Android Fragment实现底部通知栏

截图如下：

1. 第一步先要创建fragment（动态注册）

然后将两个勾选取消掉（还有一种是自己手动创建）

会自动生成相对应的layout布局，剩下的要根据自己的需求了

2.在Activity的布局里写好四个按钮

这里不是重点…

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
   >
<LinearLayout
    android:id="@+id/ll_content_part"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >
</LinearLayout>
<LinearLayout
    android:id="@+id/ll_function"
    android:layout_alignParentBottom="true"
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

<Button
    android:id="@+id/btn_msg_list"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_weight="1"
    android:textSize="13dp"
    android:onClick="click"
    android:text="msg"/>
    <Button
        android:id="@+id/btn_contact"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:textSize="13dp"
        android:onClick="click"
        android:text="contact"/>
    <Button
        android:id="@+id/btn_disc"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:textSize="13dp"
        android:onClick="click"
        android:text="disc"/>
    <Button
        android:id="@+id/btn_me"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:textSize="13dp"
        android:onClick="click"
        android:text="me"/>
</LinearLayout>
</RelativeLayout>

3.Activity的代码

• 其中定义了四个整型常量记录了四个按钮的状态，还有一个当前状态，进而判断当前点击按钮的状态，点击切换文字颜色和图标
• 每次判断四个Fragment的引用是否为空，不为空就不需要每次在new一遍Fragment

replace每次都会重新初始化fragment，它是先remove掉相同id的fragment，再add当前fragment。

add不会回每次都初始化fragment，一般配合hide()和show()方法

public class MainActivity extends AppCompatActivity {

    private Button btn_contact;
    private Button btn_disc;
    private Button btn_me;
    private Button btn_msg_list;
    private FragmentManager fragmentManager;
    private MsgListFragment msgListFragment;
    private ContactFragment contactFragment;
    private DiscoveryFragment discoveryFragment;
    private MeFragment meFragment;

    private final int STATE_MSG =1;
    private final int STATE_CON =2;
    private final int STATE_DIS =3;
    private final int STATE_ME =4;
    private int currentState;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
        initData();
        chageButtonColor(currentState,STATE_MSG);
    }

    private void initData() {
        fragmentManager = getFragmentManager();
        switchFragment(this.STATE_MSG);
    }

    private void initView() {
        btn_contact = (Button) findViewById(R.id.btn_contact);
        btn_disc = (Button) findViewById(R.id.btn_disc);
        btn_me = (Button) findViewById(R.id.btn_me);
        btn_msg_list = (Button) findViewById(R.id.btn_msg_list);
    }

    public void click(View view) {

        switch (view.getId()){
            case R.id.btn_msg_list:

                switchFragment(this.STATE_MSG);
                break;
            case R.id.btn_contact:
                switchFragment(this.STATE_CON);
                break;

            case R.id.btn_disc:
                switchFragment(this.STATE_DIS);
                break;
            case R.id.btn_me:
                switchFragment(this.STATE_ME);
                break;
        }
    }

    private void switchFragment(int toState) {

        if (toState == currentState)
            return;
        chageButtonColor(currentState,toState);
        this.currentState=toState;

        FragmentTransaction transaction = this.fragmentManager.beginTransaction();

        Fragment fragment=msgListFragment;
        switch (toState){
            case STATE_DIS:
                if (discoveryFragment == null)
                    discoveryFragment= new DiscoveryFragment();
                fragment= discoveryFragment;
                break;
            case STATE_ME:
                if (meFragment == null)
                    meFragment= new MeFragment();
                fragment= meFragment;
                break;
            case STATE_CON:
                if (contactFragment == null)
                    contactFragment= new ContactFragment();
                fragment= contactFragment;
                break;
            case STATE_MSG:
                if (msgListFragment == null)
                    msgListFragment= new MsgListFragment();
                fragment= msgListFragment;
                break;
        }
        transaction.replace(R.id.ll_content_part,fragment);
        transaction.commit();
    }

    private void chageButtonColor(int currentState,int toState){

        switch (currentState){
            case STATE_DIS:
                this.btn_disc.setTextColor(Color.BLACK);
                break;
                case STATE_ME:
                    this.btn_me.setTextColor(Color.BLACK);
                break;
            case STATE_CON:
                this.btn_contact.setTextColor(Color.BLACK);
                break;
            case STATE_MSG:
                this.btn_msg_list.setTextColor(Color.BLACK);
                break;
        }
        switch (toState){
            case STATE_DIS:
                this.btn_disc.setTextColor(Color.GREEN);
                break;
            case STATE_ME:
                this.btn_me.setTextColor(Color.GREEN);
                break;
            case STATE_CON:
                this.btn_contact.setTextColor(Color.GREEN);
                break;
            case STATE_MSG:
                this.btn_msg_list.setTextColor(Color.GREEN);
                break;
        }
    }
}