Android在片段之间传递数据
时间：2020-02-23 14:29:08 来源:igfitidea点击:
在本教程中，我们将开发一个包含TabLayout，ViewPager和Fragments的应用程序。
我们将实现一项功能，将数据从一个片段传递到另一个片段。
Android在片段之间传递数据
意图仅可用于在活动级别上发送数据。
为了在片段之间传递数据，我们需要创建自己的接口。
下面显示了将String数据从一个Fragment发送到另一个Fragment的流程。
让我们开始执行上述流程。
Android在片段项目结构之间传递数据
MainActivity.java类的xml布局如下。
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="https://schemas.android.com/apk/res/android"
xmlns:app="https://schemas.android.com/apk/res-auto"
xmlns:tools="https://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context="com.theitroad.passingdatabetweenfragments.MainActivity">
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="@style/AppTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:popupTheme="@style/AppTheme.PopupOverlay"
<android.support.design.widget.TabLayout
android:id="@+id/tabs"
style="@style/MyStyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:tabGravity="fill"
app:tabMode="fixed"
</android.support.design.widget.AppBarLayout>
<android.support.v4.view.ViewPager
android:id="@+id/viewPager"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
</android.support.design.widget.CoordinatorLayout>
TabLayout和ToolBar的样式在styles.xml文件中定义，如下所示。
<resources>
<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
<!-- Customize your theme here. -->
<item name="colorPrimary">@color/colorPrimary</item>
<item name="colorPrimaryDark">@color/colorPrimaryDark</item>
<item name="colorAccent">@color/colorAccent</item>
</style>
<style name="AppTheme.AppBarOverlay" parent="ThemeOverlay.AppCompat.Dark.ActionBar"
<style name="AppTheme.PopupOverlay" parent="ThemeOverlay.AppCompat.Light"
<style name="MyStyle" parent="Widget.Design.TabLayout">
<item name="tabIndicatorColor">#FFFF</item>
<item name="tabIndicatorHeight">5dp</item>
<item name="tabPaddingStart">8dp</item>
<item name="tabPaddingEnd">8dp</item>
</style>
</resources>
ViewPagerAdapter.java是片段的初始化位置。
代码如下。
public class ViewPagerAdapter extends FragmentPagerAdapter {
public ViewPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
Fragment fragment = null;
if (position == 0) {
fragment = new FragmentOne();
} else if (position == 1) {
fragment = new FragmentTwo();
}
return fragment;
}
@Override
public int getCount() {
return 2;
}
@Override
public CharSequence getPageTitle(int position) {
String title = null;
if (position == 0) {
title = "Tab-1";
} else if (position == 1) {
title = "Tab-2";
}
return title;
}
}
FragmentOne会将在EditText中输入的数据发送到FragmentTwo。
下面给出fragment_one.xml的xml布局。
<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="https://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:fillViewport="true">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<EditText
android:id="@+id/inMessage"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_above="@+id/btnPassData"
android:layout_margin="16dp"
android:hint="Enter here"
<Button
android:id="@+id/btnPassData"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:text="PASS DATA TO FRAGMENT TWO"
</RelativeLayout>
</ScrollView>
以下给出fragment_two.xml的xml布局。
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="https://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="@+id/txtData"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="20sp"
android:layout_centerInParent="true"
android:text="No data received"
</RelativeLayout>
FragmentOne.java类的代码如下。
package com.theitroad.passingdatabetweenfragments;
import android.content.Context;
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.Button;
import android.widget.EditText;
public class FragmentOne extends Fragment {
SendMessage SM;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View rootView = inflater.inflate(
R.layout.fragment_one, container, false);
return rootView;
}
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
Button btnPassData = (Button) view.findViewById(R.id.btnPassData);
final EditText inData = (EditText) view.findViewById(R.id.inMessage);
btnPassData.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SM.sendData(inData.getText().toString().trim());
}
});
}
interface SendMessage {
void sendData(String message);
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
try {
SM = (SendMessage) getActivity();
} catch (ClassCastException e) {
throw new ClassCastException("Error in retrieving data. Please try again");
}
}
}
自定义接口SendMessage是在上面的onAttach方法中初始化的。
该接口将在我们即将看到的MainActivity.java中实现。
FragmentTwo.java类的代码如下。
package com.theitroad.passingdatabetweenfragments;
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;
public class FragmentTwo extends Fragment {
TextView txtData;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View rootView = inflater.inflate(
R.layout.fragment_two, container, false);
return rootView;
}
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
txtData = (TextView)view.findViewById(R.id.txtData);
}
protected void displayReceivedData(String message)
{
txtData.setText("Data received: "+message);
}
}
如下所示，将从MainActivity.java中自定义接口的方法内部的FragmentTwo.java实例上调用" displayReceivedData()"。
package com.theitroad.passingdatabetweenfragments;
import android.support.design.widget.TabLayout;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
public class MainActivity extends AppCompatActivity implements FragmentOne.SendMessage{
TabLayout tabLayout;
ViewPager viewPager;
ViewPagerAdapter viewPagerAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
viewPager = (ViewPager) findViewById(R.id.viewPager);
viewPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager());
viewPager.setAdapter(viewPagerAdapter);
tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(viewPager);
}
@Override
public void sendData(String message) {
String tag = "android:switcher:" + R.id.viewPager + ":" + 1;
FragmentTwo f = (FragmentTwo) getSupportFragmentManager().findFragmentByTag(tag);
f.displayReceivedData(message);
}
}
一旦按下FragmentOne中的Button，就会触发上述代码中的sendData()方法。
我们使用findFragmentByTag方法获取在ViewPagerAdapter中已经初始化的FragmentTwo。
