如何从 main activity 调用非静态方法到片段?

How to call a non-static method from the main activity to a fragment?

我在片段中的侦听器从主 activity 调用非静态方法时遇到问题。 Android studio 提供了一种使方法静态化的解决方案,但这会中断程序的运行。 具体来说,我有一个包含多个按钮的不同片段。按下按钮时,它会激活后台进程以向 Arduino Web 服务器发送消息。这意味着该方法不能静态才能工作。

主要Activity.

package com.example.ethernettest1;

import android.os.AsyncTask;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Button;
import android.widget.CompoundButton;
import android.widget.TextView;
import android.widget.ToggleButton;

import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager.widget.PagerAdapter;
import androidx.viewpager.widget.ViewPager;

import com.google.android.material.tabs.TabItem;
import com.google.android.material.tabs.TabLayout;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

import static android.view.View.*;

public class MainActivity extends AppCompatActivity {

    private TabLayout tabLayout;
    private ViewPager viewPager;
    private TabItem tab1, tab2, tab3;
    public PagerAdapter pageradapter;
    int dayNumber = 0;
    int[] hourOpen = {0, 0, 0, 0, 0, 0, 0, 0};
    int[] minutesOpen = {0, 0, 0, 0, 0, 0, 0, 0};
    int[] hourClose = {0, 0, 0, 0, 0, 0, 0, 0};
    int[] minutesClose = {0, 0, 0, 0, 0, 0, 0, 0};

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        tabLayout = findViewById(R.id.tablayout);
        tab1 =  findViewById(R.id.Tab1);
        tab2 =  findViewById(R.id.Tab2);
        tab3 =  findViewById(R.id.Tab3);
        viewPager = findViewById(R.id.viewpager);

        pageradapter = new PageAdapter(getSupportFragmentManager(), tabLayout.getTabCount());
        viewPager.setAdapter(pageradapter);

        //noinspection deprecation
        tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                viewPager.setCurrentItem(tab.getPosition());
                if(tab.getPosition() == 0)
                {
                    pageradapter.notifyDataSetChanged();
                }
                else if (tab.getPosition() == 1)
                {
                    pageradapter.notifyDataSetChanged();
                }
                else if (tab.getPosition() == 2)
                {
                    pageradapter.notifyDataSetChanged();
                }
            }

            @Override
            public void onTabUnselected(TabLayout.Tab tab) {

            }

            @Override
            public void onTabReselected(TabLayout.Tab tab) {

            }
        });

        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        /*
        Handle action bar item clicks here. The action bar will
        automatically handle clicks on the Home/Up button, so long
        as you specify a parent activity in AndroidManifest.xml.
        */
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    /*****************************************************/
    /*  This is a background process for connecting      */
    /*   to the arduino server and sending               */
    /*    the GET request withe the added data           */
    /*****************************************************/

    public class Background_get extends AsyncTask<String, Void, String> {
        @Override
        protected String doInBackground(String... params) {
            try {
                URL url = new URL("http://rolluiksturing.ddns.net/?" + params[0]);
                HttpURLConnection connection = (HttpURLConnection) url.openConnection();

                BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
                StringBuilder result = new StringBuilder();
                String inputLine;
                while ((inputLine = in.readLine()) != null)
                    result.append(inputLine).append("\n");

                in.close();
                connection.disconnect();
                return result.toString();

            } catch (IOException e) {
                e.printStackTrace();
            }
            return null;
        }
    }

}

还有一个碎片

package com.example.ethernettest1;


import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.CompoundButton;
import android.widget.ToggleButton;

import androidx.fragment.app.Fragment;


/**
 * A simple {@link Fragment} subclass.
 */
public class tab1 extends Fragment {

    public tab1() {
        // Required empty public constructor
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        View view = inflater.inflate(R.layout.fragment_tab1, container, false);

        Button open = view.findViewById(R.id.open);
        Button sluit = view.findViewById(R.id.sluit);
        Button openAlles = view.findViewById(R.id.SelectAll);
        Button sluitAlles = view.findViewById(R.id.DeselectAll);
        Button naarBoven = view.findViewById(R.id.naarBoven);
        Button naarOnder = view.findViewById(R.id.naarOnder);
        ToggleButton Roluik1Button = view.findViewById(R.id.roluik1Button);
        ToggleButton Roluik2Button = view.findViewById(R.id.roluik2Button);
        ToggleButton Roluik3Button =  view.findViewById(R.id.roluik3Button);

        open.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                if (event.getAction() == MotionEvent.ACTION_DOWN)
                    new MainActivity.Background_get().execute("Open");
                else if (event.getAction() == MotionEvent.ACTION_UP) {
                    // Do nothing
                }
                return true;
            }
        });

        sluit.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                if (event.getAction() == MotionEvent.ACTION_DOWN) {
                    new MainActivity.Background_get().execute("Sluit");
                } else if (event.getAction() == MotionEvent.ACTION_UP) {
                    // Do nothing
                }
                return true;
            }
        });

        openAlles.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                if (event.getAction() == MotionEvent.ACTION_DOWN) {
                    new MainActivity.Background_get().execute("OpenAlles");
                } else if (event.getAction() == MotionEvent.ACTION_UP) {
                    // Do nothing
                }
                return true;
            }
        });

        sluitAlles.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                if (event.getAction() == MotionEvent.ACTION_DOWN) {
                    new MainActivity.Background_get().execute("SluitAlles");
                } else if (event.getAction() == MotionEvent.ACTION_UP) {
                    // Do nothing
                }
                return true;
            }
        });

        naarBoven.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                if (event.getAction() == MotionEvent.ACTION_DOWN) {
                    new MainActivity.Background_get().execute("GaNaarBoven");
                } else if (event.getAction() == MotionEvent.ACTION_UP) {
                    new MainActivity.Background_get().execute("stop");
                }
                return true;
            }
        });

        naarOnder.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                if (event.getAction() == MotionEvent.ACTION_DOWN) {
                    new MainActivity.Background_get().execute("GaNaarBeneden");
                } else if (event.getAction() == MotionEvent.ACTION_UP) {
                    new MainActivity.Background_get().execute("stop");
                }
                return true;
            }
        });

        Roluik1Button.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                if(isChecked) {
                    new MainActivity.Background_get().execute("Zet1InArray");
                } else {
                    new MainActivity.Background_get().execute("Zet1UitArray");
                }
            }
        });

        Roluik2Button.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                if(isChecked) {
                    new MainActivity.Background_get().execute("Zet2InArray");
                } else {
                    new MainActivity.Background_get().execute("Zet2UitArray");
                }
            }
        });

        Roluik3Button.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                if(isChecked) {
                    new MainActivity.Background_get().execute("Zet3InArray");
                } else {
                    new MainActivity.Background_get().execute("Zet3UitArray");
                }
            }
        });

        return inflater.inflate(R.layout.fragment_tab1, container, false);
    }
}

好几篇文章都给出了与我需要的相反的答案,所以我希望有人能给我一个明确的答案。

您可以做的一件事是向您的 MainActivity 添加一个方法,如下所示

//note the following method
public void runBackgroundGet(String... params){
    new Background_get().execute(params);
}

并让您的片段按如下方式调用它:

        Roluik3Button.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                if(isChecked) {
                    (MainAticity(getActivity()).runBackgroundGet("Zet3InArray");
                } else {
                    MainAticity(getActivity()).runBackgroundGet("Zet3UitArray");
                }
            }
        });

但我必须警告你,使用 AsyncTask 会导致很多问题和泄漏,而且它们很快就会被标记为已弃用。我建议尝试使用视图模型和 Kotlin 协程来替换 AsyncTask。

:)