class MainViewHolder extends RecyclerView.ViewHolder { private TextView tv_content; private TextView tvtime; private TextView tv_title; Button tv_delete; Button tv_pinglun; private ImageView image; public MainViewHolder(View itemView) { super(itemView); tv_content = itemView.findViewById(R.id.tv_content); tv_delete = itemView.findViewById(R.id.tv_delete); image = itemView.findViewById(R.id.image); tv_pinglun = itemView.findViewById(R.id.tv_pinglun); tvtime = itemView.findViewById(R.id.tvtime); tv_title = itemView.findViewById(R.id.tv_title); } }

这是一个 RecyclerView 的 ViewHolder 类，用于显示每个列表项的视图。它包含了一些子视图，如文本框、图像视图和按钮等。在构造函数中，通过调用findViewById()方法来获取每个子视图的引用，以便在代码中进一步操作和定制它们的属性和行为。例如，您可以使用tv_content.setText("Hello World")方法来设置文本框的文本内容。ViewHolder 是 RecyclerView 的重要组成部分，它可以帮助提高列表项显示的效率和性能。

相关问题

使用android studio编写个人理财要求提供登录界面给用户 3. 要求有界面让用户输入每天的收入和支出（包括但不限于以下字段：项目名称，金额，录入时间，类别(信用卡/现金) 4. 可以对某笔记录添加文字或者照片备注。 5. 支持按照每日，每月，每年进行统计、查询。 6. 以上内容要求记入SQLITE或者文件系统中，APP重启后不丢失。的代码

很抱歉，由于篇幅限制，无法提供完整的代码。但我可以提供一些思路和参考代码供您参考。

首先，您需要创建一个登录界面，可以使用 Android Studio 提供的模板来快速创建。登录界面需要提供用户名和密码输入框，以及登录按钮。在用户输入正确的用户名和密码后，可以跳转到主界面。

在主界面中，您需要创建一个收支记录列表，用于显示用户输入的收入和支出记录。您可以使用 RecyclerView 来实现列表，每个列表项需要包含项目名称、金额、录入时间和类别等信息。同时，您需要提供一个添加记录的按钮，点击后跳转到添加记录界面。

在添加记录界面中，您需要提供输入框让用户输入每天的收入和支出，以及选择类别（信用卡或现金），并且可以添加文字备注或者照片备注。添加记录界面需要提供一个保存按钮，点击后将记录保存到 SQLite 数据库或者文件系统中。

最后，您需要提供一个统计查询界面，用户可以选择按照每日、每月或每年进行统计查询。您可以使用 Android Studio 提供的图表库来实现图表展示。

以下是参考代码：

1. 创建登录界面

activity_login.xml

<LinearLayout
    ...
    android:orientation="vertical">

    <EditText
        ...
        android:id="@+id/etUsername"
        android:hint="用户名"/>

    <EditText
        ...
        android:id="@+id/etPassword"
        android:hint="密码"
        android:inputType="textPassword"/>

    <Button
        ...
        android:text="登录"
        android:onClick="onLoginButtonClick"/>

</LinearLayout>

LoginActivity.java

public class LoginActivity extends AppCompatActivity {

    private EditText etUsername;
    private EditText etPassword;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        etUsername = findViewById(R.id.etUsername);
        etPassword = findViewById(R.id.etPassword);
    }

    public void onLoginButtonClick(View view) {
        String username = etUsername.getText().toString();
        String password = etPassword.getText().toString();
        // TODO: 验证用户名和密码是否正确
        Intent intent = new Intent(this, MainActivity.class);
        startActivity(intent);
    }
}

2. 创建主界面和收支记录列表

activity_main.xml

<LinearLayout
    ...
    android:orientation="vertical">

    <Button
        ...
        android:text="添加记录"
        android:onClick="onAddRecordButtonClick"/>

    <androidx.recyclerview.widget.RecyclerView
        ...
        android:id="@+id/rvRecords"/>

</LinearLayout>

RecordAdapter.java

public class RecordAdapter extends RecyclerView.Adapter<RecordAdapter.RecordViewHolder> {

    private List<Record> recordList;

    public RecordAdapter(List<Record> recordList) {
        this.recordList = recordList;
    }

    @NonNull
    @Override
    public RecordViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_record, parent, false);
        return new RecordViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull RecordViewHolder holder, int position) {
        Record record = recordList.get(position);
        holder.tvName.setText(record.getName());
        holder.tvAmount.setText(String.format(Locale.getDefault(), "%.2f", record.getAmount()));
        holder.tvTime.setText(record.getTime());
        holder.tvType.setText(record.getType());
    }

    @Override
    public int getItemCount() {
        return recordList.size();
    }

    public static class RecordViewHolder extends RecyclerView.ViewHolder {

        public TextView tvName;
        public TextView tvAmount;
        public TextView tvTime;
        public TextView tvType;

        public RecordViewHolder(@NonNull View itemView) {
            super(itemView);
            tvName = itemView.findViewById(R.id.tvName);
            tvAmount = itemView.findViewById(R.id.tvAmount);
            tvTime = itemView.findViewById(R.id.tvTime);
            tvType = itemView.findViewById(R.id.tvType);
        }
    }
}

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private List<Record> recordList;
    private RecordAdapter recordAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        recordList = new ArrayList<>();
        recordAdapter = new RecordAdapter(recordList);
        RecyclerView rvRecords = findViewById(R.id.rvRecords);
        rvRecords.setLayoutManager(new LinearLayoutManager(this));
        rvRecords.setAdapter(recordAdapter);
    }

    public void onAddRecordButtonClick(View view) {
        Intent intent = new Intent(this, AddRecordActivity.class);
        startActivityForResult(intent, 1);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == 1 && resultCode == RESULT_OK && data != null) {
            Record record = data.getParcelableExtra("record");
            recordList.add(record);
            recordAdapter.notifyDataSetChanged();
        }
    }
}

3. 创建添加记录界面

activity_add_record.xml

<LinearLayout
    ...
    android:orientation="vertical">

    <EditText
        ...
        android:id="@+id/etName"
        android:hint="项目名称"/>

    <EditText
        ...
        android:id="@+id/etAmount"
        android:hint="金额"
        android:inputType="numberDecimal"/>

    <EditText
        ...
        android:id="@+id/etTime"
        android:hint="录入时间"/>

    <RadioGroup
        ...
        android:id="@+id/rgType">

        <RadioButton
            ...
            android:text="信用卡"/>

        <RadioButton
            ...
            android:text="现金"/>

    </RadioGroup>

    <Button
        ...
        android:text="添加备注"
        android:onClick="onAddRemarkButtonClick"/>

    <Button
        ...
        android:text="保存"
        android:onClick="onSaveButtonClick"/>

</LinearLayout>

AddRecordActivity.java

public class AddRecordActivity extends AppCompatActivity {

    private EditText etName;
    private EditText etAmount;
    private EditText etTime;
    private RadioGroup rgType;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_add_record);
        etName = findViewById(R.id.etName);
        etAmount = findViewById(R.id.etAmount);
        etTime = findViewById(R.id.etTime);
        rgType = findViewById(R.id.rgType);
    }

    public void onAddRemarkButtonClick(View view) {
        // TODO: 添加文字或者照片备注
    }

    public void onSaveButtonClick(View view) {
        String name = etName.getText().toString();
        double amount = Double.parseDouble(etAmount.getText().toString());
        String time = etTime.getText().toString();
        String type = rgType.getCheckedRadioButtonId() == R.id.rbCreditCard ? "信用卡" : "现金";
        Record record = new Record(name, amount, time, type);
        Intent intent = new Intent();
        intent.putExtra("record", record);
        setResult(RESULT_OK, intent);
        finish();
    }
}

4. 创建统计查询界面

activity_statistics.xml

<LinearLayout
    ...
    android:orientation="vertical">

    <RadioGroup
        ...
        android:id="@+id/rgTimeSpan">

        <RadioButton
            ...
            android:text="每日"/>

        <RadioButton
            ...
            android:text="每月"/>

        <RadioButton
            ...
            android:text="每年"/>

    </RadioGroup>

    <Button
        ...
        android:text="查询"
        android:onClick="onQueryButtonClick"/>

    <com.github.mikephil.charting.charts.BarChart
        ...
        android:id="@+id/chart"/>

</LinearLayout>

StatisticsActivity.java

public class StatisticsActivity extends AppCompatActivity {

    private BarChart chart;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_statistics);
        chart = findViewById(R.id.chart);
    }

    public void onQueryButtonClick(View view) {
        // TODO: 根据时间段统计查询
        List<BarEntry> entries = new ArrayList<>();
        entries.add(new BarEntry(1, 100));
        entries.add(new BarEntry(2, 200));
        entries.add(new BarEntry(3, 300));
        BarDataSet dataSet = new BarDataSet(entries, "统计结果");
        dataSet.setColors(ColorTemplate.COLORFUL_COLORS);
        BarData barData = new BarData(dataSet);
        chart.setData(barData);
        chart.invalidate();
    }
}

5. 创建 Record 实体类

public class Record implements Parcelable {

    private String name;
    private double amount;
    private String time;
    private String type;

    public Record(String name, double amount, String time, String type) {
        this.name = name;
        this.amount = amount;
        this.time = time;
        this.type = type;
    }

    protected Record(Parcel in) {
        name = in.readString();
        amount = in.readDouble();
        time = in.readString();
        type = in.readString();
    }

    public static final Creator<Record> CREATOR = new Creator<Record>() {
        @Override
        public Record createFromParcel(Parcel in) {
            return new Record(in);
        }

        @Override
        public Record[] newArray(int size) {
            return new Record[size];
        }
    };

    public String getName() {
        return name;
    }

    public double getAmount() {
        return amount;
    }

    public String getTime() {
        return time;
    }

    public String getType() {
        return type;
    }

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(name);
        dest.writeDouble(amount);
        dest.writeString(time);
        dest.writeString(type);
    }
}

6. 创建 SQLite 数据库

RecordDatabaseHelper.java

public class RecordDatabaseHelper extends SQLiteOpenHelper {

    public static final String DATABASE_NAME = "records.db";
    public static final int DATABASE_VERSION = 1;

    public static final String TABLE_NAME = "record";
    public static final String COLUMN_NAME = "name";
    public static final String COLUMN_AMOUNT = "amount";
    public static final String COLUMN_TIME = "time";
    public static final String COLUMN_TYPE = "type";

    public RecordDatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String createTableSql = "CREATE TABLE " + TABLE_NAME + " (" +
                "_id INTEGER PRIMARY KEY AUTOINCREMENT, " +
                COLUMN_NAME + " TEXT NOT NULL, " +
                COLUMN_AMOUNT + " REAL NOT NULL, " +
                COLUMN_TIME + " TEXT NOT NULL, " +
                COLUMN_TYPE + " TEXT NOT NULL)";
        db.execSQL(createTableSql);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO: 数据库升级操作
    }

    public long insertRecord(Record record) {
        SQLiteDatabase db = getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(COLUMN_NAME, record.getName());
        values.put(COLUMN_AMOUNT, record.getAmount());
        values.put(COLUMN_TIME, record.getTime());
        values.put(COLUMN_TYPE, record.getType());
        long id = db.insert(TABLE_NAME, null, values);
        db.close();
        return id;
    }

    public List<Record> queryRecords() {
        SQLiteDatabase db = getReadableDatabase();
        String[] projection = {
                COLUMN_NAME,
                COLUMN_AMOUNT,
                COLUMN_TIME,
                COLUMN_TYPE
        };
        Cursor cursor = db.query(
                TABLE_NAME,
                projection,
                null,
                null,
                null,
                null,
                null
        );
        List<Record> recordList = new ArrayList<>();
        while (cursor.moveToNext()) {
            String name = cursor.getString(cursor.getColumnIndexOrThrow(COLUMN_NAME));
            double amount = cursor.getDouble(cursor.getColumnIndexOrThrow(COLUMN_AMOUNT));
            String time = cursor.getString(cursor.getColumnIndexOrThrow(COLUMN_TIME));
            String type = cursor.getString(cursor.getColumnIndexOrThrow(COLUMN_TYPE));
            Record record = new Record(name, amount, time, type);
            recordList.add(record);
        }
        cursor.close();
        db.close();
        return recordList;
    }
}

AddRecordActivity.java 中调用数据库操作：

public void onSaveButtonClick(View view) {
    ...
    Record record = new Record(name, amount, time, type);
    RecordDatabaseHelper dbHelper = new RecordDatabaseHelper(this);
    dbHelper.insertRecord(record);
    dbHelper.close();
    ...
}

MainActivity.java 中调用数据库操作：

public class MainActivity extends AppCompatActivity {

    private List<Record> recordList;
    private RecordAdapter recordAdapter;
    private RecordDatabaseHelper dbHelper;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        dbHelper = new RecordDatabaseHelper(this);
        recordList = dbHelper.queryRecords();
        recordAdapter = new RecordAdapter(recordList);
        RecyclerView rvRecords = findViewById(R.id.rvRecords);
        rvRecords.setLayoutManager(new LinearLayoutManager(this));
        rvRecords.setAdapter(recordAdapter);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == 1 && resultCode == RESULT_OK && data != null) {
            Record record = data.getParcelableExtra("record");
            long id = dbHelper.insertRecord(record);
            record.setId(id);
            recordList.add(record);
            recordAdapter.notifyDataSetChanged();
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        dbHelper.close();
    }
}