How to send view to back ? How to control the z-order programmatically?

问题

I have a problem to send the view to back. In Android we have a method like bringToFront(), to place the view on top of the another view. Like that, I want to put the view on below the previous image.

Is there any method like sendToBack() or bringToBack() in Android. If so, can any one help me in this.

Note: that I do not want to control the z-order by the order of placing items in layout I want to control the z-order programmatically.

I do not want to hide the views on the front I just want them to be behind the view that is moving.

回答1:

Afaik there's no built-in solution for this. I guess you're trying to modify the z-order in a FrameLayout, or something similar.

However, I think you can modify the order of the contained child elements in the layout. RemoveChild...() and addView() methods can take position values, so you could most likely swap child elements around, and that would modify the z-order. It seems a bit hacky solution however.

Or consider modifying the visibility property of the child views, you may get similar behaviour, and that'd be much cleaner I think.

Edit:

With the new Android version, the L Developer Preview it seems that at last we have the ability to easily change the Z ordering of Views. 'Elevation' and 'TranslationZ' properties to the rescue: https://developer.android.com/preview/material/views-shadows.html

回答2:

I realize that this has been implied in other answers, but no one posted the code. I keep the following in a utility class where I have "helper" functions for dealing with views:

public static void sendViewToBack(final View child) {
    final ViewGroup parent = (ViewGroup)child.getParent();
    if (null != parent) {
        parent.removeView(child);
        parent.addView(child, 0);
    }
}

回答3:

There is no sendToBack() method. But if you call bringToFront() on the lower positioned view you get almost the same effect.

回答4:

Call bringToFront() on the view you want to get in the front, and then call the invalidate() method on all the view including the view which you want in the front. Repeat same for all the listeners.

So when another view's listener will get called, the previous view will get invalidated and will be in background.

回答5:

Here is the method I am using to send a View to the back (so opposite of bringToFront, kind of sendToBack):

    private void moveToBack(View myCurrentView) 
    {
        ViewGroup myViewGroup = ((ViewGroup) myCurrentView.getParent());
        int index = myViewGroup.indexOfChild(myCurrentView);
        for(int i = 0; i<index; i++)
        {
            myViewGroup.bringChildToFront(myViewGroup.getChildAt(i));
        }
    }

Hope this helps!

回答6:

Please note that you can use view.setZ(float) starting from API level 21. Here you can find more info.

回答7:

it work's fine like bringToBack()

public void moveToBack(ViewGroup viewGroup, View v) {
    int s = 1;
    for (int i = 1; i < viewGroup.getChildCount(); i++) {
        if (viewGroup.getChildAt(1) == v) {
            s = 2;
        } else {
            viewGroup.getChildAt(s).bringToFront();
        }
    }
}

回答8:

In your XML File you must to write in order:

<FrameLayout
android:id="@+id/frameLayoutXML"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
<ImageView
 android:id="@+id/imageViewXML"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<android.support.design.widget.FloatingActionButton
android:id="@+id/floatB_XML"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center" />
</FrameLayout>

In this case, the imageView will be back of the FloatingActionButton.

If you want change something, and you will do it programmatically then:

public class SomeActivity extends AppCompatActivity {

    //declare variables
    ImageView imageView;
    FrameLayout frameLayout;
    FloatingActionButton floatingActionButtonNew;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        //Here is to call what already exists at XML file
        frameLayout=findViewById(R.id.frameLayoutXML);   
        imageView = findViewById(R.id.imageViewXML);
        //Here is to declare a new Element to add to the view, but is not at XML File
        floatingActionButtonNew=New FloatingActionButton(this);
        frameLayout.removeAllViews();  //here you remove all views.
        frameLayout.addView(imageView);//And you add again the imageView first
        floatingActionButtonNew.setLayoutParams(new 
         RelativeLayout.LayoutParams(
          RelativeLayout.LayoutParams.WRAP_CONTENT,
          RelativeLayout.LayoutParams.WRAP_CONTENT
        )); //Then you can give some format to your floatingButtonNew

        //And finally  add to the frameLayout the new View in this case the floatingButtonNew
        frameLayout.addView(floatingActionButtonNew);
    }
}

In this order of view declarations, you will have again the image back from the floating button. So the view that is declared first will be back from the view that is declared secondly, and the key to achieve the order, is to removeAllViews of a FrameLayout or LinearLayout and add again this views when you are adding programmatically.

回答9:

You can also try to use functionality of ViewGroup.addViewInLayout() method which take an index, determining should the view be at the end or at the beginning of the list

回答10:

I would either set it's visibility to 0 or just bring the view under it in front of it.

回答11:

If you're using appCompat library, there's another way to change Z order for devices lower than 21 API level:

ViewCompat.setTranslationZ(view, zValue);

回答12:

You could try doing view.setVisibility(View.INVISIBLE) or view.setVisibility(View.GONE).

UPDATE:

This shows you how to accomplish what you want to do.

来源：https://stackoverflow.com/questions/6759036/how-to-send-view-to-back-how-to-control-the-z-order-programmatically

标签

android

android-layout

view

z-order