如何从我的 Activity 中调用我的 Fragment 的 TextView 和 Button？

我建议您有两种方法可以将数据更新到活动片段的文本视图。

1. 从Activity调用方法更新片段的文本视图（简单方式）

• 在 fragment 类中创建一个方法，以将数据更新到文本视图。updateData()
• 您可以在活动类中声明一个参数，并在向活动添加片段时分配给此参数。fragment
• 当您在活动中从 api 接收数据时，调用fragment.updateData()

fragment_layout.xml

<?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:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/temp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="16dp"
        android:text="TextView"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/hud"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="16dp"
        android:text="TextView"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/temp" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

home_activity.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <FrameLayout
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

FirstFragment.kt

class FirstFragment : Fragment(R.layout.fragment_layout) {

    private lateinit var temp: TextView
    private lateinit var hud: TextView

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        temp = view.findViewById(R.id.temp)
        hud = view.findViewById(R.id.hud)
    }

    fun setDataToView(data: WeatherResponse) {
        temp.text = data.temp
        hud.text = data.hud
    }
}

家活动.kt

class HomeActivity: AppCompatActivity() {

    private val fragment = FirstFragment()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.home_activity)

        addFragment()

        fragment.view?.findViewById<Button>(R.id.button2)?.setOnClickListener {
            getCurrentData()
        }


    }

    private fun addFragment(){
        val fm = supportFragmentManager
        fm.beginTransaction().replace(R.id.container, fragment, "FirstFragment").commit()
    }

    private fun getCurrentData(){
        //Your retrofit code in here. I only show code in onResponse()
        //.....
        @Override
        public void onResponse(@NonNull Call<WeatherResponse> call, @NonNull Response<WeatherResponse> response) {
            if (response.code() == 200) {
                fragment.setDataToView(response)
            }
        }

        //....
    }
}

2. 使用 ViewModel

• 创建一个带有 livedata 参数的 SharedViewModel 类。

• 在活动中，创建一个 SharedViewModel 参数，如下所示：onCreate()

  SharedViewModel viewModel = new SharedViewModel(this).get(SharedViewModel .class);

• 在 fragment 中，创建一个 SharedViewModel 参数，如下所示：onActivityCreated()

  SharedViewModel viewModel = new SharedViewModel(requireActivity()).get(SharedViewModel .class);

• 最后，Activity 和 Fragment 中具有相同的 ViewModel 实例，因为两者都使用活动上下文。当您从 api 接收数据时，在 activity 中更新您的 livedata 参数，fragment 也会接收 livedata 参数事件，然后您可以更新文本视图。onChanged

在设置片段中设置要更新的数据，然后调用 然后相应地更新视图。bundleargumentsnewInstance

从活动

   FirstFragment.newInstance("yourData","yourData");

在您的 Fragment 中

if (getArguments() != null) {
        mParam1 = getArguments().getString(ARG_PARAM1);
        mParam2 = getArguments().getString(ARG_PARAM2);
    }

有很多方法可以实现你要做的事情，我将使用 RxJava。

1. 添加您的项目：RxJava

implementation 'io.reactivex.rxjava3:rxandroid:3.0.0'

2. 创建一个 POJO 类来保存您的数据，然后以后可以使用总线传输这些数据RxJava

public class WeatherReport {

    private String time_zone;
    private String time_field;
    private String current_temp;
    private String current_output;
    private String rise_time;
    private String set_time;
    private String temp_out;
    private String Press_out;
    private String Humid_out;
    private String Ws_out;
    private String Visi_out;

    public String getCurrent_output() {
        return current_output;
    }

    public String getCurrent_temp() {
        return current_temp;
    }

    public String getHumid_out() {
        return Humid_out;
    }

    public String getPress_out() {
        return Press_out;
    }

    public String getRise_time() {
        return rise_time;
    }

    public String getSet_time() {
        return set_time;
    }

    public String getTemp_out() {
        return temp_out;
    }

    public String getTime_field() {
        return time_field;
    }

    public String getTime_zone() {
        return time_zone;
    }

    public String getVisi_out() {
        return Visi_out;
    }

    public String getWs_out() {
        return Ws_out;
    }

    public void setCurrent_output(String current_output) {
        this.current_output = current_output;
    }

    public void setCurrent_temp(String current_temp) {
        this.current_temp = current_temp;
    }

    public void setHumid_out(String humid_out) {
        Humid_out = humid_out;
    }

    public void setPress_out(String press_out) {
        Press_out = press_out;
    }

    public void setRise_time(String rise_time) {
        this.rise_time = rise_time;
    }

    public void setSet_time(String set_time) {
        this.set_time = set_time;
    }

    public void setTemp_out(String temp_out) {
        this.temp_out = temp_out;
    }

    public void setTime_field(String time_field) {
        this.time_field = time_field;
    }

    public void setTime_zone(String time_zone) {
        this.time_zone = time_zone;
    }

    public void setVisi_out(String visi_out) {
        Visi_out = visi_out;
    }

    public void setWs_out(String ws_out) {
        Ws_out = ws_out;
    }
}

3. 创建 RxJava 总线

import io.reactivex.rxjava3.subjects.BehaviorSubject;

public class RxJavaBus {

    private static final BehaviorSubject<WeatherReport> behaviorSubject
            = BehaviorSubject.create();


    public static BehaviorSubject<WeatherReport> getSubject() {
        return behaviorSubject;
    }

}

4. 现在，从您的活动（或从您想要传输数据的任何位置）使用如下：RxBus

WeatherReport weatherReport = new WeatherReport();
        
weatherReport.setCurrent_output("Some DATA");
weatherReport.setCurrent_temp("Some DATA");
weatherReport.setHumid_out("Some DATA");
weatherReport.setPress_out("Some DATA");
weatherReport.setRise_time("Some DATA");
weatherReport.setSet_time("Some DATA");
weatherReport.setTime_field("Some DATA");
weatherReport.setVisi_out("Some DATA");
weatherReport.setTemp_out("Some DATA");
weatherReport.setWs_out("Some DATA");
weatherReport.setTime_zone("some DATA");

RxJavaBus.getSubject().onNext(weatherReport);

5. 现在，您可以在片段（或您想要的任何位置）中接收数据，如下所示：

RxJavaBus.getSubject().subscribe(weatherReportFromActivity -> {

            weatherReportFromActivity.getCurrent_output();
            weatherReportFromActivity.getCurrent_temp();
            weatherReportFromActivity.getHumid_out();
            weatherReportFromActivity.getPress_out();
            weatherReportFromActivity.getRise_time();
            weatherReportFromActivity.getSet_time();
            weatherReportFromActivity.getWs_out();
            weatherReportFromActivity.getTime_zone();
            weatherReportFromActivity.getVisi_out();
            weatherReportFromActivity.getTime_field();
            weatherReportFromActivity.getTemp_out();
});

你收到一个 NullPointerException，因为返回 null。findViewById(R.id.button2)

• 您需要使用片段的视图作为根。调用使用活动的视图作为根 - 它正在搜索，它没有 button2。您可以使用 访问片段的版本，但是：activity.findViewById(...)activity_home.xmlfragment.getView().findViewById(R.id._)
• 您需要确保片段在生命周期中完成了其步骤。所以它必须被启动和充气。否则，该按钮将再次不存在。onCreateView()

您可以通过在片段生命周期中将其设置为回调来确保在正确的时间和视图中调用设置。

//This class can be anywhere - it can be global, private inner, anonymous
class SetupCallback extends FragmentLifeCycleCallback {
    @Override
    void onFragmentViewCreated(FragmentManager fm, Fragment f, View v, Bundle savedInstanceState) {
        ButtonView button = v.findViewById(R.id.button2);
        if(button != null) {    //This gets called for all fragments so check for null
            button.setOnClickListener(new OnClickListener {...});

        }

        //Repeat for any other elements in the view e.g.
        TextView someText = v.findViewById(R.id.someTextView);
        someText.setText(R.string.message);
    }
}

//In the activity setup - I usually put in onCreate()
SupportFragmentManager.supportFragmentManager = getSupportFragmentManager();
supportFragmentManager.registerFragmentLifecycleCallbacks(new SetupCallback());
//anonymous version:
//supportFragmentManager.registerFragmentLifecycleCallbacks(new FragmentLifecycleCallback() { /*contents of class*/ });

或者，您可以在 Activity 中初始化 Retrofit 和 Weather 服务，将它们与构造函数或捆绑包一起传递到片段中，然后使用它们来设置 .onClickListeneronCreateView()

RxJava 和 SharedView 方法是让侦听器卡在所有片段生命周期调用上的替代方案，而不是使用使片段更具响应性的替代架构。

这需要依赖关系。如果您使用的是 gradle，那将是：androidx.lifecycle.common

dependencies {
    implementation 'androidx.lifecycle:lifecycle-common:2.3.0-rc1'
}

创建一个类来获取改造客户端，如下所示

 class RetrofitClient {
    private Retrofit retrofit;
    private String BASE_URL = "";

    public ServiceAPI getRetrofitInstance() {
        if (retrofit == null) {
            retrofit = new Retrofit.Builder()
                    .baseUrl(BASE_URL)
                    .addConverterFactory(GsonConverterFactory.create())
                    .build();
        }
        return retrofit.create(WeatherService.class);
   }

现在你可以像这样在 fragment 中调用 api

WeatherService service = RetrofitClient().getRetrofitInstance()
    
    void getCurrentData() {
                  
                    Call<WeatherResponse> call = service.getCurrentWeatherData(lat, lon, AppId);
                    call.enqueue(new Callback<WeatherResponse>() {
                        @Override
                        public void onResponse(@NonNull Call<WeatherResponse> call, @NonNull Response<WeatherResponse> response) {
                            if (response.code() == 200) {
                                WeatherResponse weatherResponse = response.body();
                                assert weatherResponse != null;
    
                                assert response.body() != null;
                                time_zone.setText(response.body().getTimezone());
                                time_field.setText(response.body().getCurrent().getDt());
                                current_temp.setText(getString(R.string.blank, response.body().getCurrent().getTemp() + " ℃"));
                                current_output.setText(response.body().getCurrent().getWeather().get(0).getDescription());
                                rise_time.setText(getString(R.string.blank, response.body().getCurrent().getSunrise() + " AM"));
                                set_time.setText(getString(R.string.blank, response.body().getCurrent().getSunset() + " PM"));
                                temp_out.setText(getString(R.string.blank, response.body().getCurrent().getTemp() + " ℃"));
                                Press_out.setText(getString(R.string.blank, response.body().getCurrent().getPressure() + " hpa"));
                                Humid_out.setText(getString(R.string.blank, response.body().getCurrent().getHumidity() + " %"));
                                Ws_out.setText(getString(R.string.blank, response.body().getCurrent().getWindSpeed() + " Km/h"));
                                Visi_out.setText(getString(R.string.blank, response.body().getCurrent().getVisibility() + " m"));
                            }
                        }
    
                        @Override
                        public void onFailure(@NonNull Call<WeatherResponse> call, @NonNull Throwable t) {
                        }
                    });
                }
            });
        }