(true);
      mSbSelected.append(index).append(",");
      invalidate();
    }
    mCurrentX = event.getX();
    mCurrentY = event.getY();
  }
  //根据坐标判断点击的哪个格子
  private int findCellIndex( float x , float y){
    float cellX ;
    float cellY ;
    int result = -1 ;
    for( int i = 0 ; i < 9 ; i ++ ){
      if( mCells[i].isSelected()){
        continue;
      }
      //获取每个格子的坐标
      cellX = mCells[i].getCenterX();
      cellY = mCells[i].getCenterY();
      //计算按下的点到每个格子的距离
      float tempX = cellX - x ;
      float tempY = cellY - y ;
      float distance = (float) Math.sqrt(tempX * tempX + tempY * tempY);
      //如果点击的位置在某个格子的圆内
      if( distance < mCellRadius ){
        result = i ;
        break;
      }
    }
    //返回该格子的位置
    return result ;
  }
}