Android Api Demos登頂之路（三十九）Fragment-->show hide

這個demo示範了隐藏和顯示fragment的方法，利用hide和show方法，但需要注意的是 這兩個方法在FragmentTransaction身上，要使用這兩個方法就必須首先開啟事務。

* 同時這裡示範了兩種儲存資料的方式，一種是利用fragment的onsaveInstance方法 另一種是通過設定控件儲存資料的屬性實作

activity_main.xml

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

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="@string/hello_world" />
    <LinearLayout 
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:gravity="center"
        android:orientation="horizontal">
        <Button 
            android:id="@+id/hide1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="hide"/>
        <fragment 
            android:name="com.fishtosky.fragmenthideandshow.MainActivity$FirstFragment"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/first"/>
    </LinearLayout>
    <LinearLayout 
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:gravity="center"
        android:orientation="horizontal">
        <Button 
            android:id="@+id/hide2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="hide"/>
        <fragment 
            android:name="com.fishtosky.fragmenthideandshow.MainActivity$SecondFragment"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/second"/>
    </LinearLayout>

</LinearLayout>
           

fragment_content.xml:Fragment的布局檔案

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
    <TextView 
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:id="@+id/tv_tip"/>
    <EditText 
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/edit_text"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="initial text"
        android:background="#00ff00"
        android:freezesText="true"/>
    <!-- freezesText="true"設定為true表示控件将儲存内容和光标的位置 -->

</LinearLayout>
           

MainActivity

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //定義方法将fragment與hide按鈕關聯起來
        FragmentManager fm=getFragmentManager();
        addShowHideListener(R.id.hide1,fm.findFragmentById(R.id.first));
        addShowHideListener(R.id.hide2,fm.findFragmentById(R.id.second));
    }

    private void addShowHideListener(int buttonId, final Fragment fragment) {
        final Button bt=(Button) findViewById(buttonId);
        bt.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                //開啟fragment事務
                FragmentTransaction ft=getFragmentManager().beginTransaction();
                //設定fragment的切換動畫
                ft.setCustomAnimations(android.R.animator.fade_in, android.R.animator.fade_out);
                if(fragment.isHidden()){
                    bt.setText("Hide");
                    ft.show(fragment);
                }else{
                    bt.setText("Show");
                    ft.hide(fragment);
                }
                ft.commit();
            }
        });
    }

    public static class FirstFragment extends Fragment {
        private TextView et;
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View v=inflater.inflate(R.layout.fragment_content, container, false);
            TextView tv=(TextView) v.findViewById(R.id.tv_tip);
            tv.setText("The fragment saves and restores the text");
            et=(TextView) v.findViewById(R.id.edit_text);
            if(savedInstanceState!=null){
                String text=savedInstanceState.getString("text");
                et.setText(text);
            }
            return v;
        }

        @Override
        public void onSaveInstanceState(Bundle outState) {
            super.onSaveInstanceState(outState);
            String value=(String) et.getText();
            outState.putString("text", value);
        }

    }

    public static class SecondFragment extends Fragment {
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View v=inflater.inflate(R.layout.fragment_content, container, false);
            TextView tv=(TextView) v.findViewById(R.id.tv_tip);
            tv.setText("The TextView saves and restores the text");
            EditText et=(EditText) v.findViewById(R.id.edit_text);
            //雖然我們在布局檔案中設定了EditText儲存内容和光标位置的屬性，但由于這個布局
            //檔案是和其它fragment共享的，是以還需要在這裡進行設定
            et.setSaveEnabled(true);
            return v;
        }
    }
}