Android Studio：保存水平进度条状态并在Fragment与Activity间传递

MainActivity（无ProgressBar） #

@Override
public void onClick(View view) {
    switch (view.getId()){
        case R.id.submitBttn:
            if (questionTwo.getText().toString().isEmpty() & questionFour.getText().toString().isEmpty() & questionFive.getText().toString().isEmpty()){
                questionTwo.setError("You haven't completed this question!");
                questionFour.setError("You haven't completed this question!");
                questionFive.setError("You haven't completed this question!");
            }else{
                if (questionOne.isChecked() & questionThree.isChecked()){
                    startActivity(new Intent(getApplicationContext(),HomeActivity.class));
                    Toast.makeText(this, "Received Report", Toast.LENGTH_SHORT).show();
                }else{
                    Toast.makeText(this, "The question is not fully answered.", Toast.LENGTH_SHORT).show();
                }
            }
    }
}

Fragment（含ProgressBar） #

progressBar = view.findViewById(R.id.progressBar);
startProgress = view.findViewById(R.id.addProgress);

startProgress.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        startActivity(new Intent(getActivity(),ReportQuestion.class));
    }
});

起始页面是带有水平进度条的Fragment，点击按钮跳转到无进度条的MainActivity。需实现：

• 保存水平进度条的状态
• 点击MainActivity中的按钮时增加进度条进度
• 实现进度条状态在Fragment与Activity之间的传递

方案一：用SharedPreferences持久化进度（适合重启APP后保留进度） #

1. Fragment中初始化并读取进度

修改Fragment的onViewCreated方法，读取已保存的进度值：

@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    progressBar = view.findViewById(R.id.progressBar);
    startProgress = view.findViewById(R.id.addProgress);

    // 读取本地保存的进度，默认0
    SharedPreferences sp = requireActivity().getSharedPreferences("ProgressPrefs", Context.MODE_PRIVATE);
    int savedProgress = sp.getInt("current_progress", 0);
    progressBar.setProgress(savedProgress);

    startProgress.setOnClickListener(v -> {
        startActivity(new Intent(getActivity(), MainActivity.class));
    });
}

2. MainActivity中更新并保存进度

修改MainActivity的点击事件，在提交成功后更新进度：

@Override
public void onClick(View view) {
    switch (view.getId()){
        case R.id.submitBttn:
            if (questionTwo.getText().toString().isEmpty() && questionFour.getText().toString().isEmpty() && questionFive.getText().toString().isEmpty()){
                questionTwo.setError("你还没完成这道题！");
                questionFour.setError("你还没完成这道题！");
                questionFive.setError("你还没完成这道题！");
            }else{
                if (questionOne.isChecked() && questionThree.isChecked()){
                    // 更新进度，每次加20（可根据需求调整）
                    SharedPreferences sp = getSharedPreferences("ProgressPrefs", MODE_PRIVATE);
                    int currentProgress = sp.getInt("current_progress", 0);
                    int newProgress = Math.min(currentProgress + 20, 100); // 进度不超过100
                    sp.edit().putInt("current_progress", newProgress).apply();

                    startActivity(new Intent(getApplicationContext(), HomeActivity.class));
                    Toast.makeText(this, "已收到报告", Toast.LENGTH_SHORT).show();
                }else{
                    Toast.makeText(this, "题目未完全作答。", Toast.LENGTH_SHORT).show();
                }
            }
    }
}

3. 返回Fragment时刷新进度

在Fragment的onResume方法中重新读取进度，确保返回时显示最新状态：

@Override
public void onResume() {
    super.onResume();
    SharedPreferences sp = requireActivity().getSharedPreferences("ProgressPrefs", Context.MODE_PRIVATE);
    int savedProgress = sp.getInt("current_progress", 0);
    progressBar.setProgress(savedProgress);
}

方案二：用ViewModel共享实时进度（适合临时状态同步，无需持久化） #

如果不需要重启APP保留进度，可通过ViewModel实现组件间实时状态共享：

1. 创建共享ViewModel

public class ProgressViewModel extends ViewModel {
    private MutableLiveData<Integer> progressLiveData = new MutableLiveData<>(0);

    // 设置进度，确保不超过100
    public void setProgress(int progress) {
        progressLiveData.setValue(Math.min(progress, 100));
    }

    // 增加指定进度值
    public void addProgress(int addValue) {
        int current = progressLiveData.getValue() != null ? progressLiveData.getValue() : 0;
        setProgress(current + addValue);
    }

    // 提供进度观察入口
    public LiveData<Integer> getProgressLiveData() {
        return progressLiveData;
    }
}

2. Fragment中观察进度变化

@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    progressBar = view.findViewById(R.id.progressBar);
    startProgress = view.findViewById(R.id.addProgress);

    ProgressViewModel viewModel = new ViewModelProvider(requireActivity()).get(ProgressViewModel.class);
    // 观察进度变化，实时更新进度条
    viewModel.getProgressLiveData().observe(getViewLifecycleOwner(), progress -> {
        progressBar.setProgress(progress);
    });

    startProgress.setOnClickListener(v -> {
        startActivity(new Intent(getActivity(), MainActivity.class));
    });
}

3. MainActivity中更新进度

@Override
public void onClick(View view) {
    switch (view.getId()){
        case R.id.submitBttn:
            if (questionTwo.getText().toString().isEmpty() && questionFour.getText().toString().isEmpty() && questionFive.getText().toString().isEmpty()){
                questionTwo.setError("你还没完成这道题！");
                questionFour.setError("你还没完成这道题！");
                questionFive.setError("你还没完成这道题！");
            }else{
                if (questionOne.isChecked() && questionThree.isChecked()){
                    ProgressViewModel viewModel = new ViewModelProvider(this).get(ProgressViewModel.class);
                    viewModel.addProgress(20); // 增加进度

                    startActivity(new Intent(getApplicationContext(), HomeActivity.class));
                    Toast.makeText(this, "已收到报告", Toast.LENGTH_SHORT).show();
                }else{
                    Toast.makeText(this, "题目未完全作答。", Toast.LENGTH_SHORT).show();
                }
            }
    }
}

补充说明 #

• 若需要重启APP后仍保留进度，可结合两种方案：在ViewModel初始化时读取SharedPreferences的进度值，更新时同时保存到SharedPreferences。
• 进度增量可根据实际业务调整，比如按任务完成比例计算。

内容的提问来源于stack exchange，提问作者Mohamed Danysh Rozaily