安卓核心技术中级——Fragment

要创建一个fragment，必须创建一个fragment的子类。
除了基类fragment，还有：
DialogFragment
ListFragment
PreferenceFragment

与Activity的对应生命周期

运行

创建Fragment

方式一

<fragment
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:id="@+id/title_fragment"
        android:name="com.example.fragmentapplication.TitleFragment"/>

方式二

//通过代码添加Fragment
    private void addContentLayout() {
        FragmentManager fm = getSupportFragmentManager();
        //开启一个事务
        FragmentTransaction ft = fm.beginTransaction();

        contentFragment = new ContentFragment();
        //添加fragment
        ft.add(R.id.cf,contentFragment);
//        ft.remove()//删除
//        ft.replace()//替换

        ft.commit();
    }
//ContentFragment.java
public class ContentFragment extends Fragment {

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.content_layout,container,false);
        return view;
    }
}

管理Fragment

public class PopBackFragment extends Fragment {

    private String title;
    public PopBackFragment(){}
    @SuppressLint("ValidFragment")
    public PopBackFragment(String title){
        this.title = title;
    }
    
//Fragment的传参方法
//    public static PopBackFragment getInstance(String title){
//        PopBackFragment p = new PopBackFragment();
//
//        Bundle b = new Bundle();
//        b.putString("title",title);
//        p.setArguments(b);
//        return p;
//    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.activity_pop_back_fragment,container,false);
        TextView tv = (TextView)view.findViewById(R.id.textView_text);
        tv.setText(title);
        return view;
    }
}

public void oneClick(View v){
        PopBackFragment p1 = new PopBackFragment("one");
        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
        ft.replace(R.id.content,p1);
        //把当前Fragment添加到Activity栈中
        ft.addToBackStack(null);
        ft.commit();
    }


    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if(keyCode == KeyEvent.KEYCODE_BACK){
            if(getSupportFragmentManager().getBackStackEntryCount()==0){
                finish();
            }else {
                getSupportFragmentManager().popBackStack();
            }
            return true;
        }
        return super.onKeyDown(keyCode, event);
    }

与Activity交互

<!--fragment_menu-->
<?xml version="1.0" encoding="utf-8"?>
<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"
    tools:context=".MenuFragment"
    android:orientation="vertical">

    <Button
        android:id="@+id/button_news"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="News"/>

    <Button
        android:id="@+id/button_music"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Musics" />

</LinearLayout>

<!--fragment_main-->
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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"
    tools:context=".MainFragment">

    <!-- TODO: Update blank fragment layout -->
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="@string/hello_blank_fragment"
        android:id="@+id/value"
        android:gravity="center"/>

</FrameLayout>

//MenuFragment

import android.content.Context;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;


public class MenuFragment extends Fragment implements View.OnClickListener {

    private MyMenuListener myMenuListener;

    public MenuFragment() {
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        myMenuListener = (MyMenuListener)context;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_menu, container, false);
        view.findViewById(R.id.button_news).setOnClickListener(this);
        view.findViewById(R.id.button_music).setOnClickListener(this);
        return view;
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()){
            case R.id.button_news:
                myMenuListener.changeValue("news");
                break;
            case R.id.button_music:
                myMenuListener.changeValue("musics");
                break;
        }
    }

    //定义一个回调接口
    public static interface MyMenuListener{
        public void changeValue(String value);
    }

}


//MainFragment
import android.content.Context;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class MainFragment extends Fragment {

    private TextView tv_value;

    public MainFragment() {
        // Required empty public constructor
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_main, container, false);
        tv_value = (TextView)view.findViewById(R.id.value);
        return view;
    }

    public void changeTextViewValue(String value){
        tv_value.setText(value);
    }
}

//MainActivity
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class MainActivity3 extends AppCompatActivity implements MenuFragment.MyMenuListener{

    private MenuFragment menuFragment;
    private MainFragment mainFragment;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main3);
        menuFragment = (MenuFragment) getSupportFragmentManager().findFragmentById(R.id.menuFragment);
        mainFragment = (MainFragment) getSupportFragmentManager().findFragmentById(R.id.mainFragment);
    }

    @Override
    public void changeValue(String value) {
        mainFragment.changeTextViewValue(value);
    }
}

PrefernceFragment

在res中新建一个名为xml的文件夹，在文件夹中新建一个preference.xml文件

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
<PreferenceCategory
    android:title="是否打开声音">
    <CheckBoxPreference
        android:key="checkbox_preference"
        android:title="打开声音"
        android:summary="设置打开声音后可以自动开启音乐"/>
</PreferenceCategory>
    <PreferenceCategory
        android:title="城市">

        <EditTextPreference
            android:key="edittext_preference"
            android:title="昵称"
            android:summary="请输入昵称"
            android:dialogTitle="昵称" />

        <ListPreference
            android:key="list_preference"
            android:title="城市名称"
            android:summary="请选择一个城市"
            android:entries="@array/city"
            android:entryValues="@array/city"
            android:dialogTitle="城市名称" />

    </PreferenceCategory>
</PreferenceScreen>

然后新建一个fragment，实现addPreferencesFromResource方法

public class PerfsFragment extends PreferenceFragment {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.preferences);
    }

}

最后新建一个activity使用fragment

<fragment
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/prefs_fragment"
        android:name="com.example.fragmentapplication.PerfsFragment"/>