android记事本代码

以下是一个简单的Android记事本应用程序的代码示例。你可以根据自己的需求和喜好进行修改和优化。

MainActivity.java

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.EditText;
import android.widget.Toast;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

public class MainActivity extends Activity {

    private EditText mEditText;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mEditText = (EditText) findViewById(R.id.editText);
    }

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

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.menu_save:
                saveText();
                return true;
            case R.id.menu_load:
                loadText();
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }

    private void saveText() {
        try {
            FileOutputStream fileOut = openFileOutput("note.txt", MODE_PRIVATE);
            OutputStreamWriter outputWriter = new OutputStreamWriter(fileOut);
            outputWriter.write(mEditText.getText().toString());
            outputWriter.close();
            Toast.makeText(this, "Note saved!", Toast.LENGTH_SHORT).show();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void loadText() {
        try {
            FileInputStream fileIn = openFileInput("note.txt");
            InputStreamReader inputStreamReader = new InputStreamReader(fileIn);
            char[] inputBuffer = new char[100];
            String s = "";
            int charRead;
            while ((charRead = inputStreamReader.read(inputBuffer)) > 0) {
                String readString = String.copyValueOf(inputBuffer, 0, charRead);
                s += readString;
            }
            inputStreamReader.close();
            mEditText.setText(s);
            Toast.makeText(this, "Note loaded!", Toast.LENGTH_SHORT).show();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <EditText
        android:id="@+id/editText"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_marginTop="20dp"
        android:gravity="top"
        android:hint="Write your note here"
        android:padding="10dp"
        android:textSize="16sp" />

</RelativeLayout>

menu_main.xml

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

    <item
        android:id="@+id/menu_save"
        android:icon="@drawable/ic_menu_save"
        android:title="Save" />
    <item
        android:id="@+id/menu_load"
        android:icon="@drawable/ic_menu_load"
        android:title="Load" />

</menu>

请注意，在使用此代码之前，你需要在项目的AndroidManifest.xml文件中添加以下权限：

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