5.2.3 Fragment實例精講——底部導航欄的實現(方法3) · Android基礎入門教程

## 本節引言 > 前面我們已經跟大家講解了實現底部導航欄的兩種方案，但是這兩種方案只適合普通的情況，如果是像新浪微博那樣的，想在底部導航欄上的item帶有一個紅色的小點，然后加上一個消息數目這樣，前面兩種方案就顯得無力了，我們來看看別人的APP是怎么做的，打開手機的開發者選項，勾選里面的：?**顯示布局邊界**，然后打開我們參考的那個App，可以看到底部導航欄是這樣的： > > ![](https://box.kancloud.cn/2015-12-01_565daa922329e.jpg)?從上面這個圖我們就可以看出，這種底部導航欄不是簡單的TextView或者RadioGroup構成的，大概布局方案可能是：外層一個LinearLayout，中間一個RelativeLayout，而在中間有一個TextView，然后再在TextView的右上角有一個紅色圓圈背景的TextView或者一個紅色的小點；大概就這樣，而這些小點平時的時候應該設置的不可見，當收到信息推送，即有相關類別信息的時候再可見，并且顯示對應的信息數目！那么下面我們就來實現下這種底部導航欄的效果，另外，為了方便演示，這里就不演示Fragment的切換效果了！另外順道復習下Fragment獲得Activity 中的組件的知識點！ * * * ## 1.實現效果圖：為了方便理解，這里通過點擊按鈕的形式，模擬收到推送信息，然后顯示紅色點！ **運行效果圖：** ![](https://box.kancloud.cn/2015-12-01_565daa92810d4.jpg) ## 2.實現流程：好的，接下來我們就來實現上面這個效果~ ### Step 1：相關資源文件的準備：和前面一樣，準備好drawable系列的資源：文字資源：**tab_menu_text.xml** ~~~ <?xml version="1.0" encoding="utf-8"?> <selector xmlns:android="http://schemas.android.com/apk/res/android"> <item android:color="@color/text_yellow" android:state_selected="true" /> <item android:color="@color/text_gray" /> </selector> ~~~ 圖標資源：**tab_menu_better.xml** ~~~ <?xml version="1.0" encoding="utf-8"?> <selector xmlns:android="http://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> ~~~ 照著把其他三個也擼出來~！ * * * ### Step 2：編寫activity的布局代碼：因為四個選項的TextView以及右上角的紅點數字屬性都差不多，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"/> ~~~ 我們將他們抽取出來，寫到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> ~~~ 然后開始編寫我們的activity.xml布局： ~~~ <RelativeLayout 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" 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：編寫Fragment界面布局以及類 Fragment布局由四個普通按鈕構成： **fg_my.xml**: ~~~ <?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:orientation="vertical" android:padding="5dp"> <Button android:id="@+id/btn_one" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="第一個顯示信息"/> <Button android:id="@+id/btn_two" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="第二個顯示信息"/> <Button android:id="@+id/btn_three" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="第三個顯示信息"/> <Button android:id="@+id/btn_four" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="第四個顯示信息"/> </LinearLayout> ~~~ 接著是自定義的Fragment類，這里的話我們通過getActivity.findViewById()來獲得Activity 中的小紅點，這里僅僅是簡單的控制顯示而已！?**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：編寫MainActivity 我們在這里完成主要的邏輯實現，有些部分和前面TextView實現底部導航欄的效果類似，就不具體講解了，代碼如下： **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; } } //重置所有文本的選中狀態 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.代碼下載： **FragmentDemo3.zip**：[FragmentDemo3.zip下載](http://www.runoob.com/try/download/FragmentDemo3.zip) * * * ## 4.本節小結： > 好的，本節相比前面兩節稍微復雜了一點，不過還是比較容易弄懂的！另外，關于實現普通底部導航欄的實現例子就寫這么多吧，下一節開始我們來寫下在此基礎上的根據手勢操作切換頁面的例子，嗯，就說這么多，謝謝~