正在试用测试应用，但遇到导入问题。代码可以编译，但我在模拟器中看不到任何东西。
Androidmanifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.nyctourguide" >
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme" >
<activity android:name=".MainActivity" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
管理“景点”标签的 AttractionsActivity 类
package com.example.nyctourguide;
import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
public class AttractionsActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
getSupportFragmentManager().beginTransaction()
.replace(R.id.container, new AttractionsFragment())
.commit();
}
}
与上述活动类相关联的AttractionsFragment
package com.example.nyctourguide;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
import androidx.fragment.app.Fragment;
import java.util.ArrayList;
/**
* A simple {@link Fragment} subclass.
* Use the {@link AttractionsFragment#newInstance} factory method to
* create an instance of this fragment.
*/
public class AttractionsFragment extends Fragment {
public AttractionsFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
// return inflater.inflate(R.layout.word_list, container, false);
View rootView = inflater.inflate(R.layout.site_list, container, false);
//create a list of sites
final ArrayList<Site> siteslist = new ArrayList<Site>();
//populate the siteslist with the sites to be shown
siteslist.add(new Site ("Empire State building","123 Main Street, NYC",R.drawable.color_green));
siteslist.add(new Site ("Statue of Liberty","13 Main Street, NYC",R.drawable.color_brown));
siteslist.add(new Site ("Bannon City Hall","133 Main Street, NYC",R.drawable.color_mustard_yellow));
siteslist.add(new Site ("Brookyln Bridge","13 Main Street, NYC",R.drawable.color_gray));
siteslist.add(new Site ("Staten Island","163 Main Street, NYC",R.drawable.color_white));
siteslist.add(new Site ("Manhattan Bridge","133 Main Street, NYC",R.drawable.color_green));
siteslist.add(new Site ("Chrysler Building","113 Main Street, NYC",R.drawable.color_dusty_yellow));
siteslist.add(new Site ("Daimler Building","3 Main Street, NYC",R.drawable.color_brown));
siteslist.add(new Site ("Rockefeller Center","15 Main Street, NYC",R.drawable.color_green));
// view recycling with adaptor
SiteAdapter adaptor = new SiteAdapter(getActivity(), siteslist, R.color.category_attractions);
ListView listView = (ListView) rootView.findViewById(R.id.list);
listView.setAdapter(adaptor);
//return the entire root view
return rootView;
}
}
主要活动
package com.example.nyctourguide;
import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager.widget.ViewPager;
import com.google.android.material.tabs.TabLayout;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Set the content of the activity to use the activity_main.xml layout file
setContentView(R.layout.activity_main);
// Find the view pager that will allow the user to swipe between fragments
ViewPager viewPager = (ViewPager) findViewById(R.id.viewpager);
// Create an adapter that knows which fragment should be shown on each page
SimpleFragmentPagerAdapter adapter = new SimpleFragmentPagerAdapter(this,getSupportFragmentManager());
// Set the adapter onto the view pager
viewPager.setAdapter(adapter);
// Find the tab layout that shows the tabs - 7/28
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
// Connect the tab layout with the view pager. This will
// 1. Update the tab layout when the view pager is swiped
// 2. Update the view pager when a tab is selected
// 3. Set the tab layout's tab names with the view pager's adapter's titles
// by calling onPageTitle()
tabLayout.setupWithViewPager(viewPager);
}
}
简单片段适配器
package com.example.nyctourguide;
import android.content.Context;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentPagerAdapter;
//import android.support.design.widget.TabLayout;
//import androidx.fragment.app.FragmentPagerAdapter;
//import android.support.v4.app.FragmentManager;
//import android.support.v4.app.FragmentPagerAdapter;
/*Provides the appropriate {@link Fragment} for a view pager.*/
public class SimpleFragmentPagerAdapter extends FragmentPagerAdapter {
/** Context of the app */
private Context mContext;
//context is the context of the app
//fm is the fragment manager that will keep each fragment's state in the adapter across swipes.
public SimpleFragmentPagerAdapter(Context context, FragmentManager fm) {
super(fm);
mContext = context;
}
//Return the Fragment that should be displayed for the given page
@Override
public Fragment getItem(int position) {
if (position == 0) {
return new AttractionsFragment();
} else if (position == 1){
return new MuseumFragment();
} else if (position == 2){
return new ParksFragment();
} else {
return new RestaurantFragment();
}
}
//return the total number of pages
@Override
public int getCount() {
return 4;
}
//show the right tab layout name
@Override
public CharSequence getPageTitle(int position) {
if (position == 0){
return mContext.getString(R.string.category_attractions);
} else if (position == 1){
return mContext.getString(R.string.category_museums);
} else if (position == 2){
return mContext.getString(R.string.category_parks);
} else {
return mContext.getString(R.string.category_restaurants);
}
}
}
Activity_main.xml
<!-- Layout for the main screen -->
<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"
android:orientation="vertical">
<!-- added for tabbed layout -->
<android.support.design.widget.TabLayout
android:id="@+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<!-- added for viewpager -->
<android.support.v4.view.ViewPager
android:id="@+id/viewpager"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
Build.gradle（您可以在此处查看我在添加正确内容时的所有试验和错误）
plugins {
id 'com.android.application'
}
android {
compileSdkVersion 30
buildToolsVersion "30.0.3"
defaultConfig {
applicationId "com.example.nyctourguide"
minSdkVersion 16
targetSdkVersion 30
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
}
dependencies {
// implementation 'androidx.appcompat:appcompat:1.3.0' //original
implementation 'com.google.android.material:material:1.4.0' //original
// implementation 'androidx.constraintlayout:constraintlayout:2.0.4' //original
// implementation 'androidx.legacy:legacy-support-v4:1.0.0' //original
testImplementation 'junit:junit:4.+' //original
// androidTestImplementation 'androidx.test.ext:junit:1.1.3' //original
//androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0' //original
implementation 'com.android.support:appcompat-v7:28.0.0' //added
implementation 'com.android.support:support-v4:28.0.0' //added
implementation 'com.android.support:design:28.0.0'//added
implementation 'com.android.support:viewpager:28.0.0'//added
implementation 'com.android.support:design:26.0.+'//added
implementation 'com.android.support:design:23.3.0' //added
implementation "com.google.android.material:material:1.0.0" //added
//noinspection GradleCompatible,GradleCompatible
}
gradle.properties
# Project-wide Gradle settings.
# IDE (e.g. Android Studio) users:
# Gradle settings configured through the IDE *will override*
# any settings specified in this file.
# For more details on how to configure your build environment visit
# http://www.gradle.org/docs/current/userguide/build_environment.html
# Specifies the JVM arguments used for the daemon process.
# The setting is particularly useful for tweaking memory settings.
org.gradle.jvmargs=-Xmx2048m -Dfile.encoding=UTF-8
# When configured, Gradle will run in incubating parallel mode.
# This option should only be used with decoupled projects. More details, visit
# http://www.gradle.org/docs/current/userguide/multi_project_builds.html#sec:decoupled_projects
# org.gradle.parallel=true
# AndroidX package structure to make it clearer which packages are bundled with the
# Android operating system, and which are packaged with your app"s APK
# https://developer.android.com/topic/libraries/support-library/androidx-rn
android.useAndroidX=true
android.enableJetifier=true