Android(安卓)文件读写最全解析
16lz
2021-12-04
本文目录
- Android文件读写概述
- 读取raw目录文件
- 读取assets目录文件
- data/data/(包名) 目录文件读写
- 写数据
- 读数据
- sdcard文件读写
- 申请动态权限
- 写数据
- 读数据
- sdcard文件读写完整代码
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Android文件读写概述
在Androi中文件读写一共有以下目录
- raw目录
- asserts目录
- data/data/包名
- sdcard目录
其中raw下的和asserts下的文件可以以资源文件的形式读取，这些目录的数据只能读取，不能写入，两者目录下的文件在打包后会原封不动的保存在apk包中，不会被编译成二进制。
data/data/包名和sdcard目录文件可读可写。其中data/data/包名目录不需要申请权限,sdcard目录需要申请权限
读取raw目录文件
Android工程默认是没有raw文件夹的在读文件前我们先把raw 文件夹以及文件建好
- 点中工程的
res目录 右键New->Directory-> 弹窗中输入raw - 点中刚刚新建的
raw目录 右键New->File-> 弹窗中输入test.txt - 点开刚刚新建的
test.txt文件 ，往里面输入hello world
读数据方法
InputStream inputStream = null; Reader reader = null; BufferedReader bufferedReader = null; try { //得到资源中的Raw数据流 inputStream = getResources().openRawResource(R.raw.test); reader = new InputStreamReader(inputStream);// 字符流 bufferedReader = new BufferedReader(reader); //缓冲流 StringBuilder result = new StringBuilder(); String temp; while ((temp = bufferedReader.readLine()) != null) { result.append(temp); } Log.i("MainActivity", "result:" + result); } catch (Exception e) { e.printStackTrace(); } finally { if (reader != null) { try { reader.close(); } catch (IOException e) { e.printStackTrace(); } } if (inputStream != null) { try { inputStream.close(); } catch (IOException e) { e.printStackTrace(); } } if (bufferedReader != null) { try { bufferedReader.close(); } catch (IOException e) { e.printStackTrace(); } } }从打印的结果中我们可以看出数据读取成功
读取assets目录文件
Android工程默认是没有assets文件夹的，在读文件前我们先把assets 文件夹以及文件建好
- 点中工程 右键
New->Folder->Assets Folder - 点中刚刚新建的
Assets Folde目录 右键New->File-> 弹窗中输入test.txt - 点开刚刚新建的
test.txt文件 ，往里面输入hello world
读去assets文件中的数据方法
InputStream inputStream = null; Reader reader = null; BufferedReader bufferedReader = null; try { //得到资源中的asset数据流 inputStream = getResources().getAssets().open("test.txt"); reader = new InputStreamReader(inputStream);// 字符流 bufferedReader = new BufferedReader(reader); //缓冲流 StringBuilder result = new StringBuilder(); String temp; while ((temp = bufferedReader.readLine()) != null) { result.append(temp); } Log.i("MainActivity", "result:" + result); } catch (Exception e) { e.printStackTrace(); } finally { if (reader != null) { try { reader.close(); } catch (IOException e) { e.printStackTrace(); } } if (inputStream != null) { try { inputStream.close(); } catch (IOException e) { e.printStackTrace(); } } if (bufferedReader != null) { try { bufferedReader.close(); } catch (IOException e) { e.printStackTrace(); } } }从打印的结果中我们可以看出数据读取成功
data/data/(包名) 目录文件读写
将数据以普通文件的形式保存在 /data/data/包名中，该方法不需要申请权限。
存放在数据区(/data/data/包名)的文件可以使用openFileOutput和openFileInput进行操作。
也可以直接指定文件/data/data/包名路径读写。
该目录存放文件类型规则如下：
| 路径 | 功能 |
|---|---|
data/data/包名/shared_prefs | 存放SharedPreferences数据 |
data/data/包名/databases | 存放数据库数据 |
data/data/包名/files | 存放普通数据 |
data/data/包名/cache | 存放缓存文件 |
写数据
方法1：openFileOutput
FileOutputStream fileOutputStream = null; try { String text = "hello world"; fileOutputStream = openFileOutput("test.txt", MODE_PRIVATE); fileOutputStream.write(text.getBytes()); } catch (Exception e) { e.printStackTrace(); } finally { if (fileOutputStream != null) { try { fileOutputStream.close(); } catch (IOException e) { e.printStackTrace(); } } }openFileOutput方法参数详解
@Override public FileOutputStream openFileOutput(String name, int mode) throws FileNotFoundException { }- name 存储文件名字
- mode 存储方式 其值的含义如下
| 参数值 | 参数含义 |
|---|---|
| Context.MODE_PRIVATE | 指定该文件数据只能被本应用程序读、写 |
| Context.MODE_WORLD_READABLE | 指定该文件数据能被其他应用程序读，但不能写 |
| Context.MODE_WORLD_WRITEABLE | 指定该文件数据能被其他应用程序读 |
| Context.MODE_APPEND | 该模式会检查文件是否存在，存在就往文件追加内容，否则就创建新文件； |
方法2：传统方法读写
String text = "hello world"; File file1=new File("/data/data/com.lucashu.file/","test.txt"); FileOutputStream fileOutputStream = null; try { fileOutputStream = new FileOutputStream(file1); fileOutputStream.write(text.getBytes()); } catch (Exception e) { e.printStackTrace(); }finally { if (fileOutputStream != null) { try { fileOutputStream.close(); } catch (IOException e) { e.printStackTrace(); } } }执行以后我们可以看到添加了一个文件
读数据
方法1：openFileInput
FileInputStream fileInputStream = null; Reader reader = null; BufferedReader bufferedReader = null; try { fileInputStream = openFileInput("test.txt"); reader = new InputStreamReader(fileInputStream);// 字符流 bufferedReader = new BufferedReader(reader); //缓冲流 StringBuilder result = new StringBuilder(); String temp; while ((temp = bufferedReader.readLine()) != null) { result.append(temp); } Log.i("MainActivity", "result:" + result); } catch (Exception e) { e.printStackTrace(); } finally { if (reader != null) { try { reader.close(); } catch (IOException e) { e.printStackTrace(); } } if (fileInputStream != null) { try { fileInputStream.close(); } catch (IOException e) { e.printStackTrace(); } } if (bufferedReader != null) { try { bufferedReader.close(); } catch (IOException e) { e.printStackTrace(); } } }方法2：openFileInput
InputStream inputStream = null; Reader reader = null; BufferedReader bufferedReader = null; try { File file=new File("/data/data/com.lucashu.file/", "test.txt"); inputStream = new FileInputStream(file); reader = new InputStreamReader(inputStream); bufferedReader = new BufferedReader(reader); StringBuilder result = new StringBuilder(); String temp; while ((temp = bufferedReader.readLine()) != null) { result.append(temp); } Log.i("MainActivity", "result:" + result); } catch (Exception e) { e.printStackTrace(); } finally { if (reader != null) { try { reader.close(); } catch (IOException e) { e.printStackTrace(); } } if (inputStream != null) { try { inputStream.close(); } catch (IOException e) { e.printStackTrace(); } } if (bufferedReader != null) { try { bufferedReader.close(); } catch (IOException e) { e.printStackTrace(); } } }从打印的结果中我们可以看出数据读取成功
我们也可以用一下方法来获取改文件的路径
getFilesDir();// data/data/包名/files 目录getFilesDir().getParent(),;// data/data/包名/ 目录sdcard文件读写
sdcard读写的数据将数据保存在 /mnt/sdcard目录,该目录读写需要先申请动态权限，动态权限申请方法如下
申请动态权限
Android 动态权限最全解析
首先需要在manifest.xml中添加权限
如果是AndroidQ 或者更高的版本还需要在manifest.xml文件中的application节点下加入
android:requestLegacyExternalStorage="true"
申请动态权限方法：
private static final int REQUEST_EXTERNAL_STORAGE = 1;private static String[] PERMISSIONS_STORAGE = {"android.permission.READ_EXTERNAL_STORAGE", "android.permission.WRITE_EXTERNAL_STORAGE"};private void checkPermission() {//检查权限（NEED_PERMISSION）是否被授权 PackageManager.PERMISSION_GRANTED表示同意授权 if (ActivityCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) { if (ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission .WRITE_EXTERNAL_STORAGE)) { Toast.makeText(this, "请开通相关权限，否则无法正常使用本应用！", Toast.LENGTH_SHORT).show(); } //申请权限 ActivityCompat.requestPermissions(this, PERMISSIONS_STORAGE, REQUEST_EXTERNAL_STORAGE); } else { Toast.makeText(this, "已授权成功！", Toast.LENGTH_SHORT).show(); writeSdcard(); }}Activity中动态权限的回调方法
@Overridepublic void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) { switch (requestCode) { case REQUEST_EXTERNAL_STORAGE: { if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) { Toast.makeText(this, "授权成功！", Toast.LENGTH_SHORT).show(); writeSdcard(); } else { Toast.makeText(this, "授权被拒绝！", Toast.LENGTH_SHORT).show(); } return; } }}写数据
private void writeSdcard() { String text = "hello world"; if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) { if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) { File storage = Environment.getExternalStorageDirectory(); File tmepfile = new File(storage.getPath()); if (! tmepfile.exists()) { tmepfile.mkdirs(); } File file1=new File(tmepfile,"test.txt"); if (!file1.exists()){ try { file1.createNewFile(); } catch (IOException e) { e.printStackTrace(); } } FileOutputStream fileOutputStream = null; try { fileOutputStream = new FileOutputStream(file1); fileOutputStream.write(text.getBytes()); } catch (Exception e) { e.printStackTrace(); }finally { if (fileOutputStream != null) { try { fileOutputStream.close(); } catch (IOException e) { e.printStackTrace(); } } } } } }执行以后我们可以看到添加了一个文件
读数据
private void readSdcard() { if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) { if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) { InputStream inputStream = null; Reader reader = null; BufferedReader bufferedReader = null; try { File storage = Environment.getExternalStorageDirectory(); File tmepfile = new File(storage.getPath()); File file=new File(tmepfile, "test.txt"); inputStream = new FileInputStream(file); reader = new InputStreamReader(inputStream); bufferedReader = new BufferedReader(reader); StringBuilder result = new StringBuilder(); String temp; while ((temp = bufferedReader.readLine()) != null) { result.append(temp); } Log.i("MainActivity", "result:" + result); } catch (Exception e) { e.printStackTrace(); } finally { if (reader != null) { try { reader.close(); } catch (IOException e) { e.printStackTrace(); } } if (inputStream != null) { try { inputStream.close(); } catch (IOException e) { e.printStackTrace(); } } if (bufferedReader != null) { try { bufferedReader.close(); } catch (IOException e) { e.printStackTrace(); } } } } } }sdcard文件读写完整代码
package com.lucashu.file;import androidx.appcompat.app.AppCompatActivity;import androidx.core.app.ActivityCompat;import android.Manifest;import android.content.pm.PackageManager;import android.os.Bundle;import android.os.Environment;import android.util.Log;import android.widget.Toast;import java.io.BufferedReader;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.FileWriter;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.io.Reader;import java.io.Writer;public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); checkPermission(); } private void writeSdcard() { String text = "hello world"; if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) { if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) { File storage = Environment.getExternalStorageDirectory(); File tmepfile = new File(storage.getPath()); if (! tmepfile.exists()) { tmepfile.mkdirs(); } File file1=new File(tmepfile,"test.txt"); if (!file1.exists()){ try { file1.createNewFile(); } catch (IOException e) { e.printStackTrace(); } } FileOutputStream fileOutputStream = null; try { fileOutputStream = new FileOutputStream(file1); fileOutputStream.write(text.getBytes()); } catch (Exception e) { e.printStackTrace(); }finally { if (fileOutputStream != null) { try { fileOutputStream.close(); } catch (IOException e) { e.printStackTrace(); } } } } } } private void readSdcard() { if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) { if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) { InputStream inputStream = null; Reader reader = null; BufferedReader bufferedReader = null; try { File storage = Environment.getExternalStorageDirectory(); File tmepfile = new File(storage.getPath()); File file=new File(tmepfile, "test.txt"); inputStream = new FileInputStream(file); reader = new InputStreamReader(inputStream); bufferedReader = new BufferedReader(reader); StringBuilder result = new StringBuilder(); String temp; while ((temp = bufferedReader.readLine()) != null) { result.append(temp); } Log.i("MainActivity", "result:" + result); } catch (Exception e) { e.printStackTrace(); } finally { if (reader != null) { try { reader.close(); } catch (IOException e) { e.printStackTrace(); } } if (inputStream != null) { try { inputStream.close(); } catch (IOException e) { e.printStackTrace(); } } if (bufferedReader != null) { try { bufferedReader.close(); } catch (IOException e) { e.printStackTrace(); } } } } } } private static final int REQUEST_EXTERNAL_STORAGE = 1; private static String[] PERMISSIONS_STORAGE = {"android.permission.READ_EXTERNAL_STORAGE", "android.permission.WRITE_EXTERNAL_STORAGE"}; private void checkPermission() { //检查权限（NEED_PERMISSION）是否被授权 PackageManager.PERMISSION_GRANTED表示同意授权 if (ActivityCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) { if (ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission .WRITE_EXTERNAL_STORAGE)) { Toast.makeText(this, "请开通相关权限，否则无法正常使用本应用！", Toast.LENGTH_SHORT).show(); } //申请权限 ActivityCompat.requestPermissions(this, PERMISSIONS_STORAGE, REQUEST_EXTERNAL_STORAGE); } else { Toast.makeText(this, "已授权成功！", Toast.LENGTH_SHORT).show(); readSdcard(); } } @Override public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) { switch (requestCode) { case REQUEST_EXTERNAL_STORAGE: { if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) { Toast.makeText(this, "授权成功！", Toast.LENGTH_SHORT).show(); readSdcard(); } else { Toast.makeText(this, "授权被拒绝！", Toast.LENGTH_SHORT).show(); } return; } } }}作者：lucashu
出处：https://blog.csdn.net/huweiliyi/category_8913738.html
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