Develop--Training(八)Getting Started--用碎片来构建动态的UI

FragmentActivity 是一个特殊的 Activity，提供了支持库处理 Fragment 在系统版本低于 API 级别 11 的时候。如果你支持的最低系统版本的 API 级别是 11 或更高版本，那么你可以使用常规的的活动。

如果你使用的是 V7 appcompat 库，你的活动应继承 AppCompatActivity，它是 FragmentActivity 的子类。

// 布局添加 Fragment
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.ViewGroup;

public class ArticleFragment extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.article_view, container, false);
}
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="fill_parent">

<fragment android:name="com.example.android.fragments.HeadlinesFragment"
android:id="@+id/headlines_fragment"
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="match_parent" />

<fragment android:name="com.example.android.fragments.ArticleFragment"
android:id="@+id/article_fragment"
android:layout_weight="2"
android:layout_width="0dp"
android:layout_height="match_parent" />

</LinearLayout>

import android.os.Bundle;
import android.support.v4.app.FragmentActivity;

public class MainActivity extends FragmentActivity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.news_articles);
}
}

// 动态添加 Fragment

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/fragment_container"
android:layout_width="match_parent"
android:layout_height="match_parent" />
// 这是一个布局，这个容器是用来承载各种不同的 Fragment的

import android.os.Bundle;
import android.support.v4.app.FragmentActivity;

public class MainActivity extends FragmentActivity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.news_articles);
// Check that the activity is using the layout version with the fragment_container FrameLayout
if (findViewById(R.id.fragment_container) != 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
HeadlinesFragment firstFragment = new HeadlinesFragment();
// 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());

// Add the fragment to the 'fragment_container' FrameLayout
getSupportFragmentManager().beginTransaction()
.add(R.id.fragment_container, firstFragment).commit();
}
}
}
// 这是动态添加 Fragment，一定要开启一个事务，在所有操作完成之后，事务提交才能奏效。

Fragment 之间的数据通信，最好的话通过接口。定义一个接口，Activity 来实现这个接口，Fragment 来调用这个接口。

public class HeadlinesFragment extends ListFragment {

OnHeadlineSelectedListener mCallback;
// Container Activity must implement this interface
public interface OnHeadlineSelectedListener {
public void onArticleSelected(int position);
}

@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
mCallback = (OnHeadlineSelectedListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement OnHeadlineSelectedListener");
}
}

...
}

public static class MainActivity extends Activity
implements HeadlinesFragment.OnHeadlineSelectedListener{
...

public void onArticleSelected(int position) {
// Do something here to display that article
}
}