FragmentTabHost+Fragment實現底部導航欄功能

一、效果圖

 

二、FragmentTabHost+Fragment實現

1.activity布局文件

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

    <FrameLayout
        android:id="@+id/fragment_content"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1">

    </FrameLayout>

    <View
        android:layout_width="match_parent"
        android:layout_height="0.5dp"
        android:background="@color/colorGray" />

    <android.support.v4.app.FragmentTabHost
        android:id="@+id/tab"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="5dp"
        android:layout_marginBottom="5dp">

    </android.support.v4.app.FragmentTabHost>

</LinearLayout>

注意：其中FrameLayout標簽為fragment展示的容器，FragmentTabHost標簽才是用來展示底部tab的容器，這這種布局下，兩者的id命名可以隨意。

2.activity文件

package com.matrix.navigation;

import android.support.v4.app.FragmentTabHost;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;

import com.matrix.navigation.fragment.CaseFragment;
import com.matrix.navigation.fragment.ClassificationFragment;
import com.matrix.navigation.fragment.HomeFragment;
import com.matrix.navigation.fragment.SettingFragment;

public class FragmentTabHostActivity extends AppCompatActivity {

    private String[] tabs = new String[]{"首頁", "分類", "案例", "設置"};
    private Class[] mFragmentClasses = new Class[]{HomeFragment.class, ClassificationFragment.class,
            CaseFragment.class, SettingFragment.class};
    private int[] selectorImg = new int[]{R.drawable.tab_home_selector, R.drawable.tab_classification_selector,
            R.drawable.tab_case_selector, R.drawable.tab_setting_selector};

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_fragment_tab_host_two);

        FragmentTabHost tabHost = findViewById(R.id.tab);
        // 初始化tabHost
        tabHost.setup(FragmentTabHostTwoActivity.this, getSupportFragmentManager(), R.id.fragment_content);
        for (int i = 0; i < 4; i++) {
            tabHost.addTab(tabHost.newTabSpec(tabs[i]).setIndicator(getTabView(i)), mFragmentClasses[i], null);
        }
        // 設置默認tab
        tabHost.setCurrentTab(2);
    }

    /**
     * tab的view對象
     *
     * @param index 索引
     * @return view對象
     */
    private View getTabView(int index) {
        View inflate = LayoutInflater.from(FragmentTabHostTwoActivity.this).inflate(R.layout.item_tab, null);
        ImageView tabImage = inflate.findViewById(R.id.tab_image);
        TextView tabTitle = inflate.findViewById(R.id.tab_title);
        tabImage.setImageResource(selectorImg[index]); // 通過selector來控制圖片的改變
        tabTitle.setText(tabs[index]);// 通過selector來控制文字顏色的改變
        return inflate;
    }
}

其中item_tab的布局代碼如下：

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

    <ImageView
        android:id="@+id/tab_image"
        android:layout_width="20dp"
        android:layout_height="20dp" />

    <TextView
        android:id="@+id/tab_title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textColor="@color/tab_text_color_selector"
        android:textSize="12sp" />

</LinearLayout>

 tab_text_color_selector用來控制tab文字選中和未選中時顏色變化，一定要用android:state_selected

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:color="@color/colorOrangeRed" android:state_selected="true" />
    <item android:color="@color/colorGray" android:state_selected="false"/>
</selector>

同樣對於tab圖片的控制如下（舉一例說明），一定要用android:state_selected

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@drawable/ic_home_selected" android:state_selected="true" />
    <item android:drawable="@drawable/ic_home_common" android:state_selected="false" />
</selector>

正常情況下，按照上述步驟應該就可以實現所要的效果了。

三、其他一些說明

1.當布局文件使用下面這種的話

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

    <android.support.v4.app.FragmentTabHost
        android:id="@+id/tab_host"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical">

            <FrameLayout
                android:id="@android:id/tabcontent"
                android:layout_width="match_parent"
                android:layout_height="0dp"
                android:layout_weight="1">

            </FrameLayout>

            <View
                android:layout_width="match_parent"
                android:layout_height="0.5dp"
                android:background="@color/colorGray" />

            <TabWidget
                android:id="@android:id/tabs"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginTop="5dp"
                android:layout_marginBottom="5dp">

            </TabWidget>

        </LinearLayout>

    </android.support.v4.app.FragmentTabHost>

</LinearLayout>

則FrameLayout和TabWidget標簽的id必須使用系統默認的，不能隨意命名，否則會報錯

2.使用系統的android.support.v4.app.FragmentTabHost，每次點擊tab進行切換時，對應的fragment都會被重新創建，因為源碼中是通過attach和detach方法來管理fragment的。所以如果需要點擊時不重新創建的話，可以自定義一個FragmentTabHost，使用show和hide方法來管理fragment。自定義代碼如下：

package com.matrix.navigation.widget;

import android.content.Context;
import android.content.res.TypedArray;
import android.os.Bundle;
import android.os.Parcel;
import android.os.Parcelable;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import android.widget.LinearLayout;
import android.widget.TabHost;
import android.widget.TabWidget;

import java.util.ArrayList;

/**
 * <p> 描述：自定義FragmentTabHost解決切換時fragment重新創建的問題</p>
 * <p> 作者：xc</p>
 * <p> 時間：2019/03/19</p>
 */
public class MyFragmentTabHost extends TabHost
        implements TabHost.OnTabChangeListener {
    private final ArrayList<TabInfo> mTabs = new ArrayList<>();

    private FrameLayout mRealTabContent;
    private Context mContext;
    private FragmentManager mFragmentManager;
    private int mContainerId;
    private TabHost.OnTabChangeListener mOnTabChangeListener;
    private TabInfo mLastTab;
    private boolean mAttached;

    static final class TabInfo {
        final @NonNull
        String tag;
        final @NonNull
        Class<?> clss;
        final @Nullable
        Bundle args;
        Fragment fragment;

        TabInfo(@NonNull String _tag, @NonNull Class<?> _class, @Nullable Bundle _args) {
            tag = _tag;
            clss = _class;
            args = _args;
        }
    }

    static class DummyTabFactory implements TabHost.TabContentFactory {
        private final Context mContext;

        public DummyTabFactory(Context context) {
            mContext = context;
        }

        @Override
        public View createTabContent(String tag) {
            View v = new View(mContext);
            v.setMinimumWidth(0);
            v.setMinimumHeight(0);
            return v;
        }
    }

    static class SavedState extends BaseSavedState {
        String curTab;

        SavedState(Parcelable superState) {
            super(superState);
        }

        SavedState(Parcel in) {
            super(in);
            curTab = in.readString();
        }

        @Override
        public void writeToParcel(Parcel out, int flags) {
            super.writeToParcel(out, flags);
            out.writeString(curTab);
        }

        @Override
        public String toString() {
            return "FragmentTabHost.SavedState{"
                    + Integer.toHexString(System.identityHashCode(this))
                    + " curTab=" + curTab + "}";
        }

        public static final Parcelable.Creator<SavedState> CREATOR
                = new Parcelable.Creator<SavedState>() {
            @Override
            public SavedState createFromParcel(Parcel in) {
                return new SavedState(in);
            }

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

    public MyFragmentTabHost(Context context) {
        // Note that we call through to the version that takes an AttributeSet,
        // because the simple Context construct can result in a broken object!
        super(context, null);
        initFragmentTabHost(context, null);
    }

    public MyFragmentTabHost(Context context, AttributeSet attrs) {
        super(context, attrs);
        initFragmentTabHost(context, attrs);
    }

    private void initFragmentTabHost(Context context, AttributeSet attrs) {
        final TypedArray a = context.obtainStyledAttributes(attrs,
                new int[]{android.R.attr.inflatedId}, 0, 0);
        mContainerId = a.getResourceId(0, 0);
        a.recycle();

        super.setOnTabChangedListener(this);
    }

    private void ensureHierarchy(Context context) {
        // If owner hasn't made its own view hierarchy, then as a convenience
        // we will construct a standard one here.
        if (findViewById(android.R.id.tabs) == null) {
            LinearLayout ll = new LinearLayout(context);
            ll.setOrientation(LinearLayout.VERTICAL);
            addView(ll, new FrameLayout.LayoutParams(
                    ViewGroup.LayoutParams.MATCH_PARENT,
                    ViewGroup.LayoutParams.MATCH_PARENT));

            TabWidget tw = new TabWidget(context);
            tw.setId(android.R.id.tabs);
            tw.setOrientation(TabWidget.HORIZONTAL);
            ll.addView(tw, new LinearLayout.LayoutParams(
                    ViewGroup.LayoutParams.MATCH_PARENT,
                    ViewGroup.LayoutParams.WRAP_CONTENT, 0));

            FrameLayout fl = new FrameLayout(context);
            fl.setId(android.R.id.tabcontent);
            ll.addView(fl, new LinearLayout.LayoutParams(0, 0, 0));

            mRealTabContent = fl = new FrameLayout(context);
            mRealTabContent.setId(mContainerId);
            ll.addView(fl, new LinearLayout.LayoutParams(
                    LinearLayout.LayoutParams.MATCH_PARENT, 0, 1));
        }
    }

    /**
     * @deprecated Don't call the original TabHost setup, you must instead
     * call {@link #setup(Context, FragmentManager)} or
     * {@link #setup(Context, FragmentManager, int)}.
     */
    @Override
    @Deprecated
    public void setup() {
        throw new IllegalStateException(
                "Must call setup() that takes a Context and FragmentManager");
    }

    public void setup(Context context, FragmentManager manager) {
        ensureHierarchy(context);  // Ensure views required by super.setup()
        super.setup();
        mContext = context;
        mFragmentManager = manager;
        ensureContent();
    }

    public void setup(Context context, FragmentManager manager, int containerId) {
        ensureHierarchy(context);  // Ensure views required by super.setup()
        super.setup();
        mContext = context;
        mFragmentManager = manager;
        mContainerId = containerId;
        ensureContent();
        mRealTabContent.setId(containerId);

        // We must have an ID to be able to save/restore our state.  If
        // the owner hasn't set one at this point, we will set it ourselves.
        if (getId() == View.NO_ID) {
            setId(android.R.id.tabhost);
        }
    }

    private void ensureContent() {
        if (mRealTabContent == null) {
            mRealTabContent = (FrameLayout) findViewById(mContainerId);
            if (mRealTabContent == null) {
                throw new IllegalStateException(
                        "No tab content FrameLayout found for id " + mContainerId);
            }
        }
    }

    @Override
    public void setOnTabChangedListener(OnTabChangeListener l) {
        mOnTabChangeListener = l;
    }

    public void addTab(@NonNull TabHost.TabSpec tabSpec, @NonNull Class<?> clss,
                       @Nullable Bundle args) {
        tabSpec.setContent(new DummyTabFactory(mContext));

        final String tag = tabSpec.getTag();
        final TabInfo info = new TabInfo(tag, clss, args);

        if (mAttached) {
            // If we are already attached to the window, then check to make
            // sure this tab's fragment is inactive if it exists.  This shouldn't
            // normally happen.
            info.fragment = mFragmentManager.findFragmentByTag(tag);
//            if (info.fragment != null && !info.fragment.isDetached()) {
            if (info.fragment != null) {
                final FragmentTransaction ft = mFragmentManager.beginTransaction();
//                ft.detach(info.fragment);
                ft.hide(info.fragment);
                ft.commit();

            }
        }

        mTabs.add(info);
        addTab(tabSpec);
    }

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

        final String currentTag = getCurrentTabTag();

        // Go through all tabs and make sure their fragments match
        // the correct state.
        FragmentTransaction ft = null;
        for (int i = 0, count = mTabs.size(); i < count; i++) {
            final TabInfo tab = mTabs.get(i);
            tab.fragment = mFragmentManager.findFragmentByTag(tab.tag);
//            if (tab.fragment != null && !tab.fragment.isDetached()) {
            if (tab.fragment != null) {
                if (tab.tag.equals(currentTag)) {
                    // The fragment for this tab is already there and
                    // active, and it is what we really want to have
                    // as the current tab.  Nothing to do.
                    mLastTab = tab;
                } else {
                    // This fragment was restored in the active state,
                    // but is not the current tab.  Deactivate it.
                    if (ft == null) {
                        ft = mFragmentManager.beginTransaction();
                    }
//                    ft.detach(tab.fragment);
                    ft.hide(tab.fragment);
                }
            }
        }

        // We are now ready to go.  Make sure we are switched to the
        // correct tab.
        mAttached = true;
        ft = doTabChanged(currentTag, ft);
        if (ft != null) {
            ft.commit();
            mFragmentManager.executePendingTransactions();
        }
    }

    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        mAttached = false;
    }

    @Override
    protected Parcelable onSaveInstanceState() {
        Parcelable superState = super.onSaveInstanceState();
        SavedState ss = new SavedState(superState);
        ss.curTab = getCurrentTabTag();
        return ss;
    }

    @Override
    protected void onRestoreInstanceState(Parcelable state) {
        if (!(state instanceof SavedState)) {
            super.onRestoreInstanceState(state);
            return;
        }
        SavedState ss = (SavedState) state;
        super.onRestoreInstanceState(ss.getSuperState());
        setCurrentTabByTag(ss.curTab);
    }

    @Override
    public void onTabChanged(String tabId) {
        if (mAttached) {
            final FragmentTransaction ft = doTabChanged(tabId, null);
            if (ft != null) {
                ft.commit();
            }
        }
        if (mOnTabChangeListener != null) {
            mOnTabChangeListener.onTabChanged(tabId);
        }
    }

    @Nullable
    private FragmentTransaction doTabChanged(@Nullable String tag,
                                             @Nullable FragmentTransaction ft) {
        final TabInfo newTab = getTabInfoForTag(tag);
        if (mLastTab != newTab) {
            if (ft == null) {
                ft = mFragmentManager.beginTransaction();
            }

            if (mLastTab != null) {
                if (mLastTab.fragment != null) {
//                    ft.detach(mLastTab.fragment);
                    ft.hide(mLastTab.fragment);
                }
            }

            if (newTab != null) {
                if (newTab.fragment == null) {
                    newTab.fragment = Fragment.instantiate(mContext,
                            newTab.clss.getName(), newTab.args);
                    ft.add(mContainerId, newTab.fragment, newTab.tag);
                } else {
//                    ft.attach(newTab.fragment);
                    ft.show(newTab.fragment);
                }
            }

            mLastTab = newTab;
        }

        return ft;
    }

    @Nullable
    private TabInfo getTabInfoForTag(String tabId) {
        for (int i = 0, count = mTabs.size(); i < count; i++) {
            final TabInfo tab = mTabs.get(i);
            if (tab.tag.equals(tabId)) {
                return tab;
            }
        }
        return null;
    }

}