如何在比屏幕尺寸更大的画布上绘图？答案

【问题标题】：How can I draw on a canvas larger than my screen's dimensions?如何在比屏幕尺寸更大的画布上绘图？
【发布时间】：2016-09-17 09:25:24
【问题描述】：

我正在创建一个允许用户在表面上绘图的 Android 应用程序。不幸的是，我的应用程序中画布的最大图像尺寸在我的手机上是 1000 x 1500 像素，并且会根据设备尺寸进行缩放，但不会更大。

我的目标是允许用户在应用程序中绘图，但要使绘图包含在各种较大的画布中，例如 4032 x 3264 像素的画布。如何覆盖设备的最大画布尺寸以绘制我想要绘制的位图？绘制过程是否应该发生在服务器上，渲染的图像是否应该实时显示在客户端上？或者我可以以某种方式使画布大于屏幕，初始化图像的完全缩小视图并允许用户在其周围滚动、放大/缩小等，同时还能进行绘制？

我已经为我在这里创建的课程发布了一个公共要点：

https://gist.github.com/santafebound/57f45c636e69c53b1df79302b8946099

仅仅改变生成图像的大小会导致以下错误：

09-17 11:29:03.718 4490-4490/com.elgami.customizer E/AndroidRuntime: FATAL EXCEPTION: main

Process: com.elgami.customizer, PID: 4490
     java.lang.OutOfMemoryError: Failed to allocate a 52641804 byte allocation with 16777216 free bytes and 44MB until OOM
         at dalvik.system.VMRuntime.newNonMovableArray(Native Method)
         at android.graphics.Bitmap.nativeCreate(Native Method)
         at android.graphics.Bitmap.createBitmap(Bitmap.java:831)
         at android.graphics.Bitmap.createBitmap(Bitmap.java:808)
         at android.graphics.Bitmap.createBitmap(Bitmap.java:775)
         at com.elgami.customizer.MainActivity.SetupTemplate(MainActivity.java:451)
         at com.elgami.customizer.MainActivity.SetupTemplate(MainActivity.java:434)
         at com.elgami.customizer.MainActivity$1.onPageScrollStateChanged(MainActivity.java:289)
         at android.support.v4.view.ViewPager.dispatchOnScrollStateChanged(ViewPager.java:1944)
         at android.support.v4.view.ViewPager.setScrollState(ViewPager.java:497)
         at android.support.v4.view.ViewPager.onInterceptTouchEvent(ViewPager.java:2119)
         at com.elgami.views.ExtendedViewPager.onInterceptTouchEvent(ExtendedViewPager.java:44)
         at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2108)
         at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2553)
         at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2197)
         at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2553)
         at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2197)
         at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2553)
         at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2197)
         at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2553)
         at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2197)
         at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2553)
         at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2197)
         at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2553)
         at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2197)
         at com.android.internal.policy.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2403)
         at com.android.internal.policy.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1737)
         at android.app.Activity.dispatchTouchEvent(Activity.java:2771)
         at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:63)
         at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:63)
         at com.android.internal.policy.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2364)
         at android.view.View.dispatchPointerEvent(View.java:9520)
         at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4230)
         at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:4096)
         at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3642)
         at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3695)
         at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3661)
         at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3787)
         at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3669)
         at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3844)
         at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3642)
         at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3695)
         at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3661)
         at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3669)
         at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3642)
         at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:5922)
         at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:5896)
         at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:5857)
         at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:6025)
         at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:185)
         at android.os.MessageQueue.nativePollOnce(Native Method)
        at andr

【问题讨论】：

试试这个库。这可能会有所帮助。 github.com/square/picasso
这只是数学问题。据说获取设备资源然后进行一些百分比基础计算。

标签： java android bitmap android-bitmap bitmapimage

【解决方案1】：

尝试对 Canvas 进行子类化并使用固定的 MeasureSpec 来锁定您想要的尺寸：

private static final int fixedWidthMeasureSpec
        = View.MeasureSpec.makeMeasureSpec(4032, View.MeasureSpec.EXACTLY);

private static final int fixedHeightMeasureSpec
        = View.MeasureSpec.makeMeasureSpec(3264, View.MeasureSpec.EXACTLY);

// ...

@Override
protected void onMeasure(int widthMS, int heightMS) {
    super.onMeasure(fixedWidthMeasureSpec, fixedHeightMeasureSpec);
}

【讨论】：