Android文件目录及文件访问权限等详解
2024-04-17 22:28:53
Android文件目录一次说清
- 说明
- 应用访问权限及范围
- 在app内创建文件演示
- 在其他app内访问上面的app创建的文件
说明
android 中获取目录的API有两种，一种是通过Environment获取，另一种就是通过Context获取。两者获取到的目录区别还是很大的。
通过Environment API获取的目录，不会包含应用的内部目录，也就是带应用包名的目录。
通过Context API获取的目录，绝对路径都会带有改应用的包名，app访问自己包名下的该类文件，不需要额外申请权限
在Android10及以上设备上，即便申请了存储权限，也会报permission Denied . 在manifest文件中，添加： android:requestLegacyExternalStorage= “true”
应用访问权限及范围
这里可以将文件归纳为三种：App共享文件、App独立文件、App专属文件
在app内创建文件演示
package com.shoneworn.dirmake;import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.RequiresApi;
import androidx.appcompat.app.AppCompatActivity;import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.widget.TextView;
import android.widget.Toast;import java.io.File;
import java.io.FileOutputStream;
import java.io.OutputStreamWriter;public class MainActivity extends AppCompatActivity {private TextView tvDir;@Overrideprotected void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);tvDir = findViewById(R.id.tv_dir);}@RequiresApi(api = Build.VERSION_CODES.M)@Overrideprotected void onResume() {super.onResume();
// initDir();if (Utils.hasPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE) && Utils.hasPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE)) {initDir();return;}requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1000);}@RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)@Overridepublic void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {super.onRequestPermissionsResult(requestCode, permissions, grantResults);if (grantResults == null || grantResults.length == 0) {return;}if (requestCode != 1000) {return;}if (grantResults[0] == PackageManager.PERMISSION_GRANTED && grantResults[1] == PackageManager.PERMISSION_GRANTED) {Toast.makeText(this, "授权成功", Toast.LENGTH_SHORT).show();initDir();return;}}@RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)private void initDir() {StringBuffer sb = new StringBuffer();File externalStorageDirectory = Environment.getExternalStorageDirectory();sb.append("Environment externalStorageDirectory>>" + externalStorageDirectory.getAbsolutePath() + "\n");Log.e("cxx", "Environment externalStorageDirectory>>" + externalStorageDirectory.getAbsolutePath());makeFile(externalStorageDirectory, "env externalStorageDirectory");File dataDirectory = Environment.getDataDirectory();sb.append("Environment dataDirectory>>" + dataDirectory.getAbsolutePath() + "\n");Log.e("cxx", "Environment dataDirectory>>" + dataDirectory.getAbsolutePath());makeFile(dataDirectory, "env dataDirectory");File downloadCacheDirectory = Environment.getDownloadCacheDirectory();sb.append("Environment downloadCacheDirectory>>" + downloadCacheDirectory.getAbsolutePath() + "\n");Log.e("cxx", "Environment downloadCacheDirectory>>" + downloadCacheDirectory.getAbsolutePath());makeFile(downloadCacheDirectory, "env downloadCacheDirectory");File rootDirectory = Environment.getRootDirectory();sb.append("Environment rootDirectory>>" + rootDirectory.getAbsolutePath() + "\n");Log.e("cxx", "Environment rootDirectory>>" + rootDirectory.getAbsolutePath());makeFile(rootDirectory, "env rootDirectory");File externalStoragePublicDirectory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DCIM);sb.append("Environment externalStoragePublicDirectory>>" + externalStoragePublicDirectory.getAbsolutePath() + "\n");Log.e("cxx", "Environment externalStoragePublicDirectory>>" + externalStoragePublicDirectory.getAbsolutePath());makeFile(externalStoragePublicDirectory, "env externalStoragePublicDirectory");Context context = this;File externalFilesDir = context.getExternalFilesDir(null);sb.append("Context externalFilesDir>>" + externalFilesDir.getAbsolutePath() + "\n");Log.e("cxx", "Context externalFilesDir>>" + externalFilesDir.getAbsolutePath());makeFile(externalFilesDir, "externalFilesDir");File externalCacheDir = context.getExternalCacheDir();sb.append("Context externalCacheDir>>" + externalCacheDir.getAbsolutePath() + "\n");Log.e("cxx", "Context externalCacheDir>>" + externalCacheDir.getAbsolutePath());makeFile(externalCacheDir, "externalCacheDir");File[] externalCacheDirs = context.getExternalCacheDirs();sb.append("Context externalCacheDirs>>");for (File file : externalCacheDirs) {sb.append(file.getAbsolutePath() + " ");Log.e("cxx", "Context externalCacheDirs>>" + file.getAbsolutePath());}sb.append("\n");File filesDir = context.getFilesDir();sb.append("Context filesDir>>" + filesDir.getAbsolutePath() + "\n");Log.e("cxx", "Context filesDir>>" + filesDir.getAbsolutePath());makeFile(filesDir, "filesDir");File cacheDir = context.getCacheDir();sb.append("Context cacheDir>>" + cacheDir.getAbsolutePath() + "\n");Log.e("cxx", "Context cacheDir>>" + cacheDir.getAbsolutePath());makeFile(cacheDir, "cacheDir");File codeCacheDir = context.getCodeCacheDir();sb.append("Context codeCacheDir>>" + codeCacheDir.getAbsolutePath() + "\n");Log.e("cxx", "Context codeCacheDir>>" + codeCacheDir.getAbsolutePath());makeFile(codeCacheDir, "codeCacheDir");File noBackupFilesDir = context.getNoBackupFilesDir();sb.append("Context noBackupFilesDir>>" + noBackupFilesDir.getAbsolutePath() + "\n");Log.e("cxx", "Context noBackupFilesDir>>" + noBackupFilesDir.getAbsolutePath());makeFile(noBackupFilesDir, "noBackupFilesDir");if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {File dataDir = context.getDataDir();sb.append("Context dataDir>>" + dataDir.getAbsolutePath() + "\n");Log.e("cxx", "Context dataDir>>" + dataDir.getAbsolutePath());makeFile(dataDir, "dataDir");}File[] externalMediaDirs = context.getExternalMediaDirs();sb.append("Context externalMediaDirs>>");for (File file : externalMediaDirs) {sb.append(file.getAbsolutePath() + " ");Log.e("cxx", "Context externalMediaDirs>>" + file.getAbsolutePath());}sb.append("\n");File obbDir = context.getObbDir();sb.append("Context obbDir>>" + obbDir.getAbsolutePath() + "\n");Log.e("cxx", "Context obbDir>>" + obbDir.getAbsolutePath());makeFile(obbDir, "obbDir");String s = sb.toString();tvDir.setText(s);}//向各个目录下写入文件private void makeFile(File dir, String name) {if (dir == null || !dir.exists()) {return;}try {File file = new File(dir, "cxx.txt");if (!file.exists()) {file.createNewFile();}OutputStreamWriter out = new OutputStreamWriter(new FileOutputStream(file, false), // true to append"UTF-8");out.write(getPackageName() + " name:" + name + " dir>>" + dir.getAbsolutePath());out.close();} catch (Exception e) {Log.e("cxx", e.getMessage());}}}看下输出：
E/cxx: Environment externalStorageDirectory>>/storage/emulated/0
E/cxx: Environment dataDirectory>>/data
E/cxx: Permission denied
E/cxx: Environment downloadCacheDirectory>>/data/cache
E/cxx: Permission denied
E/cxx: Environment rootDirectory>>/system
E/cxx: Read-only file system
E/cxx: Environment externalStoragePublicDirectory>>/storage/emulated/0/DCIM//从这里开始，均由context获取的目录，访问不需要申请应用权限，随app卸载而删除
//系统分区下的app私有目录
E/cxx: Context externalFilesDir>>/storage/emulated/0/Android/data/com.shoneworn.dirmake/files
E/cxx: Context externalCacheDir>>/storage/emulated/0/Android/data/com.shoneworn.dirmake/cache
E/cxx: Context externalCacheDirs>>/storage/emulated/0/Android/data/com.shoneworn.dirmake/cache
E/cxx: Context externalMediaDirs>>/storage/emulated/0/Android/media/com.shoneworn.dirmake
E/cxx: Context obbDir>>/storage/emulated/0/Android/obb/com.shoneworn.dirmake//sdcard下应用独有目录
E/cxx: Context filesDir>>/data/user/0/com.shoneworn.dirmake/files
E/cxx: Context cacheDir>>/data/user/0/com.shoneworn.dirmake/cache
E/cxx: Context codeCacheDir>>/data/user/0/com.shoneworn.dirmake/code_cache
E/cxx: Context noBackupFilesDir>>/data/user/0/com.shoneworn.dirmake/no_backup
E/cxx: Context dataDir>>/data/user/0/com.shoneworn.dirmake可以看到有两个目录下创建文件被拒了。应用想要向这两个目录下创建文件，需要root权限。
在其他app内访问上面的app创建的文件
package com.shoneworn.readfile;import androidx.annotation.NonNull;
import androidx.annotation.RequiresApi;
import androidx.appcompat.app.AppCompatActivity;import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Toast;import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.nio.Buffer;public class MainActivity extends AppCompatActivity implements View.OnClickListener {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);findViewById(R.id.btn_ext_cache).setOnClickListener(this);findViewById(R.id.btn_ext_file).setOnClickListener(this);findViewById(R.id.btn_file_dir).setOnClickListener(this);}@RequiresApi(api = Build.VERSION_CODES.M)@Overrideprotected void onResume() {super.onResume();if (Utils.hasPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE) && Utils.hasPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE)) {return;}requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1000);}@RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)@Overridepublic void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {super.onRequestPermissionsResult(requestCode, permissions, grantResults);if (grantResults == null || grantResults.length == 0) {return;}if (requestCode != 1000) {return;}if (grantResults[0] == PackageManager.PERMISSION_GRANTED && grantResults[1] == PackageManager.PERMISSION_GRANTED) {Toast.makeText(this, "授权成功", Toast.LENGTH_SHORT).show();return;}}@Overridepublic void onClick(View view) {switch (view.getId()) {case R.id.btn_ext_file:readFile("/storage/emulated/0/Android/data/com.shoneworn.dirmake/files");break;case R.id.btn_file_dir:readFile("/data/user/0/com.shoneworn.dirmake/files");break;case R.id.btn_ext_cache:readFile("/storage/emulated/0/Android/data/com.shoneworn.dirmake/cache");break;}}private void readFile(String path) {File file = new File(path + File.separator + "cxx.txt");if (!file.exists()) {Log.e("cxx", "read " + file.getAbsolutePath() + " not exists");return;}try {StringBuilder sb = new StringBuilder();FileInputStream fileInputStream = new FileInputStream(file);byte[] buffer = new byte[1024];int len = fileInputStream.read(buffer);while (len > 0) {sb.append(new String(buffer, 0, len));len = fileInputStream.read(buffer);}fileInputStream.close();String s = sb.toString();Log.e("cxx", path + " content:" + s);} catch (Exception e) {Log.e("cxx", e.getMessage());}}
}看看日志：
E/cxx: /storage/emulated/0/Android/data/com.shoneworn.dirmake/files content:com.shoneworn.dirmake name:externalFilesDir dir>>/storage/emulated/0/Android/data/com.shoneworn.dirmake/filesE/cxx: read /data/user/0/com.shoneworn.dirmake/files/cxx.txt not existsE/cxx: /storage/emulated/0/Android/data/com.shoneworn.dirmake/cache content:com.shoneworn.dirmake name:externalCacheDir dir>>/storage/emulated/0/Android/data/com.shoneworn.dirmake/cache这里只演示了访问其他应用app独立文件和其他应用app专属文件的情况。
访问其他应用app专属文件时直接文件不存在。
Demo下载地址
https://download.csdn.net/download/shoneworn/14046663
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