在Android Ddevice中创建目录

Question

我在旧手机（v 4.4.4）中使用Android Studio创建目录时遇到问题，我在较新的手机中尝试过，并且可以正常工作，以下是代码：

public class MainActivity extends AppCompatActivity {

    private static final String LOG_TAG = "DIRECTORY";
    private Button click;

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

        setup();
    }

    private void setup() {
        click = findViewById(R.id.button);
        click.setOnClickListener(v -> getAlbumStorageDir(this, "samuel_es_dios"));
    }

    public void getAlbumStorageDir(Context context, String albumName) {

        pedirPermisos();
        // Get the directory for the app's private pictures directory.
        File file = new File(Environment.getExternalStoragePublicDirectory(
                Environment.DIRECTORY_PICTURES)+ "/"+ albumName);
        if (!file.mkdirs()) {
            Log.e(LOG_TAG, "Directory not created");
        }else {
            Log.e(LOG_TAG, "Directory created");
        }
    }

    private void pedirPermisos() {
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED){
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},50);
        }
    }
}

这是清单：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="iam47662285.escoladeltreball.org.pruebasfile">

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


    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

当它尝试创建目录时，它不会执行该操作，我认为这不是权限问题，我直接要求它们。 知道发生了什么吗？

Answer 1

您必须指定视图的类型

click = findviewbyid(R.id.button)

更改为

click=(Button)findviewbyid(R.id.button)