Android 开发 - FragmentPagerAdapter、Pair、ClipboardManager、PopupWindow

FragmentPagerAdapter

1、基本介绍

FragmentPagerAdapter 是 Android 中用于 ViewPager 与 Fragment 结合使用的适配器类

2、演示

（1）Fragment Layout

fragment_home.xml

xml 复制代码

<?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">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="首页页面"
        android:textSize="24sp" />
</LinearLayout>

fragment_discover.xml

xml 复制代码

<?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">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="发现页面"
        android:textSize="24sp" />
</LinearLayout>

fragment_profile.xml

xml 复制代码

<?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">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="个人页面"
        android:textSize="24sp" />
</LinearLayout>

（2）Fragment Code

HomeFragment.java

java 复制代码

public class HomeFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_home, container, false);
    }
}

DiscoverFragment.java

java 复制代码

public class DiscoverFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_discover, container, false);
    }
}

ProfileFragment.java

java 复制代码

public class ProfileFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_profile, container, false);
    }
}

（3）Adapter

MyViewPagerAdapter.java

java 复制代码

public class MyViewPagerAdapter extends FragmentPagerAdapter {

    private List<Fragment> fragments;

    public MyViewPagerAdapter(@NonNull FragmentManager fm, List<Fragment> fragments) {
        super(fm);

        this.fragments = fragments;
    }

    @NonNull
    @Override
    public Fragment getItem(int position) {
        if (fragments == null) return null;
        return fragments.get(position);
    }

    @Override
    public int getCount() {
        return fragments == null ? 0 : fragments.size();
    }
}

（4）Activity Layout

activity_fragment_pager_adapter_test.xml

xml 复制代码

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".FragmentPagerAdapterTestActivity">

    <androidx.viewpager.widget.ViewPager
        android:id="@+id/vp_content"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />

    <View
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:background="@color/black" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:orientation="horizontal">

        <TextView
            android:id="@+id/tv_home"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:gravity="center"
            android:text="首页"
            android:textSize="18sp" />

        <View
            android:layout_width="1dp"
            android:layout_height="match_parent"
            android:background="@color/black" />

        <TextView
            android:id="@+id/tv_discover"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:gravity="center"
            android:text="发现"
            android:textSize="18sp" />

        <View
            android:layout_width="1dp"
            android:layout_height="match_parent"
            android:background="@color/black" />

        <TextView
            android:id="@+id/tv_profile"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:gravity="center"
            android:text="我的"
            android:textSize="18sp" />
    </LinearLayout>
</LinearLayout>

（5）Activity Code

FragmentPagerAdapterTestActivity.java

java 复制代码

public class FragmentPagerAdapterTestActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        EdgeToEdge.enable(this);
        setContentView(R.layout.activity_fragment_pager_adapter_test);
        ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main), (v, insets) -> {
            Insets systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars());
            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);
            return insets;
        });

        test();
    }

    private void test() {
        ViewPager vpContent = findViewById(R.id.vp_content);
        TextView tvHome = findViewById(R.id.tv_home);
        TextView tvDiscover = findViewById(R.id.tv_discover);
        TextView tvProfile = findViewById(R.id.tv_profile);

        List<Fragment> fragments = new ArrayList<>();
        fragments.add(new HomeFragment());
        fragments.add(new DiscoverFragment());
        fragments.add(new ProfileFragment());

        MyViewPagerAdapter myViewPagerAdapter = new MyViewPagerAdapter(getSupportFragmentManager(), fragments);
        vpContent.setAdapter(myViewPagerAdapter);

        tvHome.setOnClickListener(v -> {
            tvHome.setTextColor(0xFF0000FF);
            tvDiscover.setTextColor(0xFF000000);
            tvProfile.setTextColor(0xFF000000);
            vpContent.setCurrentItem(0);
        });
        tvDiscover.setOnClickListener(v -> {
            tvDiscover.setTextColor(0xFF0000FF);
            tvHome.setTextColor(0xFF000000);
            tvProfile.setTextColor(0xFF000000);
            vpContent.setCurrentItem(1);
        });
        tvProfile.setOnClickListener(v -> {
            tvProfile.setTextColor(0xFF0000FF);
            tvHome.setTextColor(0xFF000000);
            tvDiscover.setTextColor(0xFF000000);
            vpContent.setCurrentItem(2);
        });

        tvHome.setTextColor(0xFF0000FF);
        tvDiscover.setTextColor(0xFF000000);
        tvProfile.setTextColor(0xFF000000);
        vpContent.setCurrentItem(0);
    }
}

Pair

1、基本介绍

android.util.Pair 是 Android 提供的一个简单的数据容器类，它用于存储两个相关联的对象，一对键值或两个相关值，类似于 Java 中的 Map.Entry

2、演示

创建 Pair

java 复制代码

Pair<String, Integer> userAge = new Pair<>("张三", 25);
Pair<Integer, String> errorCode = Pair.create(404, "Not Found");

Log.i(TAG, userAge.toString());
Log.i(TAG, errorCode.toString());

复制代码

# 输出结果

Pair{张三 25}
Pair{404 Not Found}

访问 Pair

java 复制代码

Pair<String, Integer> userAge = new Pair<>("张三", 25);

String name = userAge.first;
int age = userAge.second;

ClipboardManager

1、基本介绍

ClipboardManager 是 Android 系统中管理剪贴板操作的类，负责应用程序之间和内部的文本、图像、URI 等数据的复制粘贴功能

2、演示

（1）Activity Layout

xml 复制代码

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ClipboardTestActivity">

    <Button
        android:id="@+id/btn_copy"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="复制"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/btn_read"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="读取"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btn_copy" />
</androidx.constraintlayout.widget.ConstraintLayout>

（2）Activity Code

java 复制代码

Button btnCopy = findViewById(R.id.btn_copy);
Button btnRead = findViewById(R.id.btn_read);

btnCopy.setOnClickListener(v -> {
    ClipboardManager clipboardManager = getSystemService(ClipboardManager.class);
    ClipData clipData = ClipData.newPlainText("text", "hello clipboard");
    clipboardManager.setPrimaryClip(clipData);
});

btnRead.setOnClickListener(v -> {
    ClipboardManager clipboardManager = getSystemService(ClipboardManager.class);
    if (clipboardManager.hasPrimaryClip()) {
        ClipData clipData = clipboardManager.getPrimaryClip();
        if (clipData != null && clipData.getItemCount() > 0) {
            CharSequence text = clipData.getItemAt(0).getText();
            if (text != null) {
                Toast.makeText(this, "读取到的文本为：" + text, Toast.LENGTH_SHORT).show();
            }
        }
    }
});

PopupWindow

1、基本介绍

PopupWindow 是 Android 中用于在任意位置显示弹出窗口的组件，类似于对话框但更灵活

2、演示

（1）PopupWindow Layout

popup_layout.xml

xml 复制代码

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:background="@drawable/popup_background"
    android:orientation="vertical"
    android:padding="16dp">

    <TextView
        android:id="@+id/tv_title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="提示"
        android:textSize="18sp"
        android:textStyle="bold" />

    <TextView
        android:id="@+id/tv_message"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:text="这是一个弹出窗口" />

    <Button
        android:id="@+id/btn_confirm"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:text="确定" />
</LinearLayout>

popup_background.xml

xml 复制代码

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <solid android:color="@android:color/white" />
    <corners android:radius="8dp" />
    <stroke
        android:width="1dp"
        android:color="@android:color/darker_gray" />
</shape>

（2）Activity Layout

xml 复制代码

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".PopupWindowTestActivity">

    <Button
        android:id="@+id/btn_open"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="打开"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

（3）Activity Code

java 复制代码

View popupView = LayoutInflater.from(this).inflate(R.layout.popup_layout, null);
PopupWindow popupWindow = new PopupWindow(popupView, ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
popupWindow.setOutsideTouchable(false);

Button btnConfirm = popupView.findViewById(R.id.btn_confirm);

btnConfirm.setOnClickListener(v -> {
    Toast.makeText(this, "点击了确认按钮", Toast.LENGTH_SHORT).show();
    popupWindow.dismiss();
});

Button btnOpen = findViewById(R.id.btn_open);

btnOpen.setOnClickListener(v -> {
    popupWindow.showAsDropDown(v);
});