Set default menuItem für BottomNavigationView

Question

Wie kann ich den Standard MenuItem für den offiziellen BottomNavigationView (com.android.support:design:25.0.1) festlegen?

Wenn ich programmatisch menuItem.setCheckable(true).setChecked(true) rufen die Zoom-Effekt nicht durchgeführt wird und die BottomNavigationView zeigt wie folgt aus:

Answer 1

Am Ende war ich in der Lage, dieses Problem zu erreichen Verlängerung der BottomNavigationViewlike this:

public class RichBottomNavigationView extends BottomNavigationView { 
private ViewGroup mBottomItemsHolder; 
private int mLastSelection = INVALID_POSITION; 
private Drawable mShadowDrawable; 
private boolean mShadowVisible = true; 
private int mWidth; 
private int mHeight; 
private int mShadowElevation = 2; 

public RichBottomNavigationView(Context context) { 
    super(context); 
    init(); 
} 

public RichBottomNavigationView(Context context, AttributeSet attrs) { 
    super(context, attrs); 
    init(); 
} 

public RichBottomNavigationView(Context context, AttributeSet attrs, int defStyleAttr) { 
    super(context, attrs, defStyleAttr); 
    init(); 
    ; 
} 


private void init() { 
    mShadowDrawable = ContextCompat.getDrawable(getContext(), R.drawable.shadow); 
    if (mShadowDrawable != null) { 
     mShadowDrawable.setCallback(this); 
    } 
    setBackgroundColor(ContextCompat.getColor(getContext(), android.R.color.transparent)); 
    setShadowVisible(true); 
    setWillNotDraw(false); 

} 

@Override 
protected void onSizeChanged(int w, int h, int oldw, int oldh) { 
    super.onSizeChanged(w, h + mShadowElevation, oldw, oldh); 
    mWidth = w; 
    mHeight = h; 
    updateShadowBounds(); 
} 


private void updateShadowBounds() { 
    if (mShadowDrawable != null && mBottomItemsHolder != null) { 
     mShadowDrawable.setBounds(0, 0, mWidth, mShadowElevation); 
    } 
    ViewCompat.postInvalidateOnAnimation(this); 
} 

@Override 
public void draw(Canvas canvas) { 
    super.draw(canvas); 
    if (mShadowDrawable != null && mShadowVisible) { 
     mShadowDrawable.draw(canvas); 
    } 
} 

public void setShadowVisible(boolean shadowVisible) { 
    setWillNotDraw(!mShadowVisible); 
    updateShadowBounds(); 
} 

public int getShadowElevation() { 
    return mShadowVisible ? mShadowElevation : 0; 
} 

public int getSelectedItem() { 
    return mLastSelection = findSelectedItem(); 
} 

@CallSuper 
public void setSelectedItem(int position) { 
    if (position >= getMenu().size() || position < 0) return; 

    View menuItemView = getMenuItemView(position); 
    if (menuItemView == null) return; 
    MenuItemImpl itemData = ((MenuView.ItemView) menuItemView).getItemData(); 


    itemData.setChecked(true); 

    boolean previousHapticFeedbackEnabled = menuItemView.isHapticFeedbackEnabled(); 
    menuItemView.setSoundEffectsEnabled(false); 
    menuItemView.setHapticFeedbackEnabled(false); //avoid hearing click sounds, disable haptic and restore settings later of that view 
    menuItemView.performClick(); 
    menuItemView.setHapticFeedbackEnabled(previousHapticFeedbackEnabled); 
    menuItemView.setSoundEffectsEnabled(true); 


    mLastSelection = position; 

} 


@Override 
protected Parcelable onSaveInstanceState() { 
    Parcelable superState = super.onSaveInstanceState(); 
    BottomNavigationState state = new BottomNavigationState(superState); 
    mLastSelection = getSelectedItem(); 
    state.lastSelection = mLastSelection; 
    return state; 
} 

@Override 
protected void onRestoreInstanceState(Parcelable state) { 
    if (!(state instanceof BottomNavigationState)) { 
     super.onRestoreInstanceState(state); 
     return; 
    } 
    BottomNavigationState bottomNavigationState = (BottomNavigationState) state; 
    mLastSelection = bottomNavigationState.lastSelection; 
    dispatchRestoredState(); 
    super.onRestoreInstanceState(bottomNavigationState.getSuperState()); 
} 

private void dispatchRestoredState() { 
    if (mLastSelection != 0) { //Since the first item is always selected by the default implementation, dont waste time 
     setSelectedItem(mLastSelection); 
    } 
} 

private View getMenuItemView(int position) { 
    View bottomItem = mBottomItemsHolder.getChildAt(position); 
    if (bottomItem instanceof MenuView.ItemView) { 
     return bottomItem; 
    } 
    return null; 
} 

private int findSelectedItem() { 
    int itemCount = getMenu().size(); 
    for (int i = 0; i < itemCount; i++) { 
     View bottomItem = mBottomItemsHolder.getChildAt(i); 
     if (bottomItem instanceof MenuView.ItemView) { 
      MenuItemImpl itemData = ((MenuView.ItemView) bottomItem).getItemData(); 
      if (itemData.isChecked()) return i; 
     } 
    } 
    return INVALID_POSITION; 
} 

@Override 
protected void onFinishInflate() { 
    super.onFinishInflate(); 
    mBottomItemsHolder = (ViewGroup) getChildAt(0); 
    updateShadowBounds(); 
    //This sucks. 
    MarginLayoutParams layoutParams = (MarginLayoutParams) mBottomItemsHolder.getLayoutParams(); 
    layoutParams.topMargin = (mShadowElevation + 2)/2; 
} 

static class BottomNavigationState extends BaseSavedState { 
    public int lastSelection; 

    @RequiresApi(api = Build.VERSION_CODES.N) 
    public BottomNavigationState(Parcel in, ClassLoader loader) { 
     super(in, loader); 
     lastSelection = in.readInt(); 
    } 

    public BottomNavigationState(Parcelable superState) { 
     super(superState); 
    } 

    @Override 
    public void writeToParcel(@NonNull Parcel dest, int flags) { 
     super.writeToParcel(dest, flags); 
     dest.writeInt(lastSelection); 
    } 

    public static final Parcelable.Creator<NavigationView.SavedState> CREATOR 
      = ParcelableCompat.newCreator(new ParcelableCompatCreatorCallbacks<NavigationView.SavedState>() { 
     @Override 
     public NavigationView.SavedState createFromParcel(Parcel parcel, ClassLoader loader) { 
      return new NavigationView.SavedState(parcel, loader); 
     } 

     @Override 
     public NavigationView.SavedState[] newArray(int size) { 
      return new NavigationView.SavedState[size]; 
     } 
    }); 
} 
} 

und rufen setSelectedItem(2)

Answer 2

ich erreichte dies in einem viel einfacheren Weg:

//R.id.bottom_bar_icon is the icon you would like clicked by default 
    bottomNavigationView.getMenu().performIdentifierAction(R.id.bottom_bar_icon, 0); 

    //set the corresponding menu item to checked = true 
    //and the other items to checked = false 
    bottomNavigationView.getMenu().getItem(0).setChecked(false); 
    bottomNavigationView.getMenu().getItem(1).setChecked(true); 
    bottomNavigationView.getMenu().getItem(2).setChecked(false); 

Answer 3

Es ist einfacher Weg, dies seit Android Support Library 25.3.0 zu tun:

bottomNavigationView.setSelectedItemId(R.id.id_of_item_you_want_to_select_as_default);