Android文件保存于读取

这是一个用来读写文件的demo. 用户界面如下:

用到的字符串资源: res/values/strings.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="app_name">文件读写</string>
    <string name="action_settings">Settings</string>
    <string name="file_name">文件名</string>
    <string name="content_label">文件内容</string>
    <string name="save_label">保存</string>
    
    <string name="save_successful">保存成功</string>
    <string name="save_fail">保存失败</string>
</resources>

 

用户界面: res/layout/activity_main.xml

<LinearLayout 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"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/file_name" />
    
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:inputType="text"
        android:id="@+id/file_name" />
    
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/content_label" />
    
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/file_content"
        android:inputType="textMultiLine"
        android:minLines="3" />
    
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingLeft="10dp"
        android:paddingRight="10dp"
        android:id="@+id/save_btn_view"
        android:text="@string/save_label" />

</LinearLayout>

 

主activity: MainActivity.java

......
public class MainActivity extends Activity {
    private EditText fileNameView;
    private EditText fileContentView;
    private FileService fileService;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        fileNameView = (EditText) findViewById(R.id.file_name);
        fileContentView = (EditText) findViewById(R.id.file_content);
        fileService = new FileService();
        fileService.setContext(getApplicationContext());
        
        Button saveBtn = (Button) findViewById(R.id.save_btn_view);
        saveBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String fileName = fileNameView.getText().toString();
                String content = fileContentView.getText().toString();
                try {
                    fileService.saveFile(fileName, content);
                } catch (Exception e) {
                    Toast.makeText(getApplicationContext(), R.string.save_fail, Toast.LENGTH_SHORT).show();
                    e.printStackTrace();
                }
                Toast.makeText(getApplicationContext(), R.string.save_successful, Toast.LENGTH_SHORT).show();
            }
        });
    }

}

 

 

FileService.java

package com.lk.service;

import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import android.content.Context;
import android.util.Log;

public class FileService {
    private static String TAG = "FileManager";
    private Context context;

    /**
     * 写文件
     * @param fileName
     * @param content
     * @throws Exception
     */
    public void saveFile(String fileName, String content) throws Exception {
        Log.i(TAG, "fileName = " + fileName + ", content = " + content);
        FileOutputStream fos = null;
        try {
            //Context.MODE_PRIVATE表示创建的文件仅能被当前应用读写，写的方式是覆盖
            fos = context.openFileOutput(fileName, Context.MODE_PRIVATE);
            byte[] buffer = content.getBytes();
            fos.write(buffer);
            
        } catch (Exception e) {
            throw new Exception(e);
        } finally {
            if(fos != null) {
                fos.close();
            }
        }
        Log.i(TAG, "leave successful");
    }
    
    /**
     * 读文件
     * @param fileName
     * @return
     * @throws Exception
     */
    public String readFile(String fileName) throws Exception {
        Log.i(TAG, "fileName = " + fileName);
        FileInputStream fis = null;
        ByteArrayOutputStream temp = new ByteArrayOutputStream();
        String content = null;
        try {
            fis = context.openFileInput(fileName);
            byte[] buffer = new byte[1024];
            int length = 0;
            while((length = fis.read(buffer)) > 0) {
                temp.write(buffer, 0, length);
            }
            content = new String(temp.toByteArray());
        } catch (Exception e) {
            throw new Exception(e);
        } finally {
            if(temp != null) {
                temp.close();
            }
            if(fis != null) {
                fis.close();
            }
        }
        Log.i(TAG, "leave successful, content = " + content);
        return content;
    }

    public Context getContext() {
        return context;
    }

    public void setContext(Context context) {
        this.context = context;
    }
    
}

 

当用户输入内容并保存后，就可以在 /data/data/package_name/files/ 目录下就能找到该文件了。

 

下面再来总结一下文件操作模式:

Context.MODE_PRIVATE: 表示创建的文件仅能被当前应用读写，写的方式是覆盖
Context.MODE_APPEND: 表示创建的文件仅能被当前应用读写，写的方式是追加
Context.MODE_WORLD_READABLE: 表示创建的文件允许其他所有应用读，不允许写，写的方式是覆盖
Context.MODE_WORLD_WRITEABLE: 表示创建的文件允许其他所有应用写，不允许读，写的方式是覆盖
Context.MODE_WORLD_READABLE + Context.MODE_WORLD_WRITEABLE: 表示创建的文件允许所有应用读写