Question

目前我有以下代码。它将imageview添加到现有背景中。然而，在创建图像后，程序在我尝试拖动时崩溃了...任何人都有任何关于它为什么不起作用的想法？

ballbutton.setOnClickListener (new View.OnClickListener(){
        @Override
        public void onClick(View view){
            ImageView iv = new ImageView(getApplicationContext());
            iv.setImageDrawable(getDrawable(R.drawable.ball));
            RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
            lp.addRule(RelativeLayout.RIGHT_OF, R.id.resistorbutton);
            iv.setLayoutParams(lp);
            iv.setOnTouchListener(new myListener());
            relativeLayout.addView(iv);
        }
    });

日志如下：

---------崩溃的开始

E / AndroidRuntime：致命异常：主要处理：com.example.dan.ball，PID：2795 java.lang.NullPointerException：尝试调用虚方法＆＃39; void android.view.ViewGroup.invalidate（）＆＃39;在null对象引用上在com.example.dan.circuit.ball $ myListener.onTouch（MainActivity.java:77）在android.view.View.dispatchTouchEvent（View.java:9290）在android.view.ViewGroup.dispatchTransformedTouchEvent（ViewGroup.java:2553）在android.view.ViewGroup.dispatchTouchEvent（ViewGroup.java:2197）在android.view.ViewGroup.dispatchTransformedTouchEvent（ViewGroup.java:2553）在android.view.ViewGroup.dispatchTouchEvent（ViewGroup.java:2197）在android.view.ViewGroup.dispatchTransformedTouchEvent（ViewGroup.java:2553）在android.view.ViewGroup.dispatchTouchEvent（ViewGroup.java:2197）在android.view.ViewGroup.dispatchTransformedTouchEvent（ViewGroup.java:2553）在android.view.ViewGroup.dispatchTouchEvent（ViewGroup.java:2197）在com.android.internal.policy.PhoneWindow $ DecorView.superDispatchTouchEvent（PhoneWindow.java:2403）在com.android.internal.policy.PhoneWindow.superDispatchTouchEvent（PhoneWindow.java:1737）在android.app.Activity.dispatchTouchEvent（Activity.java:2765）在com.android.internal.policy.PhoneWindow $ DecorView.dispatchTouchEvent（PhoneWindow.java:2364）在android.view.View.dispatchPointerEvent（View.java:9514）在android.view.ViewRootImpl $ ViewPostImeInputStage.processPointerEvent（ViewRootImpl.java:4230）在android.view.ViewRootImpl $ ViewPostImeInputStage.onProcess（ViewRootImpl.java:4096）在android.view.ViewRootImpl $ InputStage.deliver（ViewRootImpl.java:3642）在android.view.ViewRootImpl $ InputStage.onDeliverToNext（ViewRootImpl.java:3695）在android.view.ViewRootImpl $ InputStage.forward（ViewRootImpl.java:3661）在android.view.ViewRootImpl $ AsyncInputStage.forward（ViewRootImpl.java:3787）在android.view.ViewRootImpl $ InputStage.apply（ViewRootImpl.java:3669）在android.view.ViewRootImpl $ AsyncInputStage.apply（ViewRootImpl.java:3844）在android.view.ViewRootImpl $ InputStage.deliver（ViewRootImpl.java:3642）在android.view.ViewRootImpl $ InputStage.onDeliverToNext（ViewRootImpl.java:3695）在android.view.ViewRootImpl $ InputStage.forward（ViewRootImpl.java:3661）在android.view.ViewRootImpl $ InputStage.apply（ViewRootImpl.java:3669）在android.view.ViewRootImpl $ InputStage.deliver（ViewRootImpl.java:3642）在android.view.ViewRootImpl.deliverInputEvent（ViewRootImpl.java:5922）在android.view.ViewRootImpl.doProcessInputEvents（ViewRootImpl.java:5896）在android.view.ViewRootImpl.enqueueInputEvent（ViewRootImpl.java:5857）在android.view.ViewRootImpl $ WindowInputEventReceiver.onInputEvent（ViewRootImpl.java:6025）在android.view.InputEventReceiver.dispatchInputEvent（InputEventReceiver.java:185）在android.os.MessageQueue.nativePollOnce（本机方法）在android.os.MessageQueue.next（MessageQueue.java:323）在android.os.Looper.loop（Looper.java:135）在android.app.ActivityThread.main（ActivityThread.java:5417） at java.lang.reflect.Method.invoke（Native Method）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:726）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:616）

Answer 1

好的，所以我自己设法解决了这个问题。在我的myListener类中，我使用invalidate（）来重绘我不需要的视图。

将可拖动图像视图添加到现有相对视图

1 个答案: