View.toString()读出意义

Question

我正在将视图记录到logcat以区分不同的视图以进行调试.

我注意到的是输出(主要由View.toString引起)是这样的:

com.example.app.CustomView{7b14550 IFE...C.. ........ 0,0-1440,315}

花括号之间的每个部分是什么意思？

更新:只是认为答案可能在View源代码中并看了一下.对于任何想要了解这一点的人来说,都有一个toString()方法来解释每个值.

Answer 1

当你将.toString()调用到任何给定的类时,除非被覆盖,否则它将调用Object中的toString.每个类都以某种或其他方式将Object作为根.如果扩展一个类,那么该类的超类就是Object.如果类扩展扩展了另一个类,那么该类的超类是Object.你明白这个想法.所以从Object文档中:

/**
 * Returns a string representation of the object. In general, the
 * {@code toString} method returns a string that
 * "textually represents" this object. The result should
 * be a concise but informative representation that is easy for a
 * person to read.
 * It is recommended that all subclasses override this method.
 * <p>
 * The {@code toString} method for class {@code Object}
 * returns a string consisting of the name of the class of which the
 * object is an instance, the at-sign character `{@code @}', and
 * the unsigned hexadecimal representation of the hash code of the
 * object. In other words, this method returns a string equal to the
 * value of:
 * <blockquote>
 * <pre>
 * getClass().getName() + '@' + Integer.toHexString(hashCode())
 * </pre></blockquote>
 *
 * @return  a string representation of the object.
 */
public String toString() {
    return getClass().getName() + "@" + Integer.toHexString(hashCode());
}

除非你覆盖它,否则它会打印出来.这意味着它打印出类'哈希码的十六进制字符串.

因此,除非被覆盖以打印出其他东西,否则它会打印出类'哈希码的十六进制字符串.

但是在View类的情况下,这是它具有的方法:

public String toString() {
    StringBuilder out = new StringBuilder(128);
    out.append(getClass().getName());
    out.append('{');
    out.append(Integer.toHexString(System.identityHashCode(this)));
    out.append(' ');
    switch (mViewFlags&VISIBILITY_MASK) {
        case VISIBLE: out.append('V'); break;
        case INVISIBLE: out.append('I'); break;
        case GONE: out.append('G'); break;
        default: out.append('.'); break;
    }
    out.append((mViewFlags&FOCUSABLE_MASK) == FOCUSABLE ? 'F' : '.');
    out.append((mViewFlags&ENABLED_MASK) == ENABLED ? 'E' : '.');
    out.append((mViewFlags&DRAW_MASK) == WILL_NOT_DRAW ? '.' : 'D');
    out.append((mViewFlags&SCROLLBARS_HORIZONTAL) != 0 ? 'H' : '.');
    out.append((mViewFlags&SCROLLBARS_VERTICAL) != 0 ? 'V' : '.');
    out.append((mViewFlags&CLICKABLE) != 0 ? 'C' : '.');
    out.append((mViewFlags&LONG_CLICKABLE) != 0 ? 'L' : '.');
    out.append((mViewFlags&CONTEXT_CLICKABLE) != 0 ? 'X' : '.');
    out.append(' ');
    out.append((mPrivateFlags&PFLAG_IS_ROOT_NAMESPACE) != 0 ? 'R' : '.');
    out.append((mPrivateFlags&PFLAG_FOCUSED) != 0 ? 'F' : '.');
    out.append((mPrivateFlags&PFLAG_SELECTED) != 0 ? 'S' : '.');
    if ((mPrivateFlags&PFLAG_PREPRESSED) != 0) {
        out.append('p');
    } else {
        out.append((mPrivateFlags&PFLAG_PRESSED) != 0 ? 'P' : '.');
    }
    out.append((mPrivateFlags&PFLAG_HOVERED) != 0 ? 'H' : '.');
    out.append((mPrivateFlags&PFLAG_ACTIVATED) != 0 ? 'A' : '.');
    out.append((mPrivateFlags&PFLAG_INVALIDATED) != 0 ? 'I' : '.');
    out.append((mPrivateFlags&PFLAG_DIRTY_MASK) != 0 ? 'D' : '.');
    out.append(' ');
    out.append(mLeft);
    out.append(',');
    out.append(mTop);
    out.append('-');
    out.append(mRight);
    out.append(',');
    out.append(mBottom);
    final int id = getId();
    if (id != NO_ID) {
        out.append(" #");
        out.append(Integer.toHexString(id));
        final Resources r = mResources;
        if (id > 0 && Resources.resourceHasPackage(id) && r != null) {
            try {
                String pkgname;
                switch (id&0xff000000) {
                    case 0x7f000000:
                        pkgname="app";
                        break;
                    case 0x01000000:
                        pkgname="android";
                        break;
                    default:
                        pkgname = r.getResourcePackageName(id);
                        break;
                }
                String typename = r.getResourceTypeName(id);
                String entryname = r.getResourceEntryName(id);
                out.append(" ");
                out.append(pkgname);
                out.append(":");
                out.append(typename);
                out.append("/");
                out.append(entryname);
            } catch (Resources.NotFoundException e) {
            }
        }
    }
    out.append("}");
    return out.toString();
}

打印出来的意思是:

`7b14550` - hash code identifying the view
`I` - the view is invisible  
`F` - the view is focusable  
`E` - the view is enabled  
`C` - the view is clickable  
`0,0-1440,315` indicates left, top, right and bottom offset in the screen.

但是从上面的代码中可以看出,有许多不同的键需要注意.

括号用于指导您打印出的详细信息是否与您调用的.toString的视图相关联.据我所知,他们没有任何功能在外面向你显示打印出的文本属于那个类.

您可以覆盖toString并使其打印出您想要的任何数据:字段,方法结果,或者什么都不做

未来的提示

下次你想知道方法的作用时,CTRL +左键单击有问题的方法/字段.这将打开目标类,并向您显示开发人员留下的方法和任何可能的文档.