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Introduction

This is a simple Demo for writing text to an SD card after clicking a button. The application dynamically requests permission and writes a text file to the SD card for demonstration purposes.

Implementation Cases

The implementation is divided into three main parts: UI layout creation, permission utility class creation, and the business logic implementation.

UI Layout Creation

The activity is implemented using ConstraintLayout for better layout management. The UI consists of a Button with the ID "button" and an onClick event handler. The button is set to fill the parent layout width and has the text "Write to SD Card". Importantly, the Button is constrained to all four corners of the layout via constraint attributes, ensuring it occupies the full width of the screen.

Permission Utility Class

The PermisionUtils class is designed to check and request runtime permissions. It takes the target activity, a request code, and an array of permissions. The method first checks if the current SDK version is M or higher, as runtime permissions were introduced starting from Android M. If permissions are required, it requests them dynamically.

Business Logic Implementation

In the MainActivity, the OnClickButton event handler checks if the external storage is mounted. If so, it shows a toast message, requests the necessary write permissions, and calls the Write method. The Write method creates a file in the external storage directory and writes "helloworld" to it. Exception handling is included to manage any potential errors.

The onRequestPermissionsResult method overrides the default Android method to handle the permission results. If the requested permissions are granted, it proceeds to write the file. If any permission is denied, it shows an error toast. This ensures that the user has the necessary permissions before attempting to write to the SD card.

Note: For this implementation to work, the Android app must request the WRITE_EXTERNAL_STORAGE and READ_EXTERNAL_STORAGE permissions during runtime.

The code assumes that the user has correctly implemented these steps in their project and that the necessary permission requests are properly handled.