1、手動申請
Android6.0之后系統(tǒng)對權(quán)限的管理更加嚴(yán)格了，不但要在AndroidManifest中添加，還要在應(yīng)用運(yùn)行的時(shí)候動態(tài)申請。下面是動態(tài)申請SD卡讀寫的權(quán)限
在AndroidManifest中添加SD卡讀寫的權(quán)限

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

動態(tài)申請權(quán)限

private static final int REQUEST_EXTERNAL_STORAGE = 1;
    private static String[] PERMISSIONS_STORAGE = {
            "android.permission.READ_EXTERNAL_STORAGE",
            "android.permission.WRITE_EXTERNAL_STORAGE" };


    public static void verifyStoragePermissions(Activity activity) {

        try {
        //檢測是否有寫的權(quán)限
            int permission = ActivityCompat.checkSelfPermission(activity,
                    "android.permission.WRITE_EXTERNAL_STORAGE");
            if (permission != PackageManager.PERMISSION_GRANTED) {
        // 沒有寫的權(quán)限，去申請寫的權(quán)限，會彈出對話框
                ActivityCompat.requestPermissions(activity, PERMISSIONS_STORAGE,REQUEST_EXTERNAL_STORAGE);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

把verifyStoragePermissions方法放在onCreate方法中即可。

2、默認(rèn)申請
https://github.com/Karumi/Dexter
通過上面庫，接入方式：
在build.gradle加入

dependencies{
    implementation 'com.karumi:dexter:5.0.0'
}

然后在mainactivity加入

static final String[] PERMISSIONS = new String[]{
            Manifest.permission.WRITE_EXTERNAL_STORAGE,
            Manifest.permission.READ_EXTERNAL_STORAGE,
    };
private void initPermissions() {
        Dexter.withActivity(this).withPermissions(PERMISSIONS)
                .withListener(new MultiplePermissionsListener() {
                    @Override
                    public void onPermissionsChecked(MultiplePermissionsReport report) {
                        if (report.areAllPermissionsGranted()){
                            Toast.makeText(getApplication(),"權(quán)限獲取成功！",Toast.LENGTH_LONG).show();
                        }
                    }

                    @Override
                    public void onPermissionRationaleShouldBeShown(List<PermissionRequest> permissions, PermissionToken token) {
                    }
                }).check();
    }

然后在oncreate()中加入initPermissions()就行了

以上兩種方法，親測可用。