在 FragmentManager 中更改片段

Question

New Layout

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/RelativeLayout1"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >
    
    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@+id/L1" >
        
        <fragment
            android:id="@+id/fragment_place"
            android:name="com.javacodegeeks.android.fragmentstest.HomeFrag"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
        
   </FrameLayout>     

    <RelativeLayout
        android:id="@+id/L1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true" >
        
     
       <ImageView
            android:id="@+id/button1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/home"
            android:onClick="selectFrag"
            android:layout_alignParentLeft="true"/>
        
         <ImageView
            android:id="@+id/button2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/search"
            android:onClick="selectFrag"
            android:layout_toRightOf="@+id/button1"/>
         
           <ImageView
            android:id="@+id/button3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/map"
            android:onClick="selectFrag"
            android:layout_toRightOf="@+id/button2"/>
         
         
    
    
    </RelativeLayout>

</RelativeLayout>

我正在学习使用 FragmentManager 在 ImageView 单击上更改片段。当我单击第一个 imageView 时，带有文本“home”的主要片段布局显示良好。但是当点击其他ImageViews改变fragment页面时，它会更改为新的fragment页面，但不会删除之前的页面。结果，上一页与新页混在一起。 It look like this. 截图显示主页，文本为“home”，即上一页，新页面，文本为“search”。点击新的ImageView时如何删除上一页？

MainActivity

public class MainActivity extends Activity {
	
	private static final int RESULT_SETTINGS = 1;


	@Override
	protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);

      setContentView(R.layout.demo);
      
    
      
	}
	
	
	 
	public void selectFrag(View view) {
		 Fragment fr = null;
		 
		 if(view == findViewById(R.id.button1)) {
			 fr = new HomeFrag();
		 
		 }else if(view == findViewById(R.id.button2)){
			 fr = new SearchFrag();
		 
		 }else if(view == findViewById(R.id.button3)){
			 fr = new MapFrag();
		 
		 }
		 
		 FragmentManager fm = getFragmentManager();
	     FragmentTransaction fragmentTransaction = fm.beginTransaction();
	     fragmentTransaction.replace(R.id.fragment_place, fr);
	     fragmentTransaction.commit();
		 
	}
	
	
	
	
	
	
	
	
   
}

Answer 1

作为Android guide on starting fragments says 当您希望片段更改时，您不要在布局文件中使用fragment 元素。你应该使用一些布局，例如FrameLayout

如果您计划在活动的生命周期内更改片段，这是必要的。

我认为这是导致您的问题的原因。

---

您的新 XML 布局很接近，但我的意思是完全不使用 <fragment>。

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/fragment_place"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

</FrameLayout>  

然后代码本身还有更多工作要做，因为您需要在首次创建 UI 时创建/附加“home”片段。

在你的public void onCreate(Bundle savedInstanceState) {中

添加它以创建/附加第一个“home”片段。

 if (findViewById(R.id.fragment_place) != null) {

        // However, if we're being restored from a previous state,
        // then we don't need to do anything and should return or else
        // we could end up with overlapping fragments.
        if (savedInstanceState != null) {
            return;
        }

        // Create a new Fragment to be placed in the activity layout
        HomeFrag firstFragment = new HomeFrag();

        // In case this activity was started with special instructions from an
        // Intent, pass the Intent's extras to the fragment as arguments
        //   firstFragment.setArguments(getIntent().getExtras());
        // I commented this out since you don't appear to need it right now.

        // Add the fragment to the 'fragment_container' FrameLayout
        getFragmentManager().beginTransaction()
                .add(R.id.fragment_container, firstFragment).commit();
    }

Answer 2

用框架布局包装。试试这个xml

说明here

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/RelativeLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<Framelayout
  android:layout_width="match_parent"
  android:layout_height="match_parent">
    <fragment
        android:id="@+id/fragment_place"
        android:name="com.javacodegeeks.android.fragmentstest.HomeFrag"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@+id/L1" />
  </framelayout>
<RelativeLayout
    android:id="@+id/L1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true" >


   <ImageView
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/home"
        android:onClick="selectFrag"
        android:layout_alignParentLeft="true"/>

     <ImageView
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/search"
        android:onClick="selectFrag"
        android:layout_toRightOf="@+id/button1"/>

       <ImageView
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/map"
        android:onClick="selectFrag"
        android:layout_toRightOf="@+id/button2"/>




</RelativeLayout>

Answer 3

试试这个代码 sn-p 会起作用

        FragmentManager fm = getFragmentManager();
        FragmentTransaction fragmentTransaction = fm.beginTransaction();
        Fragment currentFragment =   getSupportFragmentManager().findFragmentById(R.id.fragment_place);
        if(currentFragment!=null)
            fragmentTransaction.remove()
        else{
            fragmentTransaction.add(R.id.fragment_place, fr);
            `enter code here`
            fragmentTransaction.commit();
        }