5.2.3 Fragment实例精讲——底部导航栏的实现(方法3)

本节引言

前面我们已经跟大家讲解了实现底部导航栏的两种方案，但是这两种方案只适合普通的情况，如果是像新浪微博那样的，想在底部导航栏上的item带有一个红色的小点，然后加上一个消息数目这样，前面两种方案就显得无力了，我们来看看别人的APP是怎么做的，打开手机的开发者选项，勾选里面的：显示布局边界，然后打开我们参考的那个App，可以看到底部导航栏是这样的：

从上面这个图我们就可以看出，这种底部导航栏不是简单的TextView或者RadioGroup构成的，大概布局方案可能是：外层一个LinearLayout，中间一个RelativeLayout，而在中间有一个TextView，然后再在TextView的右上角有一个红色圆圈背景的TextView或者一个红色的小点；大概就这样，而这些小点平时的时候应该设置的不可见，当收到信息推送，即有相关类别信息的时候再可见，并且显示对应的信息数目！那么下面我们就来实现下这种底部导航栏的效果，另外，为了方便演示，这里就不演示Fragment的切换效果了！另外顺道复习下Fragment获得Activity中的组件的知识点！

1.实现效果图：

为了方便理解，这里通过点击按钮的形式，模拟收到推送信息，然后显示红色点！

运行效果图：

2.实现流程：

好的，接下来我们就来实现上面这个效果~

Step 1：相关资源文件的准备：

和前面一样，准备好drawable系列的资源：

文字资源：tab_menu_text.xml

<?xml version="1.0" encoding="utf-8"?><selector xmlns:android="https://schemas.android.com/apk/res/android">    <item android:color="@color/text_yellow" android:state_selected="true" />    <item android:color="@color/text_gray" /></selector>

图标资源：tab_menu_better.xml

<?xml version="1.0" encoding="utf-8"?><selector xmlns:android="https://schemas.android.com/apk/res/android">    <item android:drawable="@mipmap/tab_better_pressed" android:state_selected="true" />    <item android:drawable="@mipmap/tab_better_normal" /></selector>

照着把其他三个也撸出来~！

Step 2：编写activity的布局代码：

因为四个选项的TextView以及右上角的红点数字属性都差不多，如下：

 <TextView                    android:id="@+id/tab_menu_channel"                    android:layout_marginTop="5dp"                    android:layout_width="wrap_content"                    android:layout_height="48dp"                    android:layout_centerInParent="true"                    android:textColor="@drawable/tab_menu_text"                    android:drawableTop="@drawable/tab_menu_channel"                    android:text="@string/tab_menu_alert"/>                <TextView                    android:layout_width="20dp"                    android:layout_height="20dp"                    android:background="@mipmap/bg_num"                    android:layout_toRightOf="@+id/tab_menu_channel"                    android:layout_marginLeft="-10dp"                    android:text="99+"                    android:textSize="12sp"                    android:gravity="center"                    android:textColor="@color/text_white"/>

我们将他们抽取出来，写到style.xml里：

<style name="tab_menu_text">    <item name="android:layout_marginTop">5dp</item>    <item name="android:layout_width">wrap_content</item>    <item name="android:layout_height">48dp</item>    <item name="android:layout_centerInParent">true</item>    <item name="android:textColor">@drawable/tab_menu_text</item></style><style name="tab_menu_bgnum">    <item name="android:layout_width">20dp</item>    <item name="android:layout_height">20dp</item>    <item name="android:background">@mipmap/bg_num</item>    <item name="android:layout_marginLeft">-10dp</item>    <item name="android:textSize">12sp</item>    <item name="android:gravity">center</item>    <item name="android:textColor">@color/text_white</item></style>

然后开始编写我们的activity.xml布局：

<RelativeLayout xmlns:android="https://schemas.android.com/apk/res/android"    xmlns:tools="https://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    tools:context=".MainActivity">    <RelativeLayout        android:id="@+id/ly_top_bar"        android:layout_width="match_parent"        android:layout_height="48dp"        android:background="@color/bg_topbar">        <TextView            android:id="@+id/txt_topbar"            android:layout_width="match_parent"            android:layout_height="match_parent"            android:layout_centerInParent="true"            android:gravity="center"            android:text="信息"            android:textColor="@color/text_topbar"            android:textSize="18sp" />        <View            android:layout_width="match_parent"            android:layout_height="2px"            android:layout_alignParentBottom="true"            android:background="@color/div_white" />    </RelativeLayout>    <LinearLayout        android:id="@+id/ly_tab_menu"        android:layout_width="match_parent"        android:layout_height="56dp"        android:layout_alignParentBottom="true"        android:background="@color/bg_white"        android:orientation="horizontal">        <LinearLayout            android:id="@+id/ly_tab_menu_channel"            android:layout_width="0dp"            android:layout_height="match_parent"            android:layout_weight="1"            android:gravity="center">            <RelativeLayout                android:layout_width="wrap_content"                android:layout_height="match_parent"                android:padding="5dp">                <TextView                    android:id="@+id/tab_menu_channel"                    style="@style/tab_menu_text"                    android:drawableTop="@drawable/tab_menu_channel"                    android:text="@string/tab_menu_alert" />                <TextView                    android:id="@+id/tab_menu_channel_num"                    style="@style/tab_menu_bgnum"                    android:layout_toRightOf="@+id/tab_menu_channel"                    android:text="99+"                    android:visibility="gone" />            </RelativeLayout>        </LinearLayout>        <LinearLayout            android:id="@+id/ly_tab_menu_message"            android:layout_width="0dp"            android:layout_height="match_parent"            android:layout_weight="1"            android:gravity="center">            <RelativeLayout                android:layout_width="wrap_content"                android:layout_height="match_parent"                android:padding="5dp">                <TextView                    android:id="@+id/tab_menu_message"                    style="@style/tab_menu_text"                    android:drawableTop="@drawable/tab_menu_message"                    android:text="@string/tab_menu_profile" />                <TextView                    android:id="@+id/tab_menu_message_num"                    style="@style/tab_menu_bgnum"                    android:layout_toRightOf="@+id/tab_menu_message"                    android:text="99+"                    android:visibility="gone" />            </RelativeLayout>        </LinearLayout>        <LinearLayout            android:id="@+id/ly_tab_menu_better"            android:layout_width="0dp"            android:layout_height="match_parent"            android:layout_weight="1"            android:gravity="center">            <RelativeLayout                android:layout_width="wrap_content"                android:layout_height="match_parent"                android:padding="5dp">                <TextView                    android:id="@+id/tab_menu_better"                    style="@style/tab_menu_text"                    android:drawableTop="@drawable/tab_menu_better"                    android:text="@string/tab_menu_pay" />                <TextView                    android:id="@+id/tab_menu_better_num"                    style="@style/tab_menu_bgnum"                    android:layout_toRightOf="@+id/tab_menu_better"                    android:text="99+"                    android:visibility="gone" />            </RelativeLayout>        </LinearLayout>        <LinearLayout            android:id="@+id/ly_tab_menu_setting"            android:layout_width="0dp"            android:layout_height="match_parent"            android:layout_weight="1"            android:gravity="center">            <RelativeLayout                android:layout_width="wrap_content"                android:layout_height="match_parent"                android:padding="5dp">                <TextView                    android:id="@+id/tab_menu_setting"                    style="@style/tab_menu_text"                    android:drawableTop="@drawable/tab_menu_setting"                    android:text="@string/tab_menu_alert" />                <ImageView                    android:id="@+id/tab_menu_setting_partner"                    android:layout_width="12dp"                    android:layout_height="12dp"                    android:layout_marginLeft="-5dp"                    android:layout_toRightOf="@id/tab_menu_setting"                    android:visibility="gone"                    android:src="@mipmap/partner_red" />            </RelativeLayout>        </LinearLayout>    </LinearLayout>    <View        android:id="@+id/div_tab_bar"        android:layout_width="match_parent"        android:layout_height="2px"        android:layout_above="@id/ly_tab_menu"        android:background="@color/div_white" />    <FrameLayout        android:id="@+id/ly_content"        android:layout_width="match_parent"        android:layout_height="match_parent"        android:layout_above="@id/div_tab_bar"        android:layout_below="@id/ly_top_bar"/></RelativeLayout>

Step 3：编写Fragment界面布局以及类

Fragment布局由四个普通按钮构成：

fg_my.xml:

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="https://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    android:padding="5dp">    <Button        android:id="@+id/btn_one"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="第一个显示信息"/>    <Button        android:id="@+id/btn_two"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="第二个显示信息"/>    <Button        android:id="@+id/btn_three"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="第三个显示信息"/>    <Button        android:id="@+id/btn_four"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="第四个显示信息"/></LinearLayout>

接着是自定义的Fragment类，这里的话我们通过getActivity.findViewById()来获得Activity中的小红点，这里仅仅是简单的控制显示而已！MyFragment.java:

public class MyFragment extends Fragment implements View.OnClickListener{    private Context mContext;    private Button btn_one;    private Button btn_two;    private Button btn_three;    private Button btn_four;    public MyFragment() {    }    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {        View view = inflater.inflate(R.layout.fg_my,container,false);        //UI Object        btn_one = (Button) view.findViewById(R.id.btn_one);        btn_two = (Button) view.findViewById(R.id.btn_two);        btn_three = (Button) view.findViewById(R.id.btn_three);        btn_four = (Button) view.findViewById(R.id.btn_four);        //Bind Event        btn_one.setOnClickListener(this);        btn_two.setOnClickListener(this);        btn_three.setOnClickListener(this);        btn_four.setOnClickListener(this);        return view;    }    @Override    public void onClick(View v) {        switch (v.getId()){            case R.id.btn_one:                TextView tab_menu_channel_num = (TextView) getActivity ().findViewById(R.id.tab_menu_channel_num);                tab_menu_channel_num.setText("11");                tab_menu_channel_num.setVisibility(View.VISIBLE);                break;            case R.id.btn_two:                TextView tab_menu_message_num = (TextView) getActivity ().findViewById(R.id.tab_menu_message_num);                tab_menu_message_num.setText("20");                tab_menu_message_num.setVisibility(View.VISIBLE);                break;            case R.id.btn_three:                TextView tab_menu_better_num = (TextView) getActivity ().findViewById(R.id.tab_menu_better_num);                tab_menu_better_num.setText("99+");                tab_menu_better_num.setVisibility(View.VISIBLE);                break;            case R.id.btn_four:                ImageView tab_menu_setting_partner = (ImageView) getActivity ().findViewById(R.id.tab_menu_setting_partner);                tab_menu_setting_partner.setVisibility(View.VISIBLE);                break;        }    }}

Step 4：编写MainActivity

我们在这里完成主要的逻辑实现，有些部分和前面TextView实现底部导航栏的效果类似，就不具体讲解了，代码如下：

MainActivity.java：

/** * Created by Coder-pig on 2015/8/30 0030. */public class MainActivity extends AppCompatActivity implements View.OnClickListener {    //Activity UI Object    private LinearLayout ly_tab_menu_channel;    private TextView tab_menu_channel;    private TextView tab_menu_channel_num;    private LinearLayout ly_tab_menu_message;    private TextView tab_menu_message;    private TextView tab_menu_message_num;    private LinearLayout ly_tab_menu_better;    private TextView tab_menu_better;    private TextView tab_menu_better_num;    private LinearLayout ly_tab_menu_setting;    private TextView tab_menu_setting;    private ImageView tab_menu_setting_partner;    private FragmentManager fManager;    private FragmentTransaction fTransaction;    private MyFragment fg1;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        bindViews();        ly_tab_menu_channel.performClick();        fg1 = new MyFragment();        fManager = getFragmentManager();        fTransaction = fManager.beginTransaction();        fTransaction.add(R.id.ly_content, fg1).commit();    }    private void bindViews() {        ly_tab_menu_channel = (LinearLayout) findViewById(R.id.ly_tab_menu_channel);        tab_menu_channel = (TextView) findViewById(R.id.tab_menu_channel);        tab_menu_channel_num = (TextView) findViewById(R.id.tab_menu_channel_num);        ly_tab_menu_message = (LinearLayout) findViewById(R.id.ly_tab_menu_message);        tab_menu_message = (TextView) findViewById(R.id.tab_menu_message);        tab_menu_message_num = (TextView) findViewById(R.id.tab_menu_message_num);        ly_tab_menu_better = (LinearLayout) findViewById(R.id.ly_tab_menu_better);        tab_menu_better = (TextView) findViewById(R.id.tab_menu_better);        tab_menu_better_num = (TextView) findViewById(R.id.tab_menu_better_num);        ly_tab_menu_setting = (LinearLayout) findViewById(R.id.ly_tab_menu_setting);        tab_menu_setting = (TextView) findViewById(R.id.tab_menu_setting);        tab_menu_setting_partner = (ImageView) findViewById(R.id.tab_menu_setting_partner);        ly_tab_menu_channel.setOnClickListener(this);        ly_tab_menu_message.setOnClickListener(this);        ly_tab_menu_better.setOnClickListener(this);        ly_tab_menu_setting.setOnClickListener(this);    }    @Override    public void onClick(View v) {        switch (v.getId()) {            case R.id.ly_tab_menu_channel:                setSelected();                tab_menu_channel.setSelected(true);                tab_menu_channel_num.setVisibility(View.INVISIBLE);                break;            case R.id.ly_tab_menu_message:                setSelected();                tab_menu_message.setSelected(true);                tab_menu_message_num.setVisibility(View.INVISIBLE);                break;            case R.id.ly_tab_menu_better:                setSelected();                tab_menu_better.setSelected(true);                tab_menu_better_num.setVisibility(View.INVISIBLE);                break;            case R.id.ly_tab_menu_setting:                setSelected();                tab_menu_setting.setSelected(true);                tab_menu_setting_partner.setVisibility(View.INVISIBLE);                break;        }    }    //重置所有文本的选中状态    private void setSelected() {        tab_menu_channel.setSelected(false);        tab_menu_message.setSelected(false);        tab_menu_better.setSelected(false);        tab_menu_setting.setSelected(false);    }}

好的，至此，就大功告成了~

3.代码下载：

FragmentDemo3.zip：FragmentDemo3.zip下载

4.本节小结：

好的，本节相比前面两节稍微复杂了一点，不过还是比较容易弄懂的！另外，关于实现普通底部导航栏的实现例子就写这么多吧，下一节开始我们来写下在此基础上的根据手势操作切换页面的例子，嗯，就说这么多，谢谢~