如何通过拖放将图像保留在布局中

我有以下XML：

这在我的Android手机中提供了以下图像

我如何编码，以便用户可以将图像拖动到布局中的任何位置， ImageView将始终保持在布局中？

如果X<0则为X =（X + imageview.width（））

如果Y<0则为Y =（Y + imageview.height（））

如果X>layout.width()它将是X =（X-imageview.width（））

如果Y>layout.height() ，它将是Y =（Y-imageview.height（））？

与此类似的东西：

因此，如果用户拖动视图外，方形图像将保留在FrameLayout中的最后一个已知位置

我将布局背景转换为位图，以便我可以使用它来获取X和Y坐标并转换为我的应用程序的RGB值。

 f = (FrameLayout) findViewById(R.id.fl); f.setOnTouchListener(flt); iv = (ImageView) findViewById(R.id.iv); f.setDrawingCacheEnabled(true); f.buildDrawingCache(); bm = f.getDrawingCache(); 

我有以下代码可以工作，但每隔一段时间我得到一个错误NPE for x must be <= layout.width()或y must be <= layout.height(); 。 有时应用程序允许我拖动布局本身的右侧或底部，这不应该发生，因为我有条件不允许它。

  @Override public boolean onTouch(View v, MotionEvent event) { int x = (int)event.getX(); int y = (int)event.getY(); if (x<0) { iv.setX(0); iv.setY(y); x=0; Toast.makeText(getApplicationContext(), "x=0", 2000).show(); } if (ybm.getWidth()) { x=bm.getWidth()-20; iv.setX(x); iv.setY(y); Toast.makeText(getApplicationContext(), "x=bitmap.maxwidth(}", 2000).show(); } if (y>bm.getHeight()) { y=bm.getHeight()-20; iv.setY(y); iv.setX(x); Toast.makeText(getApplicationContext(), "y=bitmap.maxheight(}", 2000).show(); } if (x>0 || x0 || y<bm.getHeight()) { int action = event.getAction(); int pixel = bm.getPixel((int)x,(int) y); switch (action & MotionEvent.ACTION_MASK) { case MotionEvent.ACTION_DOWN: { Log.i("COORDINATES","Touch coordinates : x" + String.valueOf(x) + "y" + String.valueOf(y)); iv.setX(x); iv.setY(y); inRed = Color.red(pixel); inBlue = Color.blue(pixel); inGreen = Color.green(pixel); Log.d("Colors","R:" +inRed +" G:" +inGreen+" B:" + inBlue); break; } case MotionEvent.ACTION_MOVE:{ Log.i("COORDINATES","Touch coordinates : x" + String.valueOf(x) + "y" + String.valueOf(y)); iv.setX(x); iv.setY(y); inRed = Color.red(pixel); inBlue = Color.blue(pixel); inGreen = Color.green(pixel); Log.d("Colors","R:" +inRed +" G:" +inGreen+" B:" + inBlue); break; } } } return true; } 

使用下面的代码，X = 0和Y = 0的效果非常好！ imageview保持在内部但是当我将X或Y拖过位图的宽度和高度时会出现问题。

如果我向右拖动太多，这是我的LogCat：

 02-09 12:34:32.791: E/AndroidRuntime(12607): FATAL EXCEPTION: main 02-09 12:34:32.791: E/AndroidRuntime(12607): java.lang.IllegalArgumentException: x must be < bitmap.width() 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.graphics.Bitmap.checkPixelAccess(Bitmap.java:1155) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.graphics.Bitmap.getPixel(Bitmap.java:1107) 02-09 12:34:32.791: E/AndroidRuntime(12607): at com.example.dragdrop.MainActivity$1.onTouch(MainActivity.java:116) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.View.dispatchTouchEvent(View.java:7241) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2168) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1903) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2174) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1917) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2174) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1917) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2174) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1917) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2174) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1917) 02-09 12:34:32.791: E/AndroidRuntime(12607): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1953) 02-09 12:34:32.791: E/AndroidRuntime(12607): at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1405) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.app.Activity.dispatchTouchEvent(Activity.java:2410) 02-09 12:34:32.791: E/AndroidRuntime(12607): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1901) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.View.dispatchPointerEvent(View.java:7426) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.ViewRootImpl.deliverPointerEvent(ViewRootImpl.java:3220) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:3165) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:4292) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:4271) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:4363) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:179) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.InputEventReceiver.nativeConsumeBatchedInputEvents(Native Method) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.InputEventReceiver.consumeBatchedInputEvents(InputEventReceiver.java:171) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.ViewRootImpl.doConsumeBatchedInput(ViewRootImpl.java:4342) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.ViewRootImpl$ConsumeBatchedInputRunnable.run(ViewRootImpl.java:4382) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.Choreographer.doCallbacks(Choreographer.java:562) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.Choreographer.doFrame(Choreographer.java:530) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.os.Handler.handleCallback(Handler.java:725) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.os.Handler.dispatchMessage(Handler.java:92) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.os.Looper.loop(Looper.java:137) 02-09 12:34:32.791: E/AndroidRuntime(12607): at android.app.ActivityThread.main(ActivityThread.java:5195) 02-09 12:34:32.791: E/AndroidRuntime(12607): at java.lang.reflect.Method.invokeNative(Native Method) 02-09 12:34:32.791: E/AndroidRuntime(12607): at java.lang.reflect.Method.invoke(Method.java:511) 02-09 12:34:32.791: E/AndroidRuntime(12607): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795) 02-09 12:34:32.791: E/AndroidRuntime(12607): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562) 02-09 12:34:32.791: E/AndroidRuntime(12607): at dalvik.system.NativeStart.main(Native Method) 

Answer 1

看起来你有这样的错字导致你的问题。

更改

 if (x>0 || x0 || y 

进入这个

 if (x>0 && x0 && y 

也许这会解决你的问题。