Update Android java code (#7820)

Targets SDK 26 as required by the playstore.
Fixes screen auto-rotation closing game.
Hides on-screen navigation bar if present.

Update gradlew.
Fix display aspect on 18+/:9 displays (like a Samsung Galaxy S9).
Remove small app icons, not required.
Fix xml in unpacking activity.
Support Android permission: On Android 6.0+ you need to manually give write
permission (as required by google).
Background during unpacking (just a demo for now).
Material Design: no more Android 2 interface.
Immersive mode (Android 4.4+ - hide NavBar for fullscreen mode).

1 files changed, 79 insertions, 0 deletions

diff --git a/build/android/src/main/java/net.minetest.minetest/MainActivity.java b/build/android/src/main/java/net.minetest.minetest/MainActivity.java
new file mode 100644
index 000000000..1baa71668
--- /dev/null
+++ b/build/android/src/main/java/net.minetest.minetest/MainActivity.java
@@ -0,0 +1,79 @@
+package net.minetest.minetest;
+
+import android.Manifest;
+import android.app.Activity;
+import android.content.Intent;
+import android.content.pm.PackageManager;
+import android.os.Build;
+import android.os.Bundle;
+import android.support.annotation.NonNull;
+import android.support.v4.app.ActivityCompat;
+import android.support.v4.content.ContextCompat;;
+import android.widget.Toast;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public class MainActivity extends Activity {
+
+	private final static int PERMISSIONS = 1;
+	private static final String[] REQUIRED_SDK_PERMISSIONS = new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE};
+
+	@Override
+	public void onCreate(Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
+			checkPermission();
+		} else {
+			next();
+		}
+	}
+
+	protected void checkPermission() {
+		final List<String> missingPermissions = new ArrayList<String>();
+		// check required permission
+		for (final String permission : REQUIRED_SDK_PERMISSIONS) {
+			final int result = ContextCompat.checkSelfPermission(this, permission);
+			if (result != PackageManager.PERMISSION_GRANTED) {
+				missingPermissions.add(permission);
+			}
+		}
+		if (!missingPermissions.isEmpty()) {
+			// request permission
+			final String[] permissions = missingPermissions
+					.toArray(new String[missingPermissions.size()]);
+			ActivityCompat.requestPermissions(this, permissions, PERMISSIONS);
+		} else {
+			final int[] grantResults = new int[REQUIRED_SDK_PERMISSIONS.length];
+			Arrays.fill(grantResults, PackageManager.PERMISSION_GRANTED);
+			onRequestPermissionsResult(PERMISSIONS, REQUIRED_SDK_PERMISSIONS,
+					grantResults);
+		}
+	}
+
+	@Override
+	public void onRequestPermissionsResult(int requestCode, @NonNull String permissions[],
+										   @NonNull int[] grantResults) {
+		switch (requestCode) {
+			case PERMISSIONS:
+				for (int index = 0; index < permissions.length; index++) {
+					if (grantResults[index] != PackageManager.PERMISSION_GRANTED) {
+						// permission not granted - toast and exit
+						Toast.makeText(this, R.string.not_granted, Toast.LENGTH_LONG).show();
+						finish();
+						return;
+					}
+				}
+				// permission were granted - run
+				next();
+				break;
+		}
+	}
+
+	public void next() {
+		Intent intent = new Intent(this, MtNativeActivity.class);
+		intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_CLEAR_TASK);
+		startActivity(intent);
+	}
+}