app/internal/window: [Android] use app context for clipboard access

The Activity context may not be available, so it's safer and simpler
to use the always available app context.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

app/internal/window/Gio.java

@@ -2,6 +2,8 @@
 
 package org.gioui;
 
+import android.content.ClipboardManager;
+import android.content.ClipData;
 import android.content.Context;
 
 import java.io.UnsupportedEncodingException;
@@ -36,4 +38,19 @@ public final class Gio {
 	}
 
 	static private native void runGoMain(byte[] dataDir, Context context);
+
+	static void writeClipboard(Context ctx, String s) {
+		ClipboardManager m = (ClipboardManager)ctx.getSystemService(Context.CLIPBOARD_SERVICE);
+		m.setPrimaryClip(ClipData.newPlainText(null, s));
+	}
+
+	static String readClipboard(Context ctx) {
+		ClipboardManager m = (ClipboardManager)ctx.getSystemService(Context.CLIPBOARD_SERVICE);
+		ClipData c = m.getPrimaryClip();
+		if (c == null || c.getItemCount() < 1) {
+			return null;
+		}
+		return c.getItemAt(0).coerceToText(ctx).toString();
+	}
+
 }

app/internal/window/GioView.java

@@ -11,8 +11,6 @@ import android.app.Activity;
 import android.app.Fragment;
 import android.app.FragmentManager;
 import android.app.FragmentTransaction;
-import android.content.ClipboardManager;
-import android.content.ClipData;
 import android.content.Context;
 import android.graphics.Rect;
 import android.os.Build;
@@ -229,20 +227,6 @@ public final class GioView extends SurfaceView implements Choreographer.FrameCal
 		ft.commitNow();
 	}
 
-	void writeClipboard(String s) {
-		ClipboardManager m = (ClipboardManager)getContext().getSystemService(Context.CLIPBOARD_SERVICE);
-		m.setPrimaryClip(ClipData.newPlainText(null, s));
-	}
-
-	String readClipboard() {
-		ClipboardManager m = (ClipboardManager)getContext().getSystemService(Context.CLIPBOARD_SERVICE);
-		ClipData c = m.getPrimaryClip();
-		if (c == null || c.getItemCount() < 1) {
-			return null;
-		}
-		return c.getItemAt(0).coerceToText(getContext()).toString();
-	}
-
 	static private native long onCreateView(GioView view);
 	static private native void onDestroyView(long handle);
 	static private native void onStartView(long handle);

app/internal/window/os_android.go

@@ -82,8 +82,6 @@ type window struct {
 	mpostFrameCallback C.jmethodID
 	mRegisterFragment  C.jmethodID
 	mwakeupMainThread  C.jmethodID
-	mwriteClipboard    C.jmethodID
-	mreadClipboard     C.jmethodID
 }
 
 type jvalue uint64 // The largest JNI type fits in 64 bits.
@@ -97,8 +95,13 @@ var android struct {
 	mu  sync.Mutex
 	jvm *C.JavaVM
 
-	// The global Android App context.
+	// appCtx is the global Android App context.
 	appCtx C.jobject
+	// gioCls is the class of the Gio class.
+	gioCls C.jclass
+
+	mwriteClipboard C.jmethodID
+	mreadClipboard  C.jmethodID
 }
 
 var views = make(map[C.jlong]*window)
@@ -153,6 +156,9 @@ func initJVM(env *C.JNIEnv, gio C.jclass, ctx C.jobject) {
 		panic("gio: GetJavaVM failed")
 	}
 	android.appCtx = C.gio_jni_NewGlobalRef(env, ctx)
+	android.gioCls = C.jclass(C.gio_jni_NewGlobalRef(env, C.jobject(gio)))
+	android.mwriteClipboard = getStaticMethodID(env, gio, "writeClipboard", "(Landroid/content/Context;Ljava/lang/String;)V")
+	android.mreadClipboard = getStaticMethodID(env, gio, "readClipboard", "(Landroid/content/Context;)Ljava/lang/String;")
 }
 
 func JavaVM() uintptr {
@@ -188,8 +194,6 @@ func Java_org_gioui_GioView_onCreateView(env *C.JNIEnv, class C.jclass, view C.j
 		mpostFrameCallback: getMethodID(env, class, "postFrameCallback", "()V"),
 		mRegisterFragment:  getMethodID(env, class, "registerFragment", "(Ljava/lang/String;)V"),
 		mwakeupMainThread:  getMethodID(env, class, "wakeupMainThread", "()V"),
-		mwriteClipboard:    getMethodID(env, class, "writeClipboard", "(Ljava/lang/String;)V"),
-		mreadClipboard:     getMethodID(env, class, "readClipboard", "()Ljava/lang/String;"),
 	}
 	wopts := <-mainWindow.out
 	w.callbacks = wopts.window
@@ -624,13 +628,15 @@ func NewWindow(window Callbacks, opts *Options) error {
 func (w *window) WriteClipboard(s string) {
 	w.runOnMain(func(env *C.JNIEnv) {
 		jstr := javaString(env, s)
-		callVoidMethod(env, w.view, w.mwriteClipboard, jvalue(jstr))
+		callStaticVoidMethod(env, android.gioCls, android.mwriteClipboard,
+			jvalue(android.appCtx), jvalue(jstr))
 	})
 }
 
 func (w *window) ReadClipboard() {
 	w.runOnMain(func(env *C.JNIEnv) {
-		c, err := callObjectMethod(env, w.view, w.mreadClipboard)
+		c, err := callStaticObjectMethod(env, android.gioCls, android.mreadClipboard,
+			jvalue(android.appCtx))
 		if err != nil {
 			return
 		}