android studio 记事本代码

以下是一个简单的记事本应用程序的代码示例，你可以在 Android Studio 中使用它进行开发：

MainActivity.java

import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.EditText;

import androidx.appcompat.app.AppCompatActivity;

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;

public class MainActivity extends AppCompatActivity {

    private EditText mEditText;

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

        mEditText = findViewById(R.id.edit_text);
    }

    @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) {
            saveFile();
            return true;
        } else if (id == R.id.action_open) {
            openFile();
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    private void saveFile() {
        String fileName = "note.txt";
        String text = mEditText.getText().toString();

        try {
            FileOutputStream fos = openFileOutput(fileName, MODE_PRIVATE);
            fos.write(text.getBytes());
            fos.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void openFile() {
        String fileName = "note.txt";

        try {
            FileInputStream fis = openFileInput(fileName);
            InputStreamReader isr = new InputStreamReader(fis);
            BufferedReader br = new BufferedReader(isr);
            StringBuilder sb = new StringBuilder();
            String line;

            while ((line = br.readLine()) != null) {
                sb.append(line).append("\n");
            }

            mEditText.setText(sb.toString());

            br.close();
            isr.close();
            fis.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

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">

    <EditText
        android:id="@+id/edit_text"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="top|start"
        android:scrollbars="vertical"
        android:padding="16dp"/>

</LinearLayout>

menu_main.xml

<?xml version="1.0" encoding="utf-8"?>
<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_open"
          android:title="Open"
          android:icon="@drawable/ic_folder"
          app:showAsAction="ifRoom"/>

</menu>

注：此代码仅供参考，实际开发中可能需要进行修改和完善。