如何将 object（在这种情况下为 arraylist）从一个片段发送到 java（Android）中的另一个片段

Question

标题说明了一切。 我正在尝试发送一个 ArrayList，其中包含从一个片段到另一个片段的数据，然后切换并显示第二个片段（刚刚收到 ArrayList 的片段）。

这是我的 MainActivity.java：

package;

import android.os.Bundle;

import com.google.android.material.floatingactionbutton.FloatingActionButton;
import com.google.android.material.snackbar.Snackbar;

import android.view.View;

import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.ui.AppBarConfiguration;
import androidx.navigation.ui.NavigationUI;

import com.google.android.material.navigation.NavigationView;

import androidx.drawerlayout.widget.DrawerLayout;

import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;

import android.view.Menu;

public class MainActivity extends AppCompatActivity {

    private AppBarConfiguration mAppBarConfiguration;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        FloatingActionButton fab = findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });
        DrawerLayout drawer = findViewById(R.id.drawer_layout);
        NavigationView navigationView = findViewById(R.id.nav_view);
        // Passing each menu ID as a set of Ids because each menu should be considered as top level destinations.
        mAppBarConfiguration = new AppBarConfiguration.Builder(
                R.id.nav_home, R.id.nav_display)
                .setDrawerLayout(drawer)
                .build();
        NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
        NavigationUI.setupActionBarWithNavController(this, navController, mAppBarConfiguration);
        NavigationUI.setupWithNavController(navigationView, navController);
    }

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

    @Override
    public boolean onSupportNavigateUp() {
        NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);
        return NavigationUI.navigateUp(navController, mAppBarConfiguration) || super.onSupportNavigateUp();
    }
}

这是我的 HomeFragment.java （发送片段）：

package;

import android.annotation.SuppressLint;
import android.content.Intent;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import androidx.annotation.Nullable;
import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModelProviders;
import androidx.navigation.Navigation;

import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.firebase.ml.vision.FirebaseVision;
import com.google.firebase.ml.vision.common.FirebaseVisionImage;
import com.google.firebase.ml.vision.text.FirebaseVisionText;
import com.google.firebase.ml.vision.text.FirebaseVisionTextDetector;
import com.mvsolutions.snap.R;
import com.mvsolutions.snap.ui.display.DisplayFragment;

import java.io.File;
import java.util.ArrayList;
import java.util.List;
import java.util.zip.Inflater;

import static android.app.Activity.RESULT_OK;

public class HomeFragment extends Fragment {


    private HomeViewModel homeViewModel;

    private ImageView imageView;
    private Button captureImageButton, detectButton, pickButton;
    private Bitmap imageBitmap;
    private TextView capturedTextView;
    static final int REQUEST_IMAGE_CAPTURE = 1;
    private static final int RESULT_LOAD_IMAGE = 101;

    public View onCreateView(@NonNull final LayoutInflater inflater,
                             final ViewGroup container, Bundle savedInstanceState) {

        //View view = inflater.inflate(R.layout.fragment_home, container, false);
        View root = inflater.inflate(R.layout.fragment_home, container, false);

        detectButton = root.findViewById(R.id.action_homeFragment_to_displayFragment2);
        //detectButton.setOnClickListener((View.OnClickListener) this);

        //return view;

        homeViewModel = ViewModelProviders.of(this).get(HomeViewModel.class);

        //View v = inflater.inflate(R.layout.fragment_display, container, false);
        imageView = root.findViewById(R.id.home_image_view_img);
        capturedTextView = root.findViewById(R.id.home_text_view_txt);
        captureImageButton = root.findViewById(R.id.capture_image_btn);
        detectButton = root.findViewById(R.id.detect_text_btn);
        //pickButton = root.findViewById(R.id.pick_image_btn);



        captureImageButton.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                captureImage();
            }
        });
//        pickButton.setOnClickListener(new View.OnClickListener() {
//            @Override
//            public void onClick(View v) {
//                pickImage();
//            }
//        });
        detectButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                Navigation.findNavController(v).navigate(R.id.action_homeFragment_to_displayFragment2);

//                DisplayFragment displayFragment = new DisplayFragment();
//                FragmentManager fragmentManager =  getFragmentManager();
//                fragmentManager.beginTransaction()
//                        .replace(R.id.DisplayFragment, displayFragment, displayFragment.getTag())
//                        .commit();


                //detectTextFromImage();
            }
        });
        return root;
    }

    private void detectTextFromImage() {
        capturedTextView.setText("");
        FirebaseVisionImage firebaseVisionImage = FirebaseVisionImage.fromBitmap(imageBitmap);
        FirebaseVisionTextDetector visionTextDetector = FirebaseVision.getInstance().getVisionTextDetector();
        visionTextDetector.detectInImage(firebaseVisionImage).addOnSuccessListener(new OnSuccessListener<FirebaseVisionText>() {
            @Override
            public void onSuccess(FirebaseVisionText firebaseVisionText) {
                List<FirebaseVisionText.Block> textBlocks = firebaseVisionText.getBlocks();
                if (textBlocks.size() == 0) {
                    Toast.makeText(getContext(), "No Text Found", Toast.LENGTH_SHORT).show();
                } else {
                    for (FirebaseVisionText.Block block : textBlocks) {
                        String text = block.getText();
                        ArrayList textBlobs = new ArrayList();
                        textBlobs.add(text);
                        for(int i = 0; i < textBlobs.size(); i++) {
                            capturedTextView.setText(capturedTextView.getText() + ",  " + textBlobs.get(i));
                        }
//                        capturedTextView.setText(capturedTextView.getText() + " " + text);
                    }
                }
            }
        }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                Toast.makeText(getContext(), "Something went wrong", Toast.LENGTH_SHORT).show();
                Log.d("Error", e.getMessage());
            }
        });
    }

    private void pickImage() {
        Intent i = new Intent(
                Intent.ACTION_PICK, android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
        startActivityForResult(i, RESULT_LOAD_IMAGE);
    }

    private void captureImage() {
        Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
        if (takePictureIntent.resolveActivity(getActivity().getPackageManager()) != null) {
            startActivityForResult(takePictureIntent, REQUEST_IMAGE_CAPTURE);
        }
    }

    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == REQUEST_IMAGE_CAPTURE && resultCode == RESULT_OK) {
            Bundle extras = data.getExtras();
            imageBitmap = (Bitmap) extras.get("data");
            imageView.setImageBitmap(imageBitmap);
        }
//        else if (requestCode == RESULT_LOAD_IMAGE && resultCode == RESULT_OK && null != data) {
//            Uri imageUri = data.getData();
//            imageBitmap = MediaStore.Images.Media.decodeBitmap(this.);
//            imageView.setImageBitmap(imageBitmap);
//        }
    }
}

这是我的 DisplayFragment.java （接收片段）：

package com.mvsolutions.snap.ui.display;

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import androidx.annotation.Nullable;
import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModelProviders;

import com.mvsolutions.snap.R;

public class DisplayFragment extends Fragment {

    private DisplayViewModel DisplayViewModel;

    public View onCreateView(@NonNull LayoutInflater inflater,
                             ViewGroup container, Bundle savedInstanceState) {
        DisplayViewModel =
                ViewModelProviders.of(this).get(DisplayViewModel.class);
        View root = inflater.inflate(R.layout.fragment_display, container, false);
//        final TextView textView = root.findViewById(R.id.text_gallery);
        DisplayViewModel.getText().observe(this, new Observer<String>() {
            @Override
            public void onChanged(@Nullable String s) {

            }
        });
        return root;
    }
}

我目前正在使用导航片段 xml 文件将按钮从第一个片段切换到第二个片段，但我希望它也将数据发送到第二个片段。 我的两个问题是：

1. 是否可以一键将数据发送到第二个片段并切换到第二个片段？ 还是我必须把它分成两部分？
2. 如何将数据从第一个片段发送到第二个片段？

Answer 1

您正在使用 ViewModel，所以我认为最简单的方法是对两个片段使用相同的 ViewModel。 在 android 文档中，您可以找到一个在片段之间共享数据的示例

一个活动中的两个或多个片段需要相互通信是很常见的。 想象一下拆分视图（主-详细信息）片段的常见情况，其中您有一个片段，其中用户从列表中选择一个项目，另一个片段显示所选项目的内容。

public class SharedViewModel extends ViewModel {
    private final MutableLiveData<Item> selected = new MutableLiveData<Item>();

    public void select(Item item) {
        selected.setValue(item);
    }

    public LiveData<Item> getSelected() {
        return selected;
    }
}


public class MasterFragment extends Fragment {
    private SharedViewModel model;

    public void onViewCreated(@NonNull View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        model = new ViewModelProvider(requireActivity()).get(SharedViewModel.class);
        itemSelector.setOnClickListener(item -> {
            model.select(item);
        });
    }
}

public class DetailFragment extends Fragment {

    public void onViewCreated(@NonNull View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        SharedViewModel model = new ViewModelProvider(requireActivity()).get(SharedViewModel.class);
        model.getSelected().observe(getViewLifecycleOwner(), { item ->
           // Update the UI.
        });
    }
}

请注意，两个片段都检索包含它们的活动。 这样，当每个片段都获得ViewModelProvider时，它们会收到相同的SharedViewModel实例，该实例的作用域是这个活动。