Reverse the direction of a LinearLayout

问题

How can I reverse the direction of a linear layout?

for example, if my layout is [view1, view2, view3] I want to create [view3, view2, view1]. My goal is to inflate a left and a right handed instances from one XML layout.

回答1:

Generally I would say you cannot do this using the standard SDK. You could however create a method which gets all of the subviews out of the LinearLayout, removes them from the LinearLayout, and then adds them back in reverse order.

LinearLayout ll = // inflate
ArrayList<View> views = new ArrayList<View>();
for(int x = 0; x < ll.getChildCount(); x++) {
    views.add(ll.getChildAt(x));
}
ll.removeAllViews();
for(int x = views.size() - 1; x >= 0; x--) {
    ll.addView(views.get(x));
}

回答2:

this is simplest approach :)

for(int k = ll.getChildCount()-1 ; k >= 0 ; k--)
{
    View item = ll.getChildAt(k);
    ll.removeViewAt(k);
    ll.addView(item);
}

回答3:

You can control the direction of the layout directly through the layoutDirection. In this code we detect whether the natural direction is RTL, and reverse the direction, obviously one can apply your own logic to reversing:

LinearLayout buttonsContainer = (LinearLayout) findViewById(R.id.buttonsContainer);          
buttonsContainer.setLayoutDirection(isRTL() ? LinearLayout.LAYOUT_DIRECTION_LTR : 
                                    LinearLayout.LAYOUT_DIRECTION_RTL)

public static boolean isRTL() {
        return isRTL(Locale.getDefault());
}

public static boolean isRTL(Locale locale) {
    final int directionality = Character.getDirectionality(locale.getDisplayName().charAt(0));
    return directionality == Character.DIRECTIONALITY_RIGHT_TO_LEFT ||
            directionality == Character.DIRECTIONALITY_RIGHT_TO_LEFT_ARABIC;
}

Or via XML in case you want to override the natural direction constantly:

<LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="horizontal"
        android:layoutDirection="ltr"
        >
...
</LinearLayout>

Detection of RTL is taken from this question: Identifyng RTL language in Android

回答4:

Simple way try this

LinearLayout ll = (LinearLayout)findViewById(R.id.ll1);
    View v0 = ll.getChildAt(0);
    View v1 = ll.getChildAt(1);
    View v2 = ll.getChildAt(2);

    ll.removeAllViews();

    ll.addView(v2);
    ll.addView(v1);
    ll.addView(v0);

回答5:

Just add the following code to LinearLayout:

android:layoutDirection="rtl"

But it permanently reverses the order - not just for RTL locales :(

回答6:

<LinearLayout
    android:id="@+id/parent"
    ...... 
    ......>
  view1
  view2
  view2
<LinearLayout/>

Now you can try this

LinearLayout parent = (LinearLayout)findViewById(R.id.parent);
View view1 = (View)parent.getChildAt(0);  // it will give first view
View view3 = (View)parent.getChildAt(2);  // it will give you third view

Here by View , it can be TextView,Button....etc.

回答7:

How can I reverse the direction of a linear layout?

That is not supported, sorry.

My goal is to inflate a left and a right handed instances from one XML layout.

You are welcome to inflate them both from one XML layout, but you will then need to remove all the children of one and reverse their order in Java code. It may be that this is simpler than maintaining the two separate layout files, but it is definitely not automatic.

Or, you are welcome to create your own subclass of LinearLayout (or perhaps clone LinearLayout) that offers this feature.

Android 4.2 and higher offers RTL support for LinearLayout, but that is tied to locale and would apply to all horizontal LinearLayout containers in your app.

回答8:

notice for the prev answers, if you want to preserve width/height of views, calculated by direct pass (i.e. fill parent/wrap content), you have to set them explicitly:

for (int i = views.size() - 1; i >= 0; i--)
{
    View v = views.get(i);
    linearLayoutHor.addView(v, v.getWidth(), v.getHeight());
}

perhaps you will have to use post to view to be sure sizes of views are calculated. and add handler for orientation changes to have sizes recalculated correctly.

回答9:

You can try ViewCompat.setLayoutDirection(view, direction)

来源：https://stackoverflow.com/questions/13903611/reverse-the-direction-of-a-linearlayout