Android入门——UI(8)——Fragment(2)

先演示一下如何在一个activity中放置两个Fragment,先定义两个Fragment

<?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:gravity="center"
    android:orientation="vertical">

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="注销登陆" />
</LinearLayout>

<?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="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"
        android:text="上面的片段显示用户信息" />
</LinearLayout>

package com.ouc.wkp.ui1;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

/**
 * Created by wkp on 2016/8/25.
 */
public class FragmentIndexBottom extends Fragment {
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view=inflater.inflate(R.layout.fragment_indexbottom,container,false);
        return view;
    }
}

package com.ouc.wkp.ui1;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

/**
 * Created by wkp on 2016/8/25.
 */
public class FragmentIndexTop extends Fragment{
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view=inflater.inflate(R.layout.fragment_indextop,container,false);
        return view;
    }
}

然后定义Activity,放置两个FrameLayout

<?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">

    <FrameLayout
        android:id="@+id/fragment_layout_top"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"></FrameLayout>

    <FrameLayout
        android:id="@+id/fragment_layout_bottom"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"></FrameLayout>
</LinearLayout>

package com.ouc.wkp.ui1;

import android.os.Bundle;
import android.os.PersistableBundle;
import android.support.annotation.Nullable;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;

/**
 * Created by wkp on 2016/8/25.
 */
public class FragmentDemo2 extends FragmentActivity {

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_demo2);

        FragmentManager fm = getSupportFragmentManager();
        FragmentTransaction ft = fm.beginTransaction();
        ft.replace(R.id.fragment_layout_top, new FragmentIndexTop());
        ft.replace(R.id.fragment_layout_bottom, new FragmentIndexBottom());
        ft.commit();
    }
}

上面的例子比较简单，和上一篇基本类似，所以很容易看出使用Fragment是为了代码的复用。

下面介绍fragment和activity之间的通信。有两种形式，一种是fragment->activity,另一种是activity->fragment。

 实现方式是定义modify函数或者定义事件监听方法回调。方法回调的方式比较不好理解

<?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="#f00"
    android:orientation="vertical">

    <TextView
        android:id="@+id/tv_in_fragment"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="这是一个Fragment,通过动态方式加载" />

    <Button
        android:id="@+id/btn_in_fragment"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</LinearLayout>

package com.ouc.wkp.ui1;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

/**
 * Created by wkp on 2016/8/25.
 */
public class FragmentIndex extends Fragment {//app包下3.0以后才可以使用

    private OnBtnClickListener onBtnClickListener;

    public void setOnBtnClickListener(OnBtnClickListener onBtnClickListener) {
        this.onBtnClickListener = onBtnClickListener;
    }

    public interface OnBtnClickListener{
        void onBtnClick();
    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        //别遗忘第三个false参数，否则会出现 java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
        View view=inflater.inflate(R.layout.fragment_index,container,false);

        view.findViewById(R.id.btn_in_fragment).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
//                FragmentDemo fragmentDemo=(FragmentDemo) getActivity();
//                fragmentDemo.modify();
                if(onBtnClickListener!=null){
                    onBtnClickListener.onBtnClick();
                }
            }
        });
        return view;
    }

    public void modify(){
        TextView textView=(TextView) getView().findViewById(R.id.tv_in_fragment);
        textView.setText("已经修改fragment里面的UI元素的值");
    }
}

<?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">

    <Button
        android:id="@+id/btn_addd"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="增加" />

    <Button
        android:id="@+id/btn_deletee"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="减少" />

    <FrameLayout
        android:id="@+id/frame_layout"
        android:layout_width="match_parent"
        android:layout_height="200dp"></FrameLayout>

    <Button
        android:id="@+id/btn_modify"
        android:text="修改fragment的界面"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/tv_in_activity"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="哈哈哈"/>
</LinearLayout>

package com.ouc.wkp.ui1;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.view.View;
import android.widget.TextView;

/**
 * Created by wkp on 2016/8/25.
 */
public class FragmentDemo extends FragmentActivity{

    FragmentIndex fragmentIndex;

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

        fragmentIndex=new FragmentIndex();
        //接口回调
        fragmentIndex.setOnBtnClickListener(new FragmentIndex.OnBtnClickListener(){

            @Override
            public void onBtnClick() {
                TextView textView=(TextView)findViewById(R.id.tv_in_activity);
                textView.setText("修改activity中的textView（通过方法回调）");
            }
        });

        findViewById(R.id.btn_addd).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                FragmentManager fm=getSupportFragmentManager();
                FragmentTransaction ft=fm.beginTransaction();

                ft.replace(R.id.frame_layout,fragmentIndex);
                ft.commit();
            }
        });

        findViewById(R.id.btn_deletee).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                FragmentManager fm=getSupportFragmentManager();
                FragmentTransaction ft=fm.beginTransaction();

                ft.remove(fragmentIndex);
                ft.commit();
            }
        });

        findViewById(R.id.btn_modify).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //从Activity修改Fragment的值
                fragmentIndex.modify();;
            }
        });
    }

    public void modify(){
        TextView textView=(TextView) findViewById(R.id.tv_in_activity);
        textView.setText("修改activity中的textView");
    }
}