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  附上前俩天写的口算测试的代码：

主界面：

package com.example.calculationtest;

import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import androidx.navigation.fragment.NavHostFragment;
import androidx.navigation.ui.NavigationUI;

import android.content.DialogInterface;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {
    NavController controller;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        NavHostFragment hostFragment=(NavHostFragment)getSupportFragmentManager().findFragmentById(R.id.fragmentContainerView);
        controller=hostFragment.getNavController();
        NavigationUI.setupActionBarWithNavController(this,controller);
    }

    @Override
    public boolean onSupportNavigateUp() {
        if (controller.getCurrentDestination().getId() == R.id.questionFragment) {
            AlertDialog.Builder builder = new AlertDialog.Builder(this);
            builder.setTitle(getString(R.string.quit_dialog_title));
            builder.setPositiveButton(R.string.dialog_positive_message, new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialogInterface, int i) {
                    controller.navigateUp();
                }
            });
            builder.setNegativeButton(R.string.dialog_negative_message, new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialogInterface, int i) {

                }
            });
            AlertDialog dialog = builder.create();
            dialog.show();
        } else {
            controller.navigate(R.id.titleFragment);
        }
        return super.onSupportNavigateUp();
    }

    @Override
    public void onBackPressed() {
        if(controller.getCurrentDestination().getId() == R.id.titleFragment) {
            android.os.Process.killProcess(android.os.Process.myPid());
        } else {
            onSupportNavigateUp();
        }
    }
}

欢迎界面：

package com.example.calculationtest;

import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.databinding.DataBindingUtil;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.SavedStateViewModelFactory;
import androidx.lifecycle.ViewModelProvider;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.example.calculationtest.databinding.FragmentTitleBinding;

/**
 * A simple {@link Fragment} subclass.
 * Use the {@link TitleFragment#newInstance} factory method to
 * create an instance of this fragment.
 */
public class TitleFragment extends Fragment {

    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

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

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment TitleFragment.
     */
    // TODO: Rename and change types and number of parameters
    public static TitleFragment newInstance(String param1, String param2) {
        TitleFragment fragment = new TitleFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        MyViewModel viewModel;
        viewModel = new ViewModelProvider(this,new SavedStateViewModelFactory(requireActivity().getApplication(),this)).get(MyViewModel.class);
        FragmentTitleBinding banding;
        banding = DataBindingUtil.inflate(inflater,R.layout.fragment_title,container,false);
        banding.setData(viewModel);
        banding.setLifecycleOwner(requireActivity());
        banding.button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                NavController controller= Navigation.findNavController(view);
                controller.navigate(R.id.action_titleFragment_to_questionFragment);
            }
        });
        return banding.getRoot();
        // Inflate the layout for this fragment
        //return inflater.inflate(R.layout.fragment_title, container, false);
    }
}

题目界面：

package com.example.calculationtest;

import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.databinding.DataBindingUtil;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.SavedStateHandle;
import androidx.lifecycle.SavedStateViewModelFactory;
import androidx.lifecycle.ViewModelProvider;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Switch;
import android.widget.Toast;

import com.example.calculationtest.databinding.FragmentQuestionBinding;

/**
 * A simple {@link Fragment} subclass.
 * Use the {@link QuestionFragment#newInstance} factory method to
 * create an instance of this fragment.
 */
public class QuestionFragment extends Fragment {

    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

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

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment QuestionFragment.
     */
    // TODO: Rename and change types and number of parameters
    public static QuestionFragment newInstance(String param1, String param2) {
        QuestionFragment fragment = new QuestionFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        Bundle bundle = new Bundle();
        MyViewModel viewModel;
        viewModel = new ViewModelProvider(this,new SavedStateViewModelFactory(requireActivity().getApplication(),this)).get(MyViewModel.class);
        viewModel.generator();
        FragmentQuestionBinding binding;
        binding = DataBindingUtil.inflate(inflater,R.layout.fragment_question,container,false);
        binding.setData(viewModel);
        binding.setLifecycleOwner(requireActivity());
        viewModel.getCurrentScore().setValue(0);
        StringBuilder builder = new StringBuilder();
        View.OnClickListener listener = new View.OnClickListener() {
            public void onClick(View v) {
                switch (v.getId()) {
                    case R.id.button0:
                        builder.append("0");
                        break;
                    case R.id.button1:
                        builder.append("1");
                        break;
                    case R.id.button2:
                        builder.append("2");
                        break;
                    case R.id.button3:
                        builder.append("3");
                        break;
                    case R.id.button4:
                        builder.append("4");
                        break;
                    case R.id.button5:
                        builder.append("5");
                        break;
                    case R.id.button6:
                        builder.append("6");
                        break;
                    case R.id.button7:
                        builder.append("7");
                        break;
                    case R.id.button8:
                        builder.append("8");
                        break;
                    case R.id.button9:
                        builder.append("9");
                        break;
                    case R.id.buttonclera:
                        builder.setLength(0);
                        break;
                }
            if (builder.length() == 0) {
                binding.textView9.setText(getString(R.string.question_input_answer));
            } else {
                binding.textView9.setText(builder.toString());
            }
            }
        };
        binding.button0.setOnClickListener(listener);
        binding.button1.setOnClickListener(listener);
        binding.button2.setOnClickListener(listener);
        binding.button3.setOnClickListener(listener);
        binding.button4.setOnClickListener(listener);
        binding.button5.setOnClickListener(listener);
        binding.button6.setOnClickListener(listener);
        binding.button7.setOnClickListener(listener);
        binding.button8.setOnClickListener(listener);
        binding.button9.setOnClickListener(listener);
        binding.buttonclera.setOnClickListener(listener);

        binding.buttonfix.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(builder.length() != 0) {
                if(Integer.valueOf(builder.toString()).intValue() == viewModel.getAnswer().getValue()) {
                    viewModel.answerCorrect();
                    builder.setLength(0);
                    binding.textView9.setText(R.string.answer_correct_message);

                } else {
                    NavController controller= Navigation.findNavController(view);
                    if(viewModel.win_flag) {
                        controller.navigate(R.id.action_questionFragment_to_winFragment);
                        viewModel.win_flag = false;
                        viewModel.save();
                    } else {
                        String score = String.valueOf(viewModel.getCurrentScore().getValue());
                        bundle.putString("SCORE",score);
                        controller.navigate(R.id.action_questionFragment_to_loseFragment,bundle);
                    }
                }
            } else {
                    Toast.makeText(getActivity(),"请输入答案",Toast.LENGTH_SHORT).show();

                }
            }
        });
        return binding.getRoot();
        // Inflate the layout for this fragment
        //return inflater.inflate(R.layout.fragment_question, container, false);
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

    }
}

成功界面：

package com.example.calculationtest;

import android.os.Bundle;

import androidx.databinding.DataBindingUtil;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.SavedStateViewModelFactory;
import androidx.lifecycle.ViewModelProvider;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.example.calculationtest.databinding.FragmentWinBinding;

/**
 * A simple {@link Fragment} subclass.
 * Use the {@link WinFragment#newInstance} factory method to
 * create an instance of this fragment.
 */
public class WinFragment extends Fragment {

    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

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

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment WinFragment.
     */
    // TODO: Rename and change types and number of parameters
    public static WinFragment newInstance(String param1, String param2) {
        WinFragment fragment = new WinFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        MyViewModel viewModel;
        viewModel = new ViewModelProvider(this,new SavedStateViewModelFactory(requireActivity().getApplication(),this)).get(MyViewModel.class);
        FragmentWinBinding binding;
        binding = DataBindingUtil.inflate(inflater,R.layout.fragment_win,container,false);
        binding.setData(viewModel);
        binding.setLifecycleOwner(requireActivity());
        binding.button11.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                NavController controller = Navigation.findNavController(view);
                controller.navigate(R.id.action_winFragment_to_titleFragment);
            }
        });
        return binding.getRoot();
        // Inflate the layout for this fragment
        //return inflater.inflate(R.layout.fragment_win, container, false);
    }
}

失败界面：

package com.example.calculationtest;

import android.os.Bundle;

import androidx.databinding.DataBindingUtil;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.SavedStateViewModelFactory;
import androidx.lifecycle.ViewModelProvider;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.example.calculationtest.databinding.FragmentLoseBinding;

/**
 * A simple {@link Fragment} subclass.
 * Use the {@link LoseFragment#newInstance} factory method to
 * create an instance of this fragment.
 */
public class LoseFragment extends Fragment {

    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

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

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment LoseFragment.
     */
    // TODO: Rename and change types and number of parameters
    public static LoseFragment newInstance(String param1, String param2) {
        LoseFragment fragment = new LoseFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        String score = getArguments().getString("SCORE");
        MyViewModel viewModel;
        viewModel = new ViewModelProvider(this,new SavedStateViewModelFactory(requireActivity().getApplication(),this)).get(MyViewModel.class);
        FragmentLoseBinding binding;
        binding = DataBindingUtil.inflate(inflater,R.layout.fragment_lose,container,false);
        binding.setData(viewModel);
        binding.setLifecycleOwner(requireActivity());
        binding.textView11.setText("你的得分："+score);
        binding.button10.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                NavController controller=Navigation.findNavController(view);
                controller.navigate(R.id.action_loseFragment_to_titleFragment);
            }
        });
        return binding.getRoot();
        // Inflate the layout for this fragment
        //return inflater.inflate(R.layout.fragment_lose, container, false);
    }
}

数据代码：

package com.example.calculationtest;

import android.app.Application;
import android.content.Context;
import android.content.SharedPreferences;

import androidx.annotation.NonNull;
import androidx.lifecycle.AndroidViewModel;
import androidx.lifecycle.MutableLiveData;
import androidx.lifecycle.SavedStateHandle;

import java.util.Random;

public class MyViewModel extends AndroidViewModel {
    private SavedStateHandle handle;
    private static String KEY_HIGH_SCORE = "key_high_score";
    private static String KEY_LEFT_NUMBER = "key_left_number";
    private static String KEY_RIGHT_NUMBER = "key_right_number";
    private static String KEY_OPERATOR = "key_operator";
    private static String KEY_ANSWER = "key_answer";
    private static String SAVE_SHP_DATA_NAME = "save_shp_data_name";
    private static String KEY_CURRENT_SCORE = "key_current_score";
    boolean win_flag = false;
    public MyViewModel(@NonNull Application application, SavedStateHandle handle) {
        super(application);
        if(!handle.contains(KEY_HIGH_SCORE)) {
            SharedPreferences shp=getApplication().getSharedPreferences(SAVE_SHP_DATA_NAME, Context.MODE_PRIVATE);
            handle.set(KEY_HIGH_SCORE,shp.getInt(KEY_HIGH_SCORE,0));
            handle.set(KEY_LEFT_NUMBER,0);
            handle.set(KEY_RIGHT_NUMBER,0);
            handle.set(KEY_OPERATOR,"+");
            handle.set(KEY_ANSWER,0);
            handle.set(KEY_CURRENT_SCORE,0);
        }
        this.handle=handle;
    }
    public MutableLiveData<Integer>getLeftNumber() {
            return handle.getLiveData(KEY_LEFT_NUMBER);
    }
    public MutableLiveData<Integer>getRightNumber() {
        return handle.getLiveData(KEY_RIGHT_NUMBER);
    }
    public MutableLiveData<String>getOperator() {
        return handle.getLiveData(KEY_OPERATOR);
    }
    public MutableLiveData<Integer>getHighScore() {
        return handle.getLiveData(KEY_HIGH_SCORE);
    }
    public MutableLiveData<Integer>getCurrentScore() {
        return handle.getLiveData(KEY_CURRENT_SCORE);
    }
    public MutableLiveData<Integer>getAnswer() {
        return handle.getLiveData(KEY_ANSWER);
    }
    void generator() {
        int LEVEL = 100;
        Random random = new Random();
        int x,y;
        x = random.nextInt(LEVEL) + 1;
        y = random.nextInt(LEVEL) + 1;
        if (x%2==0) {
            getOperator().setValue("+");
            if(x>y) {
                getAnswer().setValue(x);
                getLeftNumber().setValue(y);
                getRightNumber().setValue(x - y);
            }else {
                getAnswer().setValue(y);
                getLeftNumber().setValue(x);
                getRightNumber().setValue(y - x);
            }
        }else {
            getOperator().setValue("-");
            if(x>y) {
                getAnswer().setValue(x - y);
                getLeftNumber().setValue(x);
                getRightNumber().setValue(y);
            }else {
                getAnswer().setValue(y - x);
                getLeftNumber().setValue(y);
                getRightNumber().setValue(x);
            }
        }
    }
    @SuppressWarnings("ConstantConditions")
    void save() {
        SharedPreferences shp=getApplication().getSharedPreferences(SAVE_SHP_DATA_NAME,Context.MODE_PRIVATE);
        SharedPreferences.Editor editor= shp.edit();
        editor.putInt(KEY_HIGH_SCORE,getHighScore().getValue());
        editor.commit();
    }

    @SuppressWarnings("ConstantConditions")
    void answerCorrect() {
        getCurrentScore().setValue(getCurrentScore().getValue() + 1);
        if(getCurrentScore().getValue()>getHighScore().getValue()) {
            getHighScore().setValue(getCurrentScore().getValue());
            win_flag = true;
        }
        generator();
    }
}