Fragment示例代码 Android开发技术

  Android 3.0平板系统的重要特性Fragment示例代码今天Android123给大家两个例子，一起来看下Fragment的实战代码:

  一、通过Fragment实现简单的上下文菜单

  public class FragmentContextMenu extends Activity {

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

         ContextMenuFragment content = new ContextMenuFragment();
         getFragmentManager().beginTransaction().add(android.R.id.content, content).commit(); //在Activity中通过这个与Fragment通讯
    }

   下面ContextMenuFragment是我们从Fragment派生的子类，里面重写了onCreateView来布局自己的Fragment

    public static class ContextMenuFragment extends Fragment {

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View root = inflater.inflate(R.layout.fragment_context_menu, container, false);
            registerForContextMenu(root.findViewById(R.id.long_press));
            return root;
        }

        @Override
        public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {
            super.onCreateContextMenu(menu, v, menuInfo);
            menu.add(Menu.NONE, R.id.a_item, Menu.NONE, "菜单1");
            menu.add(Menu.NONE, R.id.b_item, Menu.NONE, "菜单2");
        }

        @Override
        public boolean onContextItemSelected(MenuItem item) {
            switch (item.getItemId()) {
                case R.id.a_item:
                    Log.i("CWJ", "Item 1a was chosen");
                    return true;
                case R.id.b_item:
                    Log.i("CWJ", "Item 1b was chosen");
                    return true;
            }
            return super.onContextItemSelected(item);
        }
    }
}

 涉及到的布局文件fragment_context_menu.xml源码

  <?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:padding="8dp">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="@string/fragment_context_menu_msg" />

    <Button android:id="@+id/long_press"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="@string/long_press">
        <requestFocus />
    </Button>
   
</LinearLayout>

  二、控制Fragment的显示或隐藏同时包含淡入淡出效果

  public class FragmentHideShow extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_hide_show);

        FragmentManager fm = getFragmentManager();
        addShowHideListener(R.id.frag1hide, fm.findFragmentById(R.id.fragment1));
        addShowHideListener(R.id.frag2hide, fm.findFragmentById(R.id.fragment2));

        //上面的两行代码是在Activity中为Fragment中的按钮添加监听事件
    }

    void addShowHideListener(int buttonId, final Fragment fragment) {
        final Button button = (Button)findViewById(buttonId);
        button.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {
                FragmentTransaction ft = getFragmentManager().beginTransaction();
                ft.setCustomAnimations(android.R.animator.fade_in,
                        android.R.animator.fade_out); //为Fragment设置淡入淡出效果，Android开发网提示这里这两个动画资源是android内部资源无需我们手动定义。
                if (fragment.isHidden()) {
                    ft.show(fragment);
                    button.setText("隐藏");
                } else {
                    ft.hide(fragment);
                    button.setText("显示");
                }
                ft.commit();
            }
        });
    }

    public static class FirstFragment extends Fragment {
        TextView mTextView;

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View v = inflater.inflate(R.layout.labeled_text_edit, container, false);
            View tv = v.findViewById(R.id.msg);
            ((TextView)tv).setText("The fragment saves and restores this text.");

            mTextView = (TextView)v.findViewById(R.id.saved);
            if (savedInstanceState != null) {
                mTextView.setText(savedInstanceState.getCharSequence("text"));
            }
            return v;
        }

        @Override
        public void onSaveInstanceState(Bundle outState) {
            super.onSaveInstanceState(outState);

            outState.putCharSequence("text", mTextView.getText());
        }
    }

    public static class SecondFragment extends Fragment {

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View v = inflater.inflate(R.layout.labeled_text_edit, container, false);
            View tv = v.findViewById(R.id.msg);
            ((TextView)tv).setText("The TextView saves and restores this text.");

            ((TextView)v.findViewById(R.id.saved)).setSaveEnabled(true);
            return v;
        }
    }
}

 涉及资源布局文件fragment_hide_show.xml代码:

  <?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:gravity="center_horizontal"
    android:layout_width="match_parent" android:layout_height="match_parent">

    <TextView android:layout_width="match_parent" android:layout_height="wrap_content"
        android:gravity="center_vertical|center_horizontal"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="Demonstration of hiding and showing fragments." />

    <LinearLayout android:orientation="horizontal" android:padding="4dip"
        android:gravity="center_vertical" android:layout_weight="1"
        android:layout_width="match_parent" android:layout_height="wrap_content">

        <Button android:id="@+id/frag1hide"
            android:layout_width="wrap_content" android:layout_height="wrap_content"
            android:text="Hide" />

        <fragment android:name="com.android123.FragmentHideShow$FirstFragment"
                android:id="@+id/fragment1" android:layout_weight="1"
                android:layout_width="0px" android:layout_height="wrap_content" />

    </LinearLayout>

    <LinearLayout android:orientation="horizontal" android:padding="4dip"
        android:gravity="center_vertical" android:layout_weight="1"
        android:layout_width="match_parent" android:layout_height="wrap_content">

        <Button android:id="@+id/frag2hide"
            android:layout_width="wrap_content" android:layout_height="wrap_content"
            android:text="Hide" />

        <fragment android:name="com.android123.FragmentHideShow$SecondFragment"
                android:id="@+id/fragment2" android:layout_weight="1"
                android:layout_width="0px" android:layout_height="wrap_content" />

    </LinearLayout>

</LinearLayout>

 有关布局文件labeled_text_edit.xml的代码为

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:padding="4dip"
    android:layout_width="match_parent" android:layout_height="wrap_content">

    <TextView android:id="@+id/msg"
        android:layout_width="match_parent" android:layout_height="wrap_content"
        android:layout_weight="0"
        android:paddingBottom="4dip" />

    <EditText android:id="@+id/saved"
        android:layout_width="match_parent" android:layout_height="wrap_content"
        android:layout_weight="1"
        android:background="@drawable/green"
        android:text="@string/initial_text"
        android:freezesText="true">
        <requestFocus />
    </EditText>

</LinearLayout>