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我正在使用 Android Studio

目标：我想更新保持非 null 并mRecordingCanvas在MyCustomView.
即如果上次我从（0,0）到（0,100）画一条线，则不会重置null，
后来我使用自定义方法再次调用它continueRecording并从（0,100）到（100,100）再画一条线，
因此我不如果我想在 "same" 中再添加 10-100 行，则需要再次绘制所有内容mRecordingCanvas。

我希望添加 


    @NonNull
    public Canvas continueRecording() {
    return mRecordingCanvas;
    }

并删除mRecordingCanvas = null；里面 

    public void endRecording() {
    verifyValid();
    if (mRecordingCanvas != null) {
    mRequiresHwAcceleration = mRecordingCanvas.mHoldsHwBitmap;
    //mRecordingCanvas = null;
    nativeEndRecording(mNativePicture);
    }
    }

and remove // if (mRecordingCanvas != null) {
// throw new IllegalStateException("图片已经录制，必须调用 #endRecording()");
//}
并将PictureCanvas里面的变量改成(this, bitmap)
里面 

@NonNull
public Canvas beginRecording(int width, int height) {
    verifyValid();
    if (mRecordingCanvas != null) {
        throw new IllegalStateException("Picture already recording, must call #endRecording()");
    }
    //long ni = nativeBeginRecording(mNativePicture, width, height);
    Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
    mRecordingCanvas = new PictureCanvas(this, bitmap);
    mRequiresHwAcceleration = false;
    return mRecordingCanvas;
}

但是 android.graphics 包中的 Picture.java 存在一些问题；

（1）Picture.java有句@UnsupportedAppUsage(maxTargetSdk = 28)，
但TargetSdk我APP的要Sdk=29，所以我可能需要做一个MyPicture.java

(2) 当我将 Picture.java 中的所有内容复制到 MyPicture.java 并删除 @UnsupportedAppUsage(maxTargetSdk = 28).
当我尝试使用Android Studio使用移动设备运行调试APP时出现一些问题（Sdk ver = 28），
调试日志显示找不到本机 


    public class MyCustomView extends View {
       private MyPicture mPicture = new MyPicture();

       protected void onDraw(Canvas canvas) {
       if (initialTimeMillis == 0) {
        //do sth
        Canvas temp_canvas = 
        mPicture.beginRecording(MainActivity.global_int_widthpx,MainActivity.global_int_heightpx);
        mPicture.endRecording();
        initialTimeMillis = currentTimeMillis;
        return;
        }

        Canvas temp_canvas = mPicture.continueRecording();
                    current_Float_xy[0] = last_Float_xy[0]  +  deltaXY_path1[0]*tempTimeDifferencePercent;
                    current_Float_xy[1] = last_Float_xy[1]  +  deltaXY_path1[1]*tempTimeDifferencePercent;
        temp_canvas.drawLine(last_Float_xy[0],last_Float_xy[1],current_Float_xy[0],current_Float_xy[1], 
        strokePaint);
        mPicture.endRecording();
        mPicture.draw(temp_canvas);
          postInvalidate();
      ｝
    ｝

调试日志显示 

java.lang.UnsatisfiedLinkError: No implementation found for void 
 com.xxx.yyy.MyPicture.nativeEndRecording(long) (tried Java_com_xxx_yyy_MyPicture_nativeEndRecording and Java_com_xxx_yyy_MyPicture_nativeEndRecording__J)  
        at com.xxx.yyy.MyPicture.nativeEndRecording(Native Method)  
        at com.xxx.yyy.MyPicture.endRecording(MyPicture.java:140)  
        at com.xxx.yyy.MyCustomView.onDraw(MyCustomView.java:385)  
        at android.view.View.draw(View.java:20211)  
        at android.view.View.updateDisplayListIfDirty(View.java:19086)  
        at android.view.View.draw(View.java:19939)  
        at android.view.ViewGroup.drawChild(ViewGroup.java:4333)  
        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4112)  
        at android.view.View.updateDisplayListIfDirty(View.java:19077)  
        at android.view.View.draw(View.java:19939)  
        at android.view.ViewGroup.drawChild(ViewGroup.java:4333)  
        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4112)  
        at android.view.View.updateDisplayListIfDirty(View.java:19077)  
        at android.view.View.draw(View.java:19939)  
        at android.view.ViewGroup.drawChild(ViewGroup.java:4333)  
        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4112)  
        at android.view.View.updateDisplayListIfDirty(View.java:19077)  
        at android.view.View.draw(View.java:19939)  
        at android.view.ViewGroup.drawChild(ViewGroup.java:4333)  
        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4112)  
        at android.view.View.updateDisplayListIfDirty(View.java:19077)
        at android.view.View.draw(View.java:19939)  
        at android.view.ViewGroup.drawChild(ViewGroup.java:4333)  
        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4112)  
        at android.view.View.updateDisplayListIfDirty(View.java:19077)  
        at android.view.View.draw(View.java:19939)  
        at android.view.ViewGroup.drawChild(ViewGroup.java:4333)  
        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4112)  
        at android.view.View.updateDisplayListIfDirty(View.java:19077)  
        at android.view.View.draw(View.java:19939)  
        at android.view.ViewGroup.drawChild(ViewGroup.java:4333)  
        at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4112)  
        at android.view.View.draw(View.java:20214)  
        at com.android.internal.policy.DecorView.draw(DecorView.java:780)  
        at android.view.View.updateDisplayListIfDirty(View.java:19086)  
        at android.view.ThreadedRenderer.updateViewTreeDisplayList(ThreadedRenderer.java:686)  
        at android.view.ThreadedRenderer.updateRootDisplayList(ThreadedRenderer.java:692)  
        at android.view.ThreadedRenderer.draw(ThreadedRenderer.java:801)  
        at android.view.ViewRootImpl.draw(ViewRootImpl.java:3327)  
        at android.view.ViewRootImpl.performDraw(ViewRootImpl.java:3124)  
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2493)  
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1468)  
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:7208)  
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:1004)  
        at android.view.Choreographer.doCallbacks(Choreographer.java:816)  
        at android.view.Choreographer.doFrame(Choreographer.java:751)  
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:990)  
        at android.os.Handler.handleCallback(Handler.java:873)  
        at android.os.Handler.dispatchMessage(Handler.java:99)  
        at android.os.Looper.loop(Looper.java:193)  
        at android.app.ActivityThread.main(ActivityThread.java:6692)  
        at java.lang.reflect.Method.invoke(Native Method)  
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)  
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

我不知道什么“com.xxx.yyy.MyPicture.nativeEndRecording(long)（尝试过 Java_com_xxx_yyy_MyPicture_nativeEndRecording 和 Java_com_xxx_yyy_MyPicture_nativeEndRecording__J）”
但我认为当我使用不在原始图形包中的 MyPicture 时它找不到相应的本机代码。

问题（3）：我想跳转到本机代码“nativeEndRecording”，看看我是否可以通过使用“Ctrl+left_mouse_click”在下面的列表中知道更具体的代码，但我在另一行跳转回相同的 MyPicture.java使用它。
这意味着我不知道如何检查、修改和重新创建自定义本机方法，并将方法注入 APP... 


private static native long nativeConstructor(long nativeSrcOr0);
private static native long nativeCreateFromStream(InputStream stream, byte[] storage);
private static native int nativeGetWidth(long nativePicture);
private static native int nativeGetHeight(long nativePicture);
private static native long nativeBeginRecording(long nativeCanvas, int w, int h);
private static native void nativeEndRecording(long nativeCanvas);
private static native void nativeDraw(long nativeCanvas, long nativePicture);
private static native boolean nativeWriteToStream(long nativePicture,
                                                  OutputStream stream, byte[] storage);
private static native void nativeDestructor(long nativePicture);

我现在迷失了方向......我想做的只是保持以前的画布绘制并重复绘制更多短线（可能在 1 秒内逐渐绘制 60~166 行，长度为 30-100 像素，宽度为 30 像素）。
如果我只是重复 ondraw ~=166 次，APP 使用 83 Mb 图形内存。
当路径变得越来越长并且每次长度都略有增加时，它就像一个雪球和图形内存一样在最后几百毫秒内迅速恢复。

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