Android 文件读写最全解析

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 Android文件读写概述

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

@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();
                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：huwei0814