java– 如何通过拖放将图像保留在布局中

概述我有以下XML：<FrameLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:background="@drawable/palette2"android:id="@+id/fl"><ImageViewandroid

我有以下XML：

<FrameLayout    androID:layout_wIDth="match_parent"    androID:layout_height="match_parent"    androID:background="@drawable/palette2"    androID:ID="@+ID/fl" >    <ImageVIEw        androID:ID="@+ID/iv"        androID:layout_wIDth="10dp"        androID:layout_height="10dp"        androID:src="@drawable/esquare" /></FrameLayout>

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必须是< = layout.wIDth()或y必须是< = 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 (y<0) {            iv.setY(0);            iv.setX(x);            y=0;            Toast.makeText(getApplicationContext(), "y=0", 2000).show();        }        if (x>bm.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 || x<bm.getWIDth() || y>0 || 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: main02-09 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.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)

解决方法:

看起来你有这样的错字导致你的问题.

更改

if (x>0 || x<bm.getWIDth() || y>0 || y<bm.getHeight())

进入这个

if (x>0 && x<bm.getWIDth() && y>0 && y<bm.getHeight())

也许这会解决你的问题.

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