app/clipboard: implement clipboard for Android

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

app/clipboard/clipboard.go

@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+// +build android
+
+// Package clipboard accesses the system clipboard.
+package clipboard
+
+import (
+	"gioui.org/app/internal/window"
+)
+
+// Read the content of the clipboard as a string.
+func Read() (string, error) {
+	return window.ReadClipboard()
+}
+
+// Write a string to the clipboard.
+func Write(s string) error {
+	return window.WriteClipboard(s)
+}

app/clipboard/clipboard_test.go

@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+// +build android
+
+package clipboard
+
+import "testing"
+
+func TestClipboard(t *testing.T) {
+	const want = "Hello, 世界"
+	if err := Write(want); err != nil {
+		t.Fatal(err)
+	}
+	got, err := Read()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got != want {
+		t.Errorf("read %q from the clipboard, wanted %q", got, want)
+	}
+}