java - Android XML 图形布局查看器 - 无法实例化自定义 View ，找不到类？

Question

我有一个非常简单的自定义 View ，它尝试绘制一个 OvalShape，又名 android.graphics.drawable.shapes.OvalShape。所以它是 SDK 的原生内容。

这是错误标题:

com.dan.test.ui.ArcButton failed to instantiate.

这是错误正文:

java.lang.ClassNotFoundException: android.graphics.drawable.shapes.OvalShape
at com.android.ide.eclipse.adt.internal.resources.manager.ProjectClassLoader.findClass(ProjectClassLoader.java:105)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.Class.getDeclaredConstructors0(Native Method)
at java.lang.Class.privateGetDeclaredConstructors(Unknown Source)
at java.lang.Class.getConstructor0(Unknown Source)
at java.lang.Class.getConstructor(Unknown Source)
at com.android.ide.eclipse.adt.internal.editors.layout.ProjectCallback.instantiateClass(ProjectCallback.java:327)
at com.android.ide.eclipse.adt.internal.editors.layout.ProjectCallback.loadView(ProjectCallback.java:166)
at com.android.layoutlib.bridge.android.BridgeInflater.loadCustomView(BridgeInflater.java:205)
at com.android.layoutlib.bridge.android.BridgeInflater.createViewFromTag(BridgeInflater.java:133)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:623)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:626)
at android.view.LayoutInflater.inflate(LayoutInflater.java:408)
at android.view.LayoutInflater.inflate(LayoutInflater.java:296)
at com.android.layoutlib.bridge.impl.RenderSessionImpl.inflate(RenderSessionImpl.java:279)
at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:318)
at com.android.ide.common.rendering.LayoutLibrary.createSession(LayoutLibrary.java:325)
at com.android.ide.eclipse.adt.internal.editors.layout.gle2.RenderService.createRenderSession(RenderService.java:372)
at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.renderWithBridge(GraphicalEditorPart.java:1361)
at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.recomputeLayout(GraphicalEditorPart.java:1115)
at com.android.ide.eclipse.adt.internal.editors.layout.gle2.GraphicalEditorPart.activated(GraphicalEditorPart.java:941)
at com.android.ide.eclipse.adt.internal.editors.layout.LayoutEditorDelegate.partActivated(LayoutEditorDelegate.java:477)
at com.android.ide.eclipse.adt.internal.editors.layout.LayoutEditorDelegate.partBroughtToTop(LayoutEditorDelegate.java:487)
at org.eclipse.ui.internal.PartListenerList$2.run(PartListenerList.java:87)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.core.runtime.Platform.run(Platform.java:888)
at org.eclipse.ui.internal.PartListenerList.fireEvent(PartListenerList.java:57)
at org.eclipse.ui.internal.PartListenerList.firePartBroughtToTop(PartListenerList.java:85)
at org.eclipse.ui.internal.PartService.firePartBroughtToTop(PartService.java:208)
at org.eclipse.ui.internal.WorkbenchPagePartList.firePartBroughtToTop(WorkbenchPagePartList.java:76)
at org.eclipse.ui.internal.WorkbenchPagePartList.fireActiveEditorChanged(WorkbenchPagePartList.java:52)
at org.eclipse.ui.internal.PartList.setActiveEditor(PartList.java:162)
at org.eclipse.ui.internal.WorkbenchPage.makeActiveEditor(WorkbenchPage.java:1355)
at org.eclipse.ui.internal.WorkbenchPage.setActivePart(WorkbenchPage.java:3629)
at org.eclipse.ui.internal.WorkbenchPage.requestActivation(WorkbenchPage.java:3159)
at org.eclipse.ui.internal.PartPane.requestActivation(PartPane.java:279)
at org.eclipse.ui.internal.EditorPane.requestActivation(EditorPane.java:98)
at org.eclipse.ui.internal.PartPane.setFocus(PartPane.java:325)
at org.eclipse.ui.internal.EditorPane.setFocus(EditorPane.java:127)
at org.eclipse.ui.internal.PartStack.presentationSelectionChanged(PartStack.java:837)
at org.eclipse.ui.internal.PartStack.access$1(PartStack.java:823)
at org.eclipse.ui.internal.PartStack$1.selectPart(PartStack.java:137)
at org.eclipse.ui.internal.presentations.util.TabbedStackPresentation$1.handleEvent(TabbedStackPresentation.java:133)
at org.eclipse.ui.internal.presentations.util.AbstractTabFolder.fireEvent(AbstractTabFolder.java:269)
at org.eclipse.ui.internal.presentations.util.AbstractTabFolder.fireEvent(AbstractTabFolder.java:278)
at org.eclipse.ui.internal.presentations.defaultpresentation.DefaultTabFolder.access$1(DefaultTabFolder.java:1)
at org.eclipse.ui.internal.presentations.defaultpresentation.DefaultTabFolder$2.handleEvent(DefaultTabFolder.java:88)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1053)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1077)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1062)
at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:774)
at org.eclipse.swt.custom.CTabFolder.setSelection(CTabFolder.java:2746)
at org.eclipse.swt.custom.CTabFolder.onMouse(CTabFolder.java:1433)
at org.eclipse.swt.custom.CTabFolder$1.handleEvent(CTabFolder.java:257)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1053)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4165)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3754)
at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2701)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2665)
at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2499)
at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:679)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:668)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:123)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:344)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:622)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:577)
at org.eclipse.equinox.launcher.Main.run(Main.java:1410)
at org.eclipse.equinox.launcher.Main.main(Main.java:1386)

这是我的布局 XML 的一部分:

<com.dan.test.ui.ArcButton
android:id="@+id/btn_arc"
android:layout_width="100dip"
android:layout_height="75dip"
android:layout_gravity="center"
/>

这是我在 ArcButton 类中的 onDraw 代码:

@Override
protected void onDraw(Canvas canvas)
{
    super.onDraw(canvas);

    // SETUP
    int r = (int) radius;

    // BG WHITE
    int cx = this.getWidth() / 2, cy = this.getHeight() / 2;
    Paint bg_paint = new Paint();
    bg_paint.setAntiAlias(true);
    bg_paint.setARGB(255, 255, 255, 255);
    ShapeDrawable bg = new ShapeDrawable(new OvalShape()); // If removed, then ArcShape causes the same CNFE error
    canvas.drawCircle(cx, cy, r, bg_paint);

    // ROTATING ARC
    ShapeDrawable drawable = new ShapeDrawable(new ArcShape(-90, s));
    drawable.getPaint().setColor(0xff74AC23);
    drawable.setBounds(cx - (r-2), cy - (r-2), cx + (r-2), cy + (r-2));
    drawable.draw(canvas);

    invalidate();
}

编辑:此外，我已经准备好这些构造函数。即便如此，错误仍然发生:

public ArcButton(Context context, AttributeSet attrs, int defStyle)
{
    super(context, attrs, defStyle);
}

public ArcButton(Context context, AttributeSet attrs)
{
    super(context, attrs);
}

public ArcButton(Context context)
{
    super(context);
}

Answer 1

找到我的代码，也许你有一些不同并且还清理了项目。

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.drawable.ShapeDrawable;
import android.graphics.drawable.shapes.ArcShape;
import android.graphics.drawable.shapes.OvalShape;
import android.util.AttributeSet;
import android.view.View;

public class Button1 extends View
{
    private int radius = 100;

     /**
     * @param context
     * @param attrs
     */
    public Button1(Context context, AttributeSet attrs) 
    {
        super(context, attrs);
    }

    @Override
    protected void onDraw(Canvas canvas)
    {
        super.onDraw(canvas);

        // SETUP
        int r = (int) radius ;

        // BG WHITE
        int cx = this.getWidth() / 2, cy = this.getHeight() / 2;
        Paint bg_paint = new Paint();
        bg_paint.setAntiAlias(true);
        bg_paint.setARGB(255, 255, 255, 255);
        ShapeDrawable bg = new ShapeDrawable(new OvalShape()); // If removed, then ArcShape causes the same CNFE error
        canvas.drawCircle(cx, cy, r, bg_paint);

        // ROTATING ARC
        ShapeDrawable drawable = new ShapeDrawable(new ArcShape(-90, 60));
        drawable.getPaint().setColor(0xff74AC23);
        drawable.setBounds(cx - (r-2), cy - (r-2), cx + (r-2), cy + (r-2));
        drawable.draw(canvas);

        invalidate();
    }
}