在android中读取手机中的文本文件

if (ContextCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
    ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, REQUEST_CODE);
}

File file = new File(Environment.getExternalStorageDirectory(), "filename.txt");
if (file.exists()) {
    // 文件存在，进行读取操作
} else {
    // 文件不存在，处理错误情况
}

try {
    BufferedReader reader = new BufferedReader(new FileReader(file));
    String line;
    StringBuilder content = new StringBuilder();
    while ((line = reader.readLine()) != null) {
        content.append(line).append("\n");
    }
    reader.close();
    // 处理content中的内容
} catch (IOException e) {
    e.printStackTrace();
    // 处理异常情况
}

public class MainActivity extends AppCompatActivity {
    private static final int REQUEST_CODE = 100;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if (ContextCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, REQUEST_CODE);
        } else {
            readFile();
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == REQUEST_CODE) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                readFile();
            } else {
                Toast.makeText(this, "Permission denied", Toast.LENGTH_SHORT).show();
            }
        }
    }

    private void readFile() {
        File file = new File(Environment.getExternalStorageDirectory(), "filename.txt");
        if (file.exists()) {
            try {
                BufferedReader reader = new BufferedReader(new FileReader(file));
                String line;
                StringBuilder content = new StringBuilder();
                while ((line = reader.readLine()) != null) {
                    content.append(line).append("\n");
                }
                reader.close();
                // 处理content中的内容
                Toast.makeText(this, content.toString(), Toast.LENGTH_LONG).show();
            } catch (IOException e) {
                e.printStackTrace();
                Toast.makeText(this, "Failed to read file", Toast.LENGTH_SHORT).show();
            }
        } else {
            Toast.makeText(this, "File not found", Toast.LENGTH_SHORT).show();
        }
    }
}