Hey there! Since you're a Java/Android beginner working with a rooted Nougat 7.1.2 device, let's break down exactly how to execute that su pm disable com.android.systemui command when a user taps a button.

Core Idea #

On rooted Android devices, you can use Java's Runtime class to spawn a root shell, then write your desired command into that shell's input stream. This lets you run terminal commands directly from your app.

Complete Code Example #

Here's a ready-to-use snippet you can add to your Activity (make sure you have a button with the ID btn_disable_systemui in your layout):

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class MainActivity extends AppCompatActivity {

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

        Button disableBtn = findViewById(R.id.btn_disable_systemui);
        disableBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                executeRootCommand("pm disable com.android.systemui");
            }
        });
    }

    // Helper method to run root commands
    private void executeRootCommand(String command) {
        Process process = null;
        BufferedReader reader = null;
        try {
            // Start a root shell process
            process = Runtime.getRuntime().exec("su");
            // Write the command to the shell's input stream
            process.getOutputStream().write((command + "\n").getBytes());
            // Send an "exit" command to close the shell
            process.getOutputStream().write("exit\n".getBytes());
            process.getOutputStream().flush();

            // Wait for the command to finish and check exit code
            int exitCode = process.waitFor();
            if (exitCode == 0) {
                Toast.makeText(this, "SystemUI disabled successfully!", Toast.LENGTH_SHORT).show();
            } else {
                // Read error output to debug
                reader = new BufferedReader(new InputStreamReader(process.getErrorStream()));
                StringBuilder error = new StringBuilder();
                String line;
                while ((line = reader.readLine()) != null) {
                    error.append(line).append("\n");
                }
                Toast.makeText(this, "Failed to disable SystemUI:\n" + error, Toast.LENGTH_LONG).show();
            }
        } catch (IOException | InterruptedException e) {
            e.printStackTrace();
            Toast.makeText(this, "Error executing root command: " + e.getMessage(), Toast.LENGTH_LONG).show();
        } finally {
            // Clean up resources
            try {
                if (reader != null) reader.close();
                if (process != null) process.destroy();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

Critical Notes for You #

• Recovery Plan: Disabling SystemUI will remove the navigation bar and status bar—you won't be able to navigate back or access settings normally! Make sure you have a way to re-enable it, like connecting your device to a computer and running adb shell su pm enable com.android.systemui via ADB, or having another launcher/app that lets you run commands.
• Root Access: Your app needs to be granted root permission when it first runs the su command. Some root managers (like Magisk) will pop up a prompt asking for approval—make sure you allow it.
• Android Nougat Specifics: The pm disable command works on Nougat, but keep in mind that some devices might have vendor-specific restrictions. Test on your device first!
• Error Handling: The code includes basic error handling and reads error output—this will help you debug if something goes wrong (like if root is not properly granted).

内容的提问来源于stack exchange，提问作者redYmir