Fragment初学2——使用Fragment

不念不忘少年蓝@ 2021-09-22 04:12 313阅读 0赞

一般创建Fragment需要实现如下三个方法。

onCreate(）:系统创建Fragment对象后回调该方法，实现代码中只初始化Fragment中的组件。

onCreateView(): 当Fragment绘制界面组件时回调该方法，该方法返回的view就是该Fragment所显示的View。

onPause(): 当用户离开该Fragment时回调该方法。

好了，开始使用吧，最简单的用法—— **静态使用Fragment**

步骤：

1、首先继承Fragment，重写onCreateView（）方法设置Fragemnt的布局

2、在Activity中声明此Fragment，然后当做普通的View组件使用

下面一个具体例子：

**TitleFragment的布局文件:**

**TitleFragment.java类：**

public class TitleFragment extends Fragment \{

private ImageButton mImageButton;

@Override

public View onCreateView(LayoutInflater inflater, ViewGroup container,

Bundle savedInstanceState) \{

View view = inflater.inflate(R.layout.fragment\_title, container, false);

mImageButton = (ImageButton) view.findViewById(R.id.imgBtn\_title\_fragment);

mImageButton.setOnClickListener(new OnClickListener() \{

@Override

public void onClick(View v) \{

Toast.makeText(getActivity(), "这是TitleFragment！ ",

Toast.LENGTH\_LONG).show();

\});

return view;

**同理FirstFragment的布局文件：**

**FirstFragment .java类：**

public class FirstFragment extends Fragment \{

@Override

public View onCreateView(LayoutInflater inflater, ViewGroup container,

Bundle savedInstanceState) \{

return inflater.inflate(R.layout.fragment\_first, container, false);

**MainActivity布局如下：**

<RelativeLayout xmlns:android=" [http://schemas.android.com/apk/res/android][http_schemas.android.com_apk_res_android]"  
    xmlns:tools=" [http://schemas.android.com/tools][http_schemas.android.com_tools]"  
    android:layout\_width="match\_parent"  
    android:layout\_height="match\_parent" >  
  
    <fragment  
        android:id="@+id/fragment\_title\_main"  
        android:name="com.example.activity.TitleFragment"  
        android:layout\_width="match\_parent"  
        android:layout\_height="45dp" />  
  
    <fragment  
        android:id="@+id/fragment\_first\_main"  
        android:name="com.example.activity.FirstFragment"  
        android:layout\_width="match\_parent"  
        android:layout\_height="match\_parent"  
        android:layout\_below="@+id/fragment\_title\_main" />  
  
</RelativeLayout>

**MainActivity.java类**

public class MainActivity extends Activity \{

@Override

protected void onCreate(Bundle savedInstanceState)

super.onCreate(savedInstanceState);

requestWindowFeature(Window.FEATURE\_NO\_TITLE);

setContentView(R.layout.activity\_main);

@Override

public boolean onCreateOptionsMenu(Menu menu) \{

// Inflate the menu; this adds items to the action bar if it is present.

getMenuInflater().inflate(R.menu.main, menu);

return true;

说完了静态使用Fragment，下面再说下如何动态使用吧

首先修改下 **MainActivity**的布局文件

<?xml version="1.0" encoding="utf-8"?>  
<RelativeLayout xmlns:android=" [http://schemas.android.com/apk/res/android][http_schemas.android.com_apk_res_android]"  
    android:layout\_width="match\_parent"  
    android:layout\_height="match\_parent" >  
  
    <fragment  
        android:id="@+id/fragment\_title\_main"  
        android:name="com.example.activity.TitleFragment"  
        android:layout\_width="match\_parent"  
        android:layout\_height="45dp" />  
  
    <FrameLayout  
        android:id="@+id/framelayout\_fragment\_main"  
        android:layout\_width="match\_parent"  
        android:layout\_height="match\_parent"  
        android:layout\_above="@+id/linearlayout\_toolbar\_main"  
        android:layout\_below="@+id/fragment\_title\_main" />  
  
    <LinearLayout  
        android:id="@+id/linearlayout\_toolbar\_main"  
        android:layout\_width="match\_parent"  
        android:layout\_height="wrap\_content"  
        android:layout\_alignParentBottom="true"  
        android:layout\_alignParentLeft="true"  
        android:background="@drawable/toolbar\_bg" >  
  
        <TextView  
            android:id="@+id/textView1\_main"  
            android:layout\_width="wrap\_content"  
            android:layout\_height="match\_parent"  
            android:layout\_weight="1"  
            android:gravity="center"  
            android:text="第一个"  
            android:textColor="\#fff"  
            android:textSize="20sp" />  
  
        <TextView  
            android:id="@+id/textView2\_main"  
            android:layout\_width="wrap\_content"  
            android:layout\_height="match\_parent"  
            android:layout\_weight="1"  
            android:gravity="center"  
            android:text="第二个"  
            android:textColor="\#fff"  
            android:textSize="20sp" />  
    </LinearLayout>  
  
</RelativeLayout>

需要使用FragmentManager对Fragment进行动态的加载，这里使用的是replace方法，下一节再详细介绍FragmentManager的常用API。

我们第一节说过Fragment是Android3.0引入的API，所以如果使用以前的版本，需要引入v4的包，然后Activity继承FragmentActivity，然后通过 getSupportFragmentManager获得FragmentManager。所以还是建议把Manifest文件的uses-sdk的 minSdkVersion和targetSdkVersion都改为11以上，这样就不必引入v4包了。

**MainActivity.java类**

public class MainActivity extends Activity implements OnClickListener \{

private Fragment mFirst, mTwo;

@Override

protected void onCreate(Bundle savedInstanceState) \{

super.onCreate(savedInstanceState);

requestWindowFeature(Window.FEATURE\_NO\_TITLE);

// getWindow().setFlags(WindowManager.LayoutParams.FLAG\_FULLSCREEN,

// WindowManager.LayoutParams.FLAG\_FULLSCREEN);

setContentView(R.layout.activity\_main);

TextView First = (TextView) findViewById(R.id.textView1\_main);

TextView Two = (TextView) findViewById(R.id.textView2\_main);

First.setOnClickListener(this);

Two.setOnClickListener(this);

// 设置默认的Fragment

setDefaultFragment();

private void setDefaultFragment() \{

FragmentManager fm = getFragmentManager();

FragmentTransaction transaction = fm.beginTransaction();

mFirst = new FirstFragment();

transaction.replace(R.id.framelayout\_fragment\_main, mFirst);

transaction.commit();

@Override

public void onClick(View v) \{

// TODO Auto-generated method stub

FragmentManager fm = getFragmentManager();

// 开启Fragment事务

FragmentTransaction transaction = fm.beginTransaction();

switch (v.getId()) \{

case R.id.textView1\_main:

if (mFirst == null) \{

mFirst = new FirstFragment();

// 使用当前Fragment的布局替代id\_content的控件

transaction.replace(R.id.framelayout\_fragment\_main, mFirst);

break;

case R.id.textView2\_main:

if (mTwo == null) \{

mTwo = new TwoFragment();

transaction.replace(R.id.framelayout\_fragment\_main, mTwo);

break;

// transaction.addToBackStack();

// 事务提交

transaction.commit();

@Override

public boolean onCreateOptionsMenu(Menu menu) \{

// Inflate the menu; this adds items to the action bar if it is present.

getMenuInflater().inflate(R.menu.main, menu);

return true;

代码中的TwoFragment和FirstFragment类似，就不粘代码了，我会上传源代码  
**[源代码][Link 1]**

[http_schemas.android.com_apk_res_android]: http://schemas.android.com/apk/res/android
[http_schemas.android.com_tools]: http://schemas.android.com/tools
[Link 1]: http://download.csdn.net/detail/xuemengrui12/9212529