Android Studio记事本代码

以下是一个基本的 Android Studio 记事本应用的代码示例：

MainActivity.java:

package com.example.notepad;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

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;

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

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

    public void saveFile(View view) {
        String text = editText.getText().toString();
        FileOutputStream fileOutputStream = null;
        try {
            fileOutputStream = openFileOutput("note.txt", MODE_PRIVATE);
            fileOutputStream.write(text.getBytes());
            Toast.makeText(this, "Note saved successfully!", Toast.LENGTH_SHORT).show();
        } catch (Exception e) {
            e.printStackTrace();
            Toast.makeText(this, "Error saving note!", Toast.LENGTH_SHORT).show();
        } finally {
            try {
                fileOutputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    public void loadFile(View view) {
        FileInputStream fileInputStream = null;
        try {
            fileInputStream = openFileInput("note.txt");
            InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream);
            BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
            StringBuilder stringBuilder = new StringBuilder();
            String text;
            while ((text = bufferedReader.readLine()) != null) {
                stringBuilder.append(text).append("\n");
            }
            editText.setText(stringBuilder.toString());
            Toast.makeText(this, "Note loaded successfully!", Toast.LENGTH_SHORT).show();
        } catch (Exception e) {
            e.printStackTrace();
            Toast.makeText(this, "Error loading note!", Toast.LENGTH_SHORT).show();
        } finally {
            try {
                fileInputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    public void deleteFile(View view) {
        File file = new File(getFilesDir(), "note.txt");
        if (file.exists()) {
            if (file.delete()) {
                editText.setText("");
                Toast.makeText(this, "Note deleted successfully!", Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(this, "Error deleting note!", Toast.LENGTH_SHORT).show();
            }
        } else {
            Toast.makeText(this, "Note does not exist!", Toast.LENGTH_SHORT).show();
        }
    }
}

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/editText"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:gravity="top|start"
        android:hint="Write your note here"
        android:padding="16dp"
        android:textSize="18sp" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <Button
            android:id="@+id/buttonSave"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Save"
            android:onClick="saveFile" />

        <Button
            android:id="@+id/buttonLoad"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Load"
            android:onClick="loadFile" />

        <Button
            android:id="@+id/buttonDelete"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="Delete"
            android:onClick="deleteFile" />
    </LinearLayout>

</LinearLayout>

此示例实现了在 Android Studio 中创建一个简单的记事本应用，其中有三个按钮：保存、加载和删除。用户可以在文本框中输入文本，然后单击“保存”按钮将该文本保存到文件中，单击“加载”按钮将该文本从文件中读取并在文本框中显示，单击“删除”按钮将删除该文件。