First Commit

Signed-off-by: YuutaW <17158086+Trumeet@users.noreply.github.com>

16 files changed, 670 insertions, 0 deletions

diff --git a/library/src/androidTest/java/moe/yuuta/flow/ExampleInstrumentedTest.java b/library/src/androidTest/java/moe/yuuta/flow/ExampleInstrumentedTest.java
new file mode 100644
index 0000000..435e2e8
--- /dev/null
+++ b/library/src/androidTest/java/moe/yuuta/flow/ExampleInstrumentedTest.java
@@ -0,0 +1,26 @@
+package moe.yuuta.flow;
+
+import android.content.Context;
+import android.support.test.InstrumentationRegistry;
+import android.support.test.runner.AndroidJUnit4;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Instrumented test, which will execute on an Android device.
+ *
+ * @see <a href="http://d.android.com/tools/testing">Testing documentation</a>
+ */
+@RunWith(AndroidJUnit4.class)
+public class ExampleInstrumentedTest {
+    @Test
+    public void useAppContext() {
+        // Context of the app under test.
+        Context appContext = InstrumentationRegistry.getInstrumentation().getTargetContext();
+
+        assertEquals("moe.yuuta.flow.test", appContext.getPackageName());
+    }
+}
diff --git a/library/src/main/AndroidManifest.xml b/library/src/main/AndroidManifest.xml
new file mode 100644
index 0000000..f3b86f1
--- /dev/null
+++ b/library/src/main/AndroidManifest.xml
@@ -0,0 +1 @@
+<manifest package="moe.yuuta.flow" />
diff --git a/library/src/main/java/moe/yuuta/flow/FlowFragment.java b/library/src/main/java/moe/yuuta/flow/FlowFragment.java
new file mode 100644
index 0000000..d7d4776
--- /dev/null
+++ b/library/src/main/java/moe/yuuta/flow/FlowFragment.java
@@ -0,0 +1,194 @@
+package moe.yuuta.flow;
+
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.constraintlayout.widget.ConstraintLayout;
+import androidx.fragment.app.Fragment;
+import androidx.fragment.app.FragmentManager;
+import androidx.fragment.app.FragmentPagerAdapter;
+import androidx.viewpager.widget.ViewPager;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * The Host fragment
+ */
+public class FlowFragment extends Fragment implements IFlowFragment, View.OnClickListener {
+    private List<PageFragment> mPages = new ArrayList<>(0);
+    // true: after the view settles, update the UI immediately.
+    private volatile boolean mUIUpdateScheduled;
+
+    private Header mHeader;
+    private ViewPager mPager;
+    private NavigationBar mNav;
+
+    /**
+     * Should only be called once.
+     */
+    public void setPages(@NonNull List<PageFragment> pages) {
+        if (mPages != null && mPages.size() > 0) {
+            throw new IllegalStateException("This method should only be called once. Current size: " + mPages.size());
+        }
+        mPages = pages;
+        // Because this method can be called before setting up the layout, so we need to schedule it until the layout is set up.
+        notifyCurrentFlowInfoUpdated();
+    }
+
+    /**
+     * Update the WHOLE UI.
+     */
+    private void updateUI() {
+        final int currentIndex = mPager.getCurrentItem();
+        final PageFragment currentFragment = mPages.get(currentIndex);
+        if (currentFragment.mInfo == null) {
+            throw new NullPointerException("Info is null");
+        }
+        if (currentFragment.mInfo.getNavigationBarConfig() != null) {
+            mNav.applyInfo(currentFragment.mInfo.getNavigationBarConfig());
+        } else {
+            mNav.applyInfo(new NavigationBarConfig(getString(R.string.flow_nav_bar_next),
+                    getString(R.string.flow_nav_bar_previous),
+                    currentIndex == 0 ? View.GONE : View.VISIBLE,
+                    currentIndex >= (mPages.size() - 1) ? View.GONE : View.VISIBLE,
+                    View.VISIBLE,
+                    this,
+                    this));
+        }
+        mHeader.applyInfo(currentFragment.mInfo.getHeaderConfig());
+    }
+
+    @Override
+    public void onClick(View v) {
+        final int currentIndex = mPager.getCurrentItem();
+        if (v.getId() == R.id.flow_nav_left_button) {
+            if (currentIndex > 0) previousFlow();
+        } else if (v.getId() == R.id.flow_nav_right_button) {
+            if (currentIndex < (mPages.size() - 1)) nextFlow();
+        }
+    }
+
+    @Nullable
+    @Override
+    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
+        final View view = inflater.inflate(R.layout.fragment_flow, container, false);
+        mHeader = new Header(view.<ConstraintLayout>findViewById(R.id.flow_host_header));
+        mNav = new NavigationBar(view.<ConstraintLayout>findViewById(R.id.flow_host_nav));
+        mPager = view.findViewById(R.id.flow_host_pager);
+        mPager.setAdapter(new FragmentPagerAdapter(getChildFragmentManager()) {
+            @Override
+            public Fragment getItem(int position) {
+                PageFragment fragment = mPages.get(position);
+                return fragment;
+            }
+
+            @Override
+            public int getCount() {
+                return mPages.size();
+            }
+        });
+        mPager.addOnPageChangeListener(mPageListener);
+        getChildFragmentManager().registerFragmentLifecycleCallbacks(mCallback, false);
+        return view;
+    }
+
+    @Override
+    public void onDestroyView() {
+        getChildFragmentManager().unregisterFragmentLifecycleCallbacks(mCallback);
+        mPager.removeOnPageChangeListener(mPageListener);
+        super.onDestroyView();
+    }
+
+    @Override
+    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
+        super.onViewCreated(view, savedInstanceState);
+        if (mUIUpdateScheduled) {
+            updateUI();
+            mUIUpdateScheduled = false;
+        }
+    }
+
+    @Override
+    public void notifyCurrentFlowInfoUpdated() {
+        if (getView() != null) {
+            mUIUpdateScheduled = false;
+            updateUI();
+        } else {
+            mUIUpdateScheduled = true;
+        }
+    }
+
+    @Override
+    public void nextFlow() {
+        switchToFlow(mPager.getCurrentItem() + 1);
+    }
+
+    @Override
+    public void previousFlow() {
+        switchToFlow(mPager.getCurrentItem() - 1);
+    }
+
+    @Override
+    public int getFlowCount() {
+        return mPages.size();
+    }
+
+    @Override
+    public void switchToFlow(int index) {
+        mPager.setCurrentItem(index, true);
+    }
+
+    private FragmentManager.FragmentLifecycleCallbacks mCallback = new FragmentManager.FragmentLifecycleCallbacks() {
+        @Override
+        public void onFragmentPreCreated(@NonNull FragmentManager fm, @NonNull Fragment f, @Nullable Bundle savedInstanceState) {
+            if (f instanceof PageFragment) {
+                final PageFragment pf = (PageFragment) f;
+                pf.setHostFragment(FlowFragment.this);
+            }
+        }
+    };
+
+    private ViewPager.OnPageChangeListener mPageListener = new ViewPager.OnPageChangeListener() {
+        @Override
+        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
+
+        }
+
+        @Override
+        public void onPageSelected(int position) {
+            notifyCurrentFlowInfoUpdated();
+        }
+
+        @Override
+        public void onPageScrollStateChanged(int state) {
+
+        }
+    };
+
+    /**
+     * @return true: the fragment handled this event and you do not need to call super. false: call super.
+     */
+    public boolean onBackPressed() {
+        if (getView() == null) return false;
+        if (mPages.size() <= 0) return false;
+        final PageFragment pf = mPages.get(mPager.getCurrentItem());
+        if (pf != null) {
+            if (pf.onBackPressed()) return true;
+        }
+        // Default handling
+        if (mPager.getCurrentItem() == 0) return false;
+        mNav.getButton(NavigationBar.ButtonPosition.LEFT).performClick();
+        return true;
+    }
+
+    @Override
+    @NonNull
+    public View.OnClickListener getGeneralFlowNavListener() {
+        return this;
+    }
+}
diff --git a/library/src/main/java/moe/yuuta/flow/FlowInfo.kt b/library/src/main/java/moe/yuuta/flow/FlowInfo.kt
new file mode 100644
index 0000000..d12228c
--- /dev/null
+++ b/library/src/main/java/moe/yuuta/flow/FlowInfo.kt
@@ -0,0 +1,10 @@
+package moe.yuuta.flow;
+
+/**
+ * Stores basic info, for instance, title and subtitle for the flow. These data will
+ * be auto applied when user switch to the related flow and will be reset after leaving the flow.
+ */
+data class FlowInfo(
+        var headerConfig: HeaderConfig,
+        var navigationBarConfig: NavigationBarConfig?
+)
\ No newline at end of file
diff --git a/library/src/main/java/moe/yuuta/flow/Header.java b/library/src/main/java/moe/yuuta/flow/Header.java
new file mode 100644
index 0000000..42d9124
--- /dev/null
+++ b/library/src/main/java/moe/yuuta/flow/Header.java
@@ -0,0 +1,54 @@
+package moe.yuuta.flow;
+
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.ProgressBar;
+import android.widget.TextView;
+
+import androidx.annotation.NonNull;
+
+class Header {
+    public enum WhichView {
+        TITLE,
+        SUBTITLE
+    }
+
+    private ViewGroup mRoot;
+    private TextView mTitle;
+    private TextView mSubtitle;
+    private ProgressBar mProgressBar;
+
+    Header() {}
+
+    Header(@NonNull ViewGroup root) {
+        attach(root);
+    }
+
+    /**
+     * The config will be reset after re-attaching.
+     */
+    void attach(@NonNull ViewGroup root) {
+        mRoot = root;
+        mTitle = mRoot.findViewById(R.id.flow_header_title);
+        mSubtitle = mRoot.findViewById(R.id.flow_header_subtitle);
+        mProgressBar = mRoot.findViewById(R.id.flow_header_progressbar);
+    }
+
+    @NonNull
+    private TextView getText(@NonNull WhichView position) {
+        switch (position) {
+            case TITLE:
+                return mTitle;
+            case SUBTITLE:
+                return mSubtitle;
+            default:
+                throw new IllegalArgumentException("Unexpected position");
+        }
+    }
+
+    void applyInfo(@NonNull HeaderConfig config) {
+        mTitle.setText(config.getTitleText());
+        mSubtitle.setText(config.getSubtitleText());
+        mProgressBar.setVisibility(config.getShowProgressBar() ? View.VISIBLE : View.GONE);
+    }
+}
diff --git a/library/src/main/java/moe/yuuta/flow/HeaderConfig.kt b/library/src/main/java/moe/yuuta/flow/HeaderConfig.kt
new file mode 100644
index 0000000..0133897
--- /dev/null
+++ b/library/src/main/java/moe/yuuta/flow/HeaderConfig.kt
@@ -0,0 +1,7 @@
+package moe.yuuta.flow
+
+class HeaderConfig(
+        var titleText: CharSequence,
+        var subtitleText: CharSequence?,
+        var showProgressBar: Boolean = false
+)
\ No newline at end of file
diff --git a/library/src/main/java/moe/yuuta/flow/IFlowFragment.java b/library/src/main/java/moe/yuuta/flow/IFlowFragment.java
new file mode 100644
index 0000000..79f67f6
--- /dev/null
+++ b/library/src/main/java/moe/yuuta/flow/IFlowFragment.java
@@ -0,0 +1,17 @@
+package moe.yuuta.flow;
+
+import android.view.View;
+
+import androidx.annotation.NonNull;
+
+/**
+ * A bridge which is exposed to {@link PageFragment} for controlling the {@link FlowFragment}
+ */
+public interface IFlowFragment {
+    void notifyCurrentFlowInfoUpdated();
+    void nextFlow();
+    void previousFlow();
+    int getFlowCount();
+    void switchToFlow(int index);
+    @NonNull View.OnClickListener getGeneralFlowNavListener();
+}
diff --git a/library/src/main/java/moe/yuuta/flow/NavigationBar.java b/library/src/main/java/moe/yuuta/flow/NavigationBar.java
new file mode 100644
index 0000000..14fae26
--- /dev/null
+++ b/library/src/main/java/moe/yuuta/flow/NavigationBar.java
@@ -0,0 +1,82 @@
+package moe.yuuta.flow;
+
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+class NavigationBar {
+    public enum ButtonPosition {
+        LEFT,
+        RIGHT
+    }
+
+    private ViewGroup mRoot;
+    private Button mLeftButton;
+    private Button mRightButton;
+
+    NavigationBar() {}
+
+    NavigationBar(@NonNull ViewGroup navBarRoot) {
+        attach(navBarRoot);
+    }
+
+    /**
+     * The config will be reset after re-attaching.
+     */
+    void attach(@NonNull ViewGroup navBarRoot) {
+        mRoot = navBarRoot;
+        mLeftButton = mRoot.findViewById(R.id.flow_nav_left_button);
+        mRightButton = mRoot.findViewById(R.id.flow_nav_right_button);
+    }
+
+    @NonNull
+    Button getButton(@NonNull ButtonPosition position) {
+        switch (position) {
+            case LEFT:
+                return mLeftButton;
+            case RIGHT:
+                return mRightButton;
+            default:
+                throw new IllegalArgumentException("Unexpected position");
+        }
+    }
+
+    private void setListener(@NonNull ButtonPosition position, @Nullable View.OnClickListener listener) {
+        switch (position) {
+            case LEFT:
+                mLeftButton.setOnClickListener(listener);
+                break;
+            case RIGHT:
+                mRightButton.setOnClickListener(listener);
+                break;
+        }
+    }
+
+    void applyInfo(@NonNull NavigationBarConfig config) {
+        mLeftButton.setText(config.getLeftButtonText());
+        mRightButton.setText(config.getRightButtonText());
+        setNavigationBarVisibility(config.getNavBarVisibility());
+        setButtonVisibility(ButtonPosition.LEFT, config.getLeftButtonVisibility());
+        setButtonVisibility(ButtonPosition.RIGHT, config.getRightButtonVisibility());
+        setListener(ButtonPosition.LEFT, config.getLeftListener());
+        setListener(ButtonPosition.RIGHT, config.getRightListener());
+    }
+
+    private void setNavigationBarVisibility(@View.Visibility int visibility) {
+        mRoot.setVisibility(visibility);
+    }
+
+    private void setButtonVisibility(@NonNull ButtonPosition position, @View.Visibility int visibility) {
+        switch (position) {
+            case LEFT:
+                mLeftButton.setVisibility(visibility);
+                break;
+            case RIGHT:
+                mRightButton.setVisibility(visibility);
+                break;
+        }
+    }
+}
diff --git a/library/src/main/java/moe/yuuta/flow/NavigationBarConfig.kt b/library/src/main/java/moe/yuuta/flow/NavigationBarConfig.kt
new file mode 100644
index 0000000..e027b73
--- /dev/null
+++ b/library/src/main/java/moe/yuuta/flow/NavigationBarConfig.kt
@@ -0,0 +1,16 @@
+package moe.yuuta.flow
+
+import android.view.View
+
+class NavigationBarConfig(
+        var rightButtonText: CharSequence,
+        var leftButtonText: CharSequence,
+        @field:View.Visibility
+        var leftButtonVisibility: Int,
+        @field:View.Visibility
+        var rightButtonVisibility: Int,
+        @field:View.Visibility
+        var navBarVisibility: Int,
+        var leftListener: View.OnClickListener?,
+        var rightListener: View.OnClickListener?
+)
\ No newline at end of file
diff --git a/library/src/main/java/moe/yuuta/flow/PageFragment.java b/library/src/main/java/moe/yuuta/flow/PageFragment.java
new file mode 100644
index 0000000..dcc9f21
--- /dev/null
+++ b/library/src/main/java/moe/yuuta/flow/PageFragment.java
@@ -0,0 +1,30 @@
+package moe.yuuta.flow;
+
+import androidx.annotation.NonNull;
+import androidx.fragment.app.Fragment;
+
+public abstract class PageFragment extends Fragment {
+    private IFlowFragment mHostFragment;
+
+    /**
+     * Once mInfo is changed, you should call {@link IFlowFragment#notifyCurrentFlowInfoUpdated()} to publish it.
+     * Note: it will be permanently change the recorded info.
+     */
+    protected FlowInfo mInfo;
+
+    final void setHostFragment(@NonNull IFlowFragment hostFragment) {
+        this.mHostFragment = hostFragment;
+    }
+
+    @NonNull
+    protected final IFlowFragment getHostFragment() {
+        return mHostFragment;
+    }
+
+    /**
+     * @return true: the fragment handled this event and you do not need to call super. false: call super.
+     */
+    public boolean onBackPressed() {
+        return false;
+    }
+}
\ No newline at end of file
diff --git a/library/src/main/java/moe/yuuta/flow/widgets/FlowPager.java b/library/src/main/java/moe/yuuta/flow/widgets/FlowPager.java
new file mode 100644
index 0000000..c821eef
--- /dev/null
+++ b/library/src/main/java/moe/yuuta/flow/widgets/FlowPager.java
@@ -0,0 +1,64 @@
+package moe.yuuta.flow.widgets;
+
+import android.content.Context;
+import android.os.Build;
+import android.util.AttributeSet;
+import android.view.MotionEvent;
+import android.view.View;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.fragment.app.FragmentPagerAdapter;
+import androidx.viewpager.widget.ViewPager;
+
+public class FlowPager extends ViewPager {
+    public FlowPager(@NonNull Context context) {
+        super(context);
+    }
+
+    public FlowPager(@NonNull Context context, @Nullable AttributeSet attrs) {
+        super(context, attrs);
+    }
+
+    // Thanks to https://stackoverflow.com/a/32488566/6792243
+    @Override
+    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
+        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
+
+        if(null != getAdapter()) {
+            int height = 0;
+            View child = ((FragmentPagerAdapter) getAdapter()).getItem(getCurrentItem()).getView();
+            if (child != null) {
+                child.measure(widthMeasureSpec, MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
+                height = child.getMeasuredHeight();
+                // TODO: Support api-14 and api-15?
+                if (Build.VERSION.SDK_INT >= 16 && height < getMinimumHeight()) {
+                    height = getMinimumHeight();
+                }
+            }
+
+            int newHeight = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY);
+            if (getLayoutParams().height != 0 && heightMeasureSpec != newHeight) {
+                getLayoutParams().height = height;
+
+            } else {
+                heightMeasureSpec = newHeight;
+            }
+        }
+
+        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
+    }
+
+    // Thanks to https://stackoverflow.com/a/13437997/6792243
+    @Override
+    public boolean onTouchEvent(MotionEvent event) {
+        return false;
+    }
+
+    // Thanks to https://stackoverflow.com/a/13437997/6792243
+    @Override
+    public boolean onInterceptTouchEvent(MotionEvent event) {
+        return false;
+    }
+
+}
diff --git a/library/src/main/res/layout/fragment_flow.xml b/library/src/main/res/layout/fragment_flow.xml
new file mode 100644
index 0000000..98f6fba
--- /dev/null
+++ b/library/src/main/res/layout/fragment_flow.xml
@@ -0,0 +1,130 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:orientation="vertical"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <androidx.constraintlayout.widget.ConstraintLayout
+        android:id="@id/flow_host_header"
+        app:layout_constraintTop_toTopOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintLeft_toLeftOf="parent"
+        app:layout_constraintRight_toRightOf="parent"
+        android:layout_width="match_parent"
+        android:layout_height="0dp">
+        <!-- TODO: firstBaselineToTopHeight compat -->
+        <androidx.constraintlayout.widget.ConstraintLayout
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            app:layout_constraintTop_toTopOf="parent"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintEnd_toEndOf="parent">
+            <ProgressBar
+                android:id="@+id/flow_header_progressbar"
+                android:layout_width="0dp"
+                android:layout_height="wrap_content"
+                app:layout_constraintStart_toStartOf="parent"
+                app:layout_constraintTop_toTopOf="parent"
+                app:layout_constraintEnd_toEndOf="parent"
+                app:layout_constraintBottom_toTopOf="@id/flow_header_progressbar_guideline"
+                android:indeterminate="true"
+                android:paddingTop="-4dp"
+                style="?android:attr/progressBarStyleHorizontal"/>
+
+            <androidx.constraintlayout.widget.Guideline
+                android:layout_width="wrap_content"
+                android:layout_height="wrap_content"
+                android:id="@id/flow_header_progressbar_guideline"
+                android:orientation="horizontal"
+                app:layout_constraintGuide_begin="2dp" />
+        </androidx.constraintlayout.widget.ConstraintLayout>
+
+        <TextView
+            android:id="@id/flow_header_title"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="64dp"
+            android:textSize="24sp"
+            android:textColor="?android:attr/textColorPrimary"
+            android:layout_gravity="center_horizontal"
+            android:firstBaselineToTopHeight="32dp"
+            app:layout_constraintTop_toTopOf="parent"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintLeft_toLeftOf="parent"
+            app:layout_constraintEnd_toEndOf="parent"
+            app:layout_constraintRight_toRightOf="parent"
+            android:textAppearance="?android:attr/textAppearanceLarge"
+            tools:text="Title" />
+
+        <TextView
+            android:id="@id/flow_header_subtitle"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="8dp"
+            android:textSize="16sp"
+            android:textColor="?android:attr/textColorPrimary"
+            android:layout_gravity="center_horizontal"
+            android:firstBaselineToTopHeight="24dp"
+            android:textScaleX="1.1"
+            app:layout_constraintTop_toBottomOf="@id/flow_header_title"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintLeft_toLeftOf="parent"
+            app:layout_constraintEnd_toEndOf="parent"
+            app:layout_constraintRight_toRightOf="parent"
+            android:textAppearance="?android:attr/textAppearanceMedium"
+            tools:text="Subtitle" />
+    </androidx.constraintlayout.widget.ConstraintLayout>
+
+    <moe.yuuta.flow.widgets.FlowPager
+        android:id="@id/flow_host_pager"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="44dp"
+        app:layout_constraintTop_toBottomOf="@id/flow_host_header"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintLeft_toLeftOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintRight_toRightOf="parent"/>
+
+    <androidx.constraintlayout.widget.ConstraintLayout
+        android:id="@id/flow_host_nav"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="38dp"
+        android:layout_marginStart="44dp"
+        android:layout_marginLeft="44dp"
+        android:layout_marginEnd="44dp"
+        android:layout_marginRight="44dp"
+        app:layout_constraintTop_toBottomOf="@id/flow_host_pager"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintLeft_toLeftOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintRight_toRightOf="parent"
+        style="?android:attr/buttonBarStyle">
+        <Button
+            android:id="@id/flow_nav_left_button"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toTopOf="parent"
+            app:layout_constraintBottom_toBottomOf="parent"
+            app:layout_constraintLeft_toLeftOf="parent"
+            tools:text="Back"
+            style="?android:attr/buttonBarButtonStyle"/>
+
+        <Button
+            android:id="@id/flow_nav_right_button"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            app:layout_constraintRight_toRightOf="parent"
+            app:layout_constraintTop_toTopOf="parent"
+            app:layout_constraintBottom_toBottomOf="parent"
+            app:layout_constraintEnd_toEndOf="parent"
+            tools:text="Next"
+            style="?attr/positiveButtonStyle" />
+    </androidx.constraintlayout.widget.ConstraintLayout>
+</androidx.constraintlayout.widget.ConstraintLayout>
\ No newline at end of file
diff --git a/library/src/main/res/values/attrs.xml b/library/src/main/res/values/attrs.xml
new file mode 100644
index 0000000..0e32e81
--- /dev/null
+++ b/library/src/main/res/values/attrs.xml
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <attr name="positiveButtonStyle" format="reference" />
+</resources>
\ No newline at end of file
diff --git a/library/src/main/res/values/ids.xml b/library/src/main/res/values/ids.xml
new file mode 100644
index 0000000..a3117c8
--- /dev/null
+++ b/library/src/main/res/values/ids.xml
@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <item name="flow_host_header" type="id" />
+    <item name="flow_host_pager" type="id" />
+    <item name="flow_host_nav" type="id" />
+
+    <item name="flow_nav_left_button" type="id" />
+    <item name="flow_nav_right_button" type="id" />
+
+    <item name="flow_header_title" type="id" />
+    <item name="flow_header_subtitle" type="id" />
+    <item name="flow_header_progressbar" type="id" />
+    <item name="flow_header_progressbar_guideline" type="id" />
+</resources>
\ No newline at end of file
diff --git a/library/src/main/res/values/strings.xml b/library/src/main/res/values/strings.xml
new file mode 100644
index 0000000..ad04d0e
--- /dev/null
+++ b/library/src/main/res/values/strings.xml
@@ -0,0 +1,4 @@
+<resources>
+    <string name="flow_nav_bar_previous">Back</string>
+    <string name="flow_nav_bar_next">Next</string>
+</resources>
diff --git a/library/src/test/java/moe/yuuta/flow/ExampleUnitTest.java b/library/src/test/java/moe/yuuta/flow/ExampleUnitTest.java
new file mode 100644
index 0000000..84848a0
--- /dev/null
+++ b/library/src/test/java/moe/yuuta/flow/ExampleUnitTest.java
@@ -0,0 +1,17 @@
+package moe.yuuta.flow;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Example local unit test, which will execute on the development machine (host).
+ *
+ * @see <a href="http://d.android.com/tools/testing">Testing documentation</a>
+ */
+public class ExampleUnitTest {
+    @Test
+    public void addition_isCorrect() {
+        assertEquals(4, 2 + 2);
+    }
+}
\ No newline at end of file