android: runtime permission dialog for camera

electrum/gui/kivy/data/java-classes/org/electrum/qr/SimpleScannerActivity.java

@@ -4,6 +4,9 @@ import android.app.Activity;
 import android.os.Bundle;
 import android.util.Log;
 import android.content.Intent;
+import android.support.v4.app.ActivityCompat;
+import android.Manifest;
+import android.content.pm.PackageManager;
 
 import java.util.Arrays;
 
@@ -13,29 +16,36 @@ import com.google.zxing.Result;
 import com.google.zxing.BarcodeFormat;
 
 public class SimpleScannerActivity extends Activity implements ZXingScannerView.ResultHandler {
-    private ZXingScannerView mScannerView;
-    final String TAG = "org.electrum.SimpleScannerActivity";
+    private static final int MY_PERMISSIONS_CAMERA = 1002;
 
-    @Override
-    public void onCreate(Bundle state) {
-        super.onCreate(state);
-        mScannerView = new ZXingScannerView(this);   // Programmatically initialize the scanner view
-        mScannerView.setFormats(Arrays.asList(BarcodeFormat.QR_CODE));
-        setContentView(mScannerView);                // Set the scanner view as the content view
-    }
+    private ZXingScannerView mScannerView = null;
+    final String TAG = "org.electrum.SimpleScannerActivity";
 
     @Override
     public void onResume() {
         super.onResume();
-        mScannerView.setResultHandler(this); // Register ourselves as a handler for scan results.
-        mScannerView.startCamera();          // Start camera on resume
+        if (this.hasPermission()) {
+            this.startCamera();
+        } else {
+            this.requestPermission();
+        }
     }
 
     @Override
     public void onPause() {
         super.onPause();
+        if (null != mScannerView) {
             mScannerView.stopCamera();           // Stop camera on pause
         }
+    }
+
+    private void startCamera() {
+        mScannerView = new ZXingScannerView(this);   // Programmatically initialize the scanner view
+        mScannerView.setFormats(Arrays.asList(BarcodeFormat.QR_CODE));
+        setContentView(mScannerView);                // Set the scanner view as the content view
+        mScannerView.setResultHandler(this);         // Register ourselves as a handler for scan results.
+        mScannerView.startCamera();                  // Start camera on resume
+    }
 
     @Override
     public void handleResult(Result rawResult) {
@@ -45,4 +55,35 @@ public class SimpleScannerActivity extends Activity implements ZXingScannerView.
         setResult(Activity.RESULT_OK, resultIntent);
         this.finish();
     }
+
+    private boolean hasPermission() {
+        return (ActivityCompat.checkSelfPermission(this,
+                                                   Manifest.permission.CAMERA)
+                == PackageManager.PERMISSION_GRANTED);
+    }
+
+    private void requestPermission() {
+        ActivityCompat.requestPermissions(this,
+                    new String[]{Manifest.permission.CAMERA},
+                    MY_PERMISSIONS_CAMERA);
+    }
+
+    @Override
+    public void onRequestPermissionsResult(int requestCode,
+            String permissions[], int[] grantResults) {
+        switch (requestCode) {
+            case MY_PERMISSIONS_CAMERA: {
+                if (grantResults.length > 0
+                    && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
+                    // permission was granted, yay!
+                    this.startCamera();
+                } else {
+                    // permission denied
+                    this.finish();
+                }
+                return;
+            }
+        }
+    }
+
 }