android studio开发记事本代码

以下是一个简单的 Android Studio 记事本应用的代码示例：

MainActivity.java：

import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.EditText;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;

public class MainActivity extends AppCompatActivity {

    EditText editText;
    String fileName = "note.txt";

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

        editText = findViewById(R.id.edit_text);
        loadNote();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();

        if (id == R.id.action_save) {
            saveNote();
            return true;
        } else if (id == R.id.action_delete) {
            deleteNote();
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    private void loadNote() {
        try {
            FileInputStream inputStream = openFileInput(fileName);
            InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
            BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
            String line;
            StringBuilder stringBuilder = new StringBuilder();
            while ((line = bufferedReader.readLine()) != null) {
                stringBuilder.append(line);
            }
            editText.setText(stringBuilder.toString());
            inputStream.close();
        } catch (IOException e) {
            Toast.makeText(getApplicationContext(), "Error loading note", Toast.LENGTH_SHORT).show();
        }
    }

    private void saveNote() {
        try {
            FileOutputStream outputStream = openFileOutput(fileName, MODE_PRIVATE);
            outputStream.write(editText.getText().toString().getBytes());
            outputStream.close();
            Toast.makeText(getApplicationContext(), "Note saved", Toast.LENGTH_SHORT).show();
        } catch (IOException e) {
            Toast.makeText(getApplicationContext(), "Error saving note", Toast.LENGTH_SHORT).show();
        }
    }

    private void deleteNote() {
        File file = new File(getFilesDir(), fileName);
        if (file.exists()) {
            file.delete();
            editText.setText("");
            Toast.makeText(getApplicationContext(), "Note deleted", Toast.LENGTH_SHORT).show();
        } else {
            Toast.makeText(getApplicationContext(), "No note to delete", Toast.LENGTH_SHORT).show();
        }
    }
}

activity_main.xml：

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

    <EditText
            android:id="@+id/edit_text"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:gravity="top|left"
            android:padding="10dp"
            android:scrollbars="vertical"/>

</LinearLayout>

menu_main.xml：

<menu xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto">

    <item
            android:id="@+id/action_save"
            android:title="Save"
            android:icon="@drawable/ic_save"
            app:showAsAction="ifRoom"/>

    <item
            android:id="@+id/action_delete"
            android:title="Delete"
            android:icon="@drawable/ic_delete"
            app:showAsAction="ifRoom"/>

</menu>

这个应用程序有一个简单的文本编辑器界面，可以保存和删除文本文件。当应用程序启动时，它会尝试加载名为“note.txt”的文件。当用户点击保存按钮时，它将文本保存到名为“note.txt”的文件中，当用户点击删除按钮时，它将删除名为“note.txt”的文件。