Cursor里的方法实现

对于InstrumentedCursorWrapper.java下函数
    @Override
    public boolean moveToPosition(int position) {
        boolean result = super.moveToPosition(position);
        logQueryTime();
        return result;
    }


super执行的是父类的方法
public boolean moveToPosition(int position) {
        return mCursor.moveToPosition(position);
    }
这里的mCursor为 private Cursor mCursor;
public interface Cursor {
boolean moveToPosition(int position);
}
那么moveToPosition这个方法在哪里实现呢？

mCursor回归到AbstractCursor实现的方法。

AbstractCursor.java

public abstract class AbstractCursor implements CrossProcessCursor {
	
    public final boolean moveToPosition(int position) {
        // Make sure position isn't past the end of the cursor
        final int count = getCount();
        if (position >= count) {
            mPos = count;
            return false;
        }

        // Make sure position isn't before the beginning of the cursor
        if (position < 0) {
            mPos = -1;
            return false;
        }

        // Check for no-op moves, and skip the rest of the work for them
        if (position == mPos) {
            return true;
        }

        boolean result = onMove(mPos, position);
        if (result == false) {
            mPos = -1;
        } else {
            mPos = position;
            if (mRowIdColumnIndex != -1) {
                mCurrentRowID = Long.valueOf(getLong(mRowIdColumnIndex));
            }
        }

        return result;
    }

}


public interface CrossProcessCursor extends Cursor {
	
}

public interface Cursor {
	boolean moveToPosition(int position);
}

以下为模拟片段;

package com.jk.test.cursor;

public interface Cursor {
	boolean moveToPosition(int position);
}

package com.jk.test.cursor;


public interface CrossProcessCursor extends Cursor {


}

package com.jk.test.cursor;


public abstract class AbstractCursor implements CrossProcessCursor {


	@Override
	public boolean moveToPosition(int position) {
		System.out.println("position " + position);


		return false;
	}


}

package com.jk.test.model;


import com.jk.test.cursor.AbstractCursor;
import com.jk.test.cursor.Cursor;


public class RealModel extends AbstractCursor {
	private Cursor mCursor;
	
    public boolean onMove(int oldPosition, int newPosition)
    {
    	if(mCursor==null){
    		mCursor = new RealModel();
    	}
        mCursor.moveToPosition(newPosition - oldPosition);
        
        return true;   
    }


}

package com.jk.test;


import com.jk.test.model.RealModel;


public class CursorTest {


	/**
	 * @param args
	 */
	public static void main(String[] args) {
		RealModel rm = new RealModel();
		rm.onMove(0, 2);
	}


}