java - 如何动态更改来自不同类的 View 背景颜色

Question

如何从不同的类( Activity 或 fragment )访问标签条类？我想从其他地方更改它的背景颜色。

在原始标签条类中使用以下代码时，它可以完美运行:

  mTabStrip.setBackgroundColor(ContextCompat.getColor(getContext(), R.color.blue));

我相信需要使用这样的东西，但我不知道如何从另一个类(即 Activity 或 fragment )访问它(TabStrip 类)并更改背景颜色。

XML Activity 布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/detail_container">

    <include layout="@layout/my_toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

    <com.companyname.appname.TabStrip
        android:id="@+id/my_tabs"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

    <android.support.v4.view.ViewPager
        android:id="@+id/pager"
        android:layout_height="0dp"
        android:layout_width="match_parent"
        android:layout_weight="1"/>

</LinearLayout>

Activity 类

public class MyActivity extends AppCompatActivity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.my_activity);

        final String toolbarColour = "#868F98";

        Toolbar customToolbar = findViewById(R.id.my_toolbar);
        setActionBar(customToolbar);
        customToolbar.setBackgroundColor(Color.parseColor(toolbarColour));

        TextView mTitle = this.findViewById(R.id.toolbar_title);
        mTitle.setText(getString(R.string.toolbar));

        if (savedInstanceState == null) {
            MyFragment newFragment = new MyFragment();
            FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
            transaction.replace(R.id.detail_container, newFragment);
            transaction.commit();
        }
    }
}

MyFragment.java

public class MyFragment extends android.support.v4.app.Fragment {

    public MyFragment() {}

    ViewPager pager;
    MyFragmentViewPagerAdapter adapter;
    MyTabStrip my_tabs;
    int Numboftabs = 3;

    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.my_fragment, container, false);
        super.onCreate(savedInstanceState);

        return v;
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        View v = getView();

        adapter =  new MyFragmentViewPagerAdapter(getChildFragmentManager(), Numboftabs, getActivity());

        assert v != null;
        pager = v.findViewById(R.id.pager);
        pager.setAdapter(adapter);

        mytabs = v.findViewById(R.id.my_tabs);
        mytabs.setDistributeEvenly(false);

        my_tabs.setCustomTabColorizer(new TabStrip.TabColorizer() {
            @Override
            public int getIndicatorColor(int position) {
                return Color.WHITE;
            }
        });

        mytabs.setViewPager(pager);

        super.onActivityCreated(savedInstanceState);
    }

    private class MyFragmentViewPagerAdapter extends FragmentStatePagerAdapter {

        private int NumbOfTabs;
        private Context context;

        MyFragmentViewPagerAdapter(FragmentManager fm, int mNumbOfTabsumb, Context context) {
            super(fm);

            this.context = context;
            this.NumbOfTabs = mNumbOfTabsumb;
        }

        @Override
        public Fragment getItem(int position) {
            switch (position) {
                case 0:
                    return new Tab1();
                case 1:
                    return new Tab2();
                case 2:
                    return new Tab3();
            }
            return null;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            switch (position) {
                case 0:
                    return context.getResources().getString(R.string.tab_1);
                case 1:
                    return context.getResources().getString(R.string.tab_2);
                case 2:
                    return context.getResources().getString(R.string.tab_3);
            }
            return super.getPageTitle(position);
        }

        @Override
        public int getCount() {
            return NumbOfTabs;
        }
    }
}

TabStrip.java

public class TabStrip extends HorizontalScrollView {

    public interface TabColorizer {
        int getIndicatorColor(int position);
    }

    private static final int TITLE_OFFSET_DIPS = 24;
    private static final int TAB_VIEW_PADDING_DIPS = 16;
    private static final int TAB_VIEW_TEXT_SIZE_SP = 12;

    private int mTitleOffset;

    private int mTabViewLayoutId;
    private int mTabViewTextViewId;
    private boolean mDistributeEvenly;

    private ViewPager mViewPager;
    private SparseArray<String> mContentDescriptions = new SparseArray<>();
    private ViewPager.OnPageChangeListener mViewPagerPageChangeListener;

    private final SlidingTabStrip mTabStrip;

    public TabStrip(Context context) {
        this(context, null);
    }

    public TabStrip(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public TabStrip(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        setHorizontalScrollBarEnabled(false);
        setFillViewport(true);

        mTitleOffset = (int) (TITLE_OFFSET_DIPS * getResources().getDisplayMetrics().density);

        mTabStrip = new SlidingTabStrip(context);
        addView(mTabStrip, LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
    }


    public void setCustomTabColorizer(TabStrip.TabColorizer tabColorizer) {
        mTabStrip.setCustomTabColorizer(tabColorizer);
    }

    public void setDistributeEvenly(boolean distributeEvenly) {
        mDistributeEvenly = distributeEvenly;
    }

    public void setSelectedIndicatorColors(int... colors) {
        mTabStrip.setSelectedIndicatorColors(colors);
    }

    public void addOnPageChangeListener(ViewPager.OnPageChangeListener listener) {
        mViewPagerPageChangeListener = listener;
    }

    public void setCustomTabView(int layoutResId, int textViewId) {
        mTabViewLayoutId = layoutResId;
        mTabViewTextViewId = textViewId;
    }

    public void setViewPager(ViewPager viewPager) {
        mTabStrip.removeAllViews();

        mViewPager = viewPager;
        if (viewPager != null) {
            viewPager.addOnPageChangeListener(new TabStrip.InternalViewPagerListener());
            populateTabStrip();
        }
    }

    protected TextView createDefaultTabView(Context context) {
        TextView textView = new TextView(context);
        textView.setGravity(Gravity.CENTER);
        textView.setTextSize(TypedValue.COMPLEX_UNIT_SP, TAB_VIEW_TEXT_SIZE_SP);
        textView.setTypeface(Typeface.DEFAULT_BOLD);
        textView.setLayoutParams(new LinearLayout.LayoutParams(
                ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));

        TypedValue outValue = new TypedValue();
        getContext().getTheme().resolveAttribute(android.R.attr.selectableItemBackground,
                outValue, true);
        textView.setBackgroundResource(outValue.resourceId);
        textView.setAllCaps(true);

        int padding = (int) (TAB_VIEW_PADDING_DIPS * getResources().getDisplayMetrics().density);
        textView.setPadding(padding, padding, padding, padding);

        return textView;
    }

    private void populateTabStrip() {
        final PagerAdapter adapter = mViewPager.getAdapter();
        final View.OnClickListener tabClickListener = new TabStrip.TabClickListener();

        for (int i = 0; i < adapter.getCount(); i++) {
            View tabView = null;
            TextView tabTitleView = null;

            if (mTabViewLayoutId != 0) {
                tabView = LayoutInflater.from(getContext()).inflate(mTabViewLayoutId, mTabStrip, false);
                tabTitleView = (TextView) tabView.findViewById(mTabViewTextViewId);
            }

            if (tabView == null) {
                tabView = createDefaultTabView(getContext());
            }

            if (tabTitleView == null && TextView.class.isInstance(tabView)) {
                tabTitleView = (TextView) tabView;
            }

            if (mDistributeEvenly) {
                LinearLayout.LayoutParams lp = (LinearLayout.LayoutParams) tabView.getLayoutParams();
                lp.width = 0;
                lp.weight = 1;
            }

            assert tabTitleView != null;
            tabTitleView.setText(adapter.getPageTitle(i));
            tabView.setOnClickListener(tabClickListener);
            String desc = mContentDescriptions.get(i, null);
            if (desc != null) {
                tabView.setContentDescription(desc);
            }

            mTabStrip.addView(tabView);
            if (i == mViewPager.getCurrentItem()) {
                tabView.setSelected(true);
            }

            tabTitleView.setTextColor(Color.WHITE);
            tabTitleView.setTextSize(14);
        }
    }

    public void setContentDescription(int i, String desc) {
        mContentDescriptions.put(i, desc);
    }

    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();

        if (mViewPager != null) {
            scrollToTab(mViewPager.getCurrentItem(), 0);
        }
    }

    private void scrollToTab(int tabIndex, int positionOffset) {
        final int tabStripChildCount = mTabStrip.getChildCount();
        if (tabStripChildCount == 0 || tabIndex < 0 || tabIndex >= tabStripChildCount) {
            return;
        }

        View selectedChild = mTabStrip.getChildAt(tabIndex);
        if (selectedChild != null) {
            int targetScrollX = selectedChild.getLeft() + positionOffset;

            if (tabIndex > 0 || positionOffset > 0) {
                targetScrollX -= mTitleOffset;
            }

            scrollTo(targetScrollX, 0);
        }
    }

    private class InternalViewPagerListener implements ViewPager.OnPageChangeListener {
        private int mScrollState;

        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
            int tabStripChildCount = mTabStrip.getChildCount();
            if ((tabStripChildCount == 0) || (position < 0) || (position >= tabStripChildCount)) {
                return;
            }

            mTabStrip.onViewPagerPageChanged(position, positionOffset);

            View selectedTitle = mTabStrip.getChildAt(position);
            int extraOffset = (selectedTitle != null)
                    ? (int) (positionOffset * selectedTitle.getWidth())
                    : 0;
            scrollToTab(position, extraOffset);

            if (mViewPagerPageChangeListener != null) {
                mViewPagerPageChangeListener.onPageScrolled(position, positionOffset,
                        positionOffsetPixels);
            }
        }

        @Override
        public void onPageScrollStateChanged(int state) {
            mScrollState = state;

            if (mViewPagerPageChangeListener != null) {
                mViewPagerPageChangeListener.onPageScrollStateChanged(state);
            }
        }

        @Override
        public void onPageSelected(int position) {
            if (mScrollState == ViewPager.SCROLL_STATE_IDLE) {
                mTabStrip.onViewPagerPageChanged(position, 0f);
                scrollToTab(position, 0);
            }
            for (int i = 0; i < mTabStrip.getChildCount(); i++) {
                mTabStrip.getChildAt(i).setSelected(position == i);
            }
            if (mViewPagerPageChangeListener != null) {
                mViewPagerPageChangeListener.onPageSelected(position);
            }
        }

    }

    private class TabClickListener implements View.OnClickListener {
        @Override
        public void onClick(View v) {
            for (int i = 0; i < mTabStrip.getChildCount(); i++) {
                if (v == mTabStrip.getChildAt(i)) {
                    mViewPager.setCurrentItem(i);
                    return;
                }
            }
        }
    }
}

Answer 1

由于给定的 xml 布局正在 Activity 中使用，您可以使用 findViewById() 访问 TabStrip。此外，由于您需要在某些事件中更改其颜色，您可以声明一个全局变量来保存对 TabStrip 的引用。

代码看起来像这样:

...

public com.companyname.appname.TabStrip mTabStrip = null; /* global variable */

...

        super.onCreate(savedInstanceState);
        setContentView(R.layout.my_activity);

        final String toolbarColour = "#868F98";

        mTabStrip = findViewById(R.id.my_tabs);
        Toolbar customToolbar = findViewById(R.id.my_toolbar);
        setActionBar(customToolbar);
...

当然你可以使用:

 mTabStrip.setBackgroundColor(ContextCompat.getColor(getContext(), R.color.blue));