android Fragment

首先是創建一個項目，然後MainActivity繼承FragmentActivity，配置好佈局文件，再切換到MainFragment，其中MainFragment是一個過渡。

<?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:background="@color/white"
    android:orientation="vertical" >
    <View
        android:id="@+id/statusBarBackground"
        android:layout_width="match_parent"
        android:layout_height="0dp" />
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/white"
        android:orientation="vertical" >
        <!-- The main content view -->
        <FrameLayout
            android:id="@+id/content_frame"
            android:layout_width="match_parent"
            android:layout_height="0dip"
            android:layout_weight="1" />
    </LinearLayout>
</LinearLayout>

MainActivity中佈局文件中的content_frame是用來替換MainFragment的。

public class MainActivity extends FragmentActivity {
    private MainFragment fgt;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);//佈局文件
        switchFgt();//切換到MainFragment
    }

    private void switchFgt() {
      FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
      fgt = null;
      fgt = new MainFragment();
      ft.replace(R.id.content_frame, fgt);
      ft.commit();
    }
}

接下來就是MainFragment，首先佈局文件分爲兩部分：導航欄部分（選擇要跳轉的Fragment，帶有兩個RadioButton的LinearLayout）；fragment顯示部分（對應FrameLayout）。

<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:background="@color/white"
    android:orientation="vertical" >
    <FrameLayout
        android:id="@+id/fgt"
        android:layout_width="match_parent"
        android:layout_height="0dip"
        android:layout_weight="1" >
    </FrameLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@drawable/bottom_bar_bg"
        android:gravity="center_vertical"
        android:orientation="horizontal" >
        <RadioButton
            android:id="@+id/rbMap"
            style="@style/mainBottomRadioButton"
            android:drawableTop="@drawable/rb_map_selector"
            android:text="附近的人" />
        <RadioButton
            android:id="@+id/rbMine"
            style="@style/mainBottomRadioButton"
            android:drawableTop="@drawable/rb_mine_selector"
            android:text="我的" />
    </LinearLayout>
</LinearLayout>

注意fragment配置佈局文件的方法，onCreateView方法返回一個帶有佈局文件的View顯示。View view = inflater.inflate(R.layout.fragment_main, null);。獲取fragment的管理器，再根據用戶的選擇（監聽RadioButton）跳轉到相應的Fragment去顯示。

public class MainFragment extends Fragment{
    private FragmentManager fragmentManager;
    private RadioButton rbMap;
    private RadioButton rbMine;
    private CompoundButton lastChecked;// 上一次選中的按鈕
    private MapFragment mMapFgt;
    private MineFragment mMineFgt;
    public  Fragment curShowFragment = null;

    @Override
    public View onCreateView(LayoutInflater inflater,
            @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_main, null);
        fragmentManager = getChildFragmentManager();
        rbMap=(RadioButton) view.findViewById(R.id.rbMap);
        rbMine=(RadioButton) view.findViewById(R.id.rbMine);
        rbMap.setChecked(true);
        lastChecked=rbMap;

        //以我的模塊舉例：附近的人模塊類似
        rbMine.setOnCheckedChangeListener(new OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                checkedChanged(buttonView,isChecked);
            }
        });
        return view;
    }
//選擇之後觸發，選中重置上次選項的值，再調用switchFragmentByRbtnId方法
    public void checkedChanged(CompoundButton buttonView, boolean isChecked) {
        if (isChecked) {
            if (lastChecked != null) {
                lastChecked.setChecked(false);
            }
            switchFragmentByRbtnId(buttonView.getId());
            lastChecked = buttonView;
        }
    }
//根據選中項ID顯示相應fragment
    private void switchFragmentByRbtnId(int checkedId) {
        FragmentTransaction ft = fragmentManager.beginTransaction();
        //確定選中的ID
        String tag = String.valueOf(checkedId);
        Fragment showFragment = fragmentManager.findFragmentByTag(tag);

        boolean needAddFragment = showFragment == null ? true : false;
        switch (checkedId) {//以我的模塊舉例：附近的人模塊類似
        case R.id.rbMine:
            if (showFragment == null) {
            //設置顯示的fragment，當前爲MineFragment
                mMineFgt = new MineFragment();
                showFragment = mMineFgt;
            }
            break;
        }
        if (needAddFragment) {
            ft.add(R.id.fgt, showFragment, tag);
        }
        // 同一個rb多次觸發不再調用事務
        if (showFragment != curShowFragment) {
            if (curShowFragment != null) {
                ft.hide(curShowFragment);
            }
            if (showFragment != null) {
                // ft.replace(R.id.fgt, showFragment);
                ft.show(showFragment);
                curShowFragment = showFragment;
            }
        }
        ft.commit();
    }
}

最後MineFragment中在設置佈局文件，顯示相應的內容即可。

小結

其實Fragment最主要的還是以上兩個部分，掌握了就差不多了。