Android系統。 讀取外部存儲文件

Question

我嘗試通過此程序從外部存儲獲取文件：

public class MainActivity extends Activity {

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

        TextView textView = findViewById(R.id.textView);
        StringBuilder builder = new StringBuilder();
        File specFile = Environment.getExternalStorageDirectory();

        builder.append(Environment.getExternalStorageState() + "\n");
        if (specFile.exists()) {
            builder.append(specFile);
            if (specFile.list() != null) {
                String[] files = specFile.list();
                for (int i = 0; i < files.length; i++) {
                    builder.append(files[i] +"\n");
                }
            } else {
                builder.append(" exist but empty\n");
            }
        }
        builder.append("/storage/emulated/0/Android exist: " + new File("/storage/emulated/0/Android").exists());
        textView.setText(builder);
    }
}

此權限已添加：

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

它在模擬器中效果很好，但是在真實電話中，當我嘗試獲取列表時它返回null。 它通常也可以在存儲中找到目錄。

Answer 1

通過添加以下代碼解決了問題：

int requestCode = 0;

if (Build.VERSION.SDK_INT >= 23) {
    if(checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED){
        requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, requestCode);
    }
}