package example.com.myapplication;import android.app.Activity;import android.os.Bundle;import android.view.View;import android.widget.Button;import android.widget.EditText;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.PrintStream;public class MainActivity extends Activity{  final String FILE_NAME = "test.txt";  @Override  public void onCreate(Bundle savedInstanceState)  {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_main);    System.out.println(new StringBuilder("a").append("b").append("c")        .toString());    // 獲取兩個按鈕    Button read = (Button) findViewById(R.id.read);    Button write = (Button) findViewById(R.id.write);    // 獲取兩個文本框    final EditText edit1 = (EditText) findViewById(R.id.edit1);    final EditText edit2 = (EditText) findViewById(R.id.edit2);    // 為write按鈕綁定事件監聽器    write.setOnClickListener(new View.OnClickListener()    {      @Override      public void onClick(View source)      {        // 將edit1中的內容寫入文件中        write(edit1.getText().toString());        edit1.setText("");      }    });    read.setOnClickListener(new View.OnClickListener()    {      @Override      public void onClick(View v)      {        // 讀取指定文件中的內容，并顯示出來        edit2.setText(read());      }    });  }  private String read()  {    try    {      // 打開文件輸入流      FileInputStream fis = openFileInput(FILE_NAME);      byte[] buff = new byte[1024];      int hasRead = 0;      StringBuilder sb = new StringBuilder("");      while ((hasRead = fis.read(buff)) > 0)      {        sb.append(new String(buff, 0, hasRead));      }      return sb.toString();    }    catch (Exception e)    {      e.printStackTrace();    }    return null;  }  private void write(String content)  {    try    {      // 以追加模式打開文件輸出流      FileOutputStream fos = openFileOutput(FILE_NAME, MODE_APPEND);      // 將FileOutputStream包裝成PrintStream      PrintStream ps = new PrintStream(fos);      // 輸出文件內容      ps.println(content);      ps.close();    }    catch (Exception e)    {      e.printStackTrace();    }  }}

<!--?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/edit1"    android:layout_width="match_parent"    android:layout_height="wrap_content"    android:lines="4"/>    <Button      android:id="@+id/write"      android:layout_width="wrap_content"      android:layout_height="wrap_content"      android:text="write"/>  <EditText    android:id="@+id/edit2"    android:layout_width="fill_parent"    android:layout_height="wrap_content"    android:editable="false"    android:lines="4"/>  <Button    android:id="@+id/read"    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:text="read"/>  </LinearLayout>