在Android 7.0中运行时间权限检查

Question

When I try createFile in sdcard:

newFile.createNewFile();

I got log as follows:

W/System.err: java.io.IOException: Permission denied

W/System.err: at java.io.UnixFileSystem.createFileExclusively0(Native Method)

W/System.err: at java.io.UnixFileSystem.createFileExclusively(UnixFileSystem.java:280)

W/System.err: at java.io.File.createNewFile(File.java:948)

I know the reason is the dangerous runtime permission(WRITE_EXTERNAL_STORAGE) is not granted, but when I try to print log within PackageManagerService.java checkUidPermission() , find it is not called.

I wonder how native method(like java.io.UnixFileSystem.createFileExclusively0 ) judge that runtime Permission is not granted?

Answer 1

From Android M, Permissions can be granted / revoked runtime by user instead of install time.

So when targeting devices with M and higher you need to check for permission whether it is granted I use this class to check permissions i hope it helps:

/**
 * Created by Mani on 17/09/16.
 * Making the runtime app permissions for android marshmallow+ devices cleaner
 * Specify all the requests here
 */
public class MarshMallowPermission {
    private static final int CALL_PERMISSION_REQUEST_CODE = 1;
    public static final int EXTERNAL_STORAGE_PERMISSION_REQUEST_CODE = 2;
    public static final int CAMERA_PERMISSION_REQUEST_CODE = 3;
    public static final int SHORT_CUT_PERMISSION_REQUEST_CODE = 4;
    private Activity activity;


    public MarshMallowPermission(Activity activity) {
        this.activity = activity;
    }

    public boolean checkPermissionForCall(){
        int result = ContextCompat.checkSelfPermission(activity, Manifest.permission.CALL_PHONE);
        return result == PackageManager.PERMISSION_GRANTED;
    }

    @RequiresApi(api = Build.VERSION_CODES.KITKAT)
    public boolean checkPermissionForShortCut(){


        int result = PermissionChecker.checkSelfPermission(activity,Manifest.permission.INSTALL_SHORTCUT);
        return result == PermissionChecker.PERMISSION_GRANTED;
    }


    public boolean checkPermissionForExternalStorage(){
        int result = ContextCompat.checkSelfPermission(activity, Manifest.permission.WRITE_EXTERNAL_STORAGE);
        int readStorage = 0;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
            readStorage = ContextCompat.checkSelfPermission(activity, Manifest.permission.READ_EXTERNAL_STORAGE);
        }

        return result == PackageManager.PERMISSION_GRANTED && readStorage == PackageManager.PERMISSION_GRANTED;
    }

    public boolean checkPermissionForCamera(){
        int result = ContextCompat.checkSelfPermission(activity, Manifest.permission.CAMERA);
        return result == PackageManager.PERMISSION_GRANTED;
    }


    public void requestPermissionForCall(){
        if (ActivityCompat.shouldShowRequestPermissionRationale(activity, Manifest.permission.CALL_PHONE)){
            Toast.makeText(activity, "Call Phone Permission required to launch Dialer. Please allow in App Settings for additional functionality.", Toast.LENGTH_LONG).show();
        } else {
            ActivityCompat.requestPermissions(activity,new String[]{Manifest.permission.CALL_PHONE},CALL_PERMISSION_REQUEST_CODE);
        }
    }

    public void requestPermissionForExternalStorage(){
        if (ActivityCompat.shouldShowRequestPermissionRationale(activity, Manifest.permission.WRITE_EXTERNAL_STORAGE)){
            Toast.makeText(activity, "External Storage permission required. Please allow in App Settings for additional functionality.", Toast.LENGTH_LONG).show();
        } else {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
                ActivityCompat.requestPermissions(activity,new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE,Manifest.permission.READ_EXTERNAL_STORAGE},EXTERNAL_STORAGE_PERMISSION_REQUEST_CODE);
            }else{
                ActivityCompat.requestPermissions(activity,new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},EXTERNAL_STORAGE_PERMISSION_REQUEST_CODE);
            }
        }
    }

    public void requestPermissionForCamera(){
        if (ActivityCompat.shouldShowRequestPermissionRationale(activity, Manifest.permission.CAMERA)){
            Toast.makeText(activity, "Camera permission required. Please allow in App Settings for additional functionality.", Toast.LENGTH_LONG).show();
        } else {
            ActivityCompat.requestPermissions(activity,new String[]{Manifest.permission.CAMERA},CAMERA_PERMISSION_REQUEST_CODE);
        }
    }

    public void requestPermissionForShortCut(){
        if (ActivityCompat.shouldShowRequestPermissionRationale(activity, Manifest.permission.INSTALL_SHORTCUT)){
            Toast.makeText(activity, "Create ShortCut permission required. Please allow in App Settings for additional functionality.", Toast.LENGTH_LONG).show();
        } else {
            ActivityCompat.requestPermissions(activity,new String[]{Manifest.permission.INSTALL_SHORTCUT},SHORT_CUT_PERMISSION_REQUEST_CODE);
        }
    }
}

Usage inside activity:

MarshMallowPermission marshMallowPermission = new MarshMallowPermission(MyActivity.this);

marshMallowPermission.checkPermissionForCall();

marshMallowPermission.requestPermissionForCall();

Comment below if you have any doubts.