impl_android.go (2542B)
1 // Copyright 2016 Hajime Hoshi 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 package devicescale 16 17 /* 18 19 #include <jni.h> 20 #include <stdlib.h> 21 22 // Basically same as `getResources().getDisplayMetrics().density`; 23 static float deviceScale(uintptr_t java_vm, uintptr_t jni_env, uintptr_t ctx) { 24 JavaVM* vm = (JavaVM*)java_vm; 25 JNIEnv* env = (JNIEnv*)jni_env; 26 jobject context = (jobject)ctx; 27 28 const jclass android_content_ContextWrapper = 29 (*env)->FindClass(env, "android/content/ContextWrapper"); 30 const jclass android_content_res_Resources = 31 (*env)->FindClass(env, "android/content/res/Resources"); 32 const jclass android_util_DisplayMetrics = 33 (*env)->FindClass(env, "android/util/DisplayMetrics"); 34 35 const jobject resources = 36 (*env)->CallObjectMethod( 37 env, context, 38 (*env)->GetMethodID(env, android_content_ContextWrapper, "getResources", "()Landroid/content/res/Resources;")); 39 const jobject displayMetrics = 40 (*env)->CallObjectMethod( 41 env, resources, 42 (*env)->GetMethodID(env, android_content_res_Resources, "getDisplayMetrics", "()Landroid/util/DisplayMetrics;")); 43 const float density = 44 (*env)->GetFloatField( 45 env, displayMetrics, 46 (*env)->GetFieldID(env, android_util_DisplayMetrics, "density", "F")); 47 48 (*env)->DeleteLocalRef(env, android_content_ContextWrapper); 49 (*env)->DeleteLocalRef(env, android_content_res_Resources); 50 (*env)->DeleteLocalRef(env, android_util_DisplayMetrics); 51 (*env)->DeleteLocalRef(env, resources); 52 (*env)->DeleteLocalRef(env, displayMetrics); 53 54 return density; 55 } 56 57 */ 58 import "C" 59 60 import ( 61 "fmt" 62 63 "golang.org/x/mobile/app" 64 ) 65 66 func impl(x, y int) float64 { 67 s := 0.0 68 if err := app.RunOnJVM(func(vm, env, ctx uintptr) error { 69 // TODO: This might be crash when this is called from init(). How can we detect this? 70 s = float64(C.deviceScale(C.uintptr_t(vm), C.uintptr_t(env), C.uintptr_t(ctx))) 71 return nil 72 }); err != nil { 73 panic(fmt.Sprintf("devicescale: error %v", err)) 74 } 75 return s 76 }