" must be caught or declared to be thrown" in react native when using NativeModules

Question

I want to build a native module to react-native that reboot device. I find this Turn off device programmatically in java. It works alone in android studio but when I try to use it in a native module I got the bellow error

https://pasteboard.co/IztJ6ll.jpg

C:\Users\Ali\Desktop\Android\ReactNative\ReactNativeTest\android\app\src\main\ja
va\com\reactnativetest\ToastModule.java:42: error: unreported exception IOExcept
ion; must be caught or declared to be thrown
    Process proc = Runtime.getRuntime().exec(new String[] { "su", "-c", "reboot"
 });
                                            ^
C:\Users\Ali\Desktop\Android\ReactNative\ReactNativeTest\android\app\src\main\ja
va\com\reactnativetest\ToastModule.java:43: error: unreported exception Interrup
tedException; must be caught or declared to be thrown
      proc.waitFor();
                  ^
2 errors

> Task :app:compileDebugJavaWithJavac FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app:compileDebugJavaWithJavac'.
> Compilation failed; see the compiler error output for details.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug
option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 9s
57 actionable tasks: 1 executed, 56 up-to-date
error Could not install the app on the device, read the error above for details.

Make sure you have an Android emulator running or a device connected and have
set up your Android development environment:
https://facebook.github.io/react-native/docs/getting-started.html
error Command failed: gradlew.bat app:installDebug. Run CLI with --verbose flag
for more details.

this is my native module:

package com.reactnativetest;
import android.widget.Toast;
import com.facebook.react.bridge.NativeModule;
import com.facebook.react.bridge.ReactApplicationContext;
import com.facebook.react.bridge.ReactContext;
import com.facebook.react.bridge.ReactContextBaseJavaModule;
import com.facebook.react.bridge.ReactMethod;
import java.util.Map;
import java.util.HashMap;
import java.util.*;
import java.io.*;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.view.View.OnClickListener;


public class ToastModule extends ReactContextBaseJavaModule {
  private static final String DURATION_SHORT_KEY = "SHORT";
  private static final String DURATION_LONG_KEY = "LONG";
  public ToastModule(ReactApplicationContext reactContext) {
    super(reactContext);
  }

@Override
  public String getName() {
    return "ToastExample";
  }

  @Override
  public Map<String, Object> getConstants() {
    final Map<String, Object> constants = new HashMap<>();
    constants.put(DURATION_SHORT_KEY, Toast.LENGTH_SHORT);
    constants.put(DURATION_LONG_KEY, Toast.LENGTH_LONG);
    return constants;
  }

  @ReactMethod
  public void show(String message, int duration) {
    Toast.makeText(getReactApplicationContext(), message, duration).show();
    Process proc = Runtime.getRuntime().exec(new String[] { "su", "-c", "reboot" });
      proc.waitFor();
  }
}

That exception message is pointing to a very basic thing in Java. It seems rather unlikely that this code compiles and works in one ide but then gives that error message in another context. In any case you want to research how to correctly use checked exceptions in Java. As said: this is super basic, and that error message will lead to myriads of resources explaining it when using a search engine. — GhostCat, Sep 28 '19 at 09:42

score 1 · Accepted Answer · answered Sep 28 '19 at 10:20

it is right there in the logs:

C:\Users\Ali\Desktop\Android\ReactNative\ReactNativeTest\android\app\src\main\ja va\com\reactnativetest\ToastModule.java:43: error: unreported exception InterruptedException; must be caught or declared to be thrown proc.waitFor();

proc.waitFor() throws an exception. You should either surround it with try-catch, or declare in the method signature throws InterruptedException and handle it elsewhere

" must be caught or declared to be thrown" in react native when using NativeModules

1 Answers1