新建一个Android工程。一 布局先看效果图：
打开main.xml修改内容如下：
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android=""android:orientation="vertical"android:layout_width="fill_parent"android:layout_height="fill_parent"><TextView android:layout_width="fill_parent"android:layout_height="wrap_content"android:text="@string/filename" /><EditText android:layout_width="fill_parent"android:layout_height="wrap_content"android:id="@+id/filename" /><TextView android:layout_width="fill_parent"android:layout_height="wrap_content"android:text="@string/file_content" /><EditText android:layout_width="fill_parent"android:layout_height="wrap_content"android:minLines="3"android:id="@+id/save_file_content" /><Button android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@string/button_save"android:id="@+id/button_save"/><Button android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@string/button_read"android:id="@+id/button_read"/><EditText android:layout_width="fill_parent"android:layout_height="wrap_content"android:minLines="3"android:id="@+id/read_file_content" /></LinearLayout>二 定义字符串打开strings.xml添加内容如下：
<resources><string name="app_name">File</string><string name="action_settings">Settings</string><string name="filename">文件名称</string><string name="file_content">文件内容</string><string name="button_save">保存</string><string name="save_success">保存成功</string><string name="save_fail">保存失败</string><string name="button_read">读取</string><string name="read_success">读取成功</string><string name="read_fail">读取失败</string></resources>三 功能实现新建一个类FileService，用于文件的读写，，完整代码如下：
public class FileService {public Context context;public FileService(Context context){this.context = context;}/*** 保存字符串到文件* @param name 文件名* @param content 文件内容*/public void save(String name, String content) throws Exception{// MODE_PRIVATE 创建出来的文件，仅能被本应用访问，而且新写入的内容会覆盖原来的内容FileOutputStream os = context.openFileOutput(name, Context.MODE_PRIVATE);// 默认保存在/data/data/<package_name>/files目录os.write(content.getBytes());os.close();}/**** 读取文件内容* @param name 文件名* @return* @throws Exception*/public String read(String name) throws Exception{FileInputStream is = context.openFileInput(name);ByteArrayOutputStream os = new ByteArrayOutputStream();byte[] buf = new byte[1024];int len = 0;while( (len = is.read(buf)) != -1){os.write(buf,0, len);}byte[] data = os.toByteArray();String content = new String(data);return content;}}四 测试代码修改MainActivity.java代码如下：
public EditText nameText;public EditText saveContentText;public EditText readContentText;public Button button_read;public String filename;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);nameText = (EditText)this.findViewById(R.id.filename);saveContentText = (EditText)this.findViewById(R.id.save_file_content);readContentText = (EditText)this.findViewById(R.id.read_file_content);Button button_save = (Button) this.findViewById(R.id.button_save);button_save.setOnClickListener(new ButtonSaveClickListener());button_read = (Button) this.findViewById(R.id.button_read);button_read.setClickable(false);button_read.setOnClickListener(new ButtonReadClickListener());}private final class ButtonSaveClickListener implements View.OnClickListener{public void onClick(View v){String name = nameText.getText().toString();String content = saveContentText.getText().toString();FileService service = new FileService(getApplicationContext());try {filename = name;service.save(name, content);filename = name;button_read.setClickable(true);Toast.makeText(getApplicationContext(),R.string.save_success, Toast.LENGTH_LONG).show();}catch (Exception e){Toast.makeText(getApplicationContext(),R.string.save_fail, Toast.LENGTH_LONG).show();e.printStackTrace();}}}private final class ButtonReadClickListener implements View.OnClickListener{public void onClick(View v){FileService service = new FileService(getApplicationContext());try {String content = service.read(filename);readContentText.setText(content);Toast.makeText(getApplicationContext(),R.string.read_success, Toast.LENGTH_LONG).show();}catch (Exception e){Toast.makeText(getApplicationContext(),R.string.read_fail, Toast.LENGTH_LONG).show();e.printStackTrace();}}}运行结果如图：
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