如何在Android Studio（Java）中解析JSON为表格并仅选取部分内容？

Hey there! Let's walk through exactly how to fetch JSON data from a URL, parse it to extract only the parts you need, and display those selected fields in a table-like format in your Android Java app. Here's a step-by-step breakdown with code examples:

First, add these dependencies to your app-level build.gradle (Module level) to handle network calls, JSON parsing, and flexible table display:

dependencies {
    // For reliable network requests
    implementation 'com.squareup.okhttp3:okhttp:4.11.0'
    // For simplified JSON parsing (easier than native JSONObject)
    implementation 'com.google.code.gson:gson:2.10.1'
    // For RecyclerView (to build a responsive table)
    implementation 'androidx.recyclerview:recyclerview:1.3.2'
}

Don't forget to enable internet access in your AndroidManifest.xml:

<uses-permission android:name="android.permission.INTERNET" />

Network operations can't run on the main thread, so we'll use OkHttp's async enqueue method to handle this safely:

private void fetchJsonFromUrl(String targetUrl) {
    OkHttpClient client = new OkHttpClient();
    Request request = new Request.Builder()
            .url(targetUrl)
            .build();

    client.newCall(request).enqueue(new Callback() {
        @Override
        public void onFailure(Call call, IOException e) {
            e.printStackTrace();
            // Show error feedback to user (must run on UI thread)
            runOnUiThread(() -> 
                Toast.makeText(MainActivity.this, "Failed to load data", Toast.LENGTH_SHORT).show()
            );
        }

        @Override
        public void onResponse(Call call, Response response) throws IOException {
            if (response.isSuccessful() && response.body() != null) {
                String rawJson = response.body().string();
                // Parse and process the JSON, then update UI
                parseAndExtractNeededFields(rawJson);
            }
        }
    });
}

Let's assume your JSON structure looks like this (adjust to match your actual data):

{
  "employees": [
    {
      "id": 101,
      "name": "Alice Smith",
      "department": "Engineering",
      "email": "alice@company.com",
      "salary": 85000
    },
    {
      "id": 102,
      "name": "Bob Johnson",
      "department": "Marketing",
      "email": "bob@company.com",
      "salary": 72000
    }
  ]
}

Suppose you only need id, name, and department fields. First create a model class to hold this extracted data:

public class Employee {
    private int id;
    private String name;
    private String department;

    // Getters (required for Gson to map fields)
    public int getId() { return id; }
    public String getName() { return name; }
    public String getDepartment() { return department; }
}

Now parse the JSON and extract your target fields using Gson:

private void parseAndExtractNeededFields(String rawJson) {
    JsonObject rootObj = new JsonParser().parse(rawJson).getAsJsonObject();
    JsonArray employeesArray = rootObj.getAsJsonArray("employees");

    Gson gson = new Gson();
    List<Employee> filteredEmployees = new ArrayList<>();

    for (JsonElement element : employeesArray) {
        // Gson automatically ignores fields not present in our Employee class
        Employee employee = gson.fromJson(element, Employee.class);
        filteredEmployees.add(employee);
    }

    // Update UI with the filtered data (must run on main thread)
    runOnUiThread(() -> displayAsTable(filteredEmployees));
}

If you prefer using native JSONObject (no external library), here's an alternative approach:

private void parseWithNativeJson(String rawJson) throws JSONException {
    JSONObject rootObj = new JSONObject(rawJson);
    JSONArray employeesArray = rootObj.getJSONArray("employees");
    List<Employee> filteredEmployees = new ArrayList<>();

    for (int i = 0; i < employeesArray.length(); i++) {
        JSONObject empObj = employeesArray.getJSONObject(i);
        Employee employee = new Employee();
        // Manually extract only the fields you need
        employee.setId(empObj.getInt("id"));
        employee.setName(empObj.getString("name"));
        employee.setDepartment(empObj.getString("department"));
        filteredEmployees.add(employee);
    }

    runOnUiThread(() -> displayAsTable(filteredEmployees));
}

We'll use RecyclerView with a grid layout to create a table-like view. First, create a row layout (item_table_row.xml):

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:padding="8dp"
    android:weightSum="3">

    <TextView
        android:id="@+id/tv_id"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:textSize="14sp"
        android:textStyle="bold"/>

    <TextView
        android:id="@+id/tv_name"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:textSize="14sp"/>

    <TextView
        android:id="@+id/tv_dept"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:textSize="14sp"/>

</LinearLayout>

Create a header layout (item_table_header.xml) for column titles:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:padding="8dp"
    android:weightSum="3"
    android:background="#f5f5f5">

    <TextView
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="ID"
        android:textSize="16sp"
        android:textStyle="bold"/>

    <TextView
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="Name"
        android:textSize="16sp"
        android:textStyle="bold"/>

    <TextView
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:text="Department"
        android:textSize="16sp"
        android:textStyle="bold"/>

</LinearLayout>

Now build the RecyclerView Adapter:

public class EmployeeTableAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
    private static final int VIEW_TYPE_HEADER = 0;
    private static final int VIEW_TYPE_ROW = 1;
    private List<Employee> employeeList;

    public EmployeeTableAdapter(List<Employee> employeeList) {
        this.employeeList = employeeList;
    }

    @Override
    public int getItemViewType(int position) {
        return position == 0 ? VIEW_TYPE_HEADER : VIEW_TYPE_ROW;
    }

    @NonNull
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        LayoutInflater inflater = LayoutInflater.from(parent.getContext());
        if (viewType == VIEW_TYPE_HEADER) {
            View view = inflater.inflate(R.layout.item_table_header, parent, false);
            return new HeaderViewHolder(view);
        } else {
            View view = inflater.inflate(R.layout.item_table_row, parent, false);
            return new RowViewHolder(view);
        }
    }

    @Override
    public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
        if (holder instanceof RowViewHolder) {
            Employee emp = employeeList.get(position - 1); // Skip header position
            RowViewHolder rowHolder = (RowViewHolder) holder;
            rowHolder.tvId.setText(String.valueOf(emp.getId()));
            rowHolder.tvName.setText(emp.getName());
            rowHolder.tvDept.setText(emp.getDepartment());
        }
    }

    @Override
    public int getItemCount() {
        return employeeList.size() + 1; // +1 for the header row
    }

    static class HeaderViewHolder extends RecyclerView.ViewHolder {
        public HeaderViewHolder(@NonNull View itemView) {
            super(itemView);
        }
    }

    static class RowViewHolder extends RecyclerView.ViewHolder {
        TextView tvId, tvName, tvDept;

        public RowViewHolder(@NonNull View itemView) {
            super(itemView);
            tvId = itemView.findViewById(R.id.tv_id);
            tvName = itemView.findViewById(R.id.tv_name);
            tvDept = itemView.findViewById(R.id.tv_dept);
        }
    }
}

Set up the RecyclerView in your Activity layout (activity_main.xml):

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recycler_table"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</LinearLayout>

Initialize the RecyclerView in your Activity:

private void displayAsTable(List<Employee> employeeList) {
    RecyclerView recyclerView = findViewById(R.id.recycler_table);
    // 3 columns to match our 3 fields
    GridLayoutManager layoutManager = new GridLayoutManager(this, 3);
    recyclerView.setLayoutManager(layoutManager);
    EmployeeTableAdapter adapter = new EmployeeTableAdapter(employeeList);
    recyclerView.setAdapter(adapter);
}

Finally, trigger the fetch process (e.g., in onCreate()):

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

• Add try-catch blocks around parsing logic to handle malformed JSON errors
• Adjust the model class and layout files to match your actual JSON structure and required fields
• For large datasets, consider adding pagination to keep the app responsive

内容的提问来源于stack exchange，提问作者Taylan Selvi