params.getBehaviour（）返回null值

问题描述

我是用新的Andr​​oid设计库播放。该CollapsingToolbarLayout完美的作品。不过，我有麻烦的设置工具栏默认状态为折叠。

我想实现显示的解决方案，here和<一个href=\"http://stackoverflow.com/questions/30655939/android-programmatically-collapse-or-expand-collapsingtoolbarlayout?lq=1\">here

我打电话下面我活动onResume code：

  CoordinatorLayout.LayoutParams PARAMS =（CoordinatorLayout.LayoutParams）appBarLayout.getLayoutParams（）;
    AppBarLayout.Behavior行为=（AppBarLayout.Behavior）params.getBehavior（）;
    如果（行为！= NULL）
    {
        Log.d（调试，行为不为空）;
        INT [] =消耗的新INT [2];
        behavior.onNested preScroll（协调，appBarLayout，NULL，0，1000，消费）;
// behavior.onNestedFling（协调，appBarLayout，NULL，0，10000，真正的）;
     }
     其他
          Log.d（调试，行为为空）;
 

不过，PARAMS返回的行为为null。
我的XML是code一样的here,但我不使用抽屉CordinatorLayout是我的根布局。

编辑：刚才我试着切换到AppBarLayout.Behavior和AppBarLayout.ScrollingViewBehavior为AppBarLayout设置layout_behavior为@字符串/ appbar_scrolling_view_behavior，但它导致了奇怪的布局。

罗宾的回答很好地工作。以补充，行为也可以在XML使用以下标记设置AppBarLayout：

 应用：layout_behavior =$ android.support.design.widget.AppBarLayout行为
 

解决方案

您之前设置的布局行为。

只要使用以下code。在您的onCreate方法：

（（CoordinatorLayout.LayoutParams）YOUR_LAYOUT.getLayoutParams（））setBehavior（新AppBarLayout.Behavior（）{}）;

I was playing with the new Android Design Library. The CollapsingToolbarLayout works perfectly. However, I am having trouble setting default state of toolbar as Collapsed.

I am trying to implement the solution shown here and here

I am calling following code in my onResume of Activity:

   CoordinatorLayout.LayoutParams params = (CoordinatorLayout.LayoutParams) appBarLayout.getLayoutParams();
    AppBarLayout.Behavior behavior = (AppBarLayout.Behavior) params.getBehavior();
    if(behavior!=null)
    {
        Log.d("DEBUG", "Behaviour is Not Null ");
        int[] consumed = new int[2];
        behavior.onNestedPreScroll(coordinator, appBarLayout, null, 0, 1000,consumed);
//      behavior.onNestedFling(coordinator, appBarLayout, null, 0, 10000, true);
     }
     else
          Log.d("DEBUG", "Behaviour is Null " );

However, the behaviour returned by params is null.My xml is code same as here, except i am not using drawer and CordinatorLayout is my root Layout.

EDIT: I earlier tried switching AppBarLayout.Behavior to AppBarLayout.ScrollingViewBehavior and setting layout_behavior for AppBarLayout to @string/appbar_scrolling_view_behavior, but it resulted in weird layout.

Robin's answer works nicely. To Complement that, the behavior can also set in xml using following tag in AppBarLayout:

app:layout_behavior="android.support.design.widget.AppBarLayout$Behavior"

解决方案

You have to set a layout behavior before.

Just use following code at your onCreate method:

((CoordinatorLayout.LayoutParams) YOUR_LAYOUT.getLayoutParams()).setBehavior(new AppBarLayout.Behavior() {});

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