android - 如何使用支持操作栏将默认主页显示为向上指示器？

Question

在我的应用程序中，我在某些情况下将主页设置为非默认可绘制对象。有时主页向上指示器在更改后应重置为默认图标。

我试过

getSupportActionBar().setHomeAsUpIndicator(0);

根据documentation说将使用主题默认值。当我这样做时，应用程序崩溃并出现以下错误:

05-15 11:12:03.160: E/AndroidRuntime(13021): FATAL EXCEPTION: main
05-15 11:12:03.160: E/AndroidRuntime(13021): Process: xxxxx.yyyyyy.zzzzzz, PID: 13021
05-15 11:12:03.160: E/AndroidRuntime(13021): android.content.res.Resources$NotFoundException: Resource ID #0x0
05-15 11:12:03.160: E/AndroidRuntime(13021):    at android.content.res.Resources.getValue(Resources.java:1233)
05-15 11:12:03.160: E/AndroidRuntime(13021):    at android.content.res.Resources.getDrawable(Resources.java:756)
05-15 11:12:03.160: E/AndroidRuntime(13021):    at android.content.Context.getDrawable(Context.java:402)
05-15 11:12:03.160: E/AndroidRuntime(13021):    at android.support.v4.content.ContextCompatApi21.getDrawable(ContextCompatApi21.java:26)
05-15 11:12:03.160: E/AndroidRuntime(13021):    at android.support.v4.content.ContextCompat.getDrawable(ContextCompat.java:319)
05-15 11:12:03.160: E/AndroidRuntime(13021):    at android.support.v7.internal.widget.TintManager.getDrawable(TintManager.java:133)
05-15 11:12:03.160: E/AndroidRuntime(13021):    at android.support.v7.widget.Toolbar.setNavigationIcon(Toolbar.java:754)
05-15 11:12:03.160: E/AndroidRuntime(13021):    at android.support.v7.internal.app.ToolbarActionBar.setHomeAsUpIndicator(ToolbarActionBar.java:176)
05-15 11:12:03.160: E/AndroidRuntime(13021):    at xxxxx.yyyyyy.zzzzzz.updateHomeIndicator(aaaaa.java:1711)

我知道主题默认值设置正确，因为如果我从未将自定义主页设置为向上指示器，后退箭头显示正常。在尝试调用 setHomeAsUpIndicator(0) 之前，我调用了 setDisplayHomeAsUpEnabled(true)。

我知道我总是可以将默认主页作为向上指示器 Assets 复制到我的项目中并直接使用该 Assets ，但我想尽可能避免这种解决方法。

谢谢!

扎克

编辑:

我也试过

getSupportActionBar().setHomeAsUpIndicator(null);

这导致没有显示任何图标。

Answer 1

我遵循以下源代码:ToolbarActionBar.setHomeAsUpIndicator()

当我看到源代码时:ContextCompat.getDrawable() ，它说:“值 0 是无效标识符”。

 /**
 * Return a drawable object associated with a particular resource ID.
 * <p>
 * Starting in {@link android.os.Build.VERSION_CODES#LOLLIPOP}, the returned
 * drawable will be styled for the specified Context's theme.
 *
 * @param id The desired resource identifier, as generated by the aapt tool.
 *            This integer encodes the package, type, and resource entry.
 *            The value 0 is an invalid identifier.
 * @return Drawable An object that can be used to draw this resource.
 */
public static final Drawable getDrawable(Context context, int id) {
    final int version = Build.VERSION.SDK_INT;
    if (version >= 21) {
        return ContextCompatApi21.getDrawable(context, id);
    } else {
        return context.getResources().getDrawable(id);
    }
}

我一直关注源代码，最后看到下面的代码，这是你抛出异常的地方:Resources.getValue()

/**
 * Return the raw data associated with a particular resource ID.
 * 
 * @param id The desired resource identifier, as generated by the aapt
 *           tool. This integer encodes the package, type, and resource
 *           entry. The value 0 is an invalid identifier.
 * @param outValue Object in which to place the resource data.
 * @param resolveRefs If true, a resource that is a reference to another
 *                    resource will be followed so that you receive the
 *                    actual final resource data.  If false, the TypedValue
 *                    will be filled in with the reference itself.
 *
 * @throws NotFoundException Throws NotFoundException if the given ID does not exist.
 *
 */
public void getValue(int id, TypedValue outValue, boolean resolveRefs)
        throws NotFoundException {
    boolean found = mAssets.getResourceValue(id, 0, outValue, resolveRefs);
    if (found) {
        return;
    }
    throw new NotFoundException("Resource ID #0x"
                                + Integer.toHexString(id));
}

到目前为止，我看不到对“0”有任何特殊处理。所以，我认为这是您在上面发布的官方文档中的错误。解决此崩溃错误的简单方法是使用现有标识符，就像您的默认图标 ID 一样。