在本教程中，我们将开发一个包含TabLayout、ViewPager和片段的应用程序。我们将实现将数据从一个片段传递到另一个片段的功能。
Android分片间传递数据
意图仅适用于在活动级别上发送数据。要在片段之间传递数据，我们需要创建自己的接口。将字符串数据从一个片段发送到另一个片段的流程如下所示。
之间传递数据让我们开始实现上面的流程。
Android在Fragments Project结构之间传递数据
之间共享数据MainActivity.Java 类的xml布局如下所示。
1<?xml version="1.0" encoding="utf-8"?>
2<android.support.design.widget.CoordinatorLayout xmlns:android="https://schemas.android.com/apk/res/android"
3 xmlns:app="https://schemas.android.com/apk/res-auto"
4 xmlns:tools="https://schemas.android.com/tools"
5 android:layout_width="match_parent"
6 android:layout_height="match_parent"
7 android:fitsSystemWindows="true"
8 tools:context="com.journaldev.passingdatabetweenfragments.MainActivity">
9
10 <android.support.design.widget.AppBarLayout
11 android:layout_width="match_parent"
12 android:layout_height="wrap_content"
13 android:theme="@style/AppTheme.AppBarOverlay">
14
15 <android.support.v7.widget.Toolbar
16 android:id="@+id/toolbar"
17 android:layout_width="match_parent"
18 android:layout_height="?attr/actionBarSize"
19 android:background="?attr/colorPrimary"
20 app:popupTheme="@style/AppTheme.PopupOverlay" />
21
22 <android.support.design.widget.TabLayout
23 android:id="@+id/tabs"
24 style="@style/MyStyle"
25 android:layout_width="match_parent"
26 android:layout_height="wrap_content"
27 app:tabGravity="fill"
28 app:tabMode="fixed" />
29
30 </android.support.design.widget.AppBarLayout>
31
32 <android.support.v4.view.ViewPager
33 android:id="@+id/viewPager"
34 android:layout_width="match_parent"
35 android:layout_height="wrap_content"
36 app:layout_behavior="@string/appbar_scrolling_view_behavior" />
37
38</android.support.design.widget.CoordinatorLayout>
TabLayout和工具栏的样式在style es.xml 文件中定义，如下所示。
1<resources>
2
3 <!-- Base application theme. -->
4 <style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
5 <!-- Customize your theme here. -->
6 <item name="colorPrimary">@color/colorPrimary</item>
7 <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
8 <item name="colorAccent">@color/colorAccent</item>
9 </style>
10
11 <style name="AppTheme.AppBarOverlay" parent="ThemeOverlay.AppCompat.Dark.ActionBar" />
12
13 <style name="AppTheme.PopupOverlay" parent="ThemeOverlay.AppCompat.Light" />
14
15 <style name="MyStyle" parent="Widget.Design.TabLayout">
16 <item name="tabIndicatorColor">#FFFF</item>
17 <item name="tabIndicatorHeight">5dp</item>
18 <item name="tabPaddingStart">8dp</item>
19 <item name="tabPaddingEnd">8dp</item>
20 </style>
21
22</resources>
ViewPagerAdapter.java 是初始化碎片的地方。代码如下所示。
1public class ViewPagerAdapter extends FragmentPagerAdapter {
2
3 public ViewPagerAdapter(FragmentManager fm) {
4 super(fm);
5 }
6
7 @Override
8 public Fragment getItem(int position) {
9 Fragment fragment = null;
10 if (position == 0) {
11 fragment = new FragmentOne();
12 } else if (position == 1) {
13 fragment = new FragmentTwo();
14 }
15 return fragment;
16 }
17
18 @Override
19 public int getCount() {
20 return 2;
21 }
22
23 @Override
24 public CharSequence getPageTitle(int position) {
25 String title = null;
26 if (position == 0) {
27 title = "Tab-1";
28 } else if (position == 1) {
29 title = "Tab-2";
30 }
31 return title;
32 }
33}
FragmentOne将把在EditText中输入的数据发送给FragmentTwo。Fragment_one.xml 的XML布局如下所示。
1<?xml version="1.0" encoding="utf-8"?>
2
3<ScrollView xmlns:android="https://schemas.android.com/apk/res/android"
4 android:layout_width="match_parent"
5 android:layout_height="wrap_content"
6 android:fillViewport="true">
7
8 <RelativeLayout
9 android:layout_width="match_parent"
10 android:layout_height="wrap_content">
11
12 <EditText
13 android:id="@+id/inMessage"
14 android:layout_width="match_parent"
15 android:layout_height="wrap_content"
16 android:layout_above="@+id/btnPassData"
17 android:layout_margin="16dp"
18 android:hint="Enter here" />
19
20 <Button
21 android:id="@+id/btnPassData"
22 android:layout_width="wrap_content"
23 android:layout_height="wrap_content"
24 android:layout_centerInParent="true"
25 android:text="PASS DATA TO FRAGMENT TWO" />
26
27 </RelativeLayout>
28</ScrollView>
Fragment_two.xml 的XML布局如下所示。
1<?xml version="1.0" encoding="utf-8"?>
2<RelativeLayout xmlns:android="https://schemas.android.com/apk/res/android"
3 android:layout_width="match_parent"
4 android:layout_height="match_parent">
5
6 <TextView
7 android:id="@+id/txtData"
8 android:layout_width="wrap_content"
9 android:layout_height="wrap_content"
10 android:textSize="20sp"
11 android:layout_centerInParent="true"
12 android:text="No data received" />
13
14</RelativeLayout>
FragmentOne.java 类的代码如下。
1package com.journaldev.passingdatabetweenfragments;
2
3import android.content.Context;
4import android.os.Bundle;
5import android.support.annotation.Nullable;
6import android.support.v4.app.Fragment;
7import android.view.LayoutInflater;
8import android.view.View;
9import android.view.ViewGroup;
10import android.widget.Button;
11import android.widget.EditText;
12
13public class FragmentOne extends Fragment {
14
15 SendMessage SM;
16
17 @Nullable
18 @Override
19 public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
20 View rootView = inflater.inflate(
21 R.layout.fragment_one, container, false);
22 return rootView;
23
24 }
25
26 @Override
27 public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
28 super.onViewCreated(view, savedInstanceState);
29
30 Button btnPassData = (Button) view.findViewById(R.id.btnPassData);
31 final EditText inData = (EditText) view.findViewById(R.id.inMessage);
32 btnPassData.setOnClickListener(new View.OnClickListener() {
33 @Override
34 public void onClick(View v) {
35 SM.sendData(inData.getText().toString().trim());
36 }
37 });
38
39 }
40
41 interface SendMessage {
42 void sendData(String message);
43 }
44
45 @Override
46 public void onAttach(Context context) {
47 super.onAttach(context);
48
49 try {
50 SM = (SendMessage) getActivity();
51 } catch (ClassCastException e) {
52 throw new ClassCastException("Error in retrieving data. Please try again");
53 }
54 }
55}
自定义接口SendMessage是在上面的onAttach方法中初始化的。该接口将在我们将很快看到的MainActivity.Java 中实现。** FragmentTwo.java** 类的代码如下。
1package com.journaldev.passingdatabetweenfragments;
2
3import android.os.Bundle;
4import android.support.annotation.Nullable;
5import android.support.v4.app.Fragment;
6import android.view.LayoutInflater;
7import android.view.View;
8import android.view.ViewGroup;
9import android.widget.TextView;
10
11public class FragmentTwo extends Fragment {
12
13 TextView txtData;
14
15 @Nullable
16 @Override
17 public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
18 View rootView = inflater.inflate(
19 R.layout.fragment_two, container, false);
20 return rootView;
21 }
22
23 @Override
24 public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
25 super.onViewCreated(view, savedInstanceState);
26
27 txtData = (TextView)view.findViewById(R.id.txtData);
28 }
29
30 protected void displayReceivedData(String message)
31 {
32 txtData.setText("Data received: "+message);
33 }
34}
FragmentTwo.java 的实例上的displayReceivedData()将从** MainActivity.java** 内的Custom接口的方法中调用，如下所示。
1package com.journaldev.passingdatabetweenfragments;
2
3import android.support.design.widget.TabLayout;
4import android.support.v4.view.ViewPager;
5import android.support.v7.app.AppCompatActivity;
6import android.os.Bundle;
7import android.support.v7.widget.Toolbar;
8
9public class MainActivity extends AppCompatActivity implements FragmentOne.SendMessage{
10
11 TabLayout tabLayout;
12 ViewPager viewPager;
13 ViewPagerAdapter viewPagerAdapter;
14
15 @Override
16 protected void onCreate(Bundle savedInstanceState) {
17 super.onCreate(savedInstanceState);
18 setContentView(R.layout.activity_main);
19 Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
20 setSupportActionBar(toolbar);
21
22 viewPager = (ViewPager) findViewById(R.id.viewPager);
23 viewPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager());
24 viewPager.setAdapter(viewPagerAdapter);
25 tabLayout = (TabLayout) findViewById(R.id.tabs);
26 tabLayout.setupWithViewPager(viewPager);
27 }
28
29 @Override
30 public void sendData(String message) {
31 String tag = "android:switcher:" + R.id.viewPager + ":" + 1;
32 FragmentTwo f = (FragmentTwo) getSupportFragmentManager().findFragmentByTag(tag);
33 f.displayReceivedData(message);
34 }
35}
只要按下FragmentOne中的Button，就会触发上面代码中的sendData()方法。我们使用findFragmentByTag 方法获取已在ViewPagerAdapter中初始化的FragmentTwo。运行中的上述应用程序的输出如下所示。
本教程就此结束。您可以通过下面的链接下载最终的** Android PassingDataBetweenFragments项目** 。