java构造方法重载与多重匹配

Question

引用下面的代码:

public class ExpandableTextView extends TextView {

    public ExpandableTextView(Context context) {
        this(context, null, null);
    }

    public ExpandableTextView(Context context, AttributeSet attrs) {
        this(context, attrs, null);
    }

    public ExpandableTextView(Context context, AttributeSet attrs, Runnable runnable) {
        super(context, attrs);

        TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.ExpandableTextView);
        this.trimLength = typedArray.getInt(R.styleable.ExpandableTextView_trimLength, DEFAULT_TRIM_LENGTH);
        typedArray.recycle();

        setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                trim = !trim;
                setText();
                requestFocusFromTouch();
            }
        });
    }

    public ExpandableTextView(Context context, AttributeSet attrs, Activity activity) {
        super(context, attrs);

        TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.ExpandableTextView);
        this.trimLength = typedArray.getInt(R.styleable.ExpandableTextView_trimLength, DEFAULT_TRIM_LENGTH);
        typedArray.recycle();

        setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                trim = !trim;
                setText();
                requestFocusFromTouch();
            }
        });
    }
}

像这样的方法(context, null, null);可以引用另外两个构造函数方法，有什么方法可以指定它引用哪一个而不是更改签名或“null”？谢谢

Answer 1

当然，只需将 null 转换为签名类型即可!

    new ExpandableTextView(context, (AttributeSet)null, (Runnable)null)