在运行的Activity中添加一个Fragment
一个处理Fragment的重要原则,Fragment必须有一个在布局中有一个让其寄存的View容器,特别是对那些运行时的Fragment。
以下是一个布局文件,每次显示一个Fragment。为了用一个Fragment替换另外一个,Activity的布局文件包含一个空的FrameLayout,作为Fragment容器使用。
- res/layout/news_articles.xml:
- <FrameLayoutxmlns:android="http://schemas.android.com/apk/res/android"
- android:id="@+id/fragment_container"
- android:layout_width="match_parent"
- android:layout_height="match_parent" />
在Activity当中,利用getSupportFragmentManager()获取一个FragmentManager,以下是代码示例:
- import android.os.Bundle;
- import android.support.v4.app.FragmentActivity;
- public class MainActivity extends FragmentActivity {
- @Override
- public voidonCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
-
setContentView(R.layout.news_articles);
- // Checkthat the activity is
using the layout version with
- // thefragment_container
FrameLayout
-
if(findViewById(R.id.fragment_container) != null) {
-
//However, if we‘re being restored from a previous state,
- //
thenwe don‘t need to do anything and should return or else
- //
wecould end up with overlapping fragments.
-
if(savedInstanceState != null) {
- return;
- }
- //
Create an instance of ExampleFragment
- HeadlinesFragment
firstFragment = new HeadlinesFragment();
- //
Incase this activity was started with special instructions from an
Intent,
- //
passthe Intent‘s extras to the fragment as arguments
- firstFragment.setArguments(getIntent().getExtras());
- //
Addthe fragment to the ‘fragment_container‘ FrameLayout
- getSupportFragmentManager().beginTransaction()
-
.add(R.id.fragment_container,firstFragment).commit();
- }
- }
- }
Fragment替换
替换Fragment的流程和添加的流程类似,只不过需要利用replace方法替换add方法。
需要记住的是,当你是Fragment切换的时候,例如替换或者一处,最好让用户拥有返回或者撤销的机会
当你允许用户返回或者撤销Fragment操作的时候,你必须在调用FragmentTransaction之前调用addToBackStack。
以下是一个示例:
-
- // Create fragment and give it an argument specifying thearticle it
should show
- ArticleFragment newFragment = new ArticleFragment();
- Bundle args = new Bundle();
- args.putInt(ArticleFragment.ARG_POSITION, position);
- newFragment.setArguments(args);
- FragmentTransaction transaction
=getSupportFragmentManager().beginTransaction();
- // Replace whatever is in the fragment_container viewwith this
fragment,
- // and add the transaction to the back stack so the usercan navigate
back
- transaction.replace(R.id.fragment_container,newFragment);
- transaction.addToBackStack(null);
- // Commit the transaction
- transaction.commit();
fragment的使用
原文:http://www.cnblogs.com/ff0o0/p/3554324.html