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Fragment碎片

1.静态加载fragment

package com.example.shinelon.diyfragment;

import android.app.Fragment;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
//自定义一个类继承Fragment,继承这个android.app.Fragment,v4那个已经被淘汰,详情见菜鸟教程,及fragment的作用
public class Demo2 extends Fragment{
    @Nullable
    //重写onCreate方法
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
        //用inflate加载布局页面,布局页面命名规则 fragment_xxxx
        View view = inflater.inflate(R.layout.fragment2, null);
        return view;
    }
}
           

在activity_main布局中加载fragment

name属性值当前所要加载的fragment的全类名

标签全小写

<fragment
        android:name="com.example.shinelon.diyfragment.Demo3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"></fragment>
           

2.动态加载fragment(横竖屏切换加载不同的页面)

Fragment碎片
public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //获取手机屏幕
        WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);
        int width = wm.getDefaultDisplay().getWidth();
        int height = wm.getDefaultDisplay().getHeight();
        //获取fragment管理者
        android.app.FragmentManager manager = getFragmentManager();
        //管理者开启事务
        // 开启一个事物,事物是执行一段逻辑,要么同时成功,要么同时失败
        FragmentTransaction transaction = manager.beginTransaction();

        if(height>width){
            //加载之前的写好的页面
            transaction.replace(R.id.LL,new Demo1());
        }else {
            transaction.replace(R.id.LL,new Demo2());
        }
        //提交一个事务,业务逻辑完成后一定要提交(commit)事务
        transaction.commit();
    }
}
           

activity_main中

<LinearLayout
    android:id="@+id/LL"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"></LinearLayout>
           
Fragment碎片

3.Fragment与Activity的交互

左边的Button是一个fragment,右边的TextView在Activity上

Fragment碎片

fragment_layout

简单新建一个布局,上面只写了一个Button

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <Button
        android:id="@+id/btn"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="button"/>
</LinearLayout>
           

Fragment

/和之前的操作一样,先创建一个类继承app.Fragment,用inflate加载刚才写的布局
public class Fragment extends android.app.Fragment {
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_layout, null);
        //设置Button的监听,用匿名内部类的方法
        // 这里的view应该相当于上下文对象,理解的不是很好
        view.findViewById(R.id.btn).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //用getActivity方法,得到Activity activity = getActivity();
                //指定是MainActivity,然后进行强制转换
                MainActivity m = (MainActivity) getActivity();
                m.update("123456");
            }
        });
        return view;
    }
}
           

activity_main

主布局文件中,写了一个线性布局,用来放Fragment

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    tools:context=".MainActivity">

    <LinearLayout
        android:id="@+id/LL"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:orientation="vertical"></LinearLayout>

    <TextView
        android:id="@+id/tv"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="hello Lenovo" />
    
</LinearLayout>
           

MainActivity

public class MainActivity extends AppCompatActivity {
    TextView tv;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv = findViewById(R.id.tv);
        FragmentManager manager = getFragmentManager();
        FragmentTransaction transaction = manager.beginTransaction();
        transaction.replace(R.id.LL,new Fragment());
        transaction.commit();
    }
    //将修改文字封装成一个方法,然后在Button的点击事件中,直接调用这个方法
    public void update(String s){
        tv.setText(s);
    }
}
           
Fragment碎片

4.Fragment与Fragment之间的数据互传

效果与之前类似,不再做演示

Fragment2

//操作与上一个案例相同,布局文件也很简单,就是一个TextView
public class Fragment2 extends Fragment{
    @Nullable
    TextView tv;
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment2_layout, null);
        tv = view.findViewById(R.id.tv);
        return view;
    }
    public void setData(String s){
        tv.setText(s);
    }
}
           

Fragment1

public class Fragment1 extends Fragment{
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment1_layout, null);
        view.findViewById(R.id.bt).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                MainActivity mactivity = (MainActivity) getActivity();
                //这里用一个getFragmentManger方法,得到manger对象
                FragmentManager manager = mactivity.getFragmentManager();
                //用manger找到这个取名为"f2"的fragment
                //和上一个案例不同之处
                Fragment2 f2 = (Fragment2) manager.findFragmentByTag("f2");
                f2.setData("123654");
            }
        });
        return view;
    }
}
           

activity_main

主布局文件中就放两个LineLayout

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity"
    android:orientation="horizontal">

    <LinearLayout
    //设置id,必须要设置orientation的方向
       android:id="@+id/LL1"
        android:layout_weight="1"
        android:orientation="vertical"
        android:layout_width="0dp"
        android:layout_height="match_parent"></LinearLayout>

    <LinearLayout
        android:id="@+id/LL2"
        android:layout_weight="1"
        android:orientation="vertical"
        android:layout_width="0dp"
        android:layout_height="match_parent"></LinearLayout>

</LinearLayout>
           

MainActivity

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        FragmentManager f1 = getFragmentManager();
        FragmentTransaction t1 = f1.beginTransaction();
        //和上一个不同之处,在后面加了一个自取的fragment名字
        //用于前面FragmentManager找到这个取名的fragment
        t1.replace(R.id.LL1,new Fragment1(),"f1");
        t1.commit();

        FragmentManager f2 = getFragmentManager();
        FragmentTransaction t2 = f2.beginTransaction();
        t2.replace(R.id.LL2,new Fragment2(),"f2");
        t2.commit();
    }
}
           
Fragment碎片

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