Android permission denied原因归纳和解决办法

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.xxx">
    <uses-permission android:name="android.permission.INTERNET"/>
    ...
</manifest>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.xxx">
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <!-- 下面这行代码也非常重要，千万不要忘记加-->
    <application
    ...
    android:requestLegacyExternalStorage="true">...</application>
</manifest>

/**
     * 检查app是否拥有存储权限，如果没有的话，提醒用户开启权限
     */
    public void handlePermission() {
    	// 检查是否开启 Manifest.permission.xxx
    	// (xxx 为权限，根据自己需求添加）
        if (ActivityCompat.checkSelfPermission(this, 
                Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
            Toast.makeText(this, "Permission has been allowed", Toast.LENGTH_SHORT).show();
        } else {
            Toast.makeText(this, "ask for permission",Toast.LENGTH_SHORT).show();
            // 请求权限
            ActivityCompat.requestPermissions(this, new String[] {Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);
            Log.d(TAG, "handlePermission: has aksed");
        }
    }